P l a s m a S t e a l t h T e c h n o l o g y

1. PlasmaStealthTechnology

2. This presentation consists of • What is stealth? • What are the methods? • Why plasma stealth? • What is plasma? • About refraction and absorption stealth • Plasma generation • Characteristics of plasma • Advantages of plasma stealth • Future of plasma stealth

3. Stealth & its working principle STEALTH: • Invisible to means of detection. • Similar to the CAMOUFLAGE Tactics. • Used in Military Applications.

4. Why is stealth required • Advancements in Electronic warfare • In order to sneak into enemy territory unnoticed.

5. Detection Methods • A proven method-triangulate its location with a network of radar systems. • In this method many radar receivers are setup and the reflections from the plane in different directions is measured and hence the detection is possible…

6. Stealth’s Disadvantages • Cannot Fly Faster • Reduced Pay-Load Amounts. • Higher Costs.

7. Plasma stealth • In this stealth the aircraft injects a stream of ionized gas which envelopes the aircraft due to which the RCS of the object is reduced. • The stealth effect is caused by refraction and absorption and this can be explained by considering the plasma envelopes as shown in the subsequent slide.

8. Plasma engulfed aircraft

9. WHY PLASMA STEALTH TECHNOLOGY • Easily achieved. • Perfect than its predecessors. • More Reliable. • Quite Cheaper.

10. What is Plasma? • Partially ionized stream of gas, consisting of certain free electrons. • Quasi-neutral in nature - i.e. total electrical charge almost equal to Zero. • Applications-widely : from fluorescent lights to semiconductor manufacturing..

11. Parameters • The electron density • collision frequency(v) • Plasma frequency

12. MATLAB code • Parameters chosen: 1) electron density= 2)frequency : 1 MHz to 10 MHz

13. MATLAB generated plot of dielectric constant vs frequency

14. Plasmafrequency • Now consider the collision frequency v=0 and then the expression of propagation constant for plasma is

15. Thethree cases of interest are

16. The three cases • Therefore when the operating frequency is less than plasma frequency then there is no electromagnetic wave propagation. • The wave is reflected from the plasma surface instead of being absorbed. • For a wave to pass through plasma the operating frequency should be greater than the plasma frequency. • Hence the ionosphere(plasma) also reflects radio signals till certain frequency and then it does not.

17. Plotting reflection vs frequency Red line denotes plasma frequency . R=reflection coefficient

18. Plotting loss vs frequency Red line denotes plasma frequency Ne denotes electron density

19. Horizontal section of EMW incidence in plasma envelopes Radius of the conductor cylinder Distance between EMW rays and the circle centre

20. Refraction and absorption • Suppose the EM rays have larger incidence angle and are farther away from the centre conductor and will be refracted by plasma before they arrive at the conductor surface • The rays having shorter distance to the circle centre, supposed , have smaller incidence angle and hence they may be incidence on the conductor.

21. Refractive index • In this case applying snell’s law we get the minimum angle with which the rays should be incident on the surface…. • Here the refractive index varies with distance and hence is the distance from centre to the conductor surface and is the distance from centre till the plasma envelope.

22. In plasma the refractive index varies with distance which is why the radius of the cylinder is coming into picture. • If the angle of incidence at a small distance from the boundary of the conductor then the rays will reach the conductor . • This means that is the critical angle i.e minimum angle with which the rays should be incident so that they refract and do not reach the conductor.

23. Refraction and absorption • So when EMW enters the plasma envelope then the rays with larger incidence angle refracts and deviates greatly from original direction and hence they don’t reach the inner conductor. • EMW rays with smaller incidence angle may arrive at the inner conductor after absorption by plasma envelopes. • However the energy attenuates a lot and the minimal reflectivity is below -40dB

24. Angle of incidence/refraction m= plasma numerical density

25. As m value increases the refraction increases

26. The principle of Absorption • The remaining electromagnetic energy is then absorbed by the electrons and that energy increases the collisions among themselves and converts this energy into heat.

27. OPERATION OF PLASMA STEALTH ENERGY DISSIPATION IN THE FORM OF HEAT RADAR SIGNALS GROUND STATION

28. GENERATION OF PLASMA • Plasma can be generated in a number of ways: 1)Supply thermal energy 2)Adiabatic compression of the gas 3)Due to electric field to a neutral gas- Free charges are accelerated by the electric field and new charge particles are created when these charge particles collide with atoms and molecules in the gas.

29. Generation of plasma

30. A spark producing partially ionized plasma

31. Plasma characteristics • collision rate –The number of collisions that occur in order to bring the electron back to their normal state. e.g: In air ,20000 collisions reduce the electron energy from 1eV by a factor of 40. • Plasma lifetime-The plasma lifetime is defined as the time required plasma of initial density to decrease in concentration by a factor of 1/e.

32. Plasma lifetime of air vs altitude

33. Plasma properties • Significantly longer lifetimes are possible with helium since helium does not form negative ions, so a major electron attachment mechanisms are minimized . • Pure helium is very expensive so we add a mixture of nitrogen and oxygen which form positive ions and due to collisions and hence deionizes the helium plasma.

34. Plasma lifetime of helium

35. Plasma properties • Plasma generated in air or helium at atmospheric pressure has a property of being an excellent broadband absorber from VHF to X- band . • A neon/argon plasma has the property of high absorption from VHF to S- band and requires less power to sustain than a helium plasma because its momentum transfer collision rate is lower.

36. PLASMA STEALTH’S ADVANTAGES • Reduced Weight. • Cheaper than its predecessors. • Reduces Aerodynamic Drag. • Undetectable by any Electro-Magnetic Radiations.

37. FUTURE OF PLASMA STEALTH • Plasma Stealth Technology is clearly the future of air combat. In the future, as air defense systems grow more accurate and deadly, Plasma Stealth Technology can be a decisive factor, by a country over the other. In the future, Plasma Stealth Technology will not only be incorporated in fighters and bombers but also in ships, helicopters and tanks. Ever since the Wright brothers flew the first powered flight, the advancements in this particular field of technology has seen staggering heights. Plasma Stealth technology is just one of the advancements that we have shown here.

38. Excerpts • Plasma stealth technology will be incorporated in the MiG-35 “Super Fulcrum/Raptor Killer”. • The radar absorbing material nicknamed “Iron ball “ was installed on the F-22 aircraft . But this increased the weight of the aircraft considerable and the maneuvering became difficult……………..hence plasma stealth provided a better option …reduce weight and very economical……

39. References [1]Vidmar , R.J., ”On the use of atmospheric pressure plasmas as Electromagnetic reflectors and absorbers ,”IEEE Trans. on Plasma science , vol. 18,No. 4, 733-741, 1990. [2]Ma,L.-X., H.Zhang, ”Analysis on the stealth characteristic of two dimensional cylinder plasma envelopes”, Journal of Electromagnetic Waves and Applications , Vol. 13, pp. 83-92,2010.

40. References • A report by DAVID . C JENN, professor, Department of electrical and computer engineering, NAVAL post graduate school ,Monterey,California. • http://en.wikipedia.org/wiki/Stealth_technology • http://en.wikipedia.org/wiki/Plasma_stealth

41. THANK THANK YOU YOU