IMPACT OF STEALTH TECHNOLOGY ON AIR DEFENCE

“Stealth refers to a wide range of steps that can be taken to make aircraft harder to detect. There is a payoff and a price.”

- Jay H Goldberg [i]

CHAPTER I

INTRODUCTION

1. The latest trends in military aircraft manufacturing are towards development and incorporation of technology which can provide with means to avoid detection. This enhances its survivability by reducing its radar signature and hence reducing the possibility of being detected by enemy radars. The degree to which this is achieved differs from aircraft to aircraft. Certain aircraft like the B-2 and F-117 have been manufactured with this technology as the basis and are thus referred to as Stealth Aircraft. In other aircraft, stealth is achieved to a lesser degree but it nevertheless helps them in enhancing their survivability against enemy air defence. The day is not far when this technology is likely to find wide spread use in the field of aviation.

2. The dictionary defines stealth as "evasion of notice". Applied to Aerial Warfare, it implies the ability of an aircraft, or platform, to carry out its mission without being detected. Other terms such as "LO" - low observables, or "RO"- reduced observables, have also been used which imply the same thing. The very concept of 'Stealth' conjures up an image of something moving in secretly without being detected. 'Stealth' technology actually is all about the art of making aircraft, missiles and other military systems invisible to detection by the enemy. Development of ‘Stealth’ aircraft and missiles demands that their ability to be detected by enemy sensors be reduced to the maximum extent possible. Touted as a force-multiplier, in modern military parlance, 'Stealth' now is the buzz-word of the day. The publicity it got during the Gulf War, where 'Stealth' aircraft were reported to have operated with impunity, deep inside Iraqi territory enhancing the success of Coalition forces operations, has only played up the enigma attached to the technology. As the Coalition offensive air campaign intensified over Iraq, its planners came to the conclusion that 'Stealth' aircraft could be used very differently, in fact audaciously because of the "inherent degree of air superiority enjoyed by the platform."

3. In the late 1950's the American CIA began sending Lockheed U2 spy-planes over the Soviet Union to take photographs. The U2's flew at 80,000ft (24,000m) to be out of range of anti-aircraft fire, and inadvertently it was found that they were not being detected by Russian radars. These extraordinary planes were little more than jet-powered gliders built of plastic and plywood. On take off they jettisoned their small outrigger wheels from the ends of their wings and they landed on their main retractable wheels in the centre. It was not until May 1960, after more than four years of over flights, the Russians shot one down using new radar equipment belonging to SA-2 surface to air missiles. Even then the U-2 did not receive a direct hit. A missile exploded close enough to put the fragile aircraft into an uncontrollable dive, and the pilot, Gary Powers, had to eject.

4. The success of the U-2s led to highly classified research work in the US, known as 'Stealth', to create a military aircraft that was invisible to radar. The U-2 had gone undetected for so long because it was made of non-metallic materials which absorbed radar waves and not reflecting sufficient amount it back to be picked up by the radar ground station to create a radar signature. The Stealth programme was aimed at designing high-performance military aircraft made of as many non metallic components as possible and the exterior clad with highly absorbent material. The aircraft would almost be invisible to radar and could make most radar-controlled anti-aircraft systems redundant[ii].

5. Development of the Stealth Aircraft started in the early 70's when a number of US aerospace companies were experimenting with different technological designs to elude radar and surface to air missile defence Systems. In 1978 Lockheed's Advanced Development Projects in Burbank, California nicknamed the 'Skunk works' was contracted to turn an advanced demonstrator code named HAVE BLUE, into an operational precision strike aircraft. Using the expertise developed on the U-2 and SR-71 projects they were able to get the first F-117A airborne in about two and a half years. [iii]After being developed under a blanket of secrecy, the high-tech B-2 Stealth bomber was unveiled at the Northrop Company’s manufacturing plant in Palmdale, California, in November 1988.

6. Though the US has been credited with the development of Stealth Technology, the theoretical breakthrough behind Stealth is credited to a Russian Scientist, Pyotr Ufimtsev, Chief Scientist at the Moscow Institute of Radio Engineering, who wrote a paper in 1966 titled “ Method of Edge Waves in the Physical Theory of Diffraction”.[iv] Dr. Ufimtsev’s 1966 paper reworked some of the original 19th century formulae of the British Scientist James Clerk Maxwell. Dr Ufimtsev’s calculations predicted the way a particular geometric shape would reflect electromagnetic radiation. The US Air Force foreign technology division translated the Russian paper which was then used by Ben Rich, the man who ran the “Skunk Works”.

7. Defensive Counter Air or Air Defence is likely to remain an important facet of Air Power in days to come. Effective Air Defence requires that the enemy be detected well in time so as to shoot him down before he can release his weapons. Radar, presently, is the only means of achieving this detection capability. Most 'Stealthy' platforms today aim essentially to deceive enemy radar systems to reach their objectives in relative safety thereby negating the possibility of detection. This in turn creates voids in the Air Defence cover, which in turn makes a country’s Air Defence weak. Thus there is a need to identify methods and technologies that can effectively detect Stealth aircraft and incorporate the same to the Air Defence set up of any country. This would then make it immune to the adverse impact of Stealth on the air defence.

CHAPTER II

METHODOLOGY

Statement of the Problem

1. The dissertation seeks to analyse the impact that Stealth technology has had on the means available for detection of aerial platforms and identify methods, tools and techniques that could be used to counter the same.

Justification for the Study

2. All surveillance sensors face continuous challenge from the countermeasures industry and the two have moved forward in a series of steps to reach the present levels of enhanced capability. 'Stealth' technology is the latest and possibly the most expensive tool towards avoiding detection.

3. Certain amount of stealth characteristics can be inbuilt into most aircraft with relative ease without compromising the economy factor. Integrating stealth into the air arena brings tremendous advantages to the side employing it, tilting the scales in its favour, especially negating the advantage of a good Air Defence cover. Therefore there exists a need to discover technologies that can ‘beat ‘Stealth’.

4. Indian defence industry is in a process of developing and incorporating the latest technologies into its products indigenously. This has been necessitated primarily because of embargos, sanctions and the reluctance of Western powers and developed nations to part with modern technologies. India is still far behind the global players in this arena. Yet, a beginning has been made especially in areas pertaining to Radar Absorbent Paints. In the near future the country might have to confront adversaries with access to stealth technology - own or acquired. Since we cannot aspire to possess indigenously designed stealth aeroplanes, it would be prudent to incorporate means to negate the advantages of stealth aircraft into our air defence systems. This paper will attempt to focus on the measures that exist presently, or those that can be developed in the future to nullify the adverse impact of stealth technology on air defence.

Scope

5. Stealth and related technologies present a vast and largely technical study into the realm of the unknown due to the secrecy surrounding the subject. This paper will examine characteristics of radar reflectivity and some of the 'Stealth' methods adopted to reduce radar signature and focus on possible counters to such techniques which can then be incorporated into the Air Defence systems to make it more effective.

Operational Definitions

6. Certain terms used in this dissertation are explained below:-

(a) Radar Cross Section (RCS). RCS of an object is the fictional area intercepting that amount of power which, when scattered equally in all directions, produces an echo at the radar equal to that from the target[v].

(b) Radar Signature. It is the typical radar reflection of a particular object. It is closely related to its RCS.

(c) Radar Absorbent Materials (RAM). Special materials devised to reduce the reflection of radar beams by absorption of a large part of the incident radiation. Typically these are used as paints or coatings on surfaces to absorb and dissipate incident radar energy.

(d) Over The Horizon Radar (OTHR). Conventionally, most radars utilise transmissions that travel in near straight paths to an object and back. In fact, this property of electromagnetic radiation is an important basis of radar theory. Due to this behaviour, radar cannot be used to detect objects that may be 'below' the horizon ie. out of direct, straight-in line of sight. OTHR utilises radiation that travels to and returns from objects with a reflection each way from the ionosphere. As a result, this radar can be used to detect objects 'over the horizon' at much further distances[vi].

Methods of Data Collection

7. Stealth technology, although based on very elementary laws of physics, is a topic 'under wraps'. Most research into the subject is classified and most of the developments in the field are shrouded in secrecy and are known as ‘Black Programs’[vii]. The nature of the subject imposes limitation on free discussion and published material is hard to come by. However, some information can be gleaned from limited articles available on the subject, and from data available on the World Wide Web.

8. The factual information reproduced in this paper have been collected from the books, journals and the internet as indicated in the bibliography at the end of the paper.

Organisation of the Dissertation

9. The dissertation has been structured under the following heads:- (a) Chapter I - Introduction. (b) Chapter II - Methodology. (c) Chapter III - Stealth Technology. (d) Chapter IV - Aircrafts Using Stealth Technology. (e) Chapter V - Impact of Stealth on Air Defence Systems. (f) Chapter VI - Theory of Anti Stealth Technology. (g) Chapter VII - Anti Stealth Radars. (h) Chapter VIII - Latest Anti Stealth Technology. (j) Chapter IX - Future Trends. (K) Chapter X - Conclusion.

CHAPTER III

STEALTH TECHNOLOGY

“Be extremely subtle, even to the point of formlessness. Be extremely mysterious, even to the point of soundlessness. Thereby you can be the director of the opponent's fate” -Sun-tzu

1. A Stealth Aircraft basically incorporates features that have a low RCS, a low Infra Red (IR) signature and an avionics fit that reduce the probability of its emissions being detected. Till about 1974 stealth design was confined to strategic reconnaissance aircraft like the U2/ SR–71 and drones. Combat aircraft designers stressed on Electronic Counter Measures (ECM) to ensure survivability of the aircraft. However technological advances in the mid-1970s gave rise to the stealth combat aircraft. In air to ground operations stealth dramatically reduces the threat from air defences by more than fifty percent[viii]. Some of the technological advances[ix] that helped design better stealth aircraft are:-

(a) Super Computers. These computers provided for complex modelling and calculations at much greater speeds.

(b) Computer Aided Design and Engineering (CAD/ CAE). CAD/CAE allowed prediction of RCS and design alterations on the computer before constructing models.

(c) Composite Materials. Development of composite material permitted the use of non- less radar reflecting materials in airframes and body structures.

2. An aircraft can be detected and tracked by the physical signs of its presence in the atmosphere. The physical signs are called ‘signatures’. The important signatures[x] which make the aircraft’s presence very obvious to the sensors are:-

(a) RCS. Modern aircraft are designed to maximise performance and power. The performance and power enhancing features include large flat, slab sides to pack avionics, large exposed engines and externally carried weapon / fuel tanks. These factors contribute considerably to increase the RCS and hence they become highly visible to radar. The amount of reflected radar energy depends on the material composition, surface smoothness/ regularity, gaps and cavities in the aircraft frame.

(b) IR Signature. The IR from an aircraft is radiated from the heat of the engine, airframe and the solar reflection from the body.

(c) Electro Optical Signature. This factor depends on the weather/ atmospheric conditions, contrast with the background, and also visible emissions from the exhaust of the engine.

(d) Acoustic Signature. The noise from the engine and airframe as it passes through the air can be used to detect an aircraft manually or visually.

(e) Electro Magnetic Emissions. Emissions from active sensors and transmitters used for communications, navigation and guidance systems, fire control systems and electronic counter measures can easily be used by Electronic Support Measure (ESM) systems to detect the aircraft.

3. Modern sensors and weaponry increasingly utilise one or a combination of the signatures mentioned above to detect and track the aircraft. It is therefore essential for the designers to reduce these signatures to enhance the stealth aspect. Methods to reduce each of the signatures are discussed in the subsequent paragraphs.

Reduction of RCS

4. To be tactically significant, RCS must be drastically reduced. The radar detection range is a function of target RCS, radar parameters and environmental conditions. It varies with the fourth root of RCS. Thus halving the RCS cuts the detection range only by 16 percent. To halve the detection range requires a 93 percent reduction of the RCS[xi]. The primary stealth shaping principle is to avoid efficient radar reflectors like sharp angles, flat surfaces and irregular protrusions. This requires contoured airframes and smoothly blended body parts. Tail fins are small and canted inwards. Taken to its extreme this design would look like a flying wing like in the B-2 Stealth Bomber. The B-2s RCS is a small fraction of the B-1B which in turn is 1/100 that of the Strategic Bomber B-52.

5. Some of the methods presently used to reduce the RCS are as follows:-

(a) Avoiding Large Flat Vertical Surfaces. The most significant means is to avoid large flat vertical surfaces. If vertical fins are necessary, these are canted inwards to alter the direction of reflected radar energy away from its source.

(b) Curved Fuselage Surface. Curving of the fuselage[xii] to deflect reflections away from its source can be carried out to reduce the RCS. The curvature is concave (inwards) as convex (outward) curvature would be reflective. A flat surface has an extremely large RCS if it is 90( to a radar beam. If tilted or 'canted' away from the beam in one dimension, its RCS decreases sharply: reflectivity is reduced by a factor of 1000 (30 db) at a cant angle of just 30(. Additionally, if canting is achieved in more than one dimension by further rotation - both canted and swept back for example - the RCS reduction is much greater. It is now possible to achieve a 30 db (99.9%) reduction at just an eight degree angle[xiii].

(c) Avoiding Discontinuities. Care is taken to avoid discontinuities such as corners and abrupt change of shape/profile by blending and smoothing all wings/fins and surface junctions. This results in removal of geometric discontinuities which could result in wave scattering and increase of RCS.

(d) Shaping Cockpit Canopies and Fuselage. Cockpit canopies and fuselage sides are generally convex in shape. The curved surface reflects radar waves over a wide range of aspect angles. The shape and structure is kept in conformity with the overall design to reduce any stray regions of high reflectivity.

(e) Selection of Wing Sweep Angle. The wing leading edge can be a strong reflector in the forward area. Increase in the sweep angle will increase the amount by which the reflected energy is shifted away from the forward sector, thus reducing the chances of radar detection from the forward quarter. At high angles of sweep most of the reflected energy is deflected at angles away from the critical forward sector. As wing sweep is increased, the delta wing becomes more attractive but, by its long chord it will provide an opportunity for travelling waves to be set up. This is reduced by rounding the wing tips, Both the Lockheed F-117A and Northrop B-2 incorporate the same solution in terms of wing design incorporating wing leading edges which redirect incident radar energy well away from frontal sector and also have short chord lengths to avoid effects of travelling waves.

(f) Intake Structure Designing. Cavities such as air intakes or re-entrant structures have a high RCS, hence while designing an aircraft, the design role of the platform is kept in mind. On a high flying reconnaissance aircraft, the threat may be primarily from below, allowing high RCS features such as inlets and exhausts to be moved on to the upper surfaces where they will be screened from below by the wing.

(h) Radome and Antennae Modelling. Aircraft radomes make two contributions to RCS. One is scattering due to its structure, and the other due to its function related shape. Radar energy arriving at a conventional paraboloidal 'dish' antenna will be gathered and focussed on to the antenna feed as the echo return signal. If the incoming beam is not at the frequency for which the feed was designed it will reflect back travelling back along the same route adding to overall RCS. Flat planar array antennas have a lower RCS. The design used in B-1B in deliberately canted downward to reduce its signatures while electronic beam steering is used to direct the reflected radar energy ahead of the aircraft rather than in the directions of the planar antenna. The other techniques are the incorporation of a ‘band-pass’ radome transparent only to a relatively narrow band of frequencies used by the 'Stealth' aircraft's own radar; incorporation of an electrically switchable radome which can be turned radar transparent at will and the use of composite material rather than metals to make the radome.

(j) Radar Absorbent Structures (RAS). These are specialised structures embodying shape and absorbent materials that are tailored to absorb incident radar energy. In most cases, the radar wave is successively reflected several times into a region similar to an anechoic chamber where due to the numerous reflections, the wave loses energy constantly and only a very infinitesimal portion of it returns to the radar.

(k) Radar Absorbing Material (RAM)[xiv]. Another RCS reduction feature is the use of composite material rather than metals whenever possible. The most common type of composite material used in aerospace is graphite-epoxy-tapes / cloth woven from carbon fibres and embedded in a matrix of epoxy resin. Carbon is a poor conductor of electricity and epoxy resin is an insulator. As a result, the electrical conductivity of composite materials is quite low. Radar energy arriving at a composite panel / structure is unable to set up electric and magnetic currents which radiate the energy thus resulting in an RCS reduction. RAM coatings involve the use of ferro-magnetic materials embedded in a plastic with high-dielectric properties. The high dielectric material slows down the incident radar wave which is then largely absorbed by the ferro-magnetic particles and transformed into heat which is dissipated. Each aircraft has some areas identifiable as hotspots or 'flare-spots'. These are the critical areas which provide the maximum RCS. For example, the inlets, forward facing antennae, wing edges, broad side fuselage etc. RAM applied to these areas make the largest overall reduction in RCS.

(l) Cancelling Radar Signals. There is a possibility of reducing RCS by cancelling the scattered signal by the transmission of a second signal of equal frequency and amplitude but of opposite phase. In theory, this could be achieved by creating a suitable reflector such as an accurately machined cavity of calculated dimensions, designed to create the appropriate echo. Practically, however, it would not be effective as this would take care of only a particular frequency and not others. The incorporation of active means of cancellation would mean onboard generation of the waveforms needed for cancellation. The technical problems of such ventures are formidable. Aircraft mounted sensors would have to measure the frequency, waveform, strength and direction of the signal to be countered and adequate electronics would be required on board to reproduce a similar signal for transmission.

Reduction of IR Signature

6. IR sensors detect thermal images primarily from exhaust gas heat and engines and secondarily from the airframe. The thermal image is particularly strong at supersonic speeds, due to engine reheat. At subsonic speeds, solar reflection and sky shine are more important components of the IR signature.

7. Reduction of the IR signature can be done by a number of methods. Some of the methods[xv] are listed below:-

(a) Better Turbofan Engines. Fan engines produce much cooler exhaust than turbo jet engines which are used in the current fighter aircraft.

(b) Air/ Exhaust Mixing. A two dimensional exhaust system allows cold external air to be drawn in and mixed with engine exhaust to reduce exhaust heat.

(c) Shielding Hot Parts. Curving and shielding engine nozzles can effectively restrict exposure to a narrow angle. This reduces flight efficiency; however a variable geometry nozzle would allow greater flexibility.

(d) Coatings. Coating the tail pipe and airframe with spectrally selective paint would reduce reflections and aerodynamic heating.

(e) Cooling Systems. Closed loop cooling systems reduces thermal signatures from cabin air and electronic systems. It can also be used to cool the airframe, but may increase the weight to an unacceptable level.

(f) Composite Materials. Reinforced carbon-carbon and composites are poor conductors of heat and therefore cooler that metal in an airframe structure.
Reduction of Electro - Optical Signature

8. Currently, electro-optical refers to visibility, through laser or TV sensors. The primary features affecting this signature are contrast with background and visible emissions (mainly engine exhaust). Weather and atmospheric conditions are also important factors, notably in creating sunlight reflections, or “glint”

9. The most effective means of reducing the electro-optical signature is to minimize exhaust contrails, which is addressed via engine design and fuel mixing. Eliminating contrast is problematic due to background variations, but experiments with active camouflage are being conducted. The idea is that photo-electric sensors in the airframe skin would constantly illuminate the surface to match the background. In addition, many steps that would reduce RCS and IR images would also reduce electro-optical detectability, including shaping concepts, composite materials, radar absorbent skins and spectral selective paints (all less reflective).

Reduction of Acoustic Signature

10. The main acoustic consideration is the reduction of jet noise, particularly at supersonic speeds. This is accomplished mainly through steps taken to reduce other signatures; use of higher bypass ratio engines, cooler turbofans, and shielding of engine inlets and exhaust ducts will significantly reduce engine noise. Furthermore, the cleaner, smoother airframe configurations, body blending, advanced materials and reduced number of parts will reduce airframe and secondary engine noise (e.g., gears, blades).

Reduction of Electronic Emissions

11. Communications, various radars, avionics and electronic warfare can betray the location and other data about an aircraft. Stealth in itself will reduce but not eliminate the need for some electronics, such as ECM tools and navigation/ terrain following radar. Advances in computer technology will allow for fewer, better integrated and more passive sensors, with more efficient acquisition, storage and retrieval of mission critical data. Much effort is focused on secure communications. Use of highly directional, narrow beam transmitters, minimizing radiated power, varying frequencies and signal formats, and limiting transmission times are easily implementable measures. A more revolutionary method is laser communications, a virtually undetectable and non-interceptable means of rapid, secure transmission of large amounts of data.

12. Some of the other techniques[xvi] to reduce electronic emissions are as follows:-

(a) Passive Sensors. Non emitting sensors, such as Forward Looking IR radar (FLIR) reduce the need to emit energy for navigation and targeting purposes.

(b) Astro-Inertial Navigation. Optical star tracking systems can be utilised for navigation rather than terrain following radars that need to emit.

(c) Stable Mates. An emitting sensor can be placed on a companion aircraft/ drone/ UAV to detect and locate targets and then transmit the data to the primary vehicle. To an extent AWACS aircraft already perform this function.

(d) Fibre optics. Fibre optic cables are secure from unintentional leakage of electronic noise which in turn reduces emissions.

(e) Smart Skins. Embedding passive sensor arrays in the airframe skin to operate in the optical frequency band can observe the surroundings without the need to emit or radiate.

Design Tradeoffs

13. It is impossible to make a system stealthy from every angle, over all electromagnetic spectrum frequencies, or under all conditions. The prime consideration given to stealthiness, notably the airframe shaping and configuration, carries with it performance tradeoffs. Some of the power features of the combat aircraft will have to be compromised. Major tradeoffs in a stealth design are as follows:-

(a) Design Flexibility. Shaping constraints and internal carriage results in very less flexibility for the designer in configuration of the aircraft and usage of space optimally.

(b) Control/ Manoeuvrability. Fins, stabilisers and control surfaces contribute to RCS and hence their use is minimised. This affects flight performance which would be sub optimal. Stealth aircraft may thus fare poorly in close combat. However reduced detectabilty will generally lessen the need for high angle of attack flight or sharp turn radii.

(c) Payload. Internal or conformal carriage of fuel tanks and weapons limits the aircraft payload carrying capacity and also the mission range.

(d) Speed. Difficulty in containing noise and engine reheat at supersonic speeds limits speed or performance. Aircraft designed today are generally subsonic because of this factor.

(e) Cost. Details of exact costs are hard to quantify since the programme is cloaked in secrecy. However some sources estimate that each F-117 A would cost approximately $42.6 million[xvii] as compared to $13 million for an F-16 fighter aircraft. Such high cost of production would make the stealth aircraft uneconomical even for advanced countries.

CHAPTER IV

AIRCRAFTS USING STEALTH TECHNOLOGY

“A military operation involves deception. Even though you are competent, appear to be incompetent. Though effective, appear to be ineffective” -Sun-tzu

1. Some of the advanced countries already have stealth aircraft on their inventories while other countries are in the process of incorporating this technology into the aircraft that are under development. This chapter endeavours to analyse, some of the stealth aircrafts currently in service in some air forces as also those on the drawing board stage.

F-117A Night Hawk Stealth Fighter Attack Aircraft (USA)

[pic]
Figure -1. F- 117A Night Hawk Stealth Fighter

2. The Lockheed F-117A[xviii] Stealth fighter, also known as the ‘Frisbee’ and the ‘Wobblin' Goblin’ is the worlds first operational combat aircraft designed to exploit the stealth technology. Its development[xix] started in the early 70's. The F-117A employs a variety of technologies[xx] to mask it from detection by enemy radar. A few of them are saw toothed forward and trailing edges, fuselage made of aluminum with titanium, RAM coatings, various other sensors to reduce emissions and also a engine which is low bypass turbofan. Detailed descriptions of these are attached as Appendix A.

B-2 Spirit Stealth Bomber (USA)

[pic]
Figure - 2. B 2 Spirit Stealth Bomber
3. The B-2 Spirit stealth bomber[xxi] is a low-observable, strategic, long-range, heavy bomber capable of penetrating sophisticated and dense air-defence shields. It is capable of all-altitude attack missions up to 50,000ft, with a range of more than 6,000nm un-refueled and more than 10,000nm with one refueling, giving it the ability to fly to any point in the world within hours. Its distinctive profile comes from the unique 'flying wing' construction. The leading edges of the wings are angled at 33 degrees and the trailing edge has a double-W shape. It is manufactured at the Northrop Grumman facilities in Pico Rivera and Palmdale in California.
4. Twenty One B-2s have been delivered the US Air force since December 1993. In the first three years of service, the operational B-2s achieved a sortie reliability rate of 90%. An assessment published by the USAF showed that two B-2s armed with precision weaponry could do the job of 75 conventional aircraft. Stealth features include GPS guided weapons that are carried internally, fuselage with no 90 degree angles, Synthetic Aperture Radar, which sends smaller signals, navigation systems that minimise emissions and a well concealed and cooled engine. Detailed descriptions of these are attached as Appendix B.
Eurofighter Typhoon, Multi Role Combat Fighter (Europe)

[pic]

Fig-3. Eurofighter

5. The four-nation Eurofighter Typhoon is a foreplane delta-wing, beyond-visual-range, close combat air fighter aircraft with surface attack capability. Eurofighter has 'supercruise'[xxii] capability: it can fly at sustained speeds of over Mach 1 without the use of afterburner.

6. The Eurofighter Typhoon[xxiii] cannot be classified as a stealth fighter. However the manufacturers have taken measures to reduce the aircraft's RCS. Some examples of this design include; intakes which are shaped so as to hide the engine compressor blades, the sloped intake sides, fuselage recessed medium range weapons, wing hard point placement and design, radome construction, etc. In addition RAM coats many of the most significant reflectors, e.g. the wing leading edges, the intake edges and interior, the rudder surrounds, strakes, etc. Detailed descriptions of these are attached as Appendix C.

7. The actual RCS is classified. According to the RAF, the Eurofighter's RCS exceeds user requirements and the radar return is likely to be around four times less than the Tornado. BAE Systems stated that Typhoon's RCS is bettered only by the F-22 in the frontal hemisphere and betters the F-22 at some angles. It indicates a real attempt to reduce the Typhoon's radar signature. This should enable a Eurofighter pilot to remain undetected by his enemy until he his significantly closer than he may otherwise be able to achieve.

F/A-22 Raptor - Advanced Tactical Fighter Aircraft (USA)

[pic]
Figure -4. F-22 Raptor

8. The F/A-22 Raptor advanced tactical fighter aircraft[xxiv] is being developed for the US Air Force. The USAF requirement is for a fighter to replace the F-15, with emphasis on agility, stealth[xxv], and range. The first F-22 fighter aircraft was unveiled in April 1997 and was given the name Raptor.

9. The F/A-22 construction is 39% titanium, 24% composite, 16% aluminium and 1% thermoplastic by weight. Features of stealth include Carbon Fibre Composites in building of body parts to resist heat, RAM coatings, sensors that prevent emissions and a low bypass turbofan engine. Detailed descriptions of these are attached as Appendix D.

JSF (F35) Joint Strike Fighter (USA)

[pic]

Figure -5. F 35 JSF

10. The Joint Strike Fighter, the JSF[xxvi], is being developed by Lockheed Martin Aeronautics Company for the US Air Force, Navy and Marine Corps and the UK Royal Navy. The stealthy, supersonic multi-role fighter is to be designated the F-35. The fighter is expected to enter service in 2008

11. Design. To minimise radar signature, sweep angles are identical for the leading and trailing edges of the wing and tail (planform alignment). The fuselage and canopy have sloping sides. The seam of the canopy and the weapon bay doors are saw-toothed and the vertical tails are canted at an angle. These measures help improve stealth

12. Targeting. A Lockheed Martin electro-optical targeting system will provide long-range detection and precision targeting, along with the Northrop Grumman DAS (Distributed Aperture System) thermal imaging system. These systems are passive and hence contribute to the overall stealth.

RAH-66 Comanche Reconnaissance/ Attack Helicopter, USA
[pic]

Figure -6. RAH-66 Comanche

13. The latest addition to make use of stealth technology is Sikorsky's RAH-66 Comanche helicopter[xxvii]. The most advanced helicopter in the world, it emphasizes low emission rotor designs, sophisticated retracting gear, and weapons bay systems. The Comanche RAH-66[xxviii] is the US Army's new reconnaissance and attack helicopter. The first flight of the Comanche took place on 04 January 1996. The armed reconnaissance version is scheduled for initial operating capability in 2009 and heavy attack version in 2011.
14. Stealth features include GPS navigation, shaped fuselage, internal weapon bays, Electro-Optics Sensor System etc. Detailed description is as given in Appendix E.

Have Glass F 16 Upgrade

15. Have Glass[xxix] is the code name for a series of RCS reduction measures for the F-16 fighter. Its primary aspect is the addition of an indium-tin-oxide layer to the gold tinted cockpit canopy. This is reflective to radar frequencies. Adding a radar reflective coating actually reduces the plane's visibility to radar. The reflective layer dissipates these signals instead. Overall, Have Glass reduces an F-16's RCS by some 15 %.

Su-47 (S-37) Berkut - Experimental Fighter Aircraft (Russia)

[pic]

Figure -7. SU 47

16. The Sukhoi Design Bureau of Moscow, Russia has developed the Su-47 (previously called the S-37 Berkut[xxx] or Golden Eagle) fighter aircraft, which first flew in September 1997. Su-47 is in a forward swept wing configuration and uses a highly unstable triplane (with three main lifting surfaces) aerodynamic configuration.

17. The Su – 47 also introduces stealth characteristics in its design. Its fuselage is oval in cross section and the airframe is constructed mainly of aluminium and titanium alloys and 13 per cent by weight of composite materials. The wing panels of the Su-47 are constructed of nearly 90% composites. The forward-swept mid-wing has a high aspect ratio, which contributes to long-range performance. The leading-edge root extensions blend smoothly to the wing panels, which are fitted with deflectable slats on the leading edge; flaps and ailerons on the trailing edge.

Bird of Prey, Stealth Technology Demonstrator (USA)

[pic]

Figure -8. Bird of Prey

18. "Bird of Prey[xxxi]“, a technology demonstrator that pioneered breakthrough low-observable technologies and revolutionised aircraft design, development and production, was unveiled in 2002. The once highly classified project, ran from 1992 through 1999, and was revealed because the technologies and capabilities developed, have become industry standards, and it was no longer necessary to conceal the aircraft's existence.

19. In addition to proving many new stealth concepts, the Bird of Prey program demonstrated innovative rapid prototyping techniques. Developed by the Boeing Phantom Works[xxxii] Advanced Research and Development Organization, the Bird of Prey was among the first to initiate the use of large, single-piece composite structures; low-cost, disposable tooling; and 3-D virtual reality design and assembly processes to ensure the aircraft was affordable to build as well as high-performing.

20. Powered by a Pratt & Whitney JT15D-5C turbofan engine, the Bird of Prey has an operational speed of 260 knots and a maximum operating altitude of 20,000 feet. Boeing's current development of the X-45A Unmanned Combat Air Vehicle (UCAV), technology demonstrator draws directly on its Bird of Prey experience. Some aspects of the UCAV's innovative radar-evading design, such as its shape and inlet, were developed from this project.

Light Combat Aircraft (India)

[pic]

Figure -9. LCA

21. The Indian Light Combat Aircraft[xxxiii] (LCA) has been designed and developed by a consortium of five aircraft research, design, production and product support organizations pooled by the Bangalore-based Aeronautical Development Agency (ADA), under Department of Defense Research and Development Organization. Hindustan Aeronautics Limited is the principal partner in the design and fabrication of LCA and its integration leading to flight testing.

22. The LCA is the world's smallest, light weight, multi-role combat aircraft designed to meet the requirements of Indian Air Force. The LCA is constructed of aluminium-lithium alloys, carbon-fibre composites, and titanium to have a low RCS. LCA integrates modern design concepts and the state-of-art technologies such as relaxed static stability, flyby-wire Flight Control System, Advanced Digital Cockpit, Multi-Mode Radar, Integrated Digital Avionics System, Advanced Composite Material Structures and a Flat Rated Engine.

23. Its small size and the extensive use of composites also make this agile aircraft much stealthier[xxxiv] than its formidable competitors, without having to resort to aerodynamically inefficient compromises as in the case of the F-117 Stealth fighter. The ADA recognised right at the beginning that the LCA programme was depended on five critical technologies: the carbon composite wing, the flight control system, a glass cockpit, high performance multimode radar, and the propulsion system. The development of advanced carbon composites has been very successful in reduction of the RCS and contributing to stealth characteristics.

CHAPTER V

IMPACT OF STEALTH ON THE AIR DEFENCE SYSTEM

1. The advent of stealth technology has reduced the effects of the present day air defence systems to a great extent. Present day air defence systems can deal with conventional fighter aircraft effectively but have no measures against the modern stealth fighters. The recent conflicts in Gulf War, Kosovo, and the Iraq are stark examples of how the stealth aircraft have laid the conventional air defence structures impotent.

2. An air defence system utilises the following measures to detect presence of aircraft in the airspace:-

a) Electronic Detection. b) Visual Detection. c) Passive Measures.

Electronic Detection

3. The basic eyes and ears of any electronic air defence system is its radar. A typical air defence system would have a long range acquisition or search radar which would initially detect the presence of any aerial object in the given area of responsibility. Thereafter it identifies the object either electronically like the Identification Friend Foe (IFF) system; visually with help of observer posts or by other procedural/ tactical methods. Once confirmed hostile by identification methods, it hands over the target to the tracking radar which then accurately calculates the target parameters. These target parameters are then used by the fire control computer to predict the future position of the aircraft where the missile or the projectile fired from a gun would meet the aircraft path to achieve destruction. Based on these parameters the data is generated and fed to the weapon systems, which then fires its ordnance to cause impact with the aircraft at the future position. From the functioning described above, it is clear that one of the key factors for a successful engagement is the ability of the radar to detect a target by the search radar and then track the target by the track radar to generate target parameters.

4. Active Electronic Counter Measures (ECM) are employed by current conventional aircraft using onboard jammers or by employing dedicated ECM aircraft to degrade the defending radars, thereby achieving some advantage over the air defence system. To counter the ECM, modern day air defence systems use Electronic Counter Counter Measures (ECCM) to overcome the difficulties due to jamming and yet achieve detection, tracking and successful engagement. In a hostile ECM environment, the defending radar knows that a threat exists when it experiences electronic jamming and hence switches on its ECCM to detect the target aircraft thereby countering the hostile ECM.

5. Stealth technology on the other hand is more passive and aims at nullifying the capability of detection of the target by the radars thereby undermining the capability of any air defence system. In this case the defending radar does not even know that an aircraft has intruded into its airspace area of responsibility. The inability of the radar to detect the stealth aircraft stalls the other steps involved in utilising the anti aircraft weapons thus paralysing the entire air defence system.

Visual Detection

6. Certain anti aircraft weapon systems employ visual means of detection. These systems are extremely difficult to deceive unlike the electronic means. The weapons too incorporate passive seeking measures, like heat or photo contrast of the target aircraft to home its IR seeking warhead to cause destruction of the intruding aircraft. Shoulder fired SAM systems like the Stinger, Strela and Igla missile systems are classic examples of passive IR seeking missiles. These weapons are difficult to deceive, but there are some counter measures like flares to deceive these IR seeking missiles.

7. Stealth technology counters visual detection and IR missiles too. Firstly it avoids visual detection by operating only at night, and incorporates features that make it difficult to identify during day. Passive IR seeking missiles are rendered less effective by reducing the IR signature of the aircraft to a great extent. Thus both, means of detection and the weapon are rendered ineffective.

Passive Detection

8. Certain passive systems like the Strela 10M SAM-13 missile system utilises the aircraft’s own emissions like its navigational radar, or communication system’s emission or weapon targeting system’s emission to detect the presence of an aircraft. It then utilises the information of the presence of the aircraft to guide its missiles. Stealth technology incorporates features to even reduce emissions from the aircraft by incorporating passive navigational system like the GPS, passive targeting system like the FLIR/ DLIR and satellite communication systems. These measures thereby reduce the chance for passive systems to detect stealth aircraft.

Impact

9. Stealth aircraft have thus rendered present day air defence radars and weapon systems ineffective to deal with this new threat. There is thus a need to search for technologies that can counter the effect of stealth. Incorporating such means in radars and weapon systems to counter stealth will enable engagement of the stealthy targets and make air defence a potent weapon once again.

CHAPTER VI

THEORY OF ANTI STEALTH TECHNOLOGY

“If the enemy leaves a door open, you must rush in." - Sun Tzu

1. No matter how carefully stealth aircraft are crafted, they still reflect minute amounts of radiation[xxxv] back towards the radar. When the aircraft is "pinged" with a radar beam, the pilot alters the plane's orientation and direction to minimise the reflections bounced back towards the receiver. But as it banks or climbs, short bursts of radio waves are reflected in every direction. These are displayed as whispery traces on the radar screen. If radar operators can detect and plot these ghostly traces, they would be able to track stealth aircraft.

2. The F-117A Stealth Fighter should have been invisible to the Serbian air defences. But they shot down a F117A Stealth fighter, during the Kosovo conflict on March 27, 1999. This was a major blow[xxxvi] to the U.S. Air Force. A few nights later, Serb missiles damaged a second F-117A. There were several reasons for the loss of the US plane in Kosovo. The Serbians plugged powerful computers into their air defence system to help generate rough route tracks from the faint, whispery radar returns of the American stealth aircraft. The missiles they fired were optically sighted and automatically detonated to avoid giving off radio signals that would reveal their positions. NATO mistakenly had left three early warning radars intact, allowing Serbian defenders to plot stealth aircraft for three nights before finally shooting one. With stealth weaponry soon to be within the reach of some countries, arms researchers are now frantically designing radar systems that will improve on the Serb techniques. Some are simple. For example, among the best radar systems for revealing stealth aircraft are those based on designs dating back more than half a century. Others are great ideas for the future. Air defences in the days to come may rely on everyday radio and TV stations to detect a stealth aircraft. A day may come when even the local FM[xxxvii] radio channel could be used to defend against stealth.

3. There have been reports in the press that China, Russia and several European and U.S. companies are working on a new radar system[xxxviii] that threatens to render the $40 billion dollar stealth B-2 bomber fleet obsolete by making the radar-evading planes more detectable. Some of the theories that have been propounded, in search for the perfect anti stealth solution, are discussed in the subsequent paragraphs.

Airborne Method[xxxix]

4. A high-flying aircraft furnished with SLAR (Side-Looking Airborne Radar) and/or FLIR equipment is needed to map out the terrain below and to one side, or to the front. If a stealth craft were operating anywhere above the terrain being mapped, a small patch of terrain, which the stealth craft would perforce eclipse, would not be observed on the detecting aircraft’s output screen. That particular spot would appear black or blank, and more or less in the shape of a silhouette of the stealth craft: thereby pinpointing the stealth craft’s position within the field of vision of the detecting aircraft.

5. The initial detection of a stealth craft might be slow, since until the craft were detected, the equipment would have to scan the entire terrain over which the aircraft might be located. However, once that location were pinpointed, the aircraft could be tracked much more swiftly and accurately by zooming in on that location and some of its surrounding area, and scanning only that relatively small part of the field of vision. This would enable the searching equipment to generate much more detailed images of the silhouette of the craft in question, perhaps even identifying the craft by that silhouette. If, in addition, the SLAR or FLIR equipment were furnished with rangefinder capability the exact position of the stealth craft in three dimensions could also be determined. And with modern computers this position could be calculated very swiftly indeed; almost instantaneously.

Satellite Based Method

6. The same method may be used looking down on the battlefield from satellites equipped with radar sensors. Although satellites would be relatively far away from the battlefield hundred miles away, they would be able to remain out of range of most hostile weapons, and thus would not run much risk of being shot down, like the aircraft. Satellites would be able to cover a much larger area of the battlefield, thus being in a position to locate and track virtually all hostile stealth craft.

Surface Based Method

7. Another way of detecting a stealth aircraft would be for surface-based radar installations to scan the sky at high apertures and with high sensitivity, such as is done with radio telescopes. At all times, radio signals from the stars would reach the radar installations uninterrupted. Since the radio map of the stars is by now very well known, it may be assumed that if any star is not observed on the detecting screen or output device, that particular star must be eclipsed by some aircraft flying above the installation somewhere along the line of sight between the installation and that particular star. With very sensitive radio-astronomical equipment, virtually every part of the sky could be covered. Therefore at almost every instant in time, the stealth aircraft would be eclipsing one or another known star.

8. As with the airborne method, although the initial detection of a distant stealth aircraft might be slow, once its location is pinpointed, the aircraft could be tracked much more swiftly and accurately. If more than one detecting installation were used, by a process of triangulation the exact location in three dimensions of all aircraft within the fields of vision of the relevant installations could be determined with great accuracy. With modern computers such a determination could be arrived at almost instantaneously. By accurately observing the time intervals between sequentially-eclipsed stars, coupled with an exact knowledge of the radio-astronomical map, the aircraft’s trajectory could easily and quickly be calculated, especially if powerful computers were utilised to calculate it.

9. Advantages of the Surface Based Method. Surface based method has the following advantages:-

(a) Detecting installations need not emit any radio signals themselves. Thus it would be impossible for hostile aircraft to home in on their radio emissions in order to destroy the installations, which add to their safety factor.

(b) Surface-based installations could also be equipped with powerful SAMs, which could be much larger and possess much greater range and destructive power than air-based missiles for the destruction of hostile stealth aircraft. And since these particular SAMs need not themselves emit any radar signals either, but could merely fly along a narrow beam emanating from the installation which has detected the stealth aircraft, the latter would get no warning that one or more SAMs have been launched against it, and thus would not have a chance to take evasive action.

Technology

10. The main principle behind Anti-Stealth technology may be applied in innumerable other ways also. The most effective results are likely to be achieved by a combination of several methods, so as not to rely on only one method of detecting stealth aircraft. In addition, it will be appreciated that computers can only get more and more powerful as time passes. Radar technology is also likely to advance with time, enabling more and more detail from fainter and fainter backgrounds located farther and farther away to be discerned in less and less time. Thus in five or ten years’ time, it may be possible to detect stealth craft entirely from satellites and/or light and mobile surface-based installations, making it very hard indeed for the forces possessing stealth technology to keep their “stealth” craft stealthy any more. By the year 2015, it may not be possible for any military force to take advantage of current military stealth technology unless some new and yet unknown kind of stealth technology, capable of nullifying the effects of the above described anti-stealth measures, was developed. However, it is unlikely that such new kinds of stealth technology can be developed in such a time frame.

CHAPTER VII

ANTI STEALTH RADARS

“Rapidity is the essence of war: take advantage of the enemy's unreadiness, make your way by unexpected routes, and attack unguarded spots” -Sun-tzu

1. Normally search radars work in a lower frequency and a higher wave length. They operate from the ‘L’ to the ‘C’ band[xl]. Fire control radars operate at higher frequency ranges and lower wave length. These operate generally from the ‘X’ Band onwards. Stealth Technology is designed generally to avoid the Fire Control Radar band altogether and also achieve some stealth in the long range search radar band. A number of radars presently existing can detect stealth aircraft because of certain technological features built into them. Although not aimed at detecting stealth initially, some of them have certain features designed for other purposes that counter stealth by default.

Low Freq Radars

2. Researchers are now working on a simple way to tackle stealth, using technology[xli] that dates back to the 1930s. At that time, radar researchers used radio waves with wavelengths on the order of metres to spot ships and slow-moving planes. Since then, the wavelength of radar has shrunk to less than a centimetre, mainly because shorter wavelength radio waves make radar far more accurate.

3. With long-wavelength radar, the cloak of invisibility begins to unravel rapidly. When the wavelength of a radar beam, is of the same length of the structural elements of an aircraft such as the tail plane, wings or fuselage, they act like aerials, absorbing and then re-emitting the radio waves. The effect is enhanced when the wavelength of the radar is twice the size of the "aerial." In such situations, the radio waves are absorbed and re-emitted efficiently, making the aircraft appear far larger than it really is. The same phenomenon is exploited by chaff, metal ribbons that are used to confuse radar.

4. There are large numbers of Soviet and Chinese made long wavelength radars in use all over the world[xlii]. Enhanced with the latest computers, these can provide a powerful means to spot stealth planes. Some Soviet-made long-range surveillance radars operate at just the right wavelengths to spot stealth aircraft such as the F-117A. On the other hand, long-wavelength radar is usually accurate only to within 50 metres, so air defences must still rely on shorter-wavelength radar to guide a missile to its target. Linking two or more radar systems operating at widely separated wavelengths like the multi-band radar, a defender can overcome the problem of detection of a Stealth Aircraft.

Bistatic Radar

5. Conventional monostatic radar places the transmitter and receiver in the same location, making it simple to locate a plane when detected. One of the ways to pick up flickering signals of a faint radar echo is to separate the transmitter and receiver. Bi-static, or multi-static radar, would position the receiver at a different position from the transmitter. Since stealth aircraft reflects some radar energy away from the transmitter, Bistatic radar[xliii] receiver could conceivably receive the reflection that are deflected away from the transmitter and detect the stealth aircraft. But this arrangement makes it more difficult to compute the location of the aircraft. With high-speed computers, defenders can use these fragmentary data to plot the path flown by stealth aircraft and predict their course with enough accuracy to guide anti-aircraft fire. John Hansman[xliv], a professor of Aeronautics and Astronautics at MIT, explains, “Some stealth aircraft, like the F-117, are specifically designed to have a low RCS to monostatic, or conventional, radars. They are not stealthy to some bi-static configurations.”
Over The Horizon Radars

6. Conventionally, the High Frequency (HF) band is used more for communications than for radar applications. Electromagnetic radiation in this band exhibits significant sky-wave propagation where in ionospheric reflection is predominant and thus HF achieves extremely large ranges of propagation. Radar however, relies heavily on the straight-line propagation of electromagnetic energy to easily resolve range and azimuth. The advent of modern high-speed computers and a better understanding of the ionosphere, has made it possible to utilise the sky-wave in radar applications and yet determine the position of target to a reasonable degree of accuracy. In HF radars, the radar energy is no more restricted to line-of-sight path.

7. OTHR[xlv] directs a powerful sky wave towards the earth's ionosphere. This is refracted and returned towards the earth's surface illuminating a distant patch of terrain or sea. Reflected electromagnetic energy from the targets present in that area, follow the reverse route back to the receiver of the OTHR. Extreme radar ranges of up to 3500 km are possible with such systems[xlvi]. There is, however radar blind zone of about 900 km from the transmitter. Even then, the amount of area that can be put under surveillance by OTHR is of the order of a few million square kilometers. Owing to the nature of reflections from land surfaces, the system is well suited for surveillance of large sea and ocean regions. Lately, modern processing techniques have allowed the overland utilisation of these radars as well.

8. The relatively long wavelength used by the OTHR makes it more effective against small radar targets including Stealth aircrafts. The B2 Stealth Bomber has a fuselage which is half wavelength resonant at just over 7 MHz[xlvii]. General Electric which has operable OTH Backscatter network in the US has tested the capability of the radar to detect stealth aircraft and cruise missiles. The Australian ‘Jindalee Project’ also has similar capabilities using the OTH principle.

Relocatable OTHR

9. Another type of OTHR under development is a relocatable system, reducing the static vulnerability and increasing flexibility of such systems. One such is called the ROTHR which has been developed by Raytheon[xlviii] for the US Navy. With a range of up to 1800 miles (2900 km), it is much smaller than the fixed site OTHR. Designed to enable rapid deployment to prepared sites, it consists of two parts - a transmitter and a combined operations centre or receiver. These can be spaced at sites up to 200 km apart. Being rapidly re-deployable, the ROTHR can be located within a matter of weeks in geographic locations which will allow the establishing of emergency long range coverage of areas not normally within the OTHR umbrella. The accuracy, resolution and cost issues still need to be addressed before such systems can be deployed in large numbers. The features are similar to the OTHR as far as the detection of stealth aircraft is concerned.

Airborne Anti Stealth Radar

10. The Northrop Grumman E 8 Joint STARS Airborne Warning and Control System (AWACS), and the upgraded E-3 Sentry AWACS have the ability to detect stealth aircrafts and even stealthy cruise missiles[xlix]. It uses a technology that combines X and S band radars to detect stealth aircrafts. This technology is also being used in the Cobra Gemini airborne radar, which is under development, by the Central Measurements and Signature Intelligence Office, USA. Another secrecy cloaked programme envisages upgrades to US Air Force’s surveillance aircrafts with the aim of detecting, and initiating measures to kill stealthy cruise missiles. Such systems are likely to be operational by 2010.

Tamara Radar

11. The TAMARA MCS-93 Electronic Intelligence (ELINT) system[l] produced by the Czech company HTT-Tesla Pardubice was in the news[li] extensively during the recent US - Iraq War for its claimed capabilities to detect stealth. The TAMARA ELINT system was initially designed to detect, identify, locate and track tri-service radars, Selective Identification Feature (SIF) transponders, IFF interrogators, Tactical Air Navigation (TACAN) systems, distance measuring units, jammers and data transmission networks operating in the 0.82 to 18GHz frequency range. The equipment is available in mobile, fixed-site and platform integrated configurations.

12. Being a passive system it can pick any kind of electronic transmission made by the stealth aircraft either for navigational or targeting purposes and thus fix its location. The potency of this system has not been tried as such but theoretically it can pick up the transmission however small made by the stealth aircraft. Claims on the similar lines are also being made by the manufacturer. The system was said to have been used by the Serbs[lii] to detect the stealth aircraft in Kosovo. It was also reportedly sold to Iraq. Authorities in the Czech Republic have also investigated[liii] whether there was an attempt by Bulgarian arms dealers to broker a deal for five purported anti-stealth radar to Iraq. US commanders during Operation Enduring Freedom in Iraq feared[liv] the system would be in the Iraqi hands which could have jeopardised the operations of Stealth fighters and bombers.

Conclusion

13. From the description of the radars above it is evident that Stealth Aircraft can still be detected with the right kind of technology. However there is till a wide chasm that has to be bridged to convert ideas/ innovation into reality.

CHAPTER VIII

LATEST ANTI-STEALTH TECHNOLOGIES

1. The rapid developments in science and technology and the advancement in radar science have made it possible to increase the frontiers of research. The increase in computation capabilities with the help of increased processing power of modern computers has further helped in exploring newer technologies to detect stealth. On older TV sets, when an airplane goes over the house, a reflective wave from the aircraft ends up interfering at the antenna, and lines and artifacts can be seen on the screen. This phenomenon is being used by some to detect aircrafts. Some of the latest developments are discussed in this chapter.

The Chinese Passive Coherent Location (PCL) System

2. China may be in the process of forging a PCL system[lv]. The new Chinese system, by contrast, simply monitors civilian radio and television broadcasts and analyses the minute fluctuations caused by the passage of an aircraft through commercial wavelengths. Relying on a network of receivers similar to television aerials, the "silent" PCL system does not emit a tell tale radar signal and is therefore much harder to locate and destroy. Further details of this system are not available owing to the secret nature of the project.

The Silent Sentry (USA)
[pic]
Figure 10. Silent Sentry Test Bed

3. Newer anti-stealth technologies use the electromagnetic "noise" of cluttered airwaves to hunt stealth aircraft. After 15 years of research, Lockheed Martin Mission Systems[lvi] of Gaithersburg, USA has released details of Silent Sentry[lvii]. This system dispenses with conventional radar transmitters and instead exploits broadcasts from TV and FM radio stations.

4. Any aircraft flying through a soup of music and electronic chit-chat generates patterns of reflections. Using conventional radio receivers and powerful parallel processors, Silent Sentry sifts the soup looking for these reflections. From their angles of arrival, time delay and Doppler shift relative to the un-scattered broadcasts, Silent Sentry can pinpoint a target's location and plot its position on a three-dimensional electronic map.

5. In tests around Baltimore-Washington international airport, Lockheed Martin researchers followed targets of less than 10 square metres at ranges up to 190 kilometres, using an antenna just three by eight metres. The system can even screen out stationary targets such as tall buildings or radio masts, while still picking out helicopters by the Doppler-shifted reflections from their rotating blades. With no transmitter of its own, Silent Sentry can't be detected and destroyed by radar-seeking missiles. Since FM radio beams hug the globe, Silent Sentry should be good at detecting low-flying aircraft and cruise missiles, or even the high-speed boats. Although the technology isn't yet good enough to target an aircraft with a missile, there are plans to link it to a second, more accurate radar system.

The Roke Manor system

6. A stealth detecting system announced in November 2001 was developed at Roke Manor Research[lviii], a British defense firm based in Romsey, Hampshire. It does not try to detect emissions from careless stealth aircraft like the ELINT radars like the TAMARA as seen in the previous chapter, which by itself is a half-hearted and easily-countered move. Instead, it attacks the stealth system itself by detecting the radar waves that do reflect off it.

7. The Roke Manor system uses the principle being used by the Bistatic radars. The problem becomes one of scale and coordination when the transmitter and receiver are located at different places. The stealth aircraft will be visible only if ideal alignment exists so that the transmitter bounces a signal off the stealth aircraft to the receiver. Stealth aircraft, however, are vulnerable from a very small subset of possible combinations of angles. The Roke Manor system solves that problem with computing power and some creative thinking. Building radar every few miles to solve the first problem is prohibitively expensive. However, radar is simply an application of radio, and in today’s wireless age, radio waves surround us. In particular, in industrialised nations, cell phone towers can be found every few miles. Telephone companies also know exactly where the towers are located, and have telephone lines hooked up to them, facilitating communication.

8. In effect, the Roke Manor researchers have envisioned the use of cell phone towers as an extremely dense network of radar transmitters and receivers, interconnected via communications links. The sheer number of cell phone towers makes detection much easier than with solitary radar sites. Stealth is very effective against monostatic radars. However if a multi static radar, with a number of sources, can excite the target from a wide range of angles, and a multiplicity of receivers in many locations can receive the reflections , one can get around the stealth target’s redirection capabilities. It is highly likely that an incident wave from a cell tower will be redirected towards one or more receivers.

9. Having gotten around the stealth aircraft’s redirection capabilities, the system then puts together all the data from the cell phone towers. Until recently, this was not possible. However, increased computational power and advanced signal processing techniques have made it possible to sort through all the signals and form a coherent radar picture. Ironically, the further development of the same computing technology that originally made stealth possible has now made it possible to detect stealth aircraft.

10. Given a cell phone network, massively parallel computers, and the Roke Manor software, a lot of detection as far as uncovering the stealth can be achieved. All kinds of information can be obtained from the return signal if it can be processed sufficiently. From the Doppler shift of the returned signal, the aircraft velocity can be found and with sensitive systems, frequency effects such as engine rotation or structural vibration can be deciphered. By having several receivers or different imaging angles, the image of the target can be reconstructed. These data further reduce the effectiveness of stealth technology. While stealth has always returned a small signal, even to monostatic radars, that signal is so small that it is usually filtered out either by the radar scope or by the operator. However, with velocity and shape information, as well as software specifically designed to detect the inconsistencies that give away a stealth airplane, it becomes considerably easier to detect stealth aircraft. Defense researchers and experts in the defense industry also seem to agree that the technology is sound. Some believe this to be a natural development in radar technology.

11. Limitations of Roke Manor System. The technology is widely acknowledged to be feasible, and Roke Manor claims to have working prototypes. However, the principle of bistatic radar is neither a miracle nor a disaster that renders worthless decades of stealth research. It is yet another battle in the war between armaments and armor. The Roke Manor System is not a very mobile technology. The cell phone towers are in fixed locations. While it would be close to impossible to destroy all of them, they are susceptible to jamming just like conventional radar. Therefore, Stealth might very well be a technology with a very short half life.

CHAPTER IX

FUTURE TRENDS

“We will either find a way or make one.” -Hannibal

1. Anti Stealth Technology has been the focus of many scientific and defence research establishments in the quest for better and effective methods to counter the evasive stealth characteristics displayed by the frontline combat aircrafts. A large number of projects are currently being researched, the knowledge of which is restricted to the secret few. This chapter will attempt to bring out the areas in which current research is in progress. The material available is scarce and not validated but gives an insight into the direction in which the researches are progressing. Research and developments are also being reported in the some areas to improve stealth even better. Counter measures to the newer stealth technology is yet to be fielded.

Space

2. There are plans to move anti-stealth radar into space. At the moment, stealthy aircraft aren't shaped or treated to be invisible from above so they can be picked up by high-flying aircraft[lix] "sentries" packed with high power radar. The next step is to move long-wavelength or multiband radars into space. For example, the American military Discoverer 2 satellite constellation is expected to grow from a system designed to track moving ground targets to one capable of stealth detection.

Millimetric Wave Radars

3. Some Russian designers are known to have experimented with high-powered millimetre wave radars (with frequencies around 94 GHz) in order to outflank stealth at the other end of the radar spectrum. The challenge here is likely to be the high quantum of atmospheric absorption in this part of the electromagnetic spectrum which would severely restrict the range of any such system. In fact such frequencies are preferred for low probability of intercept radar applications on board stealthy platforms for the very short ranges of their sidelobes due to atmospheric absorption.

Laser Radar (LIDAR)

4. One possible solution to detect Stealth could be Laser Radar also termed Lidar. Developed as a means of detecting missile launches from space, this is also being effectively utilised by many companies as a seeker for air to surface weapons. Coherent Doppler Lidar has been used to detect and image aircraft wakes and air turbulence. However, although large air movements can be detected at up to 32 km, aircraft wakes are smaller and detection ranges may not be tactically useful. Focusing the Lidar beam over long distances also appears to be difficult. Also, the challenge is not to merely illuminate the target with the beam but to ensure that the reflected signal is consistent and can be detected. Yet, it is believed that work on green lasers since the late 1980s has shown that a Lidar anti-aircraft detection system is possible and has anti-stealth capabilities.

Stealth Plasma

5. Plasma[lx] is ionized gas particles and plasma flow is a flow of ionized gas particles. Ion is an electrically charged particle or group of atoms. Plasma cloud is a quasi-neutral (total electrical charge is zero) collection of free charged particles. The vast majority of matter in the universe exists in plasma state. Near the Earth plasma can be found in the form of solar wind, magnetosphere and ionosphere. The main property of plasma is its frequency. A device for generating plasma is called a Plasmatron. This device generates the temperature plasma.

6. If an object is surrounded by a cloud of plasma, several phenomena’s are observed when the cloud interacts with electromagnetic waves radiated by enemy radar. First, absorption of electromagnetic energy occurs in the cloud; since during plasma penetration it interacts with plasma charged particles, pass onto them a portion of its energy, and fades. Second, due to specific physical processes, electromagnetic wave tends to pass around plasma cloud. These phenomena result in the dramatic decrease of the reflected signal. An effective plasma stealth device would offer control over the frequency of plasma, which would be adjusted depending on the frequency of the hostile radar signal. Since there is no way of controlling chemical composition of the plasma stealth "shield" what can be controlled is the level and density of ionization[lxi].

7. The Keldysh Research Center[lxii] in Russia has developed a new technology which allows dramatic decrease in aircrafts' radar observability. Russian approach to LO technologies is completely different from US Stealth and offers complete furtiveness of the protected object at a significantly lower price, lower weight and lower power consumption.

8. American approach to Stealth technology applied on B-2, F-117A, and fifth generation fighter F-22 "Raptor" is based on the principles of reducing the RCS by avoiding all possible elements of the structure which could reflect electromagnetic radiation. In order to minimize reflected radiation RAM is also applied to the surface of the structure. The main drawbacks of this kind of Stealth technology are its negative effects on the flight and agility characteristics of the stealth aircrafts. Russian scientists[lxiii] have approached the issue from a different direction. Ionised gaseous Plasma is formed around the aircraft which prevents radars from seeing it. Thus, aero dynamical characteristics of the plane itself do not suffer. Without interfering with technical characteristics the artificially created plasma cloud surrounding the plane guarantees more than hundred times decrease in its observability[lxiv].

9. Russian research into plasma generation is spearheaded by a team of scientists led by Anatoliy Korotoyev, director of Keldysh Research Center. The institute has developed a plasma generator weighing only 100 kg[lxv], which could easily fit onboard a tactical aircraft. For the system to work there has to be an energy source on the aircraft that ionizes the surrounding air, probably at the leading surfaces. Since the resulting ions are in the boundary layer of the aircraft, they follow the airflow around the plane. The plasma generator has been reportedly tested first on flying models and then on actual aircraft. The new Su-37 strike aircraft utilizes the system and is likely the first production combat aircraft with this critical technology.

10. Work on plasma generation is not the purview of Russia alone, though. In the US, the research[lxvi] in this field is being conducted by Accurate Automation Corporation (Chattanooga, TN) and Old Dominion University (Norfolk, VA). French companies Dassault (Saint-Cloud, France) and Thales (Paris, France) are jointly working in the same area as well.

11. At present there seems to be no known antidote to the plasma version of Stealth. As and when this technology is widely used counter measures are bound to be found.

CHAPTER X

CONCLUSION

Stealth Technology

1. Stealth Aircraft incorporates features that reduce the probability of it being detected. Till about 1974, stealth design was confined to strategic reconnaissance aircraft and drones. Combat aircraft designers stressed on ECM to ensure survivability of the aircraft. However technological advances in the mid-1970s gave rise to the stealth combat aircraft. In air to ground operations stealth dramatically reduces the threat from air defences by more than fifty percent. Technological advances have helped scientists design better stealth aircraft over the years.

2. It is however impossible to make a system stealthy from every angle, over all electromagnetic spectrum frequencies, or under all conditions. The prime consideration given to stealthiness, notably the airframe shaping and configuration, carries with it performance tradeoffs. Some of the power features of the combat aircraft will have to be compromised.

3. Some of the advanced countries already have stealth aircraft on their inventories while other countries are in the process of incorporating this technology into the aircraft that are under development. A number of modern day state of the art fighters have been built with a large number of features enabling stealth. The day is not far when this technology will be widely used by aircraft builders.

Impact of Stealth Technology

4. The advent of stealth technology has reduced the effects of the present day air defence systems. Present day air defence systems can deal with only conventional fighter aircraft and have no measures against the modern stealth fighters. The recent conflicts in Gulf War, Kosovo, and the Iraq are stark examples of how the stealth aircraft have laid the conventional air defence structures impotent. Therefore, one of the primary concerns of military specialists today is to find a way to overcome the advantage gained by the enemy who uses Stealth Aircraft to neutralize air defences.

Anti Stealth Measures

5. No matter how carefully stealth aircraft are crafted, they still reflect minute amounts of radiation back towards the radar. During its manoeuvre, short bursts of radio waves are reflected in every direction. These are seen as whispery traces in the radar screen which when connected to powerful computers can indeed trace the path of Stealth Aircrafts. This technology was exploited by the Serbs during the Kosovo War. Radar technology is also likely to advance with time, enabling inference of more details from fainter backgrounds. In five or ten years’ time, it may be possible to detect stealth craft entirely from satellites and/or light and mobile surface-based installations, making it very hard indeed for the forces possessing stealth technology to keep their “stealth” craft stealthy any more.

6. Stealth Technology is designed generally to avoid the Fire Control Radar band altogether and also achieve some stealth in the long range search radar band. Some of presently existing radars like the Low Frequency Radar, Bistatic Radar, OTHR, ROTHR, TAMARA ELINT Radar, and certain Airborne Radars can detect stealth aircraft because of certain technological features built into them.

7. Anti Stealth Technology has been the focus of many scientific and defence research establishments in the quest for better and effective methods to counter the evasive stealth characteristics displayed by the frontline combat aircrafts. A large number of projects are currently being researched, the knowledge of which is restricted to the secret few.

8. The rapid developments in science and technology and the advancement in radar science have made it possible to increase the frontiers of research. The increase in computation capabilities with the help of increased processing power of modern computers has further helped in exploring newer technologies to detect stealth. Research is currently on to exploit the interference caused by flying aircrafts with the TV and FM radio stations to locate stealth aircrafts. Interference with the cell towers of mobile telephones are also being exploited to find a key to detect Stealth Aircraft.

9. Some experts have expressed serious doubts on the long term efficacy of anti stealth techniques. They warn that counter measures may be developed that they may be operational even before new Anti Stealth techniques are operational. Opinion on the subject, however, is extremely divided with each side claiming the upper hand. What actually happens is nobody’s guess. For some time yet, the cat and mouse game of stealth and counter-stealth will continue.

10. This paper has attempted to show case the capabilities of the worlds leading Stealth Aircraft and the systems that could be used presently to overcome stealth. It has also attempted to give a brief insight into the future technologies that might be put into use. How far-reaching are the implication of this anti-stealth technology? As with all military technologies, it depends on the particular application. Owen Cote, Associate Director and Principal Research Scientist of MIT’s Security Studies Program[lxvii], explains, “Even if any system works, it wouldn’t be useful if you couldn’t shoot the aircraft down. You’d have to find some way of guiding a missile very close to the target before infrared or illuminating radar could achieve a lock on the aircraft.” Thus apart from detection one also has to look into the weaponry part of it.

Recommendation

11. Indian defence establishment including its research laboratories need to carry out further research into this subject to incorporate stealth features in its planes and anti stealth features in its air defence weapons. The anti stealth weapons and radars may not be available in the open international market for a long time to come due to its high secrecy and implications. Hence the need to develop them indigenously.

12. We have today a large number of old soviet era long range radars that are presently being replaced. These can be put together with powerful computers to detect stealth aircrafts for the present, till workable technologies are invented by our scientific establishment. The need of the hour is to think in this direction and have a long term plans to incorporate emerging technologies to beat the stealth. The military and the civil establishments need to work together to accomplish these aims and convert them into reality.

SELECTED BIBLIOGRAPHY

1. Books.

(a) Richardson, Doug. Stealth Warplanes, London: Salamander Books Limited, 1989.

(b) Skolnik, Merrill I. Introduction to Radar Systems. Singapore: McGraw-Hill Book Co, 1981.

2. News Paper Reports/ Papers.

(a) ‘New Radar Could Defeat Stealth Technology’. Reuters, Jun 2001.

(b) Nicolai Novichkov. ‘Russian Plasma-Based Stealth Better, Cheaper Than US Version?’,ITAR-TASS Information Agency, Moscow, Jan 20, 1999.

c) Cyrus Mehta and Ardeshir Mehta. Paper presented on ‘Anti-Stealth Technology’, Dec 15, 1998.

3. Magazines and Periodicals.

(a) Barry M. Blechman and Ivan Oelrich. ‘B2 Stealth Bomber Costs in Perspective’, Strategic Review, Winter 1996.

(b) Bill Sweetman, 'Lifting the Curtain - Stealth Techniques Detailed', International Defence Review, Volume 25, Issue 2, Feb 1992, pp. 159 .

(c) Benjamin F. Schemmer. ‘Will Stealth Backfire’? Armed Forces Journal International, January 1991.

(d) Defence Journal (Vol.XX, No.9-10,) 1994. ‘US Took Idea from Russians’. The Guardian London.

(e) David J. Lynch. ‘How the Skunk Works Fielded Stealth’, Air Force Magazine, Nov 1992.

f) David Fulghum. ‘Seek and Destroy’ New Scientist, Nov 1999.

(g) Dan Boyle, 'Countering Stealth - Progress in OTH Sky Wave Radar', International Defense Review, Volume 23, Issue 6, Jun 1990, pp. 712.

(h) Fulvio Bessi, Francesco Zacca. ‘Introduction to Stealth’, Military Technology, May 1989. (j) G. Jacobs. ‘Airborne Radar versus Stealthy cruise Missiles’, Indian Defence Review.

k) James P. Coyne. ‘A Strike by Stealth’, Air Force Magazine, Mar 1992.

(l) James W. Cannan. ‘The Future is Stealth’, Air Force Magazine, Jan 1991.

(m) Jay H Goldberg. ‘The Secret Shape of Things to Come’. National Defense. Jul –Aug 1989.

(n) John. A. Adam, ‘How to design an Invisible Aircraft’, IEEE Spectrum, Apr 1988.

(o) Julian S Lake. ‘Stealth’. DS 26 Jan 1989.

(p) Stanley W. Kandebo. ‘Boeing Sikorsky Findings Underscore RAH 66 Stealth’. Aviation Week & Space technology, 19 Jul 1999.

(q) Martin Streetly. ‘Hide and Disguise’, Jane’s Defence Weekly, 17 Mar 1990.

(r) Michal Fiszer and Jerzy Gruszczynski. ‘Russia Working on Stealth Plasma’, Journal of Electronic Defense, Jun 2002.

4. Electronic Sources.

(a) Jane's Air & Systems Library CD-ROM 2000-2001. ‘ Tamara ELINT System’.

(b) ‘Stealth Technology. Flying in Invisibility’. 28 Jun 2003. .

(c) ‘The Stealth Fighter’. 25 Jul 2003. .

(d) ‘F117- A’. 29 Jul 2003. .

(e) ‘The Stealth Fighter’. 25 Jul 2003. .

(f) ‘B-2’. 29 Sep 2003. .

(g) ‘B 2 Stealth Bomber’ 15 Oct 2003

(h) ‘Eurofighter’. 29 Sep 2003. .

(j) ‘Typhoon’ < http://www.eurofighter.star streak.net/Eurofighter/ structure. html>.

(k) ‘F22 Raptor’. 29 Sep 2003. .

(l) ‘F22’ 29 Sep 2003. .

(m) ‘JSF’. 29 Sep 2003. .

(n) ‘Comanche’. 29 Sep 2003. .

(o) ‘Have Glass’, 29 Sep 2003 < http://danshistory.com/f16.html>.

(p) ‘Berkut Su 47’. 29 Sep 2003. .

(q) ‘Boeing Unveils Bird of Prey’, 15 Aug 2003 .

(r) Bird of Prey’ 15 Aug2003 < http://www.boeing.com/phantom>

(s) ‘Light Combat Aircraft’ 16 Oct 2003.

(t) C. Manmohan Reddy. ‘The LCA success’ Frontline Volume 20 - Issue 05, March 01 - 14, 2003

(u) US DoD News Briefing by Maj. Gen. Bruce Carlson, USAF, Director of Operational Requirements, on 20 Apr 1999. < http://www.defenselink.mil/news /Apr1999/t04211999 t420carl. html>

(v) David Fulghum. ‘Stealth Aircraft - Nowhere To Hide’, 25 Aug 2003 < http://www. globeandmail. com/ gam/ Science /20000119 /RV19STEA.html>

(x) Tao Yue. ‘Cell phones uncover stealth bombers.’ Aug 2003 < http://www-tech.mit.edu/Info/legal.html>

(y) ‘New Radar Could Defeat Stealth Technology’. 18 Sep 2003

(z) ‘Czech Anti-Stealth Radar may be Operating in Yugoslavia’ Reuters, April, 1999,18 Sepr 2003. < http://www.aeronautics .ru/tamara02.htm>

(aa) Mr. Kenneth H Bacon, Assistant Secretary of Defense, US DoD News Briefing on 13 Nov 1997. < http://www.fas.org/news/iraq/1997/11/index.html>

(ab) Sean Rayment. ‘US fears Iraq Radar can See Stealth Plane’, 14 Aug 2003 < http://www.telegraph.co.uk /htmlContent.jhtml /archive/1999/03/ 30/wair130.html>.

(ac) ‘China can see US stealth Aircraft’ 16 Sep 2003 http://www.the-times.co.uk/news/pages/tim/99/11/30/x-mfgnusa02001. html? 1984

(ad) ‘US tactics and worries in Iraq Stealth’ 25 Aug 2003 < https://www. aviation week.com/

(ae) David Fulghum. ‘Stealth Aircraft - Nowhere To Hide’, 25 Aug 2003 < http://www.globe andmail. com/ gam/ Science /20000119 /RV19STEA.html>

(af) ‘Plasma’. 16 Sep 2003 70% is comprised of Carbon Fiber Composite (CFC). Additionally a significant proportion of the structural members are also constructed from CFC. The wing leading edges, fin leading edges, rudder trailing edge and wingtip / ECM pods are made from a Lithium-Aluminium alloy imparting superior strength to weight than standard aluminium alloys. Additionally these areas are also coated with RAM. Overall only 15% of the Eurofighter shell is metal, while 40% of the structural weight comprises CFC.

4. Radar. The radome is comprised of a complex layered Glass Fibre Reinforced Plastic (GFRP) and various Frequency Selective Surface (FSS) materials. FSS materials are composed of a precisely defined array of metallic elements contained within a conducting frame. The use of these materials results in a reduction in the transmission of ‘all out of’ band frequencies. Therefore the radome can be transparent only to those frequencies and polarisations used by the aircraft's own radar. This of course leads to a reduction in the aircraft's RCS, from all frontal aspects at least.

5. Communication. The secure radio systems as well as the data link (providing the off-board target information) are said to incorporate Low Probability of Detection and Exploitation (LPI) features. In addition the aircraft features automatic Emission Controls, or EMCON. Although these precautions do not prevent an opposing aircraft from detecting EM emissions from the Typhoon they should limit the likelihood of such interception or their subsequent utilisation.

6. Targeting. A FLIR is mounted on the port side of the fuselage, forward of the windscreen. The FLIR operates in both 3 - 5 and 8 - 11 micron spectral bands. When used with the radar in the air-to-air role, it functions as an Infrared Search and Track system (IRST), providing passive target detection and tracking. In the air-to-surface role, the FLIR performs target acquisition and identification, as well as providing a night flying aid.

Appendix D

(Refer to paragraph 9 of Chapter IV of the dissertation)

F/A-22 RAPTOR - ADVANCED TACTICAL FIGHTER AIRCRAFT (USA)

1. The first F-22 fighter aircraft was unveiled in April 1997 and was given the name Raptor. In September 2002, the USAF decided to redesignate the aircraft F/A-22 to reflect its multi-mission capability in ground attack as well as air-to-air roles. During flight tests, the F/A-22 has demonstrated the ability to 'super cruise', flying at sustained speeds of over Mach 1.5 without the use of afterburner.

2. Design. The F/A-22 construction is 39% titanium, 24% composite, 16% aluminium and 1% thermoplastic by weight. Titanium is used for its high strength-to-weight ratio in critical stress areas, including some of the bulkheads, and also for its heat-resistant qualities in the hot sections of the aircraft. Carbon fiber composites have been used for the fuselage frame, doors, intermediate spars on the wings, and for the honeycomb sandwich construction skin panels. All these measures combined together provide the stealth required.

3. Radar. The AN/APG-77 radar uses an active electronically scanned antenna array of 2,000 transmitter /receiver modules, which provides agility, low radar cross-section and wide bandwidth.

4. Navigation and Communication. The communications, navigation and identification system includes an intra-flight data link, joint tactical information distribution system (JTIDS) link and an identification friend or foe (IFF) system. The aircraft has laser gyroscope inertial reference, a global positioning system and a microwave landing system. Most of these systems are passive thus reducing the emissions and hence an improvement in stealth characteristics.

5. Engine. The F-22 is powered by two Pratt and Whitney F119-100 engines. The F119-100 is a low-bypass afterburning turbofan engine. The low by pass engine makes it more efficient with less heating thus reducing the IR signature.

Appendix E

(Refer to paragraph 14 of Chapter IV of the dissertation)

RAH-66 COMANCHE RECONNAISSANCE/ ATTACK HELICOPTER, USA

1. The Comanche RAH-66[lxxv] is the US Army's new reconnaissance and attack helicopter. Stealth features are discussed below.

2. Design. The RCS has been minimised, primarily by the precisely shaped fuselage and internal weapons configuration. The helicopter has a composite five-bladed bearing less main rotor and a fantail anti-torque system.

3. Weapons. The Comanche carries its weapons internally to reduce RCS and has a weapons bay on each side of the fuselage. The missiles are mounted on the weapon bay doors, which open sideways.

4. Fire Control and Observation. The Comanche is equipped with a suite of passive sensors to reduce emissions and consequently achieve stealth. Lockheed Martin Missiles and Fire Control is developing the Electro-Optics Sensor System which comprises electro optical target acquisition and designation system, including solid state TV sensor, two colour laser rangefinder/designator and second-generation focal plane array long-wave FLIR (forward-looking infrared); and Night Vision Pilotage System with a second FLIR. These measures ensure targeting without much emission.

5. Navigation. The helicopter has a GPS to help navigate thus reducing any emission for navigational purpose.
-----------------------

[i] Jay H Goldberg. ‘The Secret Shape of Things to Come’. National Defense. July –August 1989.
[ii] ‘Stealth Technology. Flying in Invisibility’. 28 Jun 2003. [iii] ‘The Stealth Fighter’. 25 Jul 2003.
[iv] Defence Journal (Vol.XX, No.9-10,) 1994. ‘US Took Idea from Russians’. The Guardian London.

[v] Merrill I Skolnik. Introduction to Radar Systems. Singapore: Mc Graw Hill Book Co, 1981,pp. 33.
[vi] Ibid. pp. 529-35.
[vii] Julian S Lake. ‘Stealth’. DS 26 January 1989.

[viii] James W. Cannan. ‘The Future is Stealth’, Air Force Magazine, January 1991.

[ix] Jay H. Goldberg. ‘The Secret Shape of Things to Come’. National Defense. July –August 1989

[x] Ibid pp 20.

[xi] John. A. Adam, ‘How to design an Invisible Aircraft’, IEEE Spectrum, April 1988.

[xii] Fulvio Bessi, Francesco Zacca. ‘Introduction to Stealth’, Military Technology, May 1989.

[xiii] Bill Sweetman, 'Lifting the Curtain - Stealth Techniques Detailed', International Defence Review, Volume 25, Issue 2, February 1992, pp. 159 .

[xiv] Martin Streetly. ‘Hide and Disguise’, Jane’s Defence Weekly, 17 March 1990.

[xv] Jay H. Goldberg. ‘The Secret Shape of Things to Come’. National Defense. July –August 1989

[xvi] Ibid pp 22.

[xvii] Benjamin F. Schemmer. ‘Will Stealth Backfire’? Armed Forces Journal International, January 1991.

[xviii] ‘F117- A’. 29 Jul 2003.

[xix] David J. Lynch. ‘How the Skunk Works Fielded Stealth’, Air Force Magazine, Nov 1992.

[xx] ‘The Stealth Fighter’. 25 Jul 2003.

[xxi] ‘B-2’. 29 Sep 2003.

[xxii] ‘Eurofighter’. 29 Sep 2003.

[xxiii] ‘Typhoon’ < http://www.eurofighter.starstreak.net/Eurofighter/structure.html>
[xxiv] ‘F22 Raptor’. 29 Sep 2003.

[xxv] ‘F22” 29 Sep 2003.

[xxvi] ‘JSF’. 29 Sep 2003.

[xxvii] Stanley W. Kandebo. ‘Boeing Sikorsky Findings Underscore RAH 66 Stealth’. Aviation Week & Space technology, 19 Jul 1999.

[xxviii] ‘Comanche’. 29 Sep 2003.

[xxix] ‘Have Glass’, 29 Sep 2003 < http://danshistory.com/f16.html>

[xxx] ‘Berkut Su 47’. 29 Sep 2003.

[xxxi] ‘ Boeing Unveils Bird of Prey’, 15 Aug 2003

[xxxii] ‘ Bird of Prey’ 15 Aug 2003 < http://www.boeing.com/phantom>
[xxxiii] ‘Light Combat Aircraft’ 16 Oct 2003.

[xxxv] David Fulghum. ‘Seek and Destroy’ New Scientist, Nov 1999.

[xxxvi] Maj. Gen. Bruce Carlson, USAF, Director of Operational Requirements, US DoD News Briefing on 20 Apr 1999.
< http://www.defenselink.mil/news/Apr1999/t04211999_t420carl.html>

[xxxvii] David Fulghum. ‘Stealth Aircraft - Nowhere To Hide’, 25 Aug 2003 < http://www.globeandmail. com/ gam/ Science /20000119 /RV19STEA.html>

[xxxviii] ‘New Radar Could Defeat Stealth Technology’. Reuters, Jun 2001.

[xxxix] Cyrus Mehta and Ardeshir Mehta. Paper on ‘Anti-Stealth Technology’, 15 Dec 1998.

[xl] Merrill I . Skolnik. ‘Introduction to Radar Systems’ McGraw Hill Book Co, Singapore, pp 8.

[xli] David Fulghum. ‘Seek and Destroy’ New Scientist, November 1999.

[xlii] Ibid

[xliii] Skolnik. pp 553.

[xliv] Tao Yue. ‘Cell phones uncover stealth bombers.’ Aug 2003
< http://www-tech.mit.edu /Info/legal.html>

[xlv] Skolnik. pp 529.

[xlvi] Dan Boyle, 'Countering Stealth - Progress in OTH Sky Wave Radar', International Defense Review, Volume 23, Issue 6, Jun 1990, pp. 712.

[xlvii] Ibid

[xlviii] Ibid

[xlix] G. Jacobs. ‘Airborne Radar versus Stealthy cruise Missiles’, Indian Defence Review.

[l] Jane's Air & Systems Library CD-ROM 2000-2001. ‘ Tamara ELINT System’

[li] ‘New Radar Could Defeat Stealth Technology’. 18 Sep 2003

[lii] ‘Czech Anti-Stealth Radar may be Operating in Yugoslavia’ Reuters, April, 1999, 18 Sep 2003.
< http://www.aeronautics .ru/tamara02.htm> 18 Sep 2003.

[liii] Mr. Kenneth H Bacon, Assistant Secretary of Defense, US DoD News Briefing on Nov 13. 1997.< http://www.fas.org/news/iraq/1997/11/index.html>

[liv] Sean Rayment. ‘US fears Iraq Radar can See Stealth Plane’, 14 Aug 2003
< http://www. telegraph.co.uk /htmlContent.jhtml /archive/1999/03/30/wair130.html>.

[lv] ‘China can see US stealth Aircraft’ 16 Sep 2003

[lvi] ‘US tactics and worries in Iraq Stealth’ 25 Aug 2003

[lvii] David Fulghum. ‘Stealth Aircraft - Nowhere To Hide’, 25 August, 2003 < http://www.globeandmail. com/ gam/ Science /20000119 /RV19STEA.html>

[lviii] Tao Yue. ‘Cell phones uncover stealth bombers.’ 14 August 2003 < http://www-tech. mit.edu /Info /legal. html> August 2003

[lix] David Fulghum. ‘Seek and Destroy’ New Scientist, Nov 1999.

[lx] ‘Plasma’. 16 Sep 2003 < http://sdphln.ucsd.edu/~kriesel/plasma.html>.

[lxi] Venik. ‘Plasma Stealth Technology’, Veniks Aviation, 15 Jun 2003

[lxii] Nicolai Novichkov. ‘Russian Plasma-Based Stealth Better, Cheaper Than US Version?’ ITAR-TASS Information Agency, Moscow, 20 Jan 1999.

[lxiii] Russian Academy of Sciences. ‘Stealth Technology’ 20 Oct 2003

[lxiv] Venik. ‘Plasma Stealth Technology’, Veniks Aviation, 15 Jun 2003,

[lxv] Michal Fiszer and Jerzy Gruszczynski. ‘Russia Working on Stealth Plasma’, Journal of Electronic Defense, Jun 2002.

[lxvi] Ibid

[lxvii] Tao Yue. ‘Cell phones uncover stealth bombers.’ 14 August 2003
< http://www-tech. mit.edu /Info /legal. html> August 2003

[lxviii] ‘The Stealth Fighter’. 25 Jul 2003.

[lxix] Ibid

[lxx] James P. Coyne. ‘A Strike by Stealth’, Air Force Magazine, March 1992.

[lxxi] ‘F117- A’. 29 Jul 2003.

[lxxii] Barry M. Blechman and Ivan Oelrich. ‘B2 Stealth Bomber Costs in Perspective’, Strategic Review, Winter 1996.
[lxxiii] ‘B 2 Stealth Bomber’ 15 Oct 2003

[lxxiv] ‘Eurofighter’. 29 Sep 2003.

[lxxv] ‘Comanche’. 29 Sep 2003.