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LEONARDO TIMES Journal of the Society of Aerospace Engineering Students ‘Leonardo da Vinci’

CASSINIHUYGENS

THE END Amelia

Drag analysis

Flying cars

An extraordinary life

Studying a cyclist

What's in our future?

Page 13 Year 21 | N° 4 | December 2017

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Page 40


Biofuel. You won’t notice the difference, but nature will KLM has proven that aviation can be more sustainable. As a pioneer we operated the world’s first commercial flight with biofuel. However, KLM will only use biofuels with no negative effects on food production and nature. Together with partners we stimulate the development of biofuel, only when used on a large scale biofuel will make the difference - klmtakescare.com


EDITORIAL Dear reader, Welcome to the November 2017 issue of the Leonardo Times. This issue is quite a special one, not just because it contains remarkable articles on topics ranging from the life of Amelia Earhart all the way to the transformation of bainite in steels, but also due to the fact that it is my first as Editor-in-Chief. I realize the editorial is not a piece that many people tend to linger on, but for those of you whose attention I have managed to capture with that first sentence: hold on for a little longer, it gets interesting. My predecessor, Victor Gutgesell, left behind one hell of a magazine. His two years as Editor-in-Chief saw the Leonardo times raise the bar in terms of quality and standards. For this and more, I would like to express my sincere gratitude. From this issue on, I along with the rest of the editorial staff, will not let this level that the Leonardo times has strived to achieve remain stagnant. Not to be cliché, but the only way is up. Before I get into anything heavy, I would like to pay particular homage to the editorial staff, without whom, this issue would not be in your hands right now. Nicolas Ruitenbeek, Katharina Ertman, Thijs Gritter, Flavie Rometsch, Greeshma Boohalli Shivamalle-

gowda, Abhishek Mittal, Nicolo Nefri, Maria Mathew, and Raphael Klein, thank you for your dedication. I thought quite a bit on what to write this editorial on and, not to shy away from commitment, but I realized that the universe is too infinite and the human mind too infinitely curious for it to not be focused on the exploration of space. Once you start flipping through the magazine, you will notice that the Cassini-Huygens makes up quite a portion of it. This mission, apart from being a significant breakthrough in the exploration of Saturn, has also propelled mankind in the right direction: forwards and everywhere. Missions like New Horizons exhibit the same philosophy. Having launched at 16.26 kilometers per second and elapsing over two years in lifetime, New Horizons has now hurtled past Pluto and is at the edge of our solar system. There are two things worth mentioning here: 1. that we are still receiving data from a distance of 9 orders of magnitude away, and 2. the actual data itself. Another feat when it comes to exploring the unknown, is the Voyager mission. Travelling further than anyone or anything in history, and running its 40th year now, the received signal from the Voyager 1 has a power of 1 part in 10 quadrillionths of a watt. This spacecraft is expected to venture so far into space, it contains two phonograph records which contain sounds and images meant to portray the diversity of life on Earth in the case that extraterrestrial life encounters the spacecraft. I could go on, but I think you get the picture. Living in an age where we get to experience so many new firsts in space exploration is remarkable. I must say that it is an incredible privilege that we have the opportunity to learn, and eventually contribute to extend humanities reach in space by advancing our technological capabilities. Finally, I hope this, my first issue, will be an enjoyable and illuminating read for you all. Nora Sulaikha Editor-in-Chief, Leonardo Times

Last edition ...

LEONARDO TIMES Journal of the Society of Aerospace Engineering Students ‘Leonardo da Vinci’

ARE WE

ALONE?

DUT Formula student team Delft Page 24

DSE Summer edition Page 30

Ethics in Automation Is it possible? Page 43

Year 21 | N° 3 | September 2017

If you have remarks or opinions on this issue, let us know by dropping an email at: LeoTimes-VSV@student.tudelft.nl

In the 2017 September issue of the Leonardo Times, a mistake in the author’s name was made in the article: 'Airport of the Future'. We deeply regret this error and offer our sincere apologies to Rens van der Zwaard and Maaike Sickler, who should have been accredited with the authorship of the piece.

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LEONARDO TIMES N°4 2017

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CONTENTS FRONT FEATURES 03 Editorial 07 Leonardo's Desk 08 Quaterly Highlights

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AVIATION DEPARTMENT

Schiphol's Sustainability People, planet, profit. What counts and who benefits?

10 Schiphol's Sustainability

TIME FLIES 13 Amelia

AERODYNAMICS 17 Drag Analysis

SPACE ENGINEERING

24 Cassini-Huygens

20 Europa's Plumes 24 Cassini-Huygens

On the 15th of September, the Cassini spacecraft plunged into Saturn after almost thirteen years of extensive exploration. What made this mission a mission of firsts?

CONTROL & OPERATIONS (C&O) 33 Retirement Planning 38 Recovery Crew Pairing 46 Designing Quiet

AEROSPACE STRUCTURES & MATERIALS 36 Bainite in Steels

NICO'S CORNER 41 Your Future Commute

SPACE DEPARTMENT 44 Nano Goes Orbital

Retirement planning INTERNSHIP 49 Internship at LaRC Over time, an aircraft’s capability decreases while its maintenance costs increase. Replacing an aging aircraft with new acquisitions is costly, so how can we squeeze out the last drops of value before its retirement?

ADVERTISMENTS 02 KLM 06 Delft Career Platform 51 NLR 52 GKN Aerospace

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COLOPHON

Europa's Plumes

20

Flying through the plume of Europa can provide relevant information of its subsurface ocean, which is one of the environments with the most potential for finding extraterrestrial life.

Year 21, NUMBER 4, December 2017 The ‘Leonardo Times’ is issued by the Society for Aerospace Engineering students, the VSV ‘Leonardo da Vinci’ at the Delft University of Technology. The magazine is circulated four times a year with a circulation of around 5000 copies per issue.

EDITOR-IN-CHIEF: Nora Sulaikha FINAL EDITOR: Nicolas Ruitenbeek EDITORIAL STAFF: Thijs Gritter, Katharina Ertman, Flavie Rometsch, Greeshma Boohalli Shivamallegowda, Abhishek Mittal, Nicolò Nefri, Maria Mathew. THE FOLLOWING PEOPLE CONTRIBUTED: Jeff Newcamp, Salil Sainis, Niek Hoeben, Yash Hemant Shah, Mònica Aragay Verdeny, Quincy Booster, Klaas Burger, Bastiaan Bosman. DESIGN, LAYOUT: SmallDesign, Delft PRINT: Quantes Grafimedia, Rijswijk

Noise Mitigation

US AIRWAYS

Articles sent for publishing become property of ‘Leonardo Times’. No part of this publication may be reproduced by any means without written permission of the publisher. ‘Leonardo Times’ disclaims all responsibilities to return articles and pictures. Articles endorsed by name are not necessarily endorsed editorially. By sending in an article and/or photograph, the author is assured of being the owner of the copyright. ‘Leonardo Times’ disclaims all responsibility. The ‘Leonardo Times’ is distributed among all students, alumni and employees of the Aerospace Engineering faculty. The views expressed do not necessarily represent the views of the Leonardo Times or the VsV 'Leonardo da Vinci'. VSV ‘Leonardo da Vinci’ Kluyverweg 1, 2629HS Delft Phone: 015-278 32 22 Email: VSV@tudelft.nl ISSN (PRINT) : 2352-7021 ISSN (ONLINE): 2352- 703X Visit our website www.leonardotimes.com for more content. Remarks, questions and/ or suggestions can be emailed to the Editor-in-Chief at the following address:

To increase the number of aircraft operations at airports while mitigating their negative impacts, the optimal design of new departure routes with less noise and fuel consumption has becomes necessary.

LeoTimes-VSV@student.tudelft.nl

46 LEONARDO TIMES N°4 2017

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LEONARDO'S DESK

A MESSAGE FROM THE BOARD Dear reader, It is with great pleasure that I write my first preface for the first Leonardo Times of this academic year. When I read this magazine, I am extremely proud of what our society is capable of. I hope you read this magazine with the same enthusiasm and interest as I do. I would like to compliment all the Leonardo Times editors for their dedication and eagerness to deliver once more such a high-quality issue. Since the aerospace industry is so broad, a wide variety of topics are included in this Leonardo Times. One of the fascinating advances that is being made in the aerospace industry is the flying car. For some people, it might sound like fantasy, but engineers are making this a reality. Something that plays a big role in our lives is sustainability. One article looks at what measures Schiphol Airport is taking to become a more sustainable airport. This is just a glimpse of the articles that are included in this Leonardo Times. I think it is marvellous how the editors managed to cover such a wide variety of branches in the industry.

Additionally, I would like to use this opportunity to inform you on the status of the society. The 72nd year of the VSV ‘Leonardo da Vinci’ ended with one of the biggest events that year: The VSV Breda Airshow. At the Airshow, over 10,000 visitors watched over ten flying displays, an impressive static line and numerous stands. Moreover, a congress, ‘MAVCON’, themed ‘Cross-sectoral collaboration’ was held for 250 VIPs. Altogether, it was a truly fantastic day for the VSV that shows how much students can achieve when there is the dedication and energy to organize great events. The new year will also be full of great activities. Therefore, I would like to tell you something about the projects that we are working on for this year. One of these projects is a very exciting one: the Study Tour. The Study Tour will be an inter-continental tour going to Canada and the United States of America. During a tour of about four weeks in September 2018, a group of students and professors will visit various companies and taste the local culture. Besides the Study Tour, every year a symposium is organised for students and professionals to have a look at an interesting theme in the aerospace industry. This year

the symposium will feature a space theme: “Rescaling limits: engineering the new space era”. This symposium will dive into miniaturization of spacecraft and, in particular, satellites. What are the challenges for smaller satellites? How can they cooperate with the more conventional large satellites? All this, and more, will be discussed on the 6th of March. This is not the only symposium we organise. A mini symposium is organised by the Women’s Department ‘Amelia’ themed: “Be the game changer”. With this symposium, women at our faculty will be encouraged to join the aerospace industry and will become more prepared in making that step. These activities, and more, make us, the 73rd board of the VSV 'Leonardo da Vinci', look forward to the coming year with great longing and excitement. I hope you will enjoy and learn from this new issue of the Leonardo Times. With winged regards, Roger Hak President of the 73rd board of the VSV ‘Leonardo da Vinci’ LEONARDO TIMES N°4 2017

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QUARTERLY HIGHLIGHTS Green Jet Fuel Plan The “green jet fuel” plan proposes an increase of use of biofuels in aviation to five million tons a year by 2015, and 285 million tons by 2050, this would be enough to cover half of the demand for international aviation fuel. However, this represents three times more biofuels compared to what the world is producing at the moment. A few days later, 25 countries gathered by the UN as ICAO rejected the 2050 Vision on Sustainable Aviation Fuels, which encompassed volume-based targets for biofuels suggested by the ICAO Secretariat. The main reason for denial is the accelerated expansion of industrial palm oil. Friends of the Earth warned that palm oil is the most significant driver of land-grabbing across the tropics, endangering the lives and livelihoods of millions of people in the developing world.

During the 39th Session of the International Civil Aviation Organization (ICAO) assembly in Mexico City, the need for alternative fuels to be developed and used in a way that is economically, socially, and environmentally acceptable has been reaffirmed. Greenhouse emissions in the aviation sector have increased by 8% last year and keep increasing very quickly.

Klaus Schenk of Rainforest Rescue said: “Citizens around the world are very concerned about burning palm oil in planes. The vast use of palm oil for aviation biofuels would destroy the world’s rainforests, the basis of life for local people and the habitats of endangered species such as orangutans. We urge ICAO to scrap its misguided biofuels plan.” A total of 82.3 million hectares of land would be required to meet the target according to an estimation by Biofuelwatch.

What powered Rosetta’s comet fountain of dust? On July 6th 2016, close to the end of Rosetta’s mission, as comet 67P/Churyumov– Gerasimenko was moving away from the Sun, scientists observed a fountain of dust streaming from the comet. The first question that popped up was: how is it powered? In the first instance, scientists believed that the plume was surface ice evaporating in the sunlight. However, Rosetta’s measurements revealed that something more energetic had to be causing this great outburst of dust and ice grains. “We saw a bright plume of dust blowing away from the surface like a fountain,” explains Jessica Agarwal of the Max Planck Institute for Solar System Research in Göttingen, Germany. “It lasted for roughly an hour, producing around 18kg of dust every second.” “This plume was really special. We have great data from five different instruments on how 08

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the surface changed and on the ejected material because Rosetta was, by chance, flying through the plume and looking at the right part of the surface when it happened,” adds Jessica. “Rosetta hasn’t provided such detailed and comprehensive coverage of an event like this before.” “Energy must have been released from beneath the surface to power it,” says Jessica. It remains unclear how such energy is liberated. One of the theories is that pressurized gas bubbles arise via underground cavities and burst free through ancient vents. Another theory is that stores of ice react violently when exhibited to sunlight. At the moment, scientists are merging measurements from the comet and computer simulations together with laboratory work to ascertain what induces such plumes on comets.

Carlos Calvo Ambel, a spokesman for Transport and Environment, said: “Most biofuels are worse for the climate than jet fuel. Quality should always go before quantity. Establishing a goal even before the rules are set out is putting the cart before the horse. The European experience has been that biofuel targets sucked-in palm oil exports whose emissions were far greater than those of fossil fuels.” Furthermore, Almuth Ernsting, from Biofuelwatch, mentioned that the actual suggested target was “so huge that it would be unlikely to be fulfilled – but you could still have massive negative impacts from much smaller uses of palm oil”. Almost 100 environmental groups were against the proposal and about 181,000 people signed a petition appealing for the plan to be discarded. Many states also denied the biofuels plan, which if accepted, is presumed to go the ICAO assembly for formal adoption in the next two years. While Brazil and Indonesia are in favor of the plan, China questions its feasibility. The EU requires more robust sustainability criteria and the US is not willing to support the globally coordinated emissions reduction targets.


The mysterious behavior of Jupiter’s auroras For a long time, scientists believed that auroras occur in a coordinated manner, just like the polar lights on our planet Earth. Here, whenever the polar lights brighten at the North Pole, they also brighten at the South Pole. Surprisingly, this is not the case for Jupiter’s auroras. Scientists directed by William Dunn and Andrew Coates at the University College London found that the northern and southern auroras behave independently from one another. On Earth, auroras are known as glowing bands of green or red light that arise when the solar wind, which consists of a stream of electrically charged particles from the Sun, rains on the planet’s magnetic field. The magnetic field lines direct these particles to the poles, where they collide with the atmospheric layers and emit light. However, there are also auroras that the human eye cannot see, and these consist of ultraviolet, infrared light, or X-rays. While X-ray auroras only weakly occur on Earth, they are very strong on Jupiter. On Jupiter, high-energy particles are thought not only to blow in from the Sun, but also

from Jupiter’s moons. These particles align with the magnetic field of the planet and then, due to Jupiter’s fast rotation, hit the atmosphere with tens of mega electronvolts of energy. During the interaction with the atmosphere, the particles take away electrons and release X-rays in the process. ESA’s XMM-Newton and NASA’s Chandra X-ray space observatories have been used to perform studies on the high-energy X-rays released by Jupiter’s auroras. Apparently, while the South Pole auroras show a regular pulsing pattern, every 11 minutes, the North Pole auroras do not show such a periodic behavior. As William Dunn recently stated: “These auroras don’t seem to act in unison like those that we’re often familiar with here on Earth. We thought the activity would be coordinated through Jupiter’s magnetic field, but the behaviour we found is really puzzling.” A couple of questions arose after this surprising discovery. Does the solar wind influence Jupiter’s auroras as well? Why does Jupiter produce such bright and highly energetic X-ray auroras and why do they occur independently of one another? Why does Sat-

urn, a gas giant planet just like Jupiter, not produce any X-ray auroras that can be detected? NASA’s Juno spacecraft, currently orbiting Jupiter, equipped with several instruments to detect magnetic fields, could soon help scientists in providing answers to all these questions.

Uber’s Flying Cars planned for 2020 bed for the aerial vehicles, as the city is well known for its unmanageable traffic. Uber is aiming to reduce travel times for trips from Los Angeles airport to the Staples Center during rush hour by 50 minutes at comparable UberX service prices. A video showing what advantages aerial taxis would have with respect to traffic jams avoidance has also just been released. The closing line of the video is: “Closer than you think”. But how close are we for this dream to happen?

During the Web Summit, in Lisbon, at the beginning of November this year, Jeff Holden, Uber’s chief product officer, announced that the company has recently signed the Space Act Agreement with NASA. This partnership is intended to provide for collaboration between the tech company and the American Space Agency regarding the development of air traffic management systems for the companies’ flying taxi initiatives planned for 2020.

Earlier this year, Uber revealed its plans to introduce flying taxis, known as uberAIR. Now its project “Elevate” is coming back with several announcements on where the flying cars will first appear, who will be involved in the realization, and how these futuristic airplanes will look. During the tech conference, Uber also announced that Los Angeles is joining Dallas-Fort Worth and Dubai as cities where the taxis will be first operating. Los Angeles appears to be an interesting test

A spokesman of NASA mentioned that Uber will help in creating a framework for the air traffic management of drones and this will prepare the way for passenger carrying aerial vehicles. It is forecast that by 2019, NASA and its partners will share its recommendations with the Federal Aviation Administration, which will decide on how they should be combined with the existing air traffic systems.

LEONARDO TIMES N°4 2017

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SCHIPHOL’S SUSTAINABILITY People, planet, profit. What counts and who benefits? AVIATION DEPARTMENT

Quincy Booster & Klaas Burger, Aviation Department, BSc Aerospace Engineering, TU Delft

Amsterdam Schiphol Airport is one of the busiest airports in Europe. This gives it an important job as role model to other airports, which encourages it to work hard towards a sustainable future. In October 2015, the UN’s Sustainable Development Goals were defined, which tie into Schiphol’s sustainability themes.

I

n 2015, the United Nations, together with other key players in the world of sustainable development, set up the Sustainable Development Goals (SDG). These 17 goals aim to end poverty, protect the planet, and ensure prosperity for all. While the previously developed Millennium Goals, created in 2000, mainly focused on the role of governments, the Sustainable Development Goals of 2015 believe that greater sustainability should be achieved as a joint effort between countries, companies, and citizens. Schiphol Group is determined to deliver its part in the equation. It has set out to become the world’s most 10

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ment and decent work for all”. Schiphol’s effort to achieve this is mainly characterized by three pillars: mobility, inclusivity, and diversity.

sustainable airport, and has therefore acted to try to achieve the goals that most apply to aviation. In addition, Schiphol Group signed the Airports Sustainability Declaration during the Airports Going Green Conference held at Amsterdam Airport Schiphol in October 2016.

The airport is aiming to further educate and develop its workforce by encouraging a high internal mobility for its workers. Schiphol Group plans to have 15% of its employees change jobs, either within the company or at external employers, every year. This target was achieved in both 2015 and 2016.

DECENT WORK AND ECONOMIC GROWTH

Secondly, Schiphol tries to provide an inclusive business environment. This means that employees should feel comfortable in their job, regardless of their cultural background, sexual orientation, or physical disabilities.

The first goal that Schiphol Group is trying to achieve states: “Companies should promote sustained, inclusive and sustainable economic growth, full and productive employ-


SCHIPHOL GROUP

The concept of health, safety, and sustainable also extends to people working in the Group. Several measures to ensure a better working environment for everyone have already been discussed in the section ‘decent work and economic growth’. In addition to their commitment to mobility, inclusivity, and diversity, the Schiphol Group provides all its new and existing workers with regular safety training. This enables the airports to further enhance the working environments in their specific cities.

SUSTAINABLE CONSUMPTION AND PRODUCTION In the future, Schiphol Group wants to avoid waste and be able to recycle all materials, products and raw materials in compliance with the highest possible standards. This is part of an initiative called ‘Zer0 Waste’, which is set to be achieved by 2030. This idea does not only hold for the purchase of products and services, but also applies to the construction of new buildings and renovation of existing assets. This requires works and analysis of multiple areas simultaneously. Understanding the flows at the airport enables them to adjust the current processes and procedures to efficient circular systems.

Finally, the company aims to have a fair distribution of management positions among men and women. Currently, Schiphol’s management board has a 50-50 male-female ratio. In the coming years, Schiphol Group has committed to furthering women’s presence in the management at all levels of the company. Because of their commitment to these pillars, Schiphol Group is now ranked fifth in “The Netherland’s Best Employer” survey in 2016 with a score of 7.7, demonstrating the clear concrete impact of focusing on these areas.

SUSTAINABLE COMMUNITIES AND CITIES

import parts of the community in the cities where they are located, and strives to “make cities and human settlements inclusive, safe, resilient and sustainable”. Schiphol Group’s airports, in particular Amsterdam Airport Schiphol, are located in major metropolitan areas in the Netherlands. The Schiphol Group tries to improve its presence in these areas by providing accessible and healthy working environments. Great accessibility to the airport is one of the key factors for it to stay competitive in the aviation market. Additionally, easily accessible public transport at the airport ensures that fewer passengers travel by car, therefore lowering the impact per passenger on the environment.

All ideas and changes can not be promptly incorporated, however. Carefully implementing new projects enables Schiphol to keep track of what is happening, but it is most important to do this in a safe and secure environment. Setbacks can then be recognized and solved with consulting partners. In the meantime, motivation is gathered from the achieved successes, such as the international acclaim of a leading role in implementation of circular economy principles during the Airports Going Green Congress of 2016.

CLIMATE ACTION To reduce the negative results of Schiphol’s operation on the environment, Schiphol Group set out to negotiate a new 100% sustainable energy contract in 2016. One of the main criteria for the contact is that new sustainable energy generation facilities will be built. The airport commits to lowering its carbon footprint and invests in sustainable infrastructure.

Schiphol Group sees their airports as an LEONARDO TIMES N°4 2017

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SCHIPHOL GROUP

Additionally, the airport wants to improve the air quality in and around the airport, meaning NOx, CO2, and other greenhouse gas emissions need to be reduced. To achieve this, the Schiphol Group started a large electrification scheme for the airport’s vehicle fleet. Additionally, forty new electrical charging stations have been installed in 2016, with more to follow over the coming years. On the passenger side, additional charging facilities are being installed in Schiphol’s public car parks to accommodate people arriving in electric vehicles. Furthermore, Schiphol wants to increase the number of fixed electrical ground power-equipped aircraft stands. Providing the aircraft with electric ground power results in the aircraft not having to use their auxiliary power units (APUs) when stationary, this significantly decreases the NOx and CO2 emissions of the aircraft at the aircraft stand.

PARTNERSHIPS FOR THE GOALS With the Airports Sustainability Declaration, multiple airports all around the globe have signed on to help each other make the world a better place. The key points of this declaration are Collaboration, Transparency, Innovation, and Engagement. Each year the Airports Going Green Conference will enable 12

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SCHIPHOL GROUP

Schiphol also aims to use this energy more efficiently and thereby decrease the overall energy consumption of its operation. To reach this goal, the airport pays special attention to energy usage specifications when placing or replacing installations. For example, LED-lighting is being used where possible, air-conditioning is replaced with more energy-efficient units and energy-efficient pumps and electrical motors are being incorporated in the baggage system.

these airports to keep the declaration intact. Together with most of Schiphol Group’s European partners, the Single European Sky initiative has been set up. The initiative has not only been created to increase capacity and efficient utilization of the sky, but also ground processes, aircraft handling, and airport use are to be modernized. This should enable all air traffic to use shorter flight routes, thereby lowering fuel consumption leading to a CO2 emission reduction. All in all, the Royal Schiphol Group is working towards becoming a more sustainable airport operation. There is still a lot to be achieved before the airport is fully “green”, but if Schiphol Group continues their current efforts, soon they will fulfill these six Sustainable Development Goals.

References http://www.annualreportschiphol.com/ https://www.schiphol.nl/ https://sustainabledevelopment.un.org/ http://www.sustainability-reports.com/company/schiphol-group/ The Aviation Department The Aviation Department of the Society of Aerospace Engineering Students VSV ‘Leonardo da Vinci’ fulfills the needs of aviation enthusiasts by organising activities like lectures and excursions in the Netherlands and abroad.


WIKIMEDIA

TIME FLIES

AMELIA

A brief history: Part I

Katharina Ertman, Editor Leonardo Times

LEONARDO TIMES N°4 2017

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NEWSEUMED

O

n July 2, 1937, Amelia Earhart, on an attempt to circumnavigate the globe, disappeared mysteriously into the expanse of the Pacific Ocean. Somewhere en route from Lae, Papua New Guinea, and Howland Island, she and her navigator, Fred Noonan, lost communications with those on the ground. The circumstances surrounding her disappearance have been the subject of years of speculation and fruitless efforts to determine Earhart and Noonan’s fate. Numerous theories, from sensational rumors claiming Earhart was a spy for the US government, or even she was working for the Japanese government, to more technical speculation, such as the crash-and-sink theory or that she landed on a different island, continue to fuel curiosity. However, the story of Amelia Earhart did not begin with her disappearance. Quite on the contrary, she was a remarkable woman who made a name for herself in the male-dominated world of aviation. Like many aviation pioneers of her time, Amelia was driven by a spirit of adventure. This wonderment started off from an early age, where she was encouraged to explore her surroundings and reject the traditional confines of femininity, at the encouragement of her mother. Born on July 24, 1897 in a small town in Kansas, Earhart grew up at a time where women had clearly defined roles in society. Girls at the time were expected to wear dresses and prepare for a life of domesticity, while Amelia and her sister, Grace, caught bugs and explored their 14

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neighborhood together, all while wearing bloomers. She even “took flight” with the help of an uncle, creating a rollercoaster-like contraption on the roof of her parent’s shed. After her “flight” down the roof, she reportedly exclaimed, "Oh, Pidge, it's just like flying!" These experiences and opportunities instilled in Amelia a sense of adventure and a willingness to break out of societal norms. However, she was not immediately drawn to aviation. Her first airplane sighting came at age 10 at the Iowa State Fair, but she ultimately was not impressed with the experience, saying the plane was “a thing of rusty wire and wood and not at all interesting”. Though she did not pursue aviation as a career until much later, Amelia developed a love of science and math, excelling at these subjects in school, despite pressure to conform. She even kept a scrapbook detailing the accomplishments of women in male-dominated fields, such as mechanical engineering, law, management, and advertising. Her academic career took a short detour in 1918, when she spent a brief time volunteering as a nurse at a hospital in Toronto, caring for patients during the Spanish flu pandemic. This experience, though short in time, maintained a connection to the aviation world. Many of her patients were French and British pilots, and soon after beginning, she and her sister spent time at the nearby airfield watching the pilots in the Royal Flying Corps train.

She soon returned to the United States, with the intention to enroll at Columbia University and pursue a career in medicine. Which did not last long. She soon left Columbia to be with her parents in California, and had she not, we may not know her as Amelia Earhart, pioneering aviator.

PASSION SPARKED In 1920, Amelia and her father visited an airfield in Long Beach, California. There, she met aviator Frank Hawks, who agreed to take her on a short flight. In that short ten-minute flight, she knew her calling. Realizing she needed a way to pay so she could pursue her dream, Amelia took a number of odd jobs, including working as a stenographer for a telephone company. Finally, in 1921, she began lessons with Anita “Neta” Snook, another pioneering aviator, who agreed to take her on. Within six short months, she saved up enough to purchase her first plane, a bright yellow Kinner Airster, which she affectionately nicknamed “The Canary”. It wasn’t long after that, that Amelia set her first record and began making a name for herself in the aviation world. By 1922, she made a solo flight to 14,000ft, a first for a female pilot. Not long after, she became the 16th woman to obtain a pilot’s license. Despite showing promise in the field, she once again had to give up her ambitions, temporarily. During the 1918 Spanish flu pandemic, Amelia herself was a victim of the infection.


NY POST

Because of this, she suffered from chronic pain in her sinuses, which continued to plague her. Troubles in her family also forced her to reconsider her choices. After re-enrolling at Columbia in the fall of 1924 to continue her medical studies, Amelia later left to join her mother and sister in Boston. Wanting to study there, at MIT, she once again found herself unable to continue. Money was tight for the family, and the tuition costs were too steep to allow Amelia to study. Instead, she took a job as a social worker at Denison House in Boston. Though she was not actively flying, she fiercely held onto her love of aviation. During her time in Boston, she actively worked to promote aviation, specifically advocating for women in aviation. Her passion drove her to form an organization for female fliers. This dedication and work kept her name circulating in the aviation world, though she wasn’t actively flying. And that work eventually paid off.

ACROSS THE ATLANTIC

THE RISE OF AMELIA

In 1927, Charles Lindbergh made the world’s first nonstop solo transatlantic flight. With this, a frenzy began. Pilots began to line up, looking to complete the journey themselves, and push the boundaries of air travel even further. One such person was Amy Guest, a multi-billionaire, who wanted to be the first woman to be flown across the Atlantic. However, her hopes were dashed when she and her family determined the journey to be too perilous for her to undergo. Luckily for our heroine, Amelia, Amy Guest was determined to find another woman to take her place. But that flight nearly never happened, because of Amelia’s stubbornness.

Amelia’s transatlantic flight gave a public face to women in aviation. Her celebrity status was cemented, with the media nicknaming her “Lady Lindy”, a reference to her likeness to Charles Lindbergh, and “Queen of the Air”. Endorsements, product lines, lectures, all in the name of a female face of aviation. This dizzying swirl of attention did not sway Amelia. Instead of resting on her laurels, she continued to push her boundaries, and continued to help promote women in aviation. The endorsements were simply a means to keep funding her passions, even taking a position with Cosmopolitan magazine in an effort to bring aviation to the attention of a wider audience, particularly highlighting the accomplishments of women in the field. Her involvement also stemmed to an association of female aviators, called The Ninety Nines, named for the 99 women who expressed interest in forming a group for purpose of advancing and supporting the careers of women in aviation.

One day while working at Denison House, a call came for her. She initially dismissed the call, saying she was too busy. However, on the other end of the line was Captain Hilton Railey, asking if she wanted to be the first woman to cross the Atlantic by plane. Initially skeptical of this offer, she later came to realize Railey was genuine and this would be the opportunity of a lifetime. Though she would not be flying the plane herself, it was this flight that restarted Amelia’s aviation career, a path that she did not stray from for the remainder of her life. On June 17, 1928, Amelia Earhart, along with pilot Wilmer Stultz and copilot Louis Gordon, set off from Trepassey Harbor, Newfoundland in a Fokker F.VIIb, nicknamed “Friendship”. About 21 hours later, the crew landed in Pwll, South Wales to a rousing welcome. Though she was, in her own words, “just baggage, like a sack of potatoes,” she was inspired by her experience. She wanted more. She would not fade into oblivion. And fade into oblivion she did not...

When not touring and posing for endorsement photos, Amelia was hard at work solidifying her legacy as an aviator in her own right. She already held the title of “First Woman to Cross the Atlantic”, with the footnote of being a passenger. She wanted a title of her own. In the months following her Atlantic travels, Amelia gained her first title: First Woman to Solo Across the North American Continent and Back. She also took up competitive flying, participating in a number of air derby events. She continued to set records, including an altitude record for an autogyro, reaching 18,415ft, a record that was left unchallenged for years. Still not satisfied, Amelia came back around to the idea of repeating her transatlantic flight. But this time, she would be in control.

While continuing to hone her flying skills, Amelia and her husband, publisher and publicist George Putnam, began to lay the groundwork for her flight. Putnam and Earhart had met previously when working together to coordinate her first transatlantic flight. Over the years, they had developed a close friendship, which wound up in matrimony on February 7, 1931. Their marriage, like Amelia’s upbringing, was extraordinarily unconventional at the time. Amelia was accustomed to her independence, and would certainly not have been satisfied to be forced into the box of 1930s housewife-dom. She believed that women were equal partners, both emotionally and financially, in a marriage, even rejecting the term “marriage”, favoring the word “partnership.” This sentiment extended to the public sphere. The New York Times, in articles written about Amelia, would insist on referring to her as “Mrs. Putnam”, per the style guide for the time. When confronted with this, Amelia simply laughed off the matter. The roles even reversed, with Putnam eventually gaining the unofficial title of “Mr. Earhart”, due to his wife’s immense popularity and international acclaim. Luckily, Putnam was a great supporter of Amelia, and happily shared her views on marriage. Such bending of gender roles was practically unheard of at the time. Having solidified support on the ground, Amelia pushed to greater heights. With the intent to fly from Harbor Grace, Newfoundland, to Paris, Amelia set out on May 20, 1932, exactly five years after Charles Lindbergh made his transatlantic journey. She set off, but it was not smooth sailing for the trip. Poor weather conditions, strong winds, and mechanical issues plagued her for nearly the entire duration of the flight. She was forced to land in Londonderry, IreLEONARDO TIMES N°4 2017

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Equator as possible. Planning for the flight began in 1936, first with the purchase of a plane, the Lockheed Electra 10E, dubbed the “flying laboratory”. The plane provided the means, but Amelia could not complete the journey alone. She initially had two navigators, Captain Harry Manning and Fred Noonan. However, for the official attempt, only Noonan accompanied Amelia.

AROUND THE WORLD The first attempt of this historic flight was to be flown from west to east. The first leg was from Oakland, California to Honolulu, Hawaii, but the attempt was cut short. Unlike Amelia’s first Pacific crossing, this time was not so smooth sailing. Mechanical problems forced the crew to land at the US Naval Base in Pearl Harbor. Unfortunately, the aircraft was so badly damaged that the attempt had to be scrapped and the plane was sent back to the mainland US for repairs. Plans for the circumnavigational flight were reassessed and it was then decided that the set of flights would instead be flown east to west, starting in Miami, Florida. On 1 June 1937, Amelia Earhart boarded the Lockheed Electra, ready to take on the world.

land, in a pasture which, “scared most of the cows in the neighborhood.” Though she did not make it to Paris as she had planned, she had successfully crossed the Atlantic in record time, 13 hours and 30 minutes, and news spread fast. The second person and first woman to fly solo across the Atlantic. She was honored for her accomplishment, and was awarded the Distinguished Flying Cross by the US Congress, a first for a woman. She even gained a following on the other side of the Atlantic, touring the European continent, meeting with various heads of state, from the Prince of Wales, to Belgian King and Queen, and even the Pope. She was rapidly becoming an international celebrity, an incredibly accomplished woman in a boy’s club. With this, Amelia knew she was unstoppable. Back stateside, she used her status to advocate for more women in the field, and continued to smash records into oblivion. The same year she crossed the Atlantic solo, she made the fastest non-stop transcontinental flight as a female pilot, traveling from Los Angeles, California to Newark, New Jersey in 19 hours and 5 minutes. While that might seem like a long time to those of us more accustomed to the (dis) comforts of jet travel, this was an incredible feat for the early 1930s, when airplane travel was still in its infancy, and nothing was ever certain. 16

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ACROSS THE PACIFIC Still not content with holding an Atlantic crossing title, Amelia looked west. By 1935, dozens of pilots had attempted the perilous journey across the Pacific Ocean to Hawaii. Plagued with mechanical troubles and poor weather, it had not yet been successfully attempted. On January 11, 1935, Amelia took off from Honolulu, Hawaii for Oakland, California. Her flight was unusual, but not in the way one would expect. The mechanical problems that plagued her Atlantic flight were replaced by calm, functioning instruments. It was about as smooth sailing as anyone could have asked for, even going so far as to have time to enjoy a listening to the Metropolitan Opera broadcast from New York and thermos of hot chocolate, stating, “Indeed that was the most interesting cup of chocolate I have ever had, sitting up eight thousand feet over the middle of the Pacific Ocean quite alone.” And so, the story repeats: Amelia accomplishes an incredible feat, receives acclaim, and continues to push the boundaries of human flight. Rinse and repeat. Amelia’s ambition led her to aim higher and seek more. After her successful Pacific flight, Amelia set her sights on the ultimate prize: circumnavigate the globe. A number of pilots had already completed such flights, but Amelia wanted to attempt the longest route, by sticking as close to the

Along with Fred Noonan as her sole navigator, their flights took them to many locales, from Venezuela and Brazil to Senegal and Mali, Pakistan and India, Thailand, and Indonesia. Very little is known about these flights, unfortunately, nor was there much publicity in many of the cities where she landed. She gained local attention, but any written documentation is scarce, outside of airport notes indicating that she landed and took off for her next destination. Knowing that Amelia and Noonan made it to Papua New Guinea in just over a month after departing the United States, one can only assume that their travels were mostly smooth sailing. The few notes that are available from her travels show Amelia insisting that she was completing her round-the-world journey simply for fun. Until fate had her way. On 2 July 1937, Amelia Earhart boarded her Lockheed Electra for the last time… References ameliaearhart.com collections.lib.purdue.edu nytimes.com history.com aviation.hawaii.gov tripline.net Glines, C.V. (July 1997). 'Lady Lindy': The Remarkable Life of Amelia Earhart. Aviation History Goldstein, Donald M.; Dillon, Katherine V. (1997). Amelia: The Centennial Biography of an Aviation Pioneer.


AERODYNAMICS

DRAG ANALYSIS

An accuracy assessment

Yash Hemant Shah, M.Sc. Aerospace Engineering, TU Delft

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Quantitative flow visualization using large-scale 4D Particle Tracking Velocimetry (PTV) has been conducted in the wake of a full-scale time-trialing cyclist’s 3D printed model. Mean velocity fields obtained show the presence of drag contributing regions in the form of strong velocity deficits, vortex structures, and low pressure regions.

ume in the wake and capture time-resolved images (short movies) of the tracer particles. Apart from the PTV instruments, the drag forces were also measured using a wind tunnel balance in order to aid comparisons. The complete setup is shown in Figure 1.

RESULTS The raw images were processed with the 4D-PTV algorithm and post-processed to obtain statistically converged velocity fields in the wake of the cyclist. Figure 2 shows the converged results. These velocity fields were obtained for the first time using the large-scale 4D-PTV technique. They match the previous findings by other researchers who have used other techniques such as pressure probes and Particle Image Velocimetry (PIV). However, owing to a highly accurate particle positioning, 4D-PTV offers a much higher accuracy in the flow-field results [2]. Further, these results have a higher resolution as opposed to some other techniques used in the past.

Figure 1 - Experimental Setup

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he strong connection between aerodynamics and cycling is not new. In fact, elite cyclists have been known to take immense efforts and care to minimize their aerodynamic drag. Obree’s position of 1993 and 1995 are the best examples of this. Modern day cyclists try to shave off every count of drag by means of day-long wind tunnel tests. Iterations over several positions, bike accessories and helmets are performed to obtain the “optimized” configuration. However, is this really the optimum? Can’t we do something more with aerodynamics to provide cyclists with the competitive edge they seek? This is the focus of an ongoing research project at the Aerodynamics Laboratory of TU Delft, for which this thesis was a stepping-stone. The answer to the above question lies in understanding the flow around the cyclist. But how do we understand the flow if we cannot see it?

METHODOLOGY Flow visualization is an experimental technique, which allows us to visualize the flow around an object by introducing tracer particles in the medium (think about the smoke from the exhaust of your car). Further, we can deduce quantitative information, such as velocity fields, from these visualizations by taking snapshots in quick succession and analyzing the displacements of the individ18

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ual tracers. This is known as Particle Tracking Velocimetry (PTV). Modern algorithms for this analysis make use of the temporal information (fourth dimension) of these particle locations. They are able to predict and narrow their search for the subsequent time instances, thus making this search process not just efficient but also accurate. One such method called Shake-the-Box (4D-PTV) has been developed at the German Aerospace Center (DLR) and was used in this thesis project. In order to perform 4D-PTV experiments in the wake of a cyclist, a 3D printed full-scale model of the Dutch cyclist Tom Dumoulin (Team Sunweb) was used (see cover image). The model features the cyclist in the time-trial position. As a part of the collaboration the team provided us with Tom Dumoulin’s time-trial bike, which was used by him at the Rio 2016 Olympics. The bike and the mannequin were mounted on a test bench set-up in the Open Jet Facility at the High Speed Laboratory. 300 Helium Filled Soap Bubbles (HFSBs) were the tracer particles used in these experiments, since they scatter tremendous amount of light and are suitable for large-scale experiments [1]. These HFSBs were injected at a sufficient distance upstream of the model by means of tiny nozzles enclosed in four aerodynamic rakes. A high-powered laser and three high-speed cameras were set-up to illuminate a thin vol-

Streamwise velocity distribution (Figure 2a) shows the presence of a large wake, which has lower velocities than the outer region moving at the freestream velocity of 14m/s (roughly 50km/h). The asymmetric shape of the wake is due to the asymmetric leg position of the cyclist as shown by the black outline. It is interesting to note the presence of two large regions of streamwise velocity deficit in the central part of the wake, one directly behind the rear wheel axis and another behind the saddle. These deficits contribute heavily to the total drag. Vorticity is a measure of the rotation in the flow. Vortices are a common phenomenon in the case of bluff-body flows such as the spheres, cylinders or the cyclist as in this case. Here, the vorticity plot (Figure 2b) shows that the slow moving wake is full of vortex structures, especially behind the legs. These structures and their interaction with the surrounding air motion are what makes this flow so complex. Despite this, there is a pattern in which these vortices are formed and shed. Firstly, they occur in a pair of counter-rotating vortices and depend on the orientation of the section of the leg with respect to the incoming velocity. The signs of the vortices switch if the orientation switches. Following this observation it is possible to determine the points of origination (whether inner or outer) of these vortices just by knowing their signs and the orientation of the corresponding leg section. It is clear that some of these vortices are fairly large while some are small but strong. These vortex structures are formed due to low-pressure pockets and are strong contributors to the drag since they convert the streamwise momentum into the


Figure 2 - Results showing flow topology in the wake of the rider. (a) streamwise velocity (b) streamwise vorticity (c) pressure coefficient. in-plane momentum causing large streamwise deficits. Therefore, the vortices, which may be small in size, may have the potential to induce in-plane velocities in a considerable region around it depending on their strength. The pressure distribution shown in Figure 2c was obtained by reconstructing the pressure from the velocity fields [3]. The negative values of the pressure coefficient correspond to a lower than ambient pressure and they occur in places of the vortex cores that were observed in Figure 2b. Furthermore, there is a fairly large region of low pressure behind the lower back of the cyclist, which represents the flow separation owing to high curvatures in the geometry. Although it was later found that the contribution from the pressure term at the location of the measurement is almost negligible, the pressure plot reveals some interesting and unique information about the flow such as flow separation. The drag force, composed of momentum drag (integration of the momentum deficits observed between the incoming and outgoing momentum), Reynolds stresses and the pressure term was obtained from the flowfield measurements. The resulting drag force was within 2% of the drag measured by the drag balance in most cases. It was within 5% in the worst case. Having a fair understanding about the flowfield in the wake of the cyclist and the drag distribution throughout the body it is now possible to utilize this information into design considerations. Few areas of investigation are identified here. The posture of the rider

can be adjusted such that the flow separation over the lower back region is minimized. Investigation on different fabrics for the suits that may be employed to delay the separation resulting in a smaller wake may be conducted. The feet vortices may be diffused by streamlining the shoes. Drive-train vortices may be diffused or eliminated by designing a better fairing around it. Furthermore, numerous opportunities are present to reduce the strength of the vortices by flow control.

CONCLUSIONS By conducting a wake measurement on a full scale static cyclist model it was shown for the first time that the 4D-PTV technique yields accurate flow-field results and is ideally suited for large-scale measurements. Analysis of the high-resolution flow topology obtained by this method revealed interesting results about the drag distribution on the cyclist’s body. Maximum drag was contributed by the slower moving wake formed immediately behind the seat and the rear wheel axis. Furthermore, significant drag contribution was obtained from the regions of high vorticity present in wake of the lower body. The contribution of the drag from the portion below the knees was almost 50% of the total drag. Almost a third of the total drag came from the regions of streamwise vortices. It was also shown that the computation of the total drag from the flow-field measurements was within 5% of that measured with an external balance. More importantly, the differences in the drag force due to changes in the flow parameters, such as the flow speed, were accurately captured. This is an important result as it provides enough confi-

dence to utilize this technique for the industrially relevant large-scale applications. Future work in this field may focus on the application of this technique to a dynamic cycling model to study the effect of the leg motion and the moving wheels on the total drag. Current work at the Aerodynamics Lab is aimed towards conducting PIV/PTV measurements on the site of the cycling tracks by means of a Ring of Fire technique [4]. Interested students may get in touch with Dr. Andrea Sciacchitano (A.Sciacchitano@tudelft.nl). For further details about this project please send an email to yash.hshah.mec11@iitbhu. ac.in References [1] Fulvio Scarano, Sina Ghaemi, Giuseppe Carlo Alp Caridi, Johannes Bosbach, Uwe Dierksheide, and Andrea Sciacchitano. On the use of helium-filled soap bubbles for large-scale tomographic piv in wind tunnel experiments. Experiments in Fluids, 56(2):42, 2015. [2] Daniel Schanz, Sebastian Gesemann, and Andreas Schröder. Shake-the-box: Lagrangian particle tracking at high particle image densities. Experiments in fluids, 57 (5):1–27, 2016. [3] BW Van Oudheusden. PIV-based pressure measurement. Measurement Science and Technology, 24(3):032001, 2013. [4] Andrea Sciacchitano, Giuseppe Carlo Alp Caridi, and Fulvio Scarano. A quantitative flow visualization technique for on-site sport aerodynamics optimization. Procedia Engineering, 112:412–417, 2015. LEONARDO TIMES N°4 2017

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EUROPA’S PLUMES Collecting samples from Europa’s plume SPACE ENGINEERING

Mònica Aragay Verdeny, MSc Graduate Aerospace Engineering, TU Delft

The discovery of water vapor plumes on Europa, a moon of Jupiter, allows us to develop new strategies for the study of its subsurface ocean, where life could be found. By flying through the plume, the spacecraft could study the particles that are being expelled from this ocean.

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he plume of Europa was first discovered in 2012. After some failed observations, it was again observed in 2016. This plume could be expelling water vapor particles from the subsurface ocean of Europa (Roth, 2014). This ocean is one of the environments with the most potential for extraterrestrial life. The idea of this project is to take advantage of the plume in order to gain more information from the ocean. A lander mission to collect particles from the subsurface ocean is then no longer needed. Having a spacecraft flying through the plume and collecting its particles consid20

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erably eases the design of the mission and reduces the cost. In order to fly through the plume, two strategies exist: the orbiter and the pseudo-orbiter. The first one consists of a spacecraft orbiting Europa, whereas the pseudo-orbiter is a spacecraft orbiting Jupiter and doing flybys of Europa. The pseudo-orbiter strategy was chosen because it reduces the absorbed radiation dose. The objective of the Master Thesis is to find potential pseudo-orbiter trajectories, which

can lead to a maximum number of collected particles. First, the trajectory of the particles that are being expelled from the plume has been simulated to obtain a 3D density profile of the plume. After this, the design of the pseudo-orbiter strategy can be carried out while maximizing the number of collected particles.

PLUME PARTICLE MODEL Despite the plume information that was gathered with the observations, a great number of uncertainties still need to be clarified: the most important one is that scientists have not yet concluded if this phenomenon can be predicted. Some of them state that it could be a sporadic event, difficult to predict. Other uncertainties, such as its location, its physical and chemical


not enough for computing the maneuver, generating the commands, sending the commands and performing the maneuver. For this reason, it has been assumed that the plume is active when the spacecraft flies through it.

SPACECRAFT TRAJECTORY DESIGN Three requirements have been considered when designing the trajectory of the pseudo-orbiter: the number of collected particles should be maximized, the absorbed radiation dose should be a minimum (maximum value of 250krad), and the time between two consecutive flybys should be at least ten days. The method that has been used for the design of the trajectory is the Graphical Method for Same-body Transfers (Strange, 2008). Since the spacecraft has to keep meeting the Moon after each flyby, the orbit around Jupiter can be seen as a transfer orbit with the same celestial body (the Moon). This method is based on the patched conics approximation and makes use of the resonance concept and flyby theory.

properties, etc. have driven the consideration of assumptions when developing the plume particle model. It has been assumed that the plume is exactly located on the South Pole, the flow is non-collisional, there is no interaction with charged particles or photons, and all the particles are water vapor molecules. Assuming that the flow is non-collisional imposed some restrictions on the physical properties. This fact led to the simulation of a less powerful plume than the one observed. However, scientists have stated that less powerful plumes could also exist. The force model that has been implemented takes into account the gravity of Europa, the perturbations due to its oblateness, third-body perturbations due to the gravity

of Jupiter, and solar radiation pressure perturbations. Figure 1 shows the density profile of the plume when it has reached a stable state. Apart from the density profile, another important outcome was obtained from the simulation: the time between the last ejection of the plume and the disappearance of all the particles. This time period turned out to be just six hours. Since the existence of the plume is unpredictable, it could be better to have a spacecraft orbiting Jupiter and when the plume is observed, change its trajectory in order to flyby through the plume and collect some particles. However, it can only be assumed that from the moment of the observation, particles will remain in space for six hours. This amount of time is

The idea of the method is to select potential trajectories by looking at the ground-track of the flyby and by knowing the regions of interest on the surface of the Moon. If the orbit of the spacecraft is in resonance with the orbit of the moon, they meet again after a certain amount of time. In order to have a resonant orbit, the time of flight of the transfer has to be an integer multiple of the period of the moon. Therefore, the period of the orbit of the spacecraft has to be such that the time of flight fulfils this condition. The resonance is identified by the ratio R*m/n, where m is the number of revolutions of the moon and n, the number of revolutions of the spacecraft (e.g. R32 means that the moon is doing three revolutions and at the same time the spacecraft is doing two revolutions. The period of the orbit of the spacecraft is 3/2 times the period of the orbit of the Moon). The flyby theory states that the absolute velocity of the spacecraft (the velocity of the spacecraft in the orbit around Jupiter) has to be equal to the velocity of the Moon plus LEONARDO TIMES N°4 2017

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Figure 1 - Density distribution of the plume of Europa (X-axis towards Jupiter, Z-axis towards the North Pole of Europa, Y-axis completing the right-hand system).

Figure 2 - Representation of the V-Infinity Globe (left image) and the triangle of velocities (right image). the velocity of the spacecraft with respect to the Moon (relative velocity) at the beginning of the flyby:

The relative velocity is also known as infinite velocity, v∞. Considering that the point of the encounter is equal to the radius of the orbit of the Moon and by knowing the absolute velocity of the spacecraft at the point of the encounter, it is possible to know the semi-major axis of the orbit around Jupiter (using the vis-viva equation) and therefore the period of the orbit. Thus, a specific infinite velocity, corresponds to a specific absolute velocity and therefore, to a specific period (and resonant orbit).

vector. The azimuth gives the orientation of the triangle of velocities in the space. The elevation lays in the plane of the triangle of velocities and gives the orientation of the infinite velocity vector with respect to the velocity of the Moon vector. Orbits with the same elevation will have the same magnitude of absolute velocity and therefore, the same period. For this reason, each elevation is associated to a specific resonant orbit for a given infinity velocity magnitude. By looking at the sphere, if the elevation is kept and the azimuth varies, the infinity velocity vector draws a circle around the Z-axis. Each point of this circle represents an orbit with the same resonance. Therefore, resonant orbits are seen as circles on the V-Infinity sphere.

From the flyby theory, it is also known that the magnitude of the infinite velocity is the same for the incoming and outgoing velocities of the hyperbola; however, the direction changes. All the possible directions of the infinite velocity vector can be represented in a sphere of radius equal to the magnitude of the vector. This sphere is known as the V-Infinity Globe (see Figure 2). The angles elevation (α) and azimuth (κ) serve to identify the direction of a specific infinite velocity

Since Europa is tidally locked (the X-axis of the reference frame shown in Figure 2 is always pointing towards Jupiter) it is possible to transform the elevation and azimuth to latitude and longitude. Therefore, the latitude-longitude 2D plot of Europa (Figure 3) represents both the projection of the surface of Europa and the projection of the V-Infinity globe. A point of this plot corresponds to a specific latitude-longitude feature of Europa, but at the same time corre-

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sponds to a specific elevation and azimuth of an infinity velocity vector, and therefore to a specific orbit of the spacecraft around Jupiter. The circles that are shown in the plot correspond to orbits with the same elevation, and therefore to orbits with the same resonance. Each circle contains all the possible values of azimuth (from 0° to 360°). By knowing the position of the spacecraft at each point of the flyby, it is possible to draw the ground-track of the flyby. Figure 3 shows two different flyby ground-tracks. Each ground-track has three characteristic points: the red circle corresponds to the point of closest approach, and the black dot and the red dot correspond to the elevation and azimuth for the incoming and outgoing infinity velocities respectively. There are two techniques that are used to identify families of flybys: pumping and cranking. Pumping consists of changing the elevation when doing the flyby. This means that the incoming and outgoing infinite velocity vectors have the same azimuth but different elevation (the incoming infinite velocity dot lays on one circle of the plot and the outgoing infinite velocity dot on another circle). There is a change in the period of the orbit around Jupiter. Cranking consists of changing the azimuth without changing the elevation. In this case, the period of the incoming and outgoing orbit is the same (the incoming infinity velocity dot lays in the same circle as the outgoing infinity velocity dot). These two techniques are represented in the two ground-tracks of Figure 3. There is a wide range of possible values for the magnitude of the infinite velocity and for the resonances. The requirements have put some restrictions on these values and thus, a specific range for the infinite velocity and resonances have been selected. The consideration that the radiation dose should be minimum and that the minimum time be-


infinite velocity vectors has the same magnitude but opposite sign. The magnitude of this angle has been determined by imposing the altitude of the closest approach to 30km. It is important to notice that the closest approach occurs exactly at the South Pole. For the case of pumping (case 2), the condition to flyby over the South Pole is that the azimuth for the incoming and outgoing infinite velocities is equal to 90° or 270°. However, in this case the altitude of closest approach cannot be imposed and the latitude of the closest approach is not in the South Pole. Figure 3 - 2D projection of the surface of Europa and of the V-Infinity Globe. Each line corresponds to the ground-track of a different flyby. The color bar indicates the altitude ranges of different parts of the flyby.

Figure 4 - South Pole passage for the cranking and pumping strategies.

In order to tune the altitude of closest approach, two possibilities exist. The first one is by modifying the magnitude of the infinite velocity (case 3): it is possible to find the infinite velocity such that the closest approach is 30km. The other possibility is by adding cranking, and therefore changing both the elevation and the azimuth during the flyby (case 4). This latter case has one disadvantage: the flyby does not cross the South Pole (see Figure 5). However, compared to the strategy with just pumping, there are some trajectories that have the closest approach at lower altitudes and latitudes, and therefore, they could provide better results. For all these four cases, and for all the ranges of velocities and resonances, the results have been computed.

RESULTS AND CONCLUSIONS By knowing the position of the spacecraft at each point of the flyby and by knowing the number of water vapor particles at each point of the space, it has been possible to couple the two parts and obtain the results: 1. 2. 3. 4.

Figure 5 - Comparison between the pumping strategy (South Pole passage) and the pumping and cranking strategy (close South Pole passage). tween two flybys should be ten days have reduced the space search to five different values for the velocity: 3.0, 3.5, 4.0, 4.5 and 5.0km/s, and to five different resonances: R32, R52, R31, R41, R51. The trajectory selection is determined by looking at the ground-tracks of the flybys and taking into account the requirement that states that the number of collected particles should be maximum. In order to

maximize this number, it has been imposed that the spacecraft flies exactly through the location of the plume, i.e. the South Pole. For the cranking and pumping strategies, the conditions that fulfil this requirement have been studied. Figure 4 shows these trajectories. For the case of cranking (case 1), the condition to flyby over the South Pole is that the azimuth for the incoming and outgoing

Cranking: ~1014particles/cm2 Pumping: ~1011particles/cm2 Pumping tuning the velocity: ~1013particles/cm2 Pumping and cranking: ~1013particles/ cm2.

It is possible to conclude that cranking is the best strategy. However, if pumping is needed, either the velocity of the spacecraft should be tuned or cranking should be added in order to obtain better results (not crossing the South Pole can lead to better results if the altitude of closest approach is low enough). References [1] L. Roth, J. Saur, K. Retherford, D. Strobel, P. Feldman, M. McGrath, F. Nimmo, “Transient water vapor at Europa’s south pole”, Science, 343(January):171–174, 2014. [2] N. Strange, R. Russell, B. Buffington, “Mapping the V-infinity globe”, Advances in the Astronautical Sciences, 129 Part 1:423– 446, 2008.

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NASA

CASSINIHUYGENS SPACE ENGINEERING

A mission of firsts

Thijs Gritter, Editor Leonardo Times LEONARDO TIMES N°4 2017

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Figure 1 - Saturn Northern summer.

On the 15th of September, the Cassini spacecraft, which had been in orbit around Saturn for thirteen years, plunged into the upper layers of the planet, which ended up to be what is now known as a mission of firsts. What made this mission so special?

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ince the beginning of planetary exploration in 1962, with the Venus encounter of the Mariner 2 spacecraft, human-made satellites have visited all eight planets in the solar system. Many insights about these planets and their moons were gained, and many moons and asteroids have been discovered. However, none of the planetary orbiters have made so many big discoveries, and no spacecraft has spent such a long time at one of the gas giants, as Cassini did. Cassini would not be the first manmade object to encounter Saturn, but after the Pioneer 11 and the Voyager missions, it was clear that there was still a lot of mystery surrounding the Saturnian system. Therefore, it was decided to return to Saturn with a dedicated mission, combined with a probe, named after the Dutch astronomer Huygens. Huygens would land on Saturn's 26

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biggest mystery, the ‘Earthlike’ moon Titan.

THE BEGINNING OF A GREAT ADVENTURE The initial idea of a joint ESA/NASA mission to Saturn originated in 1982, when two European scientists suggested a paired Saturn Orbiter and Titan Probe mission, following an investigation into future cooperative missions by the European Science Foundation and the American National Academy. In 1983, it was recommended as a core NASA project and in 1988, after joint and individual studies were carried out by NASA and ESA, Cassini-Huygens was chosen by ESA as their next major mission, after which the program was passed by Congress the following year. However, execution of the mission wasn’t as evident as it seemed. It survived many budget cuts, protests and more than once,

it was even almost cancelled. Furthermore, when the idea was conceived, NASA and ESA were not on good terms. ESA believed they were not treated fairly by NASA during previous collaborations, like Ulysses. Therefore, a new collaboration was not met with enthusiasm. However, this was an opportunity not to be missed. In fact, the damaged relationship between NASA and ESA might have saved the mission from cancellation. If another collaboration would have been cancelled, the relation between ESA and NASA would probably have reached an all-time low. Especially in the 80’s, when the Soviet Union was cooperating more closely with ESA and the European Union, it was of great importance for the United States to improve relations with Europe and not further alienate them. Because of this, NASA convinced Congress to not cancel the project, by using the argument that cancelling the mission would not be received well by the Europeans. However, over the course of the design, the Cassini-Huygens team had to strip quite some novelties due to budget cuts and over-


NASA

Cassini Design Characteristics

General Orbiter Mass – 2150kg Huygens Mass – 350kg Launch Mass – 5712kg Height – 6.8m Diameter – 4m Power – 885W Total Cost – $3.9 billion Propulsion Rocket Engine - R-4d bipropellant Thrust – 490N Propellant Mass – 3312kg Total Spacecraft Delta-V – 2040m/s Power Source Plutonium-238 RTG Plutonium Mass – 32.7kg the atmosphere and the relationship between the ionosphere, magnetic field, and plasma environment. For the rings, it had to map the composition of the ring material, study the dynamic processes responsible for their structure and study the interactions between the rings, the magnetosphere, ionosphere, and atmosphere. At the icy moons, it had to determine their geologic histories and their bulk compositions. Furthermore, it had to investigate the interactions between the moons, the magnetosphere, and the ring system. In the magnetosphere, it had to investigate its configuration and dynamics and its interactions with the moons, solar wind, and Saturn itself. Finally, Cassini had the task to discover new moons, both outside and inside the Saturnian rings.

runs. One of these novelties was the use of a so-called ‘scan platform’, which is a moving platform on which all the instruments are placed. This would have made it possible to point the instruments without rotating the spacecraft. In the end, the spacecraft did not become the 24-hour science machine it was aimed to be, but it still amazed the world with beautiful images and groundbreaking discoveries.

CASSINI The design of the Cassini spacecraft, of which the main design characteristics can be found in Box 1, is based on a proposed general NASA architecture, called Mariner Mark II. This class of satellites was an American experiment to improve design efficiency by setting a baseline for a standardized design for missions beyond the orbit of Mars. This was done to go on a more affordable course, which was needed because of economic constraints. The Mariner Mark II Class was based on the Voyager and Galileo missions, and included new technologies that

were worked out in the years after the launch of Galileo in 1989. These new technologies included an improved telemetry system using X-band only, improved sensors, and more integrated electronic circuits. At the outer planets, solar panels are not feasible for power generation, as they do not deliver enough power to supply the spacecraft. Alternatively, they could be unpractically large. Therefore, the Mark II class used three radioisotope thermoelectric generators (RTGs) to generate power. These RTGs used the heat from the natural decay of plutonium-238 to generate all the power needed to operate the spacecraft and their instruments. Although the satellites in the Mark II class have the same baseline, they differ in terms of instrumentation, tailored to each mission’s specific objectives. For Cassini, these objectives could be divided over four main elements: Saturn, Rings, Icy Satellites, and Magnetosphere. While around Saturn, it had to investigate

To help fulfill all the objectives, Cassini had twelve instruments, divided across three pallets: the Optical Remote Sensing pallet, the Fields, Particles, and Waves pallet, and the Microwave Remote Sensing pallet. The instruments can be found in the Box 2. The instruments were spread over the satellite and over the years these instruments would take 453,048 images, discover 6 new moons, and collect 635 GB of scientific data. Initially, Cassini was teamed up with another mission, called CRAF, short for Comet Rendezvous and Asteroid Flyby. As the name suggests, this mission would travel to an asteroid, after which it would fly along to study the asteroid and take samples. Both spacecraft would be based on the Mariner Mark II baseline. However, due to required budget cuts, CRAF was cancelled in 1992 and all its supplied funds were transferred to Cassini to save that mission from cancellation. Years later, ESA would base its own comet rendezvous and sample retrieval mission Rosetta on CRAF’s design and even CRAF’s trajectory was used as a reference for Rosetta’s trajectory.

HUYGENS LEONARDO TIMES N°4 2017

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Cassini Instruments Optical Remote Sensing Composite Infrared Spectrometer (CIRS) Imaging Science Subsystem (ISS) Ultraviolet Imaging Spectrograph (UVIS) Visible and Infrared Mapping Spectrometer (VIMS) Fields, Particles and Waves Cassini Plasma Spectrometer (CAPS) Cosmos Dust Analyzer (CDA) Ion and Neutral Mass Spectrometer (INMS) Magnetometer (MAG) Magnetospheric Imaging Instrument (MIMI) Radio and Plasma Wave Science (RPWS) Microwave Remote Sensing Radar Radio Science Subsystem (RSS) When Voyager 1 passed Titan, scientists were baffled. The biggest Saturnian moon has a thick atmosphere, just like Earth, and Voyager’s instruments could not see through the thick haze. This sparked interest in what could be at the surface, and speculation ranged from a planetary ethane ocean, to mountain ranges, lakes, and rivers. Therefore, already in the initial plans, the Huygens atmospheric entry probe was combined with Cassini. It consisted of two parts: the Entry Assembly Module, carrying the equipment to control Huygens during its descent and the heat shield, and the Descent Module, containing the scientific instruments and the three parachutes that would slow down and control Huygens’ descent through the atmosphere. All electronics that were needed to track the probe and to relay communications and scientific data from the probe to the Earth were combined into the Probe Support Equipment, which remained attached to Cassini. The total mass of Huygens was 318kg. Furthermore, the probe itself had a diameter of 1.3m and its heat shield had a diameter of 2.7m. It had enough power to do scientific measurements at the surface for thirty minutes, as most of its power would be used during the descent to the surface. More information on its instruments is displayed in Box 3. If the landing would succeed, it would be the farthest distance any manmade object would ever have landed. But the purpose of Huygens was not only to break that record. Just like Cassini, it had several scientific objectives. It had to determine the composition of the Titan atmosphere, particularly the more complex organic molecules. Furthermore, it had to find clues for the formation and evolution of Titan and its atmosphere. It also had to investigate weather 28

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effects, like wind and temperature, and it had to investigate the influence of the seasons. Finally, it had to determine the physical state, topography, and composition of the Titan surface and its internal structure.

CONTROVERSY Even after the budget cuts and threats of cancellation, Cassini’s faith was not secured. This time, the RTGs were food for debate. It was feared that, should an error occur during launch, possible explosions would expose the environment to the plutonium used in the RTGs. This would be a very hazardous scenario and thus, on October 4, 1994, only a day after President Bill Clinton approved the mission, 800 people protested in front of the Cape Canaveral Air Force Station. In the same year, the Florida Coalition for Peace and Justice began their campaign against the launch of Cassini, which would put experts against each other. As the launch date approached, the arguments got more and more dramatic, from a threat to an area of Florida, to a catastrophe that would affect humans all over the world. It was up to NASA to try to convince the public that the chance of such a threat was minimal and that the consequences of a failure were negligible. Though this was not easy. Although NASA brought out fact-rich explanations of the mission and risk factors of its 24th launch using nuclear power, their estimates were deemed extremely conservative by some experts. However, the RTG designers implemented various countermeasures to ensure that the consequences of a possible explosion would not pose a health risk for the population. First, the plutonium isotope used in the RTGs was different from that used in nuclear reactors. The plutonium was oxidized and packaged in ceramic chunks, such that it would not shatter to form small particles on impact. Furthermore, the plutonium was encased in many layers of protection, including graphitic material called Fine Weave Pierced Fabric, which was one of the best available material for reentry applications, and the very hard metal iridium. In the end, this was not enough to convince all the opponents of the mission, but it was enough to keep permission to launch.

Cassini took calibration images of the Moon. When Cassini passed the asteroid belt in the first months of the year 2000, it took images of Asteroid 2685 Masursky and, for the first time, it used the Cosmic Dust Analyzer to analyze the region. In December of the same year, Cassini made its closest Jupiter approach at 9.7 million km, which is equivalent to 137 Jovian radii. During this flyby, together with the Galileo spacecraft, it produced the most detailed colored planetary portrait of Jupiter, which can be seen in Figure 1. During the flyby, which took six months, Cassini took about 26,000 images of Jupiter, its rings, and its moons. Furthermore, some new discoveries were made: near Jupiter's north pole, a swirling dark oval was found, comparable to the Great Red Spot, which is one of the most famous Jovian features. Although Cassini already passed the orbit of Jupiter, it would take another 4.5 years before Cassini would end up in an orbit around Saturn. This period was mainly used to test all the systems and some minor problems were solved. However, in 2003, these tests were intermitted by a test of Einstein's general theory of gravity. This test was performed by sending radio signals past the Sun and observing the frequency shift in radio waves from and to Cassini. This test supported the theory and improved the accuracy of the theoretical predictions from one in one thousand, to about twenty parts in a million.

JOURNEYING TO SATURN On 15 October 1997, the moment had finally there. After 9 years of designing, testing, and survival, Cassini-Huygens was finally launched. At 4:43 a.m. EDT, Cassini-Huygens lifted off from Cape Canaveral onboard a Titan IVB/Centaur rocket on a trajectory to Saturn, where it would arrive seven years later, in 2004. In order to save propellant, Cassini-Huygens performed several gravity assists on the way to its destination. It would perform two gravity assists at Venus, one at Earth, and a final one at Jupiter. Already during these flybys, Cassini took the first pictures and it performed its first measurements, in order to test all the systems. During the Earth flyby, which took place two years after the launch,

Enceladus


LANDING ON A FROZEN WORLD Cassini's main mission started with its Saturn orbit insertion on June 30, 2004 and was planned to last until June 2008. It was divided into six segments, each focusing on another aspect of the Saturnian system. In the first segment, the Huygens probe would separate from Cassini and land on the surface of Titan. Throughout the nominal mission, Cassini discovered new rings, new moons, and new Saturnian landmarks. Cassini would perform dozens of fly-bys, during 74 unique orbits around Saturn, using the gravity of Titan for shaping Cassini's path. Additionally, Cassini would perform close flybys of the moons Enceladus (4x), Phoebe, Hyperion, Dione, Rhea, and Iapetus. These moons were chosen as data from previous missions suggested that they could hold the keys to understanding the Saturnian system and possibly the origins of the Solar System.

However, researching Titan was the focus of the nominal Cassini mission. On December 23, 2004, the Huygens probe successfully detached from Cassini, and went on a trajectory to the surface of Titan. However, it would take a few weeks before the landing was completed. On January 14, 2005, Huygens entered the Titan atmosphere and landed on a plateau after a twoand-a-half-hour descent. After its landing, Huygens sent 700 pictures of its descent and landing site to Cassini, 350 of which were lost due to a software error. Some of the panoramas of Titan that were made during Huygens' descent can be seen in the timeline. During the descent, Huygens also performed measurements on Titan's atmosphere and as soon as Huygens landed, it used its instruments to analyze the landing region. The landing site was covered in pebbles of between five to fifteen centimeters across. These pebbles are thought to be made from water ice, coated with hydrocarbons. The pebbles were slightly rounded, which indicated a possible interaction with fluids. The surface was initially reported to be clay-like, but can probably be better described as 'sand' made of ice grains or snow that has been frozen on top. At the landing site, the temperature was 93.8K and the pressure was 1.5 times as high as that on the surface of the Earth. Due to the greater attenuation of blue light by Titan's atmosphere than that of red light, the color of the sky and the

scene on Titan appeared orange. Thirty minutes after Huygens' landing, Cassini rotated its antennas from Huygens to the Earth, as all the planned science activities had been carried out. However, very large radio telescopes at the Earth were not able to pick up signals that were sent by Huygens until two hours after the landing. This was longer than expected, but after almost two hours at the surface, Huygens' batteries died.

BUT WAIT, THERE’S MORE... Over the course of the nominal mission, not only did Huygens land on Titan, Cassini also investigated the surface of Titan during its numerous Titan flybys. After Huygens' images made already clear that there could be fluids at Titan's surface, Cassini's observations clearly showed lakes and seas of possibly ethane or methane scattered over the polar regions of Titan. An image showing some of these lakes is given in the timeline. Furthermore, in some of the valleys, rivers were flowing. As clouds were present above the lakes, it was suspected that the liquid hydrocarbons evaporate during summer and rain down during winter. This final phenomenon had not been proven, but possible mission extensions would be able to delve more deeply into the seasonal changes at Titan. After Cassini dropped Huygens off at Titan, it performed a flyby of the moon Iapetus, which was discovered in 1671. This was a very interesting flyby, as it was discovered NASA

In the final three months until orbit insertion, Cassini already discovered two new moons, of three and five kilometers in diameter. It also observed two storms merging into one larger storm on the southern hemisphere of the Saturnian atmosphere. This was only the second time that the merging of storms was observed on the planet. Also, Cassini performed its first flyby of a Saturnian moon, Phoebe. Finally, on June 30, 2004, Cassini became the first spacecraft to orbit Saturn, almost seven years after its launch. Cassini's prime mission was about to begin.

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2004 - June 30

Saturn Orbit Insertion

1982

NASA

Initial idea pops up

1988

Chosen to be ESA's next major mission

1989

Approval by Congress

1998 - April 25 First Venus Fly-by

1999 - June 24 Second Venus Fly-by

1999 - August 17

Earth-Moon Fly-by

1997 - October 15

ESA

Launch from Cape Canaveral

1999-2000

Through the Asteroid Belt

2000 - December 29 Exploring Jupiter

2004 - December 23 NASA

Huygens probe detaches

Huygens Instruments Huygens Atmospheric Structure Instrument (HASI) Doppler Wind Experiment (DWE) Descent Imager/Spectral Radiometer (DISR) Gas Chromatograph Mass Spectrometer (GCMS) Aerosol Collector and Pyrolyser (ACP) Surface-Science Package (SSP) that the moon has quite significant features. For instance, at the poles the surface is white as snow, while at the equator it is black as tar. Furthermore, it has an equatorial ridge, with peaks that rise more than twenty kilometers above the surrounding plains. Iapetus is shown in Figure 2. Cassini would visit Iapetus again in September 2007, to make even more pictures of this oddly colored moon. In 2005, another special moon was visited. Over the course of the year, Cassini per30

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formed three flybys of Enceladus, of which two were closer than 500km. During these flybys, something strange was detected. Cassini discovered a deflection in the local magnetic field, that normally hints at the presence of a thin, but significant, atmosphere. Furthermore, Cassini observed several water ice geysers erupting from the south pole of Enceladus. Such a phenomenon, which had only been found on Jupiter's moon Europa, rose suspicion that there might be liquid water under the icy crust. Due to this stunning discovery, Enceladus was made into one of the main science objectives of the Cassini mission. Over the years, Cassini would visit the moon multiple times, for instance in March 2008. That month, Cassini passed within 50km of the surface, through the plumes extending from the southern geysers. During this flyby, Cassini's mass-spectrometer detected water, carbon dioxide, and several hydrocarbon substances. Furthermore, the plumes contained organic materials, in much higher concentrations than expected. This was a great discovery, as these organic materials could result from

life under the ice.

MISSION EXTENSIONS, EQUINOX AND SOLSTICE As Saturn is so far from the Sun, a year at Saturn lasts much longer than on Earth. However, during the thirty Earth years that it takes for Saturn to orbit the Sun once, it goes through the same seasons and phases as the Earth does. It has summer and winter, autumn and spring. Likewise, it has an equinox, the moment at which the night lasts as long as the day, and a solstice, the moment that the sun is at its greatest distance from the celestial equator. As the Saturnian Equinox would take place in 2009, an extension of two years would be a great opportunity to investigate how the seasons affect the Saturnian system. Because of this and the promising results from the nominal Cassini mission, it was decided to extend Cassini's mission by at least two years. During this extension, Cassini performed 26 Titan flybys and seven Enceladus flybys to learn more about the characteristics and of


2005 - July 13

First hints at a subsurface ocean

2006 - July 21

NASA

Finding lakes on Titan

2010 - September 26 Solstice Mission begins

2015 - December 18 Final Enceladus Fly-by

2017 - May 24 Solstice

2017 - April 26

2008 - May 31

First dive through the gap, the grand Finale begins

Primary Mission completed

2008 - October 8

2017 - September 15

Closest approach to Enceladus

2004 - January 14

2009 - August 10 Equinox

NASA

Landing on Titan

NASA

NASA

The final plunge

Figure 2 - Iapetus

these two interesting moons. Furthermore, it discovered a new moon in Saturn's G ring. During the Titan flybys, it made a map of the surface of Titan, although not the whole surface was visible. During the Enceladus flybys, Cassini dove deeper into the plumes, its closest approach to the moon being at only 25km. During this close approach, Cassini was able to carry-out detailed observations of Enceladus' surface. In a feat of interplanetary sharpshooting, Cassini identified precisely where the icy jets erupt from the surface of Enceladus. This occurs at large, blue-colored fractures at the moon's south pole, called Tiger Stripes. These fractures were measured to be 300m deep, with V-shaped inner walls. During the two subsequent Enceladus flybys, in December 2008, evidence of geologic activity was found. High resolution images showed that the south polar region surface changes over time, including surprisingly Earth-like tectonics. Furthermore, in 2009, it was announced that ammonia was present in Enceladus' plumes. This was another maLEONARDO TIMES N°4 2017

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NASA

Figure 3 - Images of the Hexagon storms on Jupiter. jor discovery, as the presence of ammonia provides strong evidence of the existence of liquid water. However, not only Enceladus' plumes provided strong evidence for the presence of a subsurface ocean. In the outermost ring of Saturn, of which the material is mainly replenished by Enceladus' jets, salty ice was found, which could be another indicator of a subsurface ocean. During the second mission extension, the Solstice mission, even more research about Saturn's rings would be done. The main reason for this extension was the fact that Saturn's solstice would occur in April 2017. The spacecraft had enough power to keep it running for a long time, and there was still a lot of insight to gain in the Saturnian system. Therefore, it was decided that the Cassini mission would be extended for a final time until September 2017. With the end date being known, the mission planners were already discussing in which way they would end the mission. As an uncontrollable Cassini would be at risk of crashing on one of the moons of Saturn, which would bring human bacteria with it, it was decided that Cassini either would leave the Saturnian system, or that it would crash into Saturn itself. Furthermore, it was decided that during the Solstice mission, Cassini would follow several highly-inclined orbits, to get to know more about Saturn's poles. Additionally, this would be a good way to get a good view on Saturn's rings. Finally, in April 2017, just weeks before solstice, Cassini would perform 22 dives through the gap between Saturn and its rings, to find out how empty that gap really is. On April 26, 2017, Cassini made contact with Earth after its successful first-ever dive through the narrow gap. With this first dive, The Grand Finale had begun.

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During the Solstice mission, Cassini experienced the seasonal changes of Saturn. Earlier, it was discovered that there are enormous storms at the poles of Saturn, which have an eye with very steep walls, just as hurricanes on Earth. However, these storms have a hexagonal shape, which is unlike any other phenomenon in the solar system. Over the years between the Equinox and Solstice, these hexagons changed color. In Figure 3, the northern hexagon can be seen, at the left in 2013 and at the right in 2017. As winter took grip of Titan's southern hemisphere, a strong, whirling atmospheric vortex was observed in the upper atmosphere of the south pole, rich of gases that are otherwise quite rare in Titan's atmosphere. Furthermore, on the southern hemisphere, the effects of winter caused a temperature drop of forty degrees Celsius over a period of four years. On the northern hemisphere, however, the temperature remained stable during early spring. Over a period of three years, the temperature on this side of Titan only increased by six degrees.

THE GRAND FINALE To get into the right orbit, Cassini performed two final Titan flybys, the first in November 2016 and the final one on April 22, 2017. These flybys set Cassini on course for its final moments. During the Grand Finale, an entirely new region around Saturn was explored. The 22 dives through the gap between Saturn and its innermost ring showed that the region between the rings and Saturn is almost empty. This puzzled scientists, as they expected there would be far more particles and debris. However, this was beneficial for the mission, as Cassini's antenna would not have to be used to protect Cassini's vital systems from impacts. Due to this, Cassini did more research than expected.

During the 22 dives, Cassini came closer to Saturn than ever before, approaching the planet closer and closer. On September 15, 2017, Cassini sent its final goodbye to Earth and just after noon CET, it burned up in the Saturnian atmosphere, ending one of the greatest space missions of all time. In the almost twenty years from Cassini's launch in 1997, Cassini completed 294 Saturn orbits, it performed 162 targeted moon flybys, of which 127 Titan flybys and 23 Enceladus flybys. It has discovered two oceans, three seas and hundreds of small lakes. Furthermore, it completed 260 engine burns and since the start of the mission, 3,948 papers have been published. Additionally, it landed the first probe on a body in the outer solar system, being the farthest any manmade object has ever landed. The mission had been extended for multiple times, and all of Cassini's instruments were working until the last moment. Due to this, and the incredible Saturnian system, it amazed the world. However, the work for the science team is not over yet. Over the next years, many observations will be analyzed and a lot more Cassini science will be published so stay tuned! Many of the things that Cassini has accomplished were premieres, and it will be long before another space mission will match the mission of firsts, Cassini-Huygens. References NASA (1995), Final Environmental Impact Statement for the Cassini Mission, NASA, Washington DC. Saturn.jpl.nasa.gov Sci.esa.int www.nytimes.com


RETIREMENT PLANNING Making sense of the inevitable can improve defense capability LOCKHEED MARTIN

C&O

Jeff Newcamp, PhD Candidate Aerospace Engineering, TU Delft

If estimates are proven right, over 3,000 F-35 Joint Strike Fighter aircraft will rule the skies globally. This aircraft has been in development since the concept demonstration phase launched in 1997 and could fly for the next five decades. It might sound preposterous, but the time to plan for the retirement is now.

T

he twilight years for any military aircraft are filled with uncertainty, cost increases, and difficult decisions. A project launched by Air Transport & Operations in 2015 has been shining light on this problem. The project found ways to extract residual value from the end-of-life aircraft fleets through simple methods that can be implemented by fleet managers. The implications of this work range well beyond military air forces, with applicability to other military services and capital equipment.

gram in the history of the U.S. Department of Defense. The U.S. Air Force alone is estimated to purchase over 1,700 F-35A models at a staggering cost of $85 million per aircraft. Despite the cost-saving Autonomic Logistics Information System (ALIS) and an assortment of advanced design characteristics, the F-35 remains, at its core, a machine which will wear out with time and use. Like every aircraft designed before it, the F-35 is destined for an aircraft boneyard, in a dry, sunny, patch of desert...

The F-35 Joint Strike Fighter is considered to be the most expensive acquisition pro-

It is hard to think of the F-35 as an aging aircraft in 2017, but the truth is that this year

marks the F-35’s 20th anniversary from its very beginning. Throughout the military aircraft community, there is hardly any consensus on the definition of aging aircraft (SAB, 2011). Most use calendar age to define an aging aircraft, some use flight hours as an indicator, yet others profile cyclic loading to show age (NRC, 1997). While the definition of aircraft aging remains unclear, we know that an aircraft ages from the moment of their conception. An idea on paper looks very different in 2017, than it would in 1997. Keating and Dixon’s landmark study on aging aircraft illustrated that the rising costs of maintaining an aging aircraft combined with the loss in mission capability can force decision-makers to consider aircraft retirements (2003). Military aircraft failure rates follows a rather standard bathtub curve, with an early LEONARDO TIMES N°4 2017

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USAF

Figure 1 - The A-10 Thunderbolt II fleet averages 32 years old. This aging aircraft is nearing retirement but has a few years of warfighting capability left. infant mortality followed by a significant decrease in failures, and finally a rising period of failures towards the end of the system lifecycle. Fleet planners have taken advantage of this knowledge to predict when their fleets should be replaced. Just like a Volvo, an F-35 will exhibit wear-out symptoms. The rust spot on a Volvo might be ugly to look at, but any evidence of corrosion on an F-35 might lead to expensive repairs or can even lead to groundings. Aircraft have ways of giving hints about their age (Gebman, 2009). Their hundreds of thousands of interworking parts produce faults. Maintenance, repair, and overhaul activities reveal widespread fatigue damage and corrosion spots. New mission types and heavy usage usually uncover latent failure modes untested by any normal operations tempo. Using all the hints given by an individual aircraft, managers can start to build a picture on the health of their fleet. Informed managers can understand normal aging patterns, spot abnormal aging, and implement changes to their fleet practices.

FLIGHT HOURS TICKING AWAY Each aircraft has a certified service life measured in flight hours. For a military fighter aircraft, this number ranges from approximately 8,000 to 12,000 flight hours. Additionally, tear-down testing and analysis can increase the certified service life, as can expensive structural enhancements. Even those steps 34

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only gain an additional few thousand flight hours. And so, each flight hour is expensive and not to be wasted. Just like driving a Volvo over mountains and through streams can shorten the lifetime of that vehicle, so too can flying aggressive mission profiles for an aircraft. In an analysis of the U.S. Air Force’s A-10 Warthog II attack fleet, two mission types stood out among the other eight. Functional Check Flight (FCF) missions and Basic Fighter Maneuver (BFM) missions eclipsed the average structural loading on the A-10’s airframes by 600%. FCFs are flown after maintenance activities to validate the aircraft repairs. This mission type reaches all corners of the flight envelope, leading to high cyclic loading. For an attack aircraft, BFM missions are used to train for air-to-air combat, pushing the aircraft to the very edge of its performance capability. Since every flight hour can look different, fleet managers and lifecycle planners must be cognizant of an aircraft’s data to understand how each tail number is being utilized. A base that flies a higher percentage of FCF and BFM missions in comparison to another base may age its aircraft at a much faster rate and thus needs to think about retirement planning sooner. It’s interesting to note that the pilot training bases stood out during this project. Not only do the flight training syllabi require more damaging air-

craft events, like landings and low-level flying but also the new pilots contribute to aggressive aircraft handling and load exceedance. One particular U.S. Air Force transport aircraft training base found that its center wing was experiencing so much aging that the aircraft used for training are now rotated away when they reach a threshold. Deployments of aircraft to contingency operations have been traditionally thought of as heavy usage scenarios. However, the data showed that some of the U.S. Air Force aircraft being flown in the Middle East in the 2000s and 2010s experienced much less cyclic loading than when operated at their home bases.

OPTIMIZING THE FLEET Noting differences in usage for mission types and for base locations raised the question, “Can we take advantage of this knowledge?” Yes, assuming an air force is willing to be flexible with a fleet of aircraft, optimization has a trade space. Fleet managers generally wish to prolong the longevity of their fleet. When they have some aircraft at a base experiencing high utilization, these aircraft would reach retirement (by whatever measure) sooner than the aircraft at other bases. Using CPLEX and Matlab, entire U.S. Air Force fleets were modeled. These were then optimized using an objective function to maximize the operational


USAF USAF

Figure 2 - Davis-Monthan Air Force Base’s boneyard stores thousands of retired military aircraft – fighters, bombers, transports and more. exhibit high uncertainty. What was flown in 2017 during a time of relative world stability might be upended in 2018 by a crisis. Fleet managers have a lot to consider. Flight safety and providing combat capability rank much higher than end-of-life optimization. Also, implementing academic findings in an air force to test the efficacy of the ideas is a difficult proposition and is unlikely to gain traction unless there is a great need. There are great benefits to aging aircraft optimization but there are also tangible costs that must be taken into account.

Figure 3 - C-17 Globemaster II low-level flying is enormously taxing on the center wing components of the aircraft. life. Instead of having a fleet of aircraft with a wide range of flight hours on them, the project sought to use the fleet in a way to equalize flight hours on the aircraft. This project found an optimal way to rotate aircraft between bases each year. Being able to move an aircraft to different bases flying different mission types allowed for the spikes in cyclic loading to be averaged out over time, resulting in a fleet that could remain at full strength for longer duration. At the surface, this optimization problem seems straight-forward. Open the door of a Volvo S60 and you see different configurations. Similarly, take a closer look at a military aircraft and you will see a plethora of differences which preclude an individual aircraft from fulfilling some mission types or being located at some bases. Specialized

mission equipment, software loading, and modifications all contribute to the individual fingerprint of each aircraft. This optimization problem quickly became complex, especially when factoring in all the peculiarities of operating military equipment across a complex operational and logistics network. Nonetheless, this study found that a fleet could be prolonged without a single retirement for years past previously thought.

AT WHAT COST? Moving an aircraft 2,000km across a large nation or across the globe each year to equalize usage across a fleet seems reasonable, but consider moving 250 aircraft each year and the cost becomes substantial. Do this for a decade and you can effectively use the equivalent of one aircraft’s certified service life. Furthermore, optimization forecasts for military aircraft utilization

As F-35s are delivered to the program’s partner countries across the globe, they will be met with anticipation and excitement. The F-35 may fly past the 2060s, so retirement planning seems distant. There will be many people thinking about the training, operations, and tactical aspects of having a new aircraft. There must also be talented aeronautical engineers thinking of ways to use every bit of every hour. The F-35’s twilight years are coming. For more information on this project, please contact Jeff Newcamp, j.m.newcamp@ tudelft.nl. References [1] Gebman, J.R., “Challenges and Issues with the Further Aging of US Air Force Aircraft: Policy Options for Effective Life-Cycle Management of Resources,” Vol. 560. 2009: Rand Corporation. [2] Keating, E.G., Dixon, M., “Investigating Optimal Replacement of Aging Air Force Systems,” 2003, DTIC Document. [3] National Research Council, “Aging of U.S. Air Force Aircraft,” 1997, National Academy Press: Washington D.C. p. 119. [4] Scientific Advisory Board, “Sustaining Air Force Aging Aircraft Into the 21st Century,” 2011, Washington, D.C. LEONARDO TIMES N°4 2017

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BAINITE IN STEELS Studying phase transformation to design better steels ASM

Salil Sainis, MSc Aerospace Engineering, TU Delft

Solid-state transformation in steels [3], [5], [6].

Modern steel design uses the theories of solid-state phase transformations, which account for not only the observed microstructural features, but also act as a utility tool for designing new alloys. Bainite steels are similarly designed based on predictive quantitative models of the reaction kinetics.

T

he bainite transformation reaction yields the desirable gamma-phase austenite (γ), which is soft and formable, and ferrite (α), which is hard and brittle. The term ‘phase’ used here is defined as a thermodynamically stable physical entity at a given temperature having a defined crystal structure. Combination of these phases in microstructures, made possible by the transformation reaction, makes the material strong yet sufficiently formable, reducing the weight of structure with good strength as well as providing the ability to deform and absorb the impact of 36

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a crash. Use of bainite in steels has resulted in cars with improved fuel efficiency, low CO2 emissions, crash-worthiness, and rigidity [1,2]. To achieve the bainite microstructure, treatments are performed with select isothermal processing routes. The effect of a processing route on the microstructure formed can be studied through the time-temperature-transformation (TTT) diagram showing diverse microstructures that can be formed in steels. Seen in the figure, a slow cooling and elevated tem-

perature transformation gives rise to a pearlite microstructure which is formed by a diffusional growth mechanism with α and cementite (Fe3C) forming simultaneously. On the other hand, fast cooling and transforming at very low temperatures forms a needle shaped martensite (α‘) microstructure by a displacive mechanism. Because bainite transformation takes place at temperatures in-between pearlite and martensite, the mechanism of transformation is complex and it is still debated today decades after its discovery [3]. Since its discovery in the 1930’s by Davenport and Bain in their study on the decomposition products of austenite at inter-critical temperatures [4], a wealth of techniques have been applied to increase


quantitative models has been controversial with divided opinions on whether the transformation is diffusion controlled, displacive and diffusionless. The displacive school of thought assumes that bainite forms by a mechanism like that seen in martensite transformation. This is illustriously explained as a ‘military’ type transformation where crystal structure change involves only slight displacements in the range of inter-atomic distances. Neighbouring atoms of parent phases hence remain neighbours even in the product phase. The growth of bainite ‘sheaf’ is said to take place through the formation of sub-units which grow displacively until their growth is stifled by the dislocation debris created due to accommodation of the product phase in the parent matrix. The driving force for transformation being still available, the transformation proceeds by autocatalytic nucleation of new sub-units on surfaces of preformed ones. The overall growth of the sheaf thus takes place by successive nucleation and growth of subunits. From the other perspective, bainite is assumed to nucleate and grow through a reconstructive and diffusion-controlled transformation mechanism. This is said to propagate through a ledge mechanism formation of a series of steps on the transformation interface.

the understanding of the underlying physics governing the mechanism of transformation. They have ranged from studying the transformation through thermodynamic considerations, to detailed crystallographic analyses and detailed investigations studying the distribution of atoms at the transformation interface using advanced characterization techniques. Enhanced understanding of the mechanism leads to the creation of quantitative models like a microstructure predictive tool for designing new steels. These tools meet high performance industry standards and can create better grades of steels, potentially opening avenues for new applications. The progress towards the creation of

Various mathematical models have been proposed that quantify the bainite reaction using different considerations of the mechanism of transformation. From a diffusional perspective, classical nucleation theory based models are proposed. The classical nucleation theory characterizes the nucleation phenomenon in a structural transformation from austenite to ferrite as the formation of small clusters of product phase in the matrix of parent which fluctuates in size. Some nucleated clusters dissolve in the matrix, others reach a critical size beyond which these nuclei no longer dissolve but grow until the transformation is complete. The quantitative nucleation rate is based on two terms with one accounting for the energy required to form a nucleus of critical size, which is a function of the driving force of transformation, and the other considers the diffusion effect. According to displacive theory, nu-

cleation of bainite is a thermally activated process with two atomic processes that influence the activation energy-dissociation of certain dislocation defects already present in the parent gamma-phase austenite and carbon partitioning to create the driving force necessary for nucleation. The activation energy here is also seen to be directly proportional to the driving force as opposed to the inverse square relationship seen in the classical nucleation theory. These differences, due to varied underlying mechanism, lead to different quantitatively predictive models. Propositions of the two theories are being used for different quantitative models which aid in steel microstructure design. It is however significant to note that the predictive ability alone does not imply the validity of the fundamental science. Evidence provided by both views are convincing and a consensus has not been reached regarding the debate between two opposing theories. Both sides however agree to the fact that: “direct experimental evidence for either theories is difficult to obtain. Therefore, one is left with indirect evidence” [3]. References [1] H. Aydin, E. Essadiqi, I.-H. Jung, and S. Yue, “Development of 3rd generation AHSS with medium Mn content alloying compositions,” Mater. Sci. Eng. A, vol. 564, pp. 501–508, Mar. 2013. [2] D. K. Matlock and J. G. Speer, “Third Generation of AHSS: Microstructure Design Concepts,” in Microstructure and Texture in Steels, London: Springer London, 2009, pp. 185–205. [3] L. C. D. Fielding, “The Bainite Controversy,” Mater. Sci. Technol., vol. 29, no. 4, pp. 383–399, Apr. 2013. [4] H. W. Paxton, “Commentary by: Transformation of austenite at constant subcritical temperatures,” Metall. Trans., vol. 1, no. 12, pp. 3479–3501, 1970. [5] W. D. Callister and D. G. Rethwisch, Materials science and engineering: an introduction, Seventh Ed., vol. 94. Wiley, 2007. [6] H. K. D. H. Bhadeshia, “Diffusional and displacive transformations,” Scr. Metall., vol. 21, no. 8, pp. 1017–1022, 1987. LEONARDO TIMES N°4 2017

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RECOVERY CREW PAIRING Development of a dynamic-decision support model C&O

Niek Hoeben, Researcher, Air Transport and Operations, Faculty of Aerospace Engineering, TU Delft.

Disruptions on the day of operation, like bad weather conditions, airport closure, crew sickness or aircraft breakdown can cause huge problems for airline schedules. Schedules can become infeasible and recovery is necessary in a short amount of time to prevent further scheduling problems. A decision support model can help alleviate these issues by optimizing crew schedules in case of disruptions.

I

n 2007, the total delay cost in the airline industry in the United States (US) was $32.9 billion, of which $8.3 billion were increased expenses for fuel, crew, and maintenance (Ball, 2010). These costs amounted to around 5% of the total revenue of US airlines ($174.7 billion) in the same year. Because of this, airlines try to improve their 38

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recovery process, thus reducing their costs. Every day, airline controllers are monitoring operations and in case of disruptions, they must recover the schedules. Dealing with all rules, regulations, preferences, and costs make the recovery process a complex problem. It is also of great importance to have solutions in a short amount of time,

in order to prevent impact on the rest of the schedule. Disruptions may not only affect the aircraft schedule, but can also impact crew schedules and passenger itineraries. Therefore, the airline recovery can be divided into three areas, which are solved sequentially: aircraft recovery, crew recovery, and passenger recovery. Since the 90s, airline recovery has been an important research topic. Decision support tools are developed to assist operation controllers during disruptions, since the tools can provide solutions in a short amount of time. This article considers the crew recov-


to be considered, after fuel costs, crew costs are one of the largest costs for an airline. The decision support model optimizes the crew schedules in case of disruptions. Recovering schedules when additional information about disruptions arise is an iterative process and called dynamic recovery. This dynamic approach is applied in the model and therefore previous recovery decisions are reconsidered. This is different from a non-dynamic approach in which a set of disruptions, happening at different times, is solved at the same time. In addition, the model considers only cockpit crewmembers, for which individual schedules are developed. This will make it possible to distinguish captains (CP) and first officers (FO) from each other, take into account particular requests, and to check feasibility at the individual level. This extends recovery possibilities as well. The academic goal of the project is to extend the body of knowledge about crew recovery and to develop a dynamic decision support tool. The operational goal is to have a decision support tool that provides recovery solutions with minimum costs within suitable computation times in order to use the model in real time operation.

In the crew rostering problem, crewmembers are assigned to the pairings. The pairings are merged to and form the personnel rosters, typically for one month. In the crew rostering problem, crew members can specify their preferences as well. Crew recovery is actually not that different from crew scheduling. One of the most important differences between the two problems is the solution’s time requirement. In crew recovery it is important to have fast solutions, but in crew scheduling the solution time is irrelevant. Table 1 shows a complete overview of the differences between crew scheduling and crew recovery. Knowing these aspects and the basics of crew scheduling the model can be described. The general outline of the model framework is illustrated in Figure 2. Together with the disruptions, flight and current crew schedules are the input of the model. After all the data is loaded into the model, the input disruptions are processed in the schedules. For example, a delayed flight implies that the times of the specific flight are changed, a crew member who called in sick is removed from the schedule which results in uncovered flights, etc. The input disruptions possible in the model are: • • • • •

Flight is cancelled Flight is delayed until a certain time Sick crew member and therefore not able to operate flights An airport is unavailable within a certain time period Change of aircraft type of a certain flight BAZARGAN

ery problem, since this is one of the hardest recovery tasks due to the many regulations involved. Besides the regulations that have

Before the model is described in more detail, it is important to know the basics of crew scheduling. Typically, crew scheduling is divided into two sub problems: crew pairing and crew rostering. In the crew pairing, problem sequences of flights are defined which start and end at the same crew base. The crew pairing consists of a sequence of duty periods and a duty period consists of a sequence of flight legs. Figure 1 illustrates

a pairing of two days in which duty periods and flight legs are defined.

Figure 1 - An example of a pairing consisting of two days (Bazargan, 2004). LEONARDO TIMES N°4 2017

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BAZARGAN

Figure 2 - Flowchart of the crew recovery model.

Crew Scheduling Crew Recovery

Scope

Time horizon

Solution time requirement

Solution quality requirement

Solution quantity requirement

Global, all crew members

Long, usually months

Not restrictive, usually a few weeks

High, optimal solutions One

Local, only a few crew members

Short, from a few hours to a few days

Restrictive, should not take more than a few minutes

Reasonable, good feasible solutions

Multiple

Table 1 - Differences between crew scheduling and crew recovery (Wei, 1997). After processing the disruptions into the schedule, a feasibility check is performed. The affected crew pairings are verified whether they are still feasible for operation, and are cross-checked with regulations. Examples of checks performed are rest times, duty times, and transition times. In case any pairing is infeasible, or a flight is not fully covered, recovery of the crew schedules is necessary. Recovery of the schedule is done by generating new feasible pairings. However, before new pairings are generated, a selection of crewmembers are defined. The more crewmembers considered in the pairing generation, the longer it will take before the model provides a solution. Therefore, a set of the best candidate crewmembers is defined to solve the problem. Several selection options are available for the user and a minimum of selected crewmembers can be set. Defining the selection of crewmembers can be based on the reporting time, duty time day, duty time in 28 days, or block hours in 28 days. Crewmembers are sorted with the best candidate first, based on the option chosen.

cancelled. Every flight should contain two crewmembers: a captain and a first officer or two captains. The second constraint ensures that every crewmember is assigned to a pairing (with duties or day-off(s)). The last constraint ensures that every flight contains none or one first officer, since flights can operate with two captains. Several test cases are performed to verify and validate the model. Data of Kenya Airways is used for these test cases. The data contained around 400 flights, which are operated by around 240 crewmembers spread over three days. Different disruption scenarios are set up and tested, and every scenario contains six different input disruptions.

For every selected crewmember, new pairings are generated in the pairing generation algorithm. A depth-first-search algorithm is used to define all possible combinations of flights. Within the algorithm a feasibility check ensures that all pairings comply with the regulations. After the pairing generation, an entire list of new feasible pairings is generated that will be used to solve the problem.

The solutions obtained by the model are generated in relatively short computation times (less than a minute), and are valid to use in real time operation, even the entire set of crewmembers provide satisfied computation times (less than three minutes). However, the selection of crewmembers is three to four times faster than using all crewmembers. Regarding costs, the selection of crewmembers generates higher costs (up to a maximum of 21%) than using all crewmembers. In addition, the selection of crewmembers provided solutions that differ to a maximum of 21% with the global optimum per disruption. However, when comparing a dynamic vs. non-dynamic approach, the dynamic approach generates higher costs, but the solutions obtained are more realistic. Therefore, the costs of the non-dynamic approach are underestimated.

The problem is described as a linear programming problem. The objective function is stated as a minimization function of the disruption costs. These costs contain the cost of operating the pairings, delay costs, and cancellation costs of flights. This objective function is subject to three constraints: flight coverage, crewmember pairing, and presence of an FO. The first constraint ensures that all flights are covered: flown or

This research contributes to the literature on crew recovery with the development of a dynamic decision support tool for crew recovery problems. Previous recovery decisions are reconsidered, and disruptions are modeled the moment of notification. The consideration of individual crewmembers made it possible to change only one crewmember from a flight instead of the entire cockpit crew. In addition, the model consid-

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ers multiple recovery options at the same time, as cancelling, delaying, swapping flights, and using standby crewmembers, which increases the recovery possibilities. Future research should focus on the implementation of the cabin crew, since recovery decisions of cockpit crew may affect cabin crew as well. It is even possible that schedules from cabin crew become infeasible because of certain decisions made. Thereafter, aircraft routing and passenger itineraries should be considered to integrate all recovery areas into one model. This will improve the quality of the recovery solutions. Currently, research is done to integrate the crew recovery model with an existing aircraft recovery model. Furthermore, the crew recovery model will be extended with connecting passenger’s data to partly implement passenger recovery as well. For a more detailed description of the crew recovery model you are referred to Hoeben (2017). If you have further ideas or want to contribute to this research as a graduate student, contact the supervisor for further information by email b.f.santos@tudelft.nl. References [1] Ball, M., Barnhart, C., Dresner, M., Hansen, M., Neels, K., Odoni, A., Zou, B. (2010). Total delay impact study (Tech. Rep.). Retrieved from www.isr.umd.edu [2] Bazargan, M. (2004). Airline Operations and Scheduling (first edit ed.). Ashgate Publishing Limited. [3] Wei, G.U.O., Yu, G., & Song, M. (1997). Optimization Model and Algorithm for Crew Management During Airline Irregular Operations. Journal of Combinatorial Optimization, 1, 305–321. [4] Hoeben, N.J.M. (2017). Dynamic Crew Pairing Recovery (MSc. Thesis, Delft University of Technology). Retrieved from www. repository.tudelft.nl


YOUR FUTURE COMMUTE Will this futuristic dream soon become a reality? AEROMOBIL

NICO’S CORNER

Nicolò Nefri, Editor Leonardo Times

We live in a technologically-advanced society, one where automation permeates every bit of our existence. The human mind is driven by the desire to pursue new ideas and constantly innovate. The aerospace sector is no exception. From the shape of fuselages to the propulsion and power systems of spacecraft, the industry is constantly innovating. But what if the future of flying doesn’t even involve aircraft?

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ne of the most recent high-tech developments in the aero-automobile sector is what most people thought only as fiction until a few decades ago: flying cars. If someone in the 1980s was asked how they would imagine the new millennium, their answer would certainly involve some sort of flying vehicle. However, this concept has been around for over 100 years. Not much longer after the Wright Brothers first designed, built, and successfully flew the first

powered aircraft in 1903. As early as 1926, American business magnate Henry Ford, famously of the ‘Ford Motor Company’, pursued the project of creating a single-seat airplane that he called the “Sky Flivver”. Unfortunately, the plan was abandoned two years later after a crash during a test flight cost the pilot his life. Though this was not a flying car at all, the concept caught the attention of the press and public. Just over a decade later, in 1940, Mr. Ford famously predicted “Mark my

word: a combination airplane and motorcar is coming. You may smile, but it will come”. Indeed, Ford was right. Nowadays, marrying a plane and a car together is not something that belongs to the imagination. Think about the magic world of Harry Potter, with the ‘Ford Anglia’ owned by Ronald Weasley’s family, or the Star Wars universe, with Luke Skywalker’s incredible ‘Landspeeder’. Bringing ‘Back to the Future’ into the present is now a reality. As flying cars have made their appearance onto the radar screen with the notoriety for being at the forefront of innovation and technological development. Nonetheless, there are countless discussions surrounding flying cars. Will we ever be able to fly with our own car? Are flying cars ever LEONARDO TIMES N°4 2017

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AIRBUS GROUP

Airbus flying car concepts. going to be mass-produced? Is it feasible with regards to safety and regulations? This is where the market is segmented in favor or against, with interesting figures on both sides of the debate.

Environmental concerns also play a substantial role in the debate. Firstly, introducing them in our everyday life would increase general traffic, thus pollution levels; it is very unlikely that manufacturers will achieve a fully electric vehicle. Furthermore, flying cars are not in harmony with nature. Think about urban flying wildlife such as birds: there are ten million starlings nesting in Rome alone, without considering the other types of winged animals.

traffic control system, something far from easy to accomplish. In fact, with flying cars, there are far more questions than answers. A plausible solution to avoid many issues related to safety is self-flying cars, as well as including a mandatory parachute in case of an emergency. Automating and computerizing aerial vehicles would not eliminate security concerns completely, but at least partially reduce them. Despite how amazing it sounds, it’s hard to imagine the flying car becoming a scalable solution. Moreover, if the biggest tech titan Elon does not believe in this technology, is it even worth trying to pursue?

Let’s consider the turbojet-powered supersonic passenger jetliner: Concorde, manufactured by British Aircraft Corporation (BAC) - later Airbus - and first flown in 1969. This aircraft was the fastest of its kind ever built, reaching a maximum speed of more than twice the speed of sound at Mach 2.04 (2,180km/h at cruise altitude). Despite enabling transportation from London to New York in less than three hours, it was retired in October of 2003. Several factors contributed to its demise. For one, supersonic transport (SST) is extremely loud; hence flying Concorde over land was not an option. Routes were restricted to trans-oceanic flights. Additionally, it was so expensive to build one SST, that it was essentially a money pit. Decline in passenger interest, stemming from high-profile accidents, such as Air France Flight 4590, contributed to Concorde’s retirement from the commercial aviation industry.

Other issues include cars dimensions, gasoline, flight independence, air traffic control, insurances, regulations, and last but not least, responsibility. Who is in charge for potential

On the other side, the supporters of flying cars believe them to be the new future of transportation. American stand-up comedi-

Coming back to the issue of noise, there are parallels to the fall of Concorde and the current debate over the potential rise of flying cars. Flying cars could be extremely noisy due to the strong downward wind force generated to keep the vehicle up in the air. Sure-

Musk once said: “Let’s just say that if something’s flying over your head, if there are a whole bunch of flying cars all over the place, that is not an anxiety-reducing situation”. For these personal air vehicles to become a reality, the world would need a brand-new air

SKEPTICISM OF FLYING CARS A few years ago, Tesla CEO Elon Musk persuaded the world with the idea that electrification was the future of cars. However, when it comes to making them airborne, “I am in favor for flying things… but there is a challenge with flying cars”. What challenge is he talking about?

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ly, it would not be pleasurable to have giant electro-wasps buzzing above a city.

FLYING CARS PROPONENTS

Mark my word: a combination airplane and motorcar is coming. You may smile, but it will come -Henry Ford, 1940

accidents? How can governmental authorities control air traffic? Is there going to be a job such as the ‘air traffic policeman’? Are we building flying cars or driving planes?

an Lewis Black once said: “This new millennium sucks! It’s exactly the same as the old millennium! You know why? No flying cars!” However, there is no doubt in anyone’s mind that flying cars are on the horizon and not too distant future. Why? Traffic sucks. Everyone who has endured a traffic jam can agree it is one of the most soul-sucking things that takes away so much of our life. Nobody wants to sit in


AEROMOBIL

traffic after a long day at work, or risk missing a plane because of congestion on the way to the airport. The average US commuter spends 42 hours in traffic per year and loses $1,400 idling away gas. This amounts to $300 billion in total cost of congestion to all American drivers. Imagine if at the beginning of your summer holidays on your way to Amsterdam Schiphol you could suddenly take off and fly straight to the airport. Maybe landing in an allocated parking lot, specifically designed for the passengers’ vehicles? This would be an interesting solution to alleviate congestions in traffic-jammed cities all around the world.

Several start-ups and big aviation firms are investing millions of dollars. Designing, prototyping, testing, and developing eco-friendly and innovative flying cars all lead to the same mission of reaching mass production. Founded in 2008, American firm Terrafugia likes to call its vehicles ‘roadable aircraft’. Aviation giant Airbus on the other hand prefers the term “multi-modal vehicle” to define Pop Up, their concept of flying car that was presented at this year Geneva Motor Show. The competition is stiff and the battlefield of flying cars is growing: who will reign?

AEROMOBIL 3.0 An example of a flying car is Aeromobil 3.0, a two-seat, 6m long prototype of Slovakian company Aeromobil. Similar to other companies, it is manufactured with a steel and carbon fiber frame, giving it a total weight of 450kg. Only 200m of runway are required for it to take-off and 50 meters for landing. The car offers a flight distance of 700km with a maximum flight speed of 200km/h, while when used as an actual car it can cruise for 875km at speed up to 160km/h. The price is between 200 and 300 thousand euros,

AEROMOBIL

AEROMOBIL

Cars have been around for a while now. If we think of when conventional cars first appeared on the market back in 1886 (regarded as the birth year of the modern car), they were a very luxurious novelty that only the wealthy could afford. The first automobile was developed by German engineer Karl Benz, a one-cylinder, three-wheeled, twostroke unit called ‘Benz Patent Motor Car’. What if flying cars are the ‘Benz Patent Motor Car’ of the 21st century? Does this mean that in one hundred years they will be owned by most people? A recently conducted survey by the University of Michigan suggested people have mostly confident feelings about flying cars. 44.7% of those surveyed said they feel very or somewhat positive about flying cars while a quarter remains neutral. In order to drive some existing prototypes of flying cars, all is required is a sport pilot certificate which can be earned in as few as 20 hours of flying experience. The benefits that come with flying cars are infinite and so are the applications in which they could be used, such as emergency rescues situations, first aid conditions, and delivery systems.

Aeromobil 3.0. slightly cheaper than a Cessna Skyhawk fixed-wing plane. The features that make Aeromobil 3.0 stand out from its competitors are the conversion between flying and driving modes (three minutes), the certification for use in the US and EU, and that it uses electricity on road and switches to conventional aircraft fuel in flight. The company has already received hundreds of orders, showing the future of Aeromobil is going in the right direction.

CONCLUSION So, what does the future hold for flying cars? There are plenty of possibilities to be discovered in this exciting flying world, which we will surely find out soon. There are many market feasibility barriers to tackle, such as certification, battery technology, and infrastructure. If these are overcome, flying cars will have a

much more influential role in our community. Clearly, there is a big market opportunity to be fulfilled. It is just a matter of time to see who will be the first firm to achieve this strategy. From what it unfortunately seems, we might not be able to count on Elon to help us out. However, if our children will be living in a world of flying cars, it is up to us. To achieve this, we must work together to understand how new technologies will shape the future of our society. References [1] The New York Times [2] BBC News [3] Business Insider [4] Interesting Engineering [5] TED

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NANO GOES ORBITAL An in-depth look on their widespread uses SPACE DEPARTMENT

Bastiaan Bosman, Space Department, BSc Student Aerospace Engineering, TU Delft

In March 1958, NASA successfully launched the VANGUARD 1C. With a weight of only 1.47 kilograms it can be considered the first nano-satellite in space. Almost 2000 satellites have been launched since. Many companies, universities, and institutions are working on improving the required technology, making these satellites capable of more tasks such as GPS, Earth mapping and communication.

N

anosats have been around for almost sixty years, but what was the incentive for this development? Was it related to cost, or were there other reasons for this development? Cost certainly plays a role regarding the decrease in size, but isn’t the only reason. In fact multiple nano-satellites can be launched in one rocket, which represents a significant advantage since it reduces the emission of greenhouse gases. This is especially convenient at times like these, when global warming and the depletion of fossil fuels are becoming serious issues. Universities and other institutions also benefit from the development of small spacecraft. It enables them to design their own technology and test it in space as our own university did with Delfi, for example. This gave the university a lot of research material, which can teach professors and students various things such as hands-on 44

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orbit control and satellite electronics. Another benefit of nano-satellites and bulk launching is the ease of creating complex satellite constellations in a fraction of the launches it used to take. This makes a constellation functional in a small timespan, which increases reliability, because the first deployment does not have to be inactive for a long time waiting for the last addition to the network.

CURRENT NANOSAT PROJECTS ELSE, a Swiss startup, is planning to build a large nanosat constellation. Their plan is to launch 64 satellites into space forming a network “to fulfill the need for global connectivity for geolocation and remote monitoring” [1], as Fabien Jordan, CEO of ELSE said. The company has already raised over four

million dollars and they are still awaiting the last one million for their first launch. The first batch will consist of eight satellites starting off the network. The total cost of the design, build and launch is estimated to be less than $50 million with manufacturing cost per satellite under $500,000, while large conventional GPS satellites cost more than $100 million. The construction cost will decrease when the amount of required spacecraft increases, “If we manufacture twenty of them, we believe we can go down to $ 300,000 or maybe $250,000’’ Jordan said [1]. The constellation will be launched in groups of eight satellites and the first set is expected to be up and running by the end of 2018 in a single orbital plane. Every year a new group will be launched in a new plane reducing latency time until the planned 64 satellites are in place. The life expectancy of each unit is roughly three to five years, which is why the company has planned to replace them every three years, but Jordan said that ELSE has proven that this can be extended to seven years. The company has not yet chosen a launcher, it is currently looking for small and new micro-launchers like the systems


TU GRAZ

is capable of bringing more than double the load of the Vector-R up into LEO. Both rockets, once operational, will be launched from Launch Complex 46 at Cape Canaveral Air Force Station, in Florida. This launch site is operated by Space Florida, a state-backed economic development agency. Next to the Vector-R and Vector-H, the company has many more rockets coming in the future.

NANOSATS IN DEEP SPACE

designed by RocketLabs and Vector Space Systems. The reasons for this are, promoting further use of such launchers and decreasing the cost for small spacecraft missions.

LAUNCHERS FOR NANOSATELLITES Vector Space Systems is one of the companies designing small rockets for micro-sats. This company is aiming to launch satellites of about 60kg or clusters of smaller satellites into Low Earth Orbit (LEO). The first test done on the Vector-R, one of their most promising models took place on May 3rd 2017. This test was done on the first stage and one of their 3D-printed injectors. The rocket was scheduled to reach an altitude of about 1400m. This test was a ‘’Sweet success’’ as tweeted by Jim Cantrell, CEO and co-founder of Vector Space Systems. The company plans to make twelve different designs in total, of which the Vector-R is the first to be fully operational at the end of 2018, or early 2019, and they will launch 100 times a year at full capacity. A second rocket that Vector Space Systems is working on is the Vector-H (Vector Heavy), a larger rocket, which

Cubesats have already made their appearance around the Earth, but some people see more potential in these small satellites. A project named the “Interplanetary Nano-Spacecraft Pathfinder In Relevant Environment” (INSPIRE) mission is planning on sending two identical Cubesats, measuring 30cm in size each, away from Earth into deep space. The plan is to send the probes about 1.5 million kilometers away from Earth for a three-month lasting mission. Both satellites have a magnetometer and an imager. The mission team also wants the spacecraft to characterize the structure of solar winds. The primary use of the INSPIRE mission however, is to show that Cubesats can function far away from Earth. "The objectives of INSPIRE are very simple: survive, communicate and navigate," said Mission Principal Investigator Andrew Klesh of NASA's Jet Propulsion Laboratory. "If you look at the technologies you need to explore deep space, it's those three things first, before anything else." Both INSPIRE satellites have already been built and are currently awaiting assignment as secondary payload to a rocket. The total mission cost will approximately be 5.5 million U.S dollars, which is inexpensive compared to other deep space missions. The INSPIRE mission will be the first Cubesats to get away from Earth, but many other companies are on their heels. One of these is NASA’s Mars InSight lander mission. This mission plans on sending two 60cm Cubesats and a lander towards Mars. The small satellites help with communication during the probe’s entry, descent and landing phase. Another three equally sized Cubesats will be launched on NASA’s Space Launch System to orbit the Moon. Next to orbiting planets and moons, another project named BioSentinel, will orbit the Sun to measure the effects of solar radiation using on-board yeast cells. No matter how fast

the technology of miniaturization advances, a nanosat will never have the same capabilities as a large satellite such as Cassini or Galileo, but this is not what they are designed for. A deep space nanosat is designed as a part of a larger mission, as a first economical way of exploration or as a deployable part of a larger spacecraft to perform tasks that require a smaller probe. The exact capabilities of Cubesats in deep space remain to be seen. And for that reason INSPIRE, BioSentinel and many more missions are under development. Time will tell whether the Cubesats will live up to their potential. But what can be said is that the coming years will show some very interesting developments in the nanospace industry.

SYMPOSIUM Interested in hearing more about miniaturization in space? Make sure to join this edition of the annual VSV symposium on March 6th 2018. The VSV symposium exists to inspire aerospace students and any other student or professional that takes interest in the current advancements in space and the possibilities it brings. More information can be found at: http://vsv-symposium.com/. References [1] Juliet van Wagenen, ELSE CEO: 2017 Big Year for Planned 64-Satellite Constellation, http://www.satellitetoday.com/ newspace/2016/12/16/else-ceo-2017-bigyear-planned-64-satellite-constellation/, Satellitetoday, 2016 [3] Mike Wall, Tiny Cubesats Set to Explore Deep Space, https://www.space. com/29306-cubesats-deep-space-exploration.html, Space.com, 2015 The Space Department The Space Department promotes astronautics among the students and employees of the faculty of Aerospace Engineering at Delft University Technology by organizing lectures and excursions.

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DESIGNING QUIET Optimal design of aircraft noise abatement departure routes C&O

Vinh Ho-Huu, PhD Candidate Aerospace Engineering, TU Delft

The continuous growth of air transport in recent years has been facing considerable challenges from an environmental perspective (noise and pollutant emissions). Therefore, the developments of feasible solutions to handle these issues effectively are extremely important.

D

ue to the high demand of air transport, the aviation industry is expected to grow rapidly in the coming years [1]. To adapt to this requirement, the extension of aircraft and airport operations becomes more important. However, the increase in these operations often results in negative impacts on the quality of life of near-airport communities caused by, for example, noise and pollutant emissions. As a result, the protest of communities surrounding airports becomes a major challenge which policymakers have to deal with when accommodating these operations. Therefore, in order to develop the air transport sustainably, it is important to determine possible solutions for decreasing its adverse impacts. In recent years, a series of projects aiming at developing the aviation sector sustainably have been launched by European and national authorities such as CleanSky, the Atlantic Interoperability Initiative to Reduce Emission (AIRE), and the Asia & South Pacific Initiative to Reduce Emission (ASPIRE). Various strategies have been proposed, such as developing new policies and standards, advanced aircraft technologies and sustainable alternative fuels, and changing aircraft/ airport operational procedures. Among them, 46

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the change of aircraft/airport operational procedures may be a potential option in the shortterm since it can be adapted more quickly and often less costly as compared to the other options. For this option, the optimal design of new routes such as departure and arrival routes is one of the possible solutions which has been broadly studied during the past few years [2]. Research on the optimal design of environmentally friendly terminal routes has obtained significant achievements, and various approaches have been proposed in recent years. For example, the development of an optimization tool called NOISHHH[3], which can generate environmentally optimal departure and arrival trajectories with less noise and fuel consumption. Other approaches can also be found in the literature, for instance, the use of a lexicographic optimization technique [4], or the application of non-gradient optimization methods such as elitist non-dominated sorting genetic algorithm (NSGA-II) [5], multi-objective mesh adaptive direct search (multi-MADS) [6], etc.

According to a recent study [7], the authors have shown that although the available methods have obtained certain acquisitions, there is still room for researchers to improve or develop the new techniques which can handle this kind of problem more efficiently. In this article, the main idea of the study is briefly presented. In this work, a new application of a Multi-Objective Evolutionary Algorithm based on Decomposition (MOEA/D) combined with a trajectory parameterization technique is proposed to optimally design Standard Instrument Departures (SID) currently in use at Schiphol Airport.

METHODOLOGIES To get an insight into the main idea of the article, it is better to start with a description of a specific case study at Schiphol Airport, The Netherlands, as shown in Figure 1, where the SID called SPIJKERBOOR2K is considered. This route starts at runway 24 and terminates at the ANDIK intersection, which passes closely by the communities of Hoofddorp, Haarlem, and Amstelveen, where most of the noise nuisance occurs. The main idea of this work is to design optimal routes which can reduce the number of people who are likely to be awakened due to aircraft noise as much as possible. From the figure, however, it is easy to recognize that if only the noise objective is considered, new routes may be longer than the current ones because of avoiding densely populated


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The second method is a multi-objective optimization method which is used to solve the formulated optimization problem. This method, firstly proposed by Zhang and Li [8], has been demonstrated to be more efficient than NSGA-II and other methods in literature. It is

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The first method is to parameterize the trajectory as well as to define design variables. This technique aims at seperating a trajectory into two parts: ground track and vertical path. For ground track generation, a modern navigation technology known as required navigation performance (RNP) is applied, where track-toa-fix (TF) and radius-to-a-fix (RF) leg types are used for constructing a flight path between waypoints. For the vertical path generation, the vertical profile is synthesized based on flight procedures derived from the International Civil Aviation Organization (ICAO).

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communities, and hence their fuel burn will increase significantly. Therefore, to cope with this problem, the formulated optimization problem will consider two conflicting objectives: the number of people who are woken up and fuel burn. As a result, a bi-objective optimization problem is formed. To solve this problem, two different methods, namely a Multi-Objective Evolutionary Algorithm based on Decomposition (MOEA/D) and a trajectory parameterization technique, are applied.

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Figure 2 - Optimal routes and the reference route.. also recognized as one of the most popular multi-objective evolutionary algorithms to date. In this method, a multi-objective optimization problem (MOP) is transformed into a set of single optimization sub-problems by applying decomposition approaches, and applying evolutionary algorithms such as genetic algorithm,

differential evolution afterwards to optimize these sub-problems simultaneously.

RESULTS The optimal routes of the case study are presented in Figure 2, where different optimal routes can be found. From the figure, it can be LEONARDO TIMES N°4 2017

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Figure 3 - Vertical profiles of cases 1, 2, 3 and the reference case (VEAS: Equivalent airspeed, h: altitude). seen that instead of providing one solution like single-objective optimization approaches, the method gives a set of non-dominated solutions which is a result of the trade-off between two conflicting objectives. All of them try to avoid noise-sensitive communities. With this set of obtained optimal solutions, the method helps provide more choices for the authorities and policymakers in selecting optimal solutions compatible with their purposes. For a performance comparison, the number of people expected to be woken up and the fuel burn of the three representative cases (as highlighted in Figure 2) are listed in Table 1, along with the results of the reference case, which is taken at Schiphol Airport. The vertical profiles of these cases are also given in Figure 3. Compared to the reference case, it can be seen that all considered solutions are non-dominated, either better at awakenings and worse at fuel burn and vice versa. Despite having almost the same ground track length, with an optimal combination of the ground track and vertical profile, case 1 offers much better performance regarding all three criteria. By taking a closer look at Figure 3, it can be seen that in the first phase of flight, for all optimal cases, the aircraft prefer to fly at a low altitude with a high speed to pass over populated regions. This is because the spread of aircraft noise at a low altitude is smaller than that at a higher altitude due to in48

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Case number

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569.69

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Table 1 - Comparison of objectives of cases 1-3 and the reference case. creased lateral attenuation, and hence it may lead to a significant reduction of awakenings. In summary, based on the gained results, it can be concluded that the use of optimization techniques to optimally design and apply new departure routes may be one of the reasonable solutions which can help authorities operate aircraft and airport operations more efficiently by dealing with the rapid growth of the air transport. References [1] Boeing. Current Market Outlook 2016– 2035. [2] H.G. Visser, Generic and site-specific criteria in the optimization of noise abatement tarajectories, Transp. Res. Part D Transp. Environ. 10 (2005) 405–419. doi:10.1016/j. trd.2005.05.001. [3] H.G. Visser, R. a. A. Wijnen, Optimization of Noise Abatement Departure Trajectories, J. Aircr. 38 (2001) 620–627. doi:10.2514/2.2838.

[4] X. Prats, V. Puig, J. Quevedo, F. Nejjari, Lexicographic optimisation for optimal departure aircraft trajectories, Aerosp. Sci. Technol. 14 (2010) 26–37. doi:10.1016/j.ast.2009.11.003. [5] S. Hartjes, H. Visser, Efficient trajectory parameterization for environmental optimization of departure flight paths using a genetic algorithm, Proc. Inst. Mech. Eng. Part G J. Aerosp. Eng. 0 (2016) 1–9. doi:10.1177/0954410016648980. [6] R. Torres, J. Chaptal, C. Bès, J.-B. Hiriart-Urruty, Optimal , Environmentally Friendly Departure Procedures for Civil Aircraft, J. Aircr. 48 (2011) 11–23. doi:10.2514/1.C031012. [7] V. Ho-Huu, S. Hartjes, H. Visser, R. Curran, An Efficient Application of the MOEA/D Algorithm for Designing Noise Abatement Departure Trajectories, Aerospace. 4 (2017) 54. doi:10.3390/ aerospace4040054. [8] Q. Zhang, H. Li, MOEA/D: A Multiobjective Evolutionary Algorithm Based on Decomposition, IEEE Trans. Evol. Comput. 11 (2007) 712– 731. doi:10.1109/TEVC.2007.892759.


INTERNSHIP AT LARC Creating and Exploring at NASA Langley Research Center NASA

INTERNSHIP

Katharina Ertman, Editor Leonardo Times

Along with about 120 other interns, I spent ten weeks of my summer in 2015 working at NASA Langley Research Center (LaRC) in Hampton, VA. Some were returner interns, a few back for their third and fourth internship, and others like me were brand new to the vast world of NASA. The common denominator was that we all were there and had this shared experience.

W

hen one thinks of NASA, most people conjure up timeless images of Mission Control monitoring a shuttle launch, or perhaps the most recent proof-of-concept for the EmDrive. These are only some examples of the incredible work that happens at the ten NASA centers each and every day. From developing technologies to making flying safer to building probes that will be sent deep into space, NASA engineers and scientists are involved in thousands of projects that advance our understanding of the world. My internship focused on a small part of this massive patchwork, specifically with regards to the production of small-scale UAVs. UAVs (not drones, as NASA engineers will stress) are a very prominent, if not controversial, topic in the aviation world. The ability to perform missions without the use of a human operator onboard opens up a new realm of aircraft designs and presents new challenges for manufacturing. Currently,

UAVs used for research purposes are produced using a labor- and material-intensive process that involves “building from the inside-out” so to say. That is, a team of engineers designs the structure, while another one builds the aircraft by creating molds and inlaying carbon fiber and structural elements. Finally, another technician is needed to outfit the avionics system. This process takes several engineers working in various departments and the production of one aircraft could take several months, depending on the workload of the different teams involved. To begin to address this issue, NASA has put forth several initiatives to try to reduce the time and cost of production of these small-scale aircraft. Concept-to-Flight-in30-Days, as implied by the name, aims to reduce the entire design process of a smallscale aircraft to around thirty days. Another initiative called “Learn to Fly” has the goal of using adaptive learning to quickly design

airplanes and do away with ground-based testing. The goal of these initiatives is the same: to put new planes in the air as fast as possible. To do this, new manufacturing methods have to be investigated. My work revolved around proving the possibility of using 3D printing to create an aircraft fuselage approximately 1m in length that would be wrapped in carbon fiber for strength. This would ideally take the entire process down from several months to a few weeks, or perhaps even days. The added advantage of this method would also be that one engineer would do the majority of the work; from the CAD work to the printing and carbon fiber layup, leaving the final stages to be done by technicians who are specialized in avionics. Most of my days were spent wrestling with Creo Parametric to create a structure that would print correctly with the right support material, to ensure a smooth surface for the carbon fiber layup. Towards the end of the internship, I got my hands dirty and focused on printing my parts, preparing them for layup by sanding down every surface, and figuring out how to wrap a complex structure with various curves and features.

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NASA

Carbon fiber layup process. To accommodate the complex geometries of the fuselage, heat shrink tape and hand-strengthening putty were used to hold carbon fiber close to the surface. The structure that was printed and wrapped was based on NASA’s GL-10 aircraft, a hybrid tilt-wing prototype aircraft capable of vertical takeoff then transitioning to forward flight. One of the most interesting parts of the design work was creating a non-traditional internal structure. Our understanding of how an aircraft is designed from a structural standpoint is a product of our manufacturing techniques and materials available. However, with the advent of 3D printing and the possibility of creating virtually any shape imaginable, the concept of what constitutes a “good” structure could well be upended. Structures could be specially designed for a specific purpose and 3D printing could be utilized to achieve an ideal form.

laxed working environment is that people generally have time to talk. A machinist happily spent fifteen minutes explaining the part he was creating in the Computer Numeric Control (CNC) machine, while a researcher brought out his telescope on a sunny day over lunch to let a group of interns look at solar flares that were particularly strong that day.

the most interesting events was the Boeing 757 ecoDemonstrator. In conjunction with Boeing, NASA worked on two technologies to improve the eco-friendliness of existing aircraft, namely the creation of an insect-repelling wing leading edge to improve laminar flow and utilizing active flow control over the rudder to maximize aerodynamic efficiency.

One did not have to look far to see the many facilities that LaRC had to offer. A large part of the internship program was the numerous events for interns where we were taken to various research spaces and had the opportunity to attend lectures given by researchers on their work.

While the majority of an intern’s day is spent working on the internship project, there is still plenty of opportunity to explore and discover what the Center has to offer. Working in government, there is a distinct difference in the environment. At NASA, work needs to be done, but there is not the same pressure on engineers and researchers to meet quarterly deadlines that would be set in a private company in the United States. The consequence of this is an atmosphere that encourages exploration, which was extended to the interns.

NASA LaRC is home to more than forty wind tunnels, ranging from small supersonic tunnels, to the looming 14ft x 22ft Subsonic Wind Tunnel. 14-by-22, as it’s referred to at Langley, is an incredible feat of engineering. The name refers to the internal dimensions of the test section. What is not captured by the name is the rest of the tunnel. The test section only constitutes a small part of the whole operation, with a large tunnel stretching for hundreds of meters in a loop, which delivers air. Walking through this part of the tunnel is an experience like none other. It is completely black, except for the faint light of someone’s smartphone, and completely silent, except for the occasional creak of metal or the whoosh of a breeze flowing through the tunnel.

The plane was rolled into one of the hangars, and employees and interns alike had the chance to tour both the outside of the plane and see the inside of the cabin. From the outside, the 757 looked like a normal plane, but the inside was outfitted with a handful of test stations and computers that monitor the plane during test flights. More interestingly, IR cameras were installed on the tail section and inside the cabin. These captured images of the wings in flight helped to determine the efficacy of the materials that were designed to repel bugs and other foreign debris.

Interns were encouraged to take the opportunity to talk to engineers and researchers in different branches and to build connections with others. Several afternoons, in the post-lunch lull, were spent in the machine shop or model shop, talking to engineers and fellow interns about what they were working on. A nice aspect of the more re50

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Another unique opportunity at NASA was the center-wide events that highlighted work done by engineers at LaRC. One of

The common thread through all of these events was a simple one: working at NASA gave each intern the opportunity to interact with the best of the best in their field. This was an invaluable part of the internship and what sets working at a NASA research center apart from other companies. In short, this was an experience I will never forget. References [1] nasa.gov


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