Lecture on Stealth Aircrafts
Dr. Theodoros G. Kostis CEng MIEE
Radar Concepts – Stealth Concepts Stealth Aircraft Types – Countermeasures HELLENIC MILITARY ACADEMY, GREECE by kind invitation of Prof. N. I. Daras, Vari, 18th MAY 2012.
Authority on Subject Dr. Theodoros G. Kostis CEng MIEE PhD in Software-defined Radar Countermeasures
NATO SET-136 Specialists Meeting in Software Radar NATO SET-160 NCI/ATR in Air-Ground and Maritime Applications Based on Radar and Acoustics
Stealth Airplanes AIR FORCE
AIR COMBAT
Air
Intelligence
Space
Surveillance
Cyberspace
Reconnaissance
Why are they so important?
Stealth Air Combat DETECTION (STEALTH IMPORTANT HERE)
Be first to have Situational Awareness See before being seen
SEE FIRST
MANEUVER TO ENGAGE
Be first to plot a firing solution Use AWACS – Use BVR Observe rules of engagement
PLOT FIRST
ENGAGE
Be first to execute the firing solution
SHOOT FIRST KILL FIRST
EVADE
Increase survivability in all cases
LEAVE FIRST
Stealth Air Combat = Situational Awareness
Battlespace Dominance STEALTH AIRPLANES DENY SITUATIONAL AWARENESS TO ADVERSARY FORCES FOR CRUCIAL AMOUNTS OF TIME LEADING TO BATTLESPACE DOMINANCE
Stealth Supercruise Altitude Maneuverability See First – Shoot First – Kill First
Existence Motivation FOR STEALTH AIRPLANES AVOID BEING DETECTED FOR AS LONG AS POSSIBLE BY CONVENTIONAL AND ADVANCED RADARS WHILE PLOTTING FIRING SOLUTIONS AND FIRING FIRST SHOULD RULES OF ENGAGEMENT PERMIT
What do we need to know
in order to understand stealth aircrafts?
Overview
Radar MASINT Measurement & Signature Intelligence Other important Intelligence Gathering Methods applicable to aircrafts are: • • • • •
HUMINT ACOUSTINT RF/EMPINT IRINT VISINT
(Human Intelligence) (Acoustic Intelligence) (RF/Electromagnetic Pulse Intelligence) (Infrared/Heat Intelligence) (Visual Intelligence)
But Radar MASINT is first line of defence!
Radar Basic Points Radar Primary Early Warning Detection Technology for Aircraft Radar Detection: Threshold Logic Radar Detection Problems: Noise and Clutter Clutter: Unwanted Radar Returns hide Targets
Basic Radar Operation Conventional Radar A system that uses sensors in order to detect targets in azimuth and distance Advanced Radar A system that uses sensors in order to collect data from detected targets in azimuth and distance Data Collection allows Decision Making
Detection and data processing at maximum distance from radar allows more time for decision making
Radar Equation
STX , SRX signal PTX , PRX power GTX , GRX antenna gain
Îť wavelength Ďƒ radar cross section Aeff antenna effective aperture R range from radar to target
Conventional Radar Basics Detection - Tracking - Recognition Threshold Logic
http://www.radartutorial.eu/18.explanations/ex10.en.html
Detected targets cross the threshold
Conventional Radar Basics Detection - Tracking - Recognition Threshold Logic
http://www.radartutorial.eu/18.explanations/ex10.en.html
Detected targets cross the threshold
Pulsed Operation Incoherent or Coherent Operation • Incoherent Radar = Range (Barometer – Atmosphere Research) • Coherent Radar = Range & Doppler (Velocity) (Specific targets)
PRF : Pulse Repetition Frequency PRI : Pulse Repetition Interval
Quality Indices • Detection Probability • Measurement Accuracy • Tracking Performance • Speed Measurement
Detection Probability Detection in Noise radar correclty sees a real target
Error Type Ι (False Alarm) radar displays a nonexistent target
prediction
real target
no target
positive
real positive
false positive
negative
false negative
real negative
Error Type ΙΙ radar does not display a real target
radar correctly does not display any targets
Measurement Accuracy Pulsed Operation
Ideal Pulse has high W and small T
Tracking Performance Range and Velocity Gates - Tracking
Speed Measurement Coherent Operation
• Incoherent Radar = Range (Barometer – Atmosphere Research) • Coherent Radar = Range & Doppler (Velocity) (Specific targets)
AIRCRAFT HISTORY, “F-15 AT THE Gulf War”, Issue 13, Oct-Nov 2001, in Hellenic, periscop@otenet.gr.
Military Radar Types Force Multipliers
• 1. Surveillance Situational Awareness sustains military superiority (AWACS) • 2. RF Tracking (Active, Semi-Active) Guide to target (Missile RF Seeker) • 3. Multifunction Horizon Search & Fire Control Requirements (Aegis AN-SPY-1..3)
The need to reveal(detect), track, classify or identify a non-cooperative target
Non-Cooperative Target No identification collaboration from the target therefore Identification Friend or Foe (IFF) decision is difficult.
Signal to Information Graph
Radar Signal
Pulse Compression
f A/φ Polarisation
PAK-FA Active Electronically Steered Array MAKS
Simple Pulse
Information Content
http://www.ausairpower.net/APA-Flanker-Radars.html
Advanced Radar Basics Coherent Radar
PAK-FA AESA MAKS CHANNELS Source: Principles of Modern Radar Vol.1 , Scitech Publishing.
Beamformimg • Take a Sensor Array • Use constructive and destructive interference for the elements results in • Directional tx and rx
Doppler Processing • Examine all pulses per range bin gives • target speed estimation (range-rate) • Look Down\Shoot Down
F-15 Doppler Radar Example http://www.youtube.com/watch?v=UNqMmN81gT0
Pulse Compression • Transmit a modulated or coded wideband signal • Compress the return signal through filtering results in • Increased Signal Power and Enhanced Range Resolution
SAR • Use the movement of the radar to synthesize a larger virtual antenna than the physical • Obtain terrain imaging
• • • •
ω-k Algorithm Polar Format Range Doppler Chirp Scaling
http://www.geos.ed.ac.uk/homes/s0094539/Research.html
ISAR • Use the movement of the target to synthesize a larger virtual antenna than the physical • Obtain target imaging
• • • •
ω-k (range migration) Polar Format Range Doppler Chirp Scaling
STAP • Suppose a target exists at a location and velocity • Create a filter with custom high gain for that specific case and start attenuating all other signals results in • Detection of weak or slow moving targets by reducing clutter or nulling jammers
Why did we analyse radar?
1st Section Main Points Radar is the longest range scanning sensor The first line of defence that can see through all atmospheric conditions in both day and night Advanced Radar can visualize targets & might also provide recognition (classification and identification) of a target Stealth Airplanes want reduction in detection performance; radar systems want to recover this advantage
Overview
Definition of Stealth General Definition the act of movement in a furtive, concealed, clandestine, unobtrusive or imperceptible manner that provides as low probability of intercept (LPI) as possible by an adversary
Stealth Airplane Specific Definition the special design of an aircraft in geometry, emissions, modulations, coating, fuel and ordnance storage that contributes to low observability (LPI) by an adversary through weak overall signature composition (radar, IR, acoustic, optical)
Therefore stealth includes movement & wake! It is different from hiding (no wake)!
Stealth in High Entropy The outer colours and form or geometry of the asset are changed in an abstract form in order to blend with the environment
Ghillie Suit
Stealth in Medium Entropy Only the outer colours of the asset are changed in order to blend with the environment No form or geometry of asset is changed
Stealth in Low Entropy The outer colours, form or geometry of the asset are changed into a specific object usually in rich natural abundance in order to blend with the environment. Also the behaviour of the copied object is imitated.
Stealth Aircraft RCS = Small Bird RCS
Overview of Stealth Entropy General Entropy
Form-Geometry
Colours
High
Abstract change to other form
Abstract - Many
Medium
Unchanged
Specific to natural environment
Low
Adaptive change to natural objects
Specific to the natural object
Stealth Airplane Entropy
Form-Geometry
Colours
Low
Adaptive change to electromagnetic signature reduction with either emphasis to RCS (F-117) or to maneuverability (F-22, PAK-FA T50)
Specific to natural environment (day – night – land –sea)
Stealth airplane electromagnetic signature is changed to be equivalent to that of a small bird
Stealth Entropy Levels & Speed
As Stealth Entropy increases so does Speed with Low Probability of Intercept by an adversary
Stealth Airplane Basics Low Observability (angled external geometry designed to deflect radar waves making aircraft virtually undetectable to threshold logic)
cone of silence
{http://www.f-16.net/f-16_forum_viewtopic-t-5525-start-510.html}
stealth vs legacy fighter aircraft rcs estimates
Minimize PRX, don’t cross the threshold means survivability, surprise, more room to operate
Stealth & Detection Range • We saw that the basic radar equation can be written in the form which shows the maximum detection range for a given target : rmax
14
PG _ L t 3 4 kT0 BF S N min 2
2
• This means that a reduction in target RCS from (say) 100m2 to 0.01m2 (which on the face of it sounds like a huge reduction) reduces the detection range by a factor of 10 – which doesn’t sound so much. • But it does reduce the time that a defence system has to react. Griffiths H. D., 2000, Lecture Notes, University College London.
Steganography and Stealth or How to conceptualize a Stealth Aircraft
Digital Steganography & Stealth Airplanes The actual identity of the relayed object is hidden by not arousing suspicions about its true colours from adversary parties
Very similar principles of operation Capacity – Security - Robustness
Kostis et al, 2012, Stealth Airplanes: Steganography in the Skies, Scientific Conference in Cryptography in the Armed Forces, Hellenic Military Academy.
Stealth Airplane Capacity A stealth design must be ideally able to provide an rcs which is 1% airframe and 99% on-board electronics and ordnance dependent
{http://gentleseas.blogspot.com/2010/01/russian-indian-pak-fa-t-50-first-test.html}
A stealthy airframe must be able to accommodate the required hidden electronics, fuel and ordnance.
Stealth Airplane Security Stealth Airplane Security (amount of time taken to achieve detection of the stealth airplane’s radar signature by adversary radar stations)
http://mariettascientific.com/understanding/under.htm
Stealth Airplane Robustness Airframe Robustness
(alterations to airframe aerodynamics must not compromise the stealth quality)
How is Stealth achieved? Low Probability of Intercept Radar
PAK-FA AESA MAKS
2nd Section Main Points Airplane Stealth is a factor of visual, infrared, acoustic and electromagnetic signature reductions in active (emissions) and passive (scattering) modes Airplane Stealth observes the principles of digital steganography (capacity, security, robustness) Airplane Stealth means reaction time reduction to the adversary air defence resources
Overview
Fighter Generations 1st (1945-1955) 2nd (1955-1960) 3rd (1960-1970) Phantom 4th (1970-1990) Mirage 2000, F-117 4+ or 4.5 (1990-2000) F-18, Su-33, Su-35, Eurofighter, Rafale • 4++ F-15SE5th (2000-2012) F-35, PAK FA T-50 • 6th (?-?) Sci-fi
• • • • •
• Special – Strategic Reconnaisance SR-71, U-2 http://www.rlm.at/cont/gal14_e.htm http://www.abovetopsecret.com/forum/thread124336/pg1
Fighter Generation I Mig-15
subsonic jet aircraft lack of radar, and WWII vintage weaponry such as dumb bombs and belt-fed machine guns. Aircraft seen in dogfights over the skies of the Korean War typify this generation. Aircraft such as the MiG-15, MiG-17, F-86 Sabre, as well as the de Havilland Vampire, Supermarine Attacker, Saab Lansen and Dasault Ouragan
http://www.abovetopsecret.com/forum/thread124336/pg1
Fighter Generation II Mirage III
aeronautical innovations, such as swept wings, delta wings, and area-ruled fuselages, small radars, air-toair missiles (semi-active radar homing), dawn of Beyond-Visual-Range (BVR) combat
Fighter Generation III Phantom II
Manoeuvrability and traditional ground-attack capabilities Air Combat Maneuvering (ACM) and Dissimilar Air Combat Training (DACT)
Fighter Generation IV
The F-16 is a single-engined, very maneuverable, supersonic, multi-role tactical aircraft. maneuverability = relaxed static stability = fly-by-wire flight control system
Stealth Aircraft Concept Ho 229 Over London just eight (8) minutes after initial detection
Horten Brothers
F-117 Nighthawk & B-2 Spirit
Emphasis in radar & IR signature reduction in an undemanding SEAD environment (Iraq, Afghanistan)
Fighter Generation IV+ Eurofighter – Rafale – Su27
AESA, enhanced digital avionics, high-capacity data link, IRST (FLIR), advanced ordnance
Fighter Generation IV++
F-15 Silent Eagle (Frontal Stealth & Hidden Ordnance and Fuel)
UCAV Reaper - nEUROn
Unmanned Combat Aerial Vehicles Special Type of Stealth covered in depth in another lecture
Fighter Generation V T-50 PAK-FA Advanced Front-Line Aviation Complex
Why 5th Generation Stealth Aircrafts? They are more economic than carpet bombing or using stand-off weapons!
Principle of War Economics Lesser valued friendly resources destroy higher valued adversary resources
F-22 Stealth + Supercruise + Maneuverability + Integrated Avionics = Air Dominance Aircraft, Sensors & Weapons Optimized to Seize and Maintain Total Air Dominance, Air Superiority, Destruction of Enemy Air Defenses, Intelligence Surveillance, Reconnaissance
Advanced Tactical Fighter
F-35 Stealth + Sensors + Integrated Avionics = Lethal & Survivable Strike Aircraft, Sensors & Weapons Optimized for Air to Ground Lethality Interdiction, Strike, Destruction of Enemy Air Defenses, Close Air Support, Time Sensitive Targets, Intelligence, Surveillance, Reconnaissance
Joint Strike Fighter
Comparison of F-16, F-22 & F-35
http://www.afa.org/professionaldevelopment/issuebriefs/F-22_v_F-35_Comparison.pdf
Comparison of T-50 to F-22
SEAD with Stealth
http://www.ausairpower.net/API-VLO-Strike.html
Stealth Tactic 1 Threading the Needle
Countermeasure Home-on Jam Mode
J S
GJAMMER ( RX )GJAMMER ( AMP )GJAMMER (TX ) 2 4
Stealth Tactic 2 Pecking the Lobe
Deception Tactic 1 Ghosting
Using ay least 7 PRFs eliminates this chance Alabaster C. M., 2012, Pulse Doppler Radar, Scitech Publishing http://www.scitechpub.com/catalog/product_info.php?products_id=757
Discrete RCS or 5thG Stealth? Dassault Raffale Eurofighter Typhoon F-15 Silent Eagle Do they perform the same tasks in more economic terms as the F-22, F-35, PAK-FA?
3rd Section Main Points Current Stealth aircrafts are multirole (air-to-air and air-to ground) There are two main types: air dominance and bomber survivability With current stealth technology is Fighter Generation 4+ or 4++ able to perform the same tasks in more economic terms? Deception & Electronic Warfare are important for hiding a Stealth Plane
Overview
Stealth Countermeasures •Bistatic/Multistatic Radar
•Optical Detection
•Wavelength Match
•ISAR & Stealthy Hotspots
•Infrared (heat) Detection
•Over-the-horizon Radar
Bistatic/Multistatic Radar RCS reduction techniques aimed principally at minimising monostatic RCS; bistatic geometry can intercept energy scattered in other directions
Forward scatter radars
Forward scatter geometry can give high RCS, even withtruly stealthy target Passive receiver, immune to interception Can utilise “illuminators of opportunity� (TV Stations, Number Stations)
Space-based Bistatic
Griffiths, H.D., Baker, C.J., 2007, Signal and interference environment in Passive Bistatic Radar, Information, Decision and Control Symposium, Adelaide.
Wavelength Match LOW FREQUENCY RADAR Advantages • Transmitted wavelength may match aircrafts physical dimensions Disadvantages • Issues with resolution, both in azimuth (antenna size) and range (bandwidth) • Also with interference with and from other users of these frequencies
Air Combat & Infrared Detection Infrared Search & Track Systems - IRST See First Shoot First http://www.ausairpower.net/APAFlanker-Radars.html
• OLS (Mig-35) Optical Locator System
Optical & Acoustical Detection Dazzle Camouglage Scheme
Since the F-22 is 25-30 percent larger than the F-15 and 40 percent larger than the F-18, it might be visually detected from ranges on the order of 10 miles. Brinkley, R., 1991, Future US Fighters Are at a Cost/Technology Crossroad," Armed Forces Journal International, p.49.
Sound, especially at low altitude may be a giveaway!
ISAR & Stealthy Hotspots Measuring a Stealth Airplane’s robustness
Stimson G. W., 1998, introduction to Airborne Radar, Scitech Publishing, http://www.amazon.com/IntroductionAirborne-Edition-Aerospace-Systems/dp/1891121014
Over-the-Horizon Radar (OTH) Weather Radar Steganography Robustness Jindalee Operational Radar Network The JORN is so sensitive it is able to track planes as small as a Cessna 172 taking off and landing in East Timor 2600 km away. It is also reportedly able to detect stealth aircraft Most stealthy aircraft are optimized for defeating much higher frequency radars from front-on rather than low-frequency radars from above JORN is reputedly able to detect aircraft wake turbulence. http://www.dsto.defence.gov.au/page/3984/ http://web.archive.org/web/20071116065249/http://defence-data.com/features/fpage37.htm http://www.drtomorrow.com/lessons/lessons6/26.html
How are Countermeasures used?
4th Section Main Points Stealth Aircrafts are not invisible Stealth Aircraft are a worthy adversary to any current relevant countermeasure Optical Locator Systems are important ISAR and OTH/Weather Radar measurements look promising because they look at the way the stealth aircraft modulates its environment
Overview
Main Conclusions Stealth technology is not only radar, but radar is the sensor for early warning purposes Stealth Aircrafts although not invisible yet a worthy adversary to any current relevant countermeasure The main point is to detect the aircraft long enough for air-defence (aerial or groundbased) proper preparation
Lecture on Stealth Aircrafts with sincere thanks to the Hellenic Military Academy
Questions? Further Questions: Theodoros G. Kostis {tkostis@iee.org}