Transcript Plasma Stealth Technology

Plasma Stealth Technology
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
Stealth & its working principle
STEALTH:
 Invisible to means of detection.
 Similar to the CAMOUFLAGE Tactics.
 Used in Military Applications.
Why is stealth required
 Advancements in Electronic warfare
 In order to sneak into enemy territory unnoticed.
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…
Stealth’s Disadvantages
 Cannot Fly Faster
 Reduced Pay-Load Amounts.
 Higher Costs.
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.
Plasma engulfed aircraft
WHY PLASMA STEALTH TECHNOLOGY
 Easily achieved.
 Perfect than its predecessors.
 More Reliable.
 Quite Cheaper.
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..
Parameters
 The electron density( N e )
 collision frequency(v)
 Plasma frequency ( p )
MATLAB code
 Parameters chosen:
1) electron density= Ne  10
8
2)frequency :
1 MHz to 10 MHz
MATLAB generated plot of dielectric
constant vs frequency
Plasma frequency
 Now consider the collision frequency v=0 and then the
expression of propagation constant for plasma is
The three cases of interest are
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.
Plotting reflection vs frequency
Red line denotes plasma frequency
.
R=reflection coefficient
Plotting loss vs frequency
Red line denotes plasma frequency
Ne denotes electron density
Horizontal section of EMW
incidence in plasma envelopes
ro 
Radius of the conductor cylinder
rd 
Distance between EMW rays and the circle
centre
Refraction and absorption
 Suppose rd
 ro 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 rd  ro , have smaller incidence angle and
hence they may be incidence on the conductor.
Refractive index
 In this case applying snell’s law we get the minimum
angle with which the rays should be incident on the
surface….
 min  arcsin(
ro
Ro
)
m
 Here the refractive index varies with distance and
hence ro is the distance from centre to the conductor
surface and Ro is the distance from centre till the
plasma envelope.
 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
min
reach the conductor .
 This means that min 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.
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
Angle of incidence/refraction
m= plasma numerical density
As m value increases the refraction increases
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.
ENERGY
DISSIPATION
IN THE FORM
OF HEAT
GROUND
STATION
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.
Generation of plasma
A spark producing partially ionized
plasma
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
1
from eV by a factor of 40.
 Plasma lifetime-The plasma lifetime is defined as the
time required plasma of initial density no to
decrease in concentration by a factor of 1/e.
Plasma lifetime of air vs altitude
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.
Plasma lifetime of helium
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.
PLASMA STEALTH’S ADVANTAGES
 Reduced Weight.
 Cheaper than its predecessors.
 Reduces Aerodynamic Drag.
 Undetectable by any Electro-Magnetic Radiations.
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.
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……
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.
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