Tài liệu STEALTH TECHNOLOGYSTEALTH TECHNOLOGY: A REVEALING ppt

STEALTH TECHNOLOGY: STEALTH TECHNOLOGY: A REVEALING A REVEALING An investigative study on stealth technology. An investigative study on stealth technology. What is it? • RADAR to detect position of objects. • Counter measures 1. ECM ( e.g. chaff cartridges) 2. Non ECM • Avoiding detection and innovating deception . • RCS reductions, acoustics, thermal and other EM emissions Examples • F 117 • B-2 Bomber • F-22 Raptor( From YF 23 Platform) • SR-71 Black bird • HMS Helsingborg How is it achieved. • Absorbs radar waves or deflects to other directions. • Minimizes heat and other emissions from engine and other spots. • Makes difficult to detect except closely. • Smooth edges maximum radio wave reflectors. • The size of a target's image on radar is measured by RCS (σ ) • For a square flat plate of 1m 2 area, σ=13982 m 2 at 10 Ghz Vehicle shape and structure • Mainly plan form alignment. • The leading edges of wing and tail surfaces set at same angles. Vehicle structure (contd ) • Use of re-entrant triangles behind skin. • Distinctive serrations used in external airframes. • Propulsion subsystem shaping. • Now in research is fluidic nozzles for thrust vectoring. Vehicle structure (contd ) Radar Absorbing Materials (RAM) • RAMs often as paints used to absorb RADAR signals. • Iron ball paint, ferrite in polymer matrix used. • The cockpit canopy coated with thin layer of indium tin oxide . • Small cell foams painted or loaded with absorbing ink. • MAGRAM • R- Card • Absorbing honeycomb • Transparent RAM RAMs (contd ) Other fields • Reducing RCS alone not enough. • More difficulty is reducing the IR signature. • Interest is near IR region. (shorter than 10 µm) [...]... aircraft with SLAR, FLIR etc are used • Same method advantageously used using satellite Stealth counter (contd….) • Uninterrupted radio waves from stars mapped • Failure or fainter image suggests probability of stealthy craft • Advantages of using lethal SAM’s and remain undetected • Low frequency radar nullifies stealth from shape Stealth counter (contd….) • Disadvantages of LFR 1 Wavelength unavailability... (passive listening) 3 Composite materials radiating switching transients • Passive sensors (LPI radar in F-22 ), LOS communication, inertial navigation are used Acoustics • Most important for submarine & ground vehicles • Rubber mountings, AIP system, slow turning propellers etc Visibility • Matte paint, gray paint in disruptive How to counter • Background of stealth craft than craft shall be searched... window absorbed by CO2 • Passive IR target acquisition systems more used Electromagnetic emissions • EM emissions other than IR • The greatest source is RADAR itself • Shutting down RADAR a solution having negative effects • Radio /radar altimeters and Doppler navigation systems EM emissions (contd…) • Use of inertial navigation , laser or millimetric wave system • Other EM emissions 1 Radio communication... • Major IR emission sources 1 Tailpipe region 2 Turbojets have EGT’s of 1000oC 3 Exhaust gas plume 4 Hot engine parts 5 Aircraft skin (frictional heating) 6 Reflected and reemitted sunlight IR Reduction • Using surface paints • Non circular tail pipe • Emissions from hot parts screened by airframe • The plume mixed with cool air IR Reduction (contd…) • IR best transmitted 2.5, 4 and 10 micron bands... (contd….) • Disadvantages of LFR 1 Wavelength unavailability 2 Inaccuracy 3 Size • 1 Bistatic radars and 2 Using reflections from civilian radio Conclusion • Stealth technology developed a lot • Investment needed is very high • High chance of low cost gain • A lot learned about signature reduction and absorption • Useful for other projects For the time spared . STEALTH TECHNOLOGY: STEALTH TECHNOLOGY: A REVEALING A REVEALING An investigative study on stealth technology. An investigative study on stealth. edges maximum radio wave reflectors. • The size of a target's image on radar is measured by RCS (σ ) • For a square flat plate of 1m 2 area, σ=13982