TABLE OF CONTENTS
Radiation in Space
Rover Starting Point
Rover Section Layout
table of contents
S.T.A.R (Space and Terrestrial Architectural Research) design is about design for extreme environments. It started in 1998 as a project in cooperation with NASA at Lyndon B. Johnson Space Center in Houston, Texas, USA. The themes have varied from year to year but the emphasis has always been on humans in space and many parts of the spaceflight has been considered. This year’s focus was “living on the moon”. The course touch upon areas such as: ergonomics, compact living, sustainability, cultural and identity issues, material and construction, life support systems, human needs and everyday life in space. After three weeks of prepatory studies in Lund, Sweden, 15 students went on a field trip to Johnson Space Center in Houston to during three intense weeks learn more about space, defining a project area and create concepts filtered and enhanced by many NASA employees. The remaining 10 weeks of the project was dedicated to develop the concepts presented at NASA. The following pages will explain the background studies, the process and the final concept.
PREPARATION WEEKS, LUND
NASA, JSC - HOUSTON
PRESENTATION ASSIGNMENT 1
INTRO ASSIGNMENT 1
LECTURE IMAGINATION DRAMATEN SNUBBE
WORKING ASSIGNMENT 1
LECTURE MOON GUY
INTRO ASSIGNMENT 2
PRESENTATION OF CONCEPTS
LECTURE ETHICS IN SPACE
SKETCHI SKETCH M
CONTINUE RESEARCH GUIDED TOUR AT NASA
WITH LARRY TOUPS
FEEDBACK FROM NASA
WORKING ON OUR OWN
ING & MODELS
NASA will return to the moon by the year of 2020 as a first step to opening the solar system to further exploration and demonstrate our ability to live and work on another world. One of the greatest and yet unsolved challenges is to protect the astronauts from the hostile environment at the moon. Without the protection of the Earthâ€™s atmosphere and magnetosphere astronauts are exposed to high levels of radiation. Galactic cosmic rays (GCR) gives constant radiation but is only lethal if exposed over a longer period of time. Solar Particle Events (SPE) and Solar Flare Event (SFE) on the other hand can kill an unprotected person in a single burst. In the habitat the crew will be protected but on longer excursions the astronauts might not have enough time to return if they receive a solar flare alarm. Within 30 minutes they have to be able to protect themselves for up to 4 days.
Moon characteristics - Dryness; the moon seems to be completely waterless. -Lifelessness; no life, living or fossil has been found on the moon. - Diversity; the moon is not homogenous. Its surface is made of a wide range of rocks, light and dark regions. - Surface weathering; the moon is weathered by the small cosmic particles that continually bombard its surface. This has gradually built up the regolith, a powdery layer that covers and conceals the moon’s bedrock. - Design limitations imposed by the fundamental strength of the regolith and its stability in excavations are still not known. - Unprocessed bulk regolith may be used for shielding purposes (from cosmic rays and solar flares). It may be scooped, shoveled or bagged and then put into position. Containerization or casting into blocks may be necessary, particularly if the shielding is to be transported and used elsewhere - The lack of an atmosphere on the moon makes it more vulnerable, it suffers more impact from the rest of the space - ISRU in-situ resource utilization = ” Living of the land” Radiation on the moon The greatest dangers come from two types of events: Galactic cosmic rays (GCR) and Solar particle events (SPE) (sometimes associated with solar flares). Galactic cosmic rays (GCR) - Dangerous if exposed over a longer period of time.
RADIATION IN SPACE
Solar Particle Events (SPE) - Capable of killing an unprotected person in a single burst. It produces electrons, protons and heavier ions AND produce electromagnetic radiation at all wavelengths. - High energy particles (most protons and alpha particles) are the main concern. Once a particle bombardment starts it takes several hours before it reach a peak before fading again.
- Highly energetic and variable particles originating from ejections of coronal mass on the sun. - Their size and frequency are hard to predict. - They are more likely during solar maximum, but possible at any time. - Ordinary events occur a few times during a solar cycle. Large events occur sporadically - The US has a program to forecast space weather trying to predict SPEs or, at least, warn astronauts (30min or more). - The radiation dose to a spacecraft, system or crew helps frame the mission lifetime. Major solar events last for hours, or sometimes even days. - A major solar event doesn’t just cut loose without warning. It is possible to observe the “weather” on the sun and predict when a major event will occur.
RADIATION IN SPACE
Solar Flare Event (SFE) - Eruption creates increase of solar wind particles. - A solar flare warning system and some form of protection will be absolutely necessary. - Because of the complexity of solar processes, not all solar flares produce SPE. General - The amount of energy deposited in a material depends on the radiation itself and the material in question. - Radiation dose unit- gray (Gy)= 1J/kg. - Structural elements are least sensitive, whereas electronics and the crew are most sensitive. - More energetic particles penetrate more deeply into a material. Electrons penetrate farther than protons because they are lighter and have higher velocities. Radiation Protection Humans - High levels of radiation can create â€˜chromosomal aberrationsâ€™ in blood lymphocytes. These cells are heavily involved in the immune system and so any damage may contribute to the lowered immunity experienced by astronauts. -Radiation has recently been linked to a higher incidence of cataracts in astronauts. - Solar flares release a cascade of high energy particles known as a proton storm. Protons can pass through the human body, doing biochemical damage. - Originally it was thought that astronauts would have two hours time to get into shelter but based on an event in January 2005, they may have as little as 15 minutes to do so.
RADIATION IN SPACE
- Necessary radiation protection features- shielding, monitoring, dosimetry - Each crew member shall be monitored throughout his/her active career. Scheduling and assigning crew activities and alerting personnel that they are approaching their radiation dose limit - NASA limits radiation exposure based on mission duration and age at first exposure. NASA allows an increase of 3% in lifetime risk of cancer mortality. Career doses are more restrictive for younger astronauts and for women. Recommendations In the design of lunar transfer vehicles, optimal use of onboard mass for radiation protection should be made. While working on the surface, crew members should remain close to the habitat or a dedicated shelter. When only protected by the suit, the recommended dose of radiation would be exceeded after 6-15 hours in the event that a SPE occurs. If the crew is in a pressurized rover and cannot construct a shelter within 2-3 days, radiation sickness effects would occur. For long expeditions on the lunar surface, shelters should provided a few hours travel apart, or a means should be provided to quickly construct a shelter. - Radiation varies with the angle of incoming radiation - Use of existing structures, light weight options (such as polyethylene) and supplies (such as water and propellant) is preferable. - In all likelihood, lunar soil will be used as a shielding material, but also as a thermal-control insulating material. A 2m regolith thickness is adequate to control heat gain and loss.
RADIATION IN SPACE
- Regolith is also a good shielding alternative, since it is desirable to minimize weight and volume for materials that needs to be transported to the lunar base. - 50 cm regolith thickness may provide adequate flare protection but larger thickness may be more desirable - 3 principles to radiation protection: Time - Reduced time of exposure reduces the effective dose proportionally. Distance - Increasing distance of radiation source (using tools) Shielding - Improper shielding can actually produce secondary radiation that absorbs in the organisms more readily. - Different types of ionizing radiation behave in different ways and require different shielding techniques. - Particle radiation- stream of charged or neutral particles, both charged ions and subatomic elementary particle: - Alpha radiation can be stopped with a piece of paper. - Beta radiation (electrons) can be stopped with a thin layer of aluminum. In cases where high energy beta particles are emitted, shielding must be accomplished with low density materials such as plastic, wood, water, acrylic glass. - Neutron radiation (fast neutrons) has to be slowed down. A large mass of hydrogen-rich material such as water (or concrete which contains a lot of chemically-bound water), polyethylene, or paraffin wax is commonly used. These can be further combined with boron for more efficient absorption of the thermal neutrons. - Electromagnetic radiation consists of electromagnetic waves which properties depends on the wavelength.
- X-ray & gamma radiation- shielding materials used are depleted uranium, lead and barium sulfate. Any material can be used but must be far thicker. - Water walls are good protection from solar flares. - It is possible to create crust on dusty surface for a good habitat foundation. - Lava tubes would function as radiation protection Radiation Shielding concepts -Passive bulk shielding -Electromagnetic shielding (no effect on GCR) -Electrostatic shielding -Chemical radio protection The two most important variables are shielding material composition and habitat geometry. The goal is to optimize crew protection while minimizing mass and cost. Shielding materials The magnitude of shielding effect varies with composition and the energy spectrum of the radiation. Light elements such as hydrogen, carbon and oxygen and their compounds like water and plastics are the most effective high-energy charged particle shields per unit mass. Shielding efficiency are evaluated as dose equivalent (Sv) versus areal density (g/cm3 ) Lunar regolith 1.5 g/cm3
Aluminum 2.7 g/cm3 - high density, light weight Litium Hydride (LiH) 0.82 g/cm3 - used as reactor shield material for neutron moderation Magnesium Hydride (MgH2) 1.6 g/cm3 - potential use as hydrogen storage ( more hydrogen is contained per unit volume than in pure liquid hydrogen). If any materials can serve a dual purpose, mission cost can be reduced! Food, water, waste water 1.0 g/cm3 - materials can serve a dual purpose, mission cost can be reduced Polyethylene 0.92 g/cm3 Polyetherimide 1.26 g/cm3 - high performance polymer - can be used as resin for composite materials allowing structural applications Regolith epoxy 1.48 g/cm3 (mixture to bind regolith to enhance shielding and structural properties) - most used resin, well understood Epoxy 1.32 g/cm3 - commonly used as binder for composite mixture The materials containing hydrogen are the most effective as SPE-shields.
Lunar Regolith Shielding Use of lunar regolith to reduce launch mass. Aspects for consideration: -Regolith moving equipment is needed -Time -Reliability Techniques for moving regolith: -Mining equipment -Pyrotechnics -Snowblowing Inflatable modules Can be produced in any shape, the simplest are spheres, cylinders and torus. The most important properties for inflatable structure materials are: -Low weight -High specific elastic modulus -Controlled thermal expansion -Damage tolerance -High specific strength -Ease of manufacture The most promising materials are advanced fiber-reinforced composites. They are fiber/matrix combinations out of polymers, ceramics and metals. Polymer matrix composite materials are of prime interest due to low weight.
approximate level of protection thickness (cm)
available in rover
available in rover
most protective polymer
polyethylene + water
20% better protection than Al
light-weight, flexible, strong
extremely reactive with air and water
negative comment positive comment
material overview 19
ROVER STARTING POINT
One of the goals of the “Lunar Pioneering Phase” is to perform surface explorations. To execute this you would need a reliable surface vehicle. Considering the type of mission a pressurized rover would be a preferable alternative. Drivers and Requirements Pressurized rovers will be highly complex systems and require the same level of study and analysis as any other pressurized human rated vehicle or habitat. - The concept of operations demonstrates the needs. - Needs drive requirements. - Requirements should drive design. Exploration Goals Lunar surface studies will require travel to locations 75 to 200 km away from the central outpost or base. Based on Apollo rovers and other rover projects, we assume 20km/hr rate, which leads to a 10 hour journey to reach some of the sites. Consumables Missions include long excursions and crew member cannot be expected to carry the consumables needed for the entire time through “on-back” weight. One week mission 40 kg of freeze-dried food for the mission and 150 kg of water for drinking, washing, and food hydration while another 100 kg of water will supply the EVA suits with cooling water.
ROVER STARTING POINT
ROVER STARTING POINT
Vehicle Design Drivers Duration - up to 5 days (one day to the site and one day back) Crew Size- 2 during multi-day exploration operations Capacity - 4 crew members to enable rescue missions or during exploration closer to the base Minimize mass, volume, power, cooling need
ROVER STARTING POINT
2) 1) Unpressurized rover 2) Surface mobility continuum for lunar outpost study. Rover range from location of base.
ROVER SECTION LAYOUT
Constraints Small volume Mobility Large variety of tasks, science and living
ROVER SECTION LAYOUT
Entry Section Suited crew to and from the lunar surface Docking mechanisms Suit maintenance Consumable replacement Small repairs Hygiene Section Body cleansing, shaving, grooming, oral hygiene, hand/face wash Urination/defecation Privacy Portable computers for personal communication Forward Section Command and Control Medical support Working with samples or experimental equipment Communication Group Functions Cleanliness and Disinfection Stowage and waste management Dust mitigation Meal Preparation, Eating, and Clean-up Group Entertainment
Life Support Systems - Primary requirements come from human metabolic loads - The rover life support is required to interface with EVA and habitat life support systems - Carry consumables for the EVA - Return wastes to the primary habitat for recycling - Air System - Atmosphere Selection: Pressure and Composition - Must dock with primary habitat - Minimization of decompression sickness - CO2, Humidity, and trace contaminant control - Fire System for Detection and Suppression, automated Waste System - Preserving the scientific value of the sites - Maintaining cleanliness and acceptable odor control - Returning the wastes to the primary habitat Water System - Potable water supply - Wastewater management - No water recovery system aboard the rover - Source separation for wastewater Heat Rejection - Vehicle power system will be of a significant size - Limited volume means limited surface area for radiators Crew External Tasks - Experiment Deployment and Sample Collection. - Easy interface from outside the vehicle to retrieve equipment and store samples
- Easy access in the vehicle to prepare equipment and sort or evaluate samples - A combination air lock-glove box interface could meet both requirements in minimal space - Repair - Critical systems should be accessible from inside the vehicle as much as possible Pressurized Rover Interfaces - Rover has to support interfaces with the crew, a second rover, and the primary habitat - Make dust mitigation systems a requirement to reduce risks, suitlock type interface looks promising - Need to consider movement and find some way to protect suits and hold them above the surface. - Vehicle to Vehicle Interface - Rover to Rover, important for rescue concept and joint operations - Rover to Primary Habitat Interface, a common docking interface is required, limited surface area on vehicle drives this choice Mechanical or Engineering Drivers - Power Generation must be compatible with the vehicles mobility - Solar arrays may not be ideal for a vehicle that may be venturing into craters and through shadows - Surviving rollover and movement loads - Radiation Protection must protect the entire vehicle - Storm durations are too long to restrain the crew to a small portion of the rover - Integrated design is crucial for mass efficient design
The information under “Rover starting point” is gathered from “Lunar Surface Scenarios: Habitation and Life Support Systems for a Pressurized Rover” - report from NASA, earth and space 2006, and from lecture notes.
For further development of the shelter concept rover prerequisites from different rover solution are collected. All rover dimensions used are inspired by the SPRITE rover concept. SPRITE prerequisites - The cabin has a diameter of 2.5 m and a length of 4.3 m. - The chassis is 2,8 x 4,8 m - One week mission requires 40 kg of freeze-dried food and 250 kg of water - On a 7 day mission the crew will produce approximately 37 kg of liquid waste
Rover design parameters - A hatch is placed in the rover floor - The water and wastewater tanks need to be located in the floor, in center of the module - When the rover is lowered the tanks must be close to ground for satisfactory protection
SPRITE - Rover Concept, University of Maryland, College Park
TABLE OF CONTENTS
Published on Dec 2, 2009
A deployable shelter that utilizes existing resources to shield lunar explorers from the harmful effects of a solar flare event on the lunar...