plasma stealth technology

Plasma Stealth Technology Seminar Report-‘06

ACKNOWLEDGEMENT

I would like to express my sincere gratitude to our Principal Prof. Aboobacker Kadengal for providing all the required facilities. It is with great pleasure that I place on record my indebtedness and gratitude to our H.O.D Mr. Shiju P.P for his valuable guidance, co-operation and encouragement. I am grateful to our Seminar Coordinator Mr. Rajesh Kumar M.V for his timely advice and guidance. I also thank Mrs. Sheeba k., Mr. Santo Mathew, Mr. Pramod P., Mrs. Shanthini K.S of Electronics and Communication Dept. for the support they have given me.

Dept. of ECE 1 LBSCE; Kasaragod


ABSTRACT

Plasma Stealth technology covers a range of techniques used with aircraft, ships and missiles, in order to make them less visible (ideally invisible) to radar and other detection methods. It is not a single technology but is a combination of technologies that attempt to greatly reduce the distances that a vehicle can be detected at; in particular radar cross section reductions, but also acoustic, thermal and other aspects specifically.Here the concept is to absorb the incoming radar waves totally and to redirect the absorbed electromagnetic energy in another direction. Electromagnetic waves have been observed to be absorbed by or bend around plasma fields for decades. If a plasma cloud could be created around the outside of an aircraft, electromagnetic waves would be absorbed by the stealth instead of reflecting back to the radar antenna. Although stealth technology has not been much effective, the United States, Russia, China , India and several other nations are in the process to explore the unknown areas of stealth technology.


http://en.wikipedia.org/wiki/China

http://en.wikipedia.org/wiki/Russia

http://en.wikipedia.org/wiki/United_States

http://en.wikipedia.org/wiki/Radar_cross_section#Reduction

http://en.wikipedia.org/wiki/Radar

http://en.wikipedia.org/wiki/Invisible

http://en.wikipedia.org/wiki/Missiles

http://en.wikipedia.org/wiki/Stealth_ship

http://en.wikipedia.org/wiki/Stealth_aircraft


INDEX

CONTENTS PAGE

1. Introduction…………………………………………………. (4)

2. Aircraft detection methods……………………………….. (5)

3. History of Stealth aircraft…………………………………. (8)

4. How does Stealth technology works.......................... (10)

5. Plasma Stealth technology………………………………. (15)

6. Plasma and its’ properties……………………………… (18)

7. Generation of Plasma on aircrafts……………………… (22)

8. Advantages…………………………………………………. (23)

9. Disadvantages……………………………………………… (23)

10. Conclusion…………………………………………………. (24)

11. Bibliography and Reference…………………………… (25)



INTRODUCTION

Plasma stealth technology is the leading edge technology and is still under considerable research. The motivation to use plasma stealth is similar to that of radar absorbent materials. Electromagnetic waves have been observed to be absorbed by or bend around plasma fields for decades. If a plasma cloud could be created around the outside of an aircraft, electromagnetic waves would be absorbed by the stealth instead of reflecting back to the radar antenna.

Plasma stealth technology is what can be called as "Active stealth technology" in scientific terms. This technology was first developed by the Russians. It is a milestone in the field of stealth technology. The technology behind this is not at all new. The plasma thrust technology was used in the Soviet / Russian space program. Later the same engine was used to power the American Deep space 1 probe. In plasma stealth, the aircraft injects a stream of plasma in front of the aircraft. The plasma will cover the entire body of the fighter and will absorb most of the electromagnetic energy of the radar waves, thus making the aircraft difficult to detect. The system developed is based on electromagnetic wave-plasma interactions. Russian stealth plasma device creates a plasma field around an aircraft. This field partially consumes electromagnetic energy of a hostile radar or causes it to bend around the aircraft, reducing the aircraft RCS by up to 100 times.

Since plasma is electrically conductive an electromagnetic field will be formed in presence of external EM signal. Creating this field requires energy and this energy comes from the radar signal. The more energy is

used in this process the better it is for lowering the aircraft's RCS. A device for generating plasma is called ‘Plasmatron’. This device generates the so-called low-temperature plasma. The generator is small and light whose power consumption ranges from kilowatts to tens of kilowatts.



2. AIRCRAFT DETECTION METHODS: The most common methods used today to detect an aircraft are:

2.1) RADAR Currently the way to detect and even identify an aircraft is the use of RADAR (radio detection and ranging). This system invented during World War II, simply works by constantly sending bursts of radio waves of certain frequencies and measures the echoes of each burst. Parts of the energy of radio waves are being reflected by objects. Depending on the material the object is made of, this echo is stronger or weaker, but there is an echo. By measuring the reflected energy as a function of position and time, computers can calculate what it is that reflects the energy, where it is in 3D space and also in what direction it moves. To get a proper overview of an area with RADAR, the transmitting and receiving antenna should rotate in angles of 360 degrees. RADAR works on the principle of echo and Doppler shift. Echo is the repetition of a note after the original note is dead. Doppler shift is the phenomenon of apparent change in the frequency of the radio wave whenever there is a relative motion between the source and the object.

2.1.1 SOURCES OF RADAR REFLECTION:

a) Gaps and breaks in surface b) Unshielded cockpit c) External weapons d) Exposed engines e) Large, right-angled tail surfaces f) Right-angle wing design

2.1.2 Radar Cross Section (RCS)



The Radar Cross Section of a target is the area intercepting that amount of power which, when scattered equally in all directions, produce an echo at radar equal to that from the target.

Contributions to RCS for a conventional aircraft:

RCS depends on aircraft shape, aspect angle or orientation with respect to radar line of sight (LOS), ratio of radar wavelength to target size, polarization of transmit and receive antennae, surface quality of target, and constitution of the target. The RCS of an aircraft is determined by the magnitudes of two distinctly different contributions:

1. Its size and shape, both overall and in detail2. The electromagnetic properties of airframe materials

Aircraft shaping is useful over a wide range of radar frequencies but over a limited range of aspect angles. Typically, for fighter aircraft, a forward cone of angles is of greatest interest and hence, large returns can be shifted aircraft can be shaped to ensure that most radar waves will be scattered and not reflected back to the transmitter. Leading and trailing edges of wings, control surfaces, inlet lips, door gaps, etc. can be aligned to ensure that the energy that is concentrated into a few spikes. This will give the opposing radar one good return when the alignment is ideal, but a much weaker return on subsequent sweeps.



2.2) HEAT DETECTION

Another way of detecting if an aircraft is flying somewhere is by measuring the heat it radiates. Normally this heat is produced by the plane engines. There are two significant sources of infrared radiation from air-breathing propulsion systems: hot parts and jet wakes. By modern heat image sensors (Infrared sensors) the difference can be seen between a flying object itself and the surrounding cold air. This is the same for the jet engine exhaust gases.

2.3) TURBULENCE DETECTION

Shape also has a lot to do with the ‘invisibility’ of stealth planes. Extreme aerodynamics keeps air turbulence to a minimum. Sophisticated Laser controlled turbulence sensors, which can measure paths of disturbed air, generated by an aircraft, which just passed.

2.4) VISUAL DETECTION

The exhaust of aircraft i.e., the white line in the sky caused by high- flying planes makes it easier to detect the aircraft even with the naked eye. Also the color of the aircraft is an important factor.

2.5) ACOUSTIC DETECTION

A very obvious source of detection is the noise, generated by jet engines. Several systems have been designed in the meantime to reduce the sound of jet engine exhausts to a minimum, making them harder to detect by just measuring sound waves.



3. HISTORY OF STEALTH AIRCRAFT:

With the increasing use of early warning detection devices such as radar by militaries around the world in the 1930’s the United States began to research and develop aircraft that would be undetectable to radar detection systems. The first documented stealth prototype was built out of two layers of plywood glued together with a core of glue and sawdust. This prototype’s surface was coated with charcoal to absorb radar signals from being reflected back to the source, which is how radar detection systems detect items in the air. Jack Northrop built a flying wing in the 1940’s. His plane was the first wave of stealth aircraft that actually flew. The aircraft proved to be highly unstable and hard to fly due to design flaws. The United States initially orders 170 of these aircraft from Northrop but cancelled the order after finding that the plane had stability Flaws. Then in 1964, SR-71 the first Stealth airplane launched. It is well known as ‘black bird’. It is a jet black bomber with slanted surfaces. This aircraft was built to fly high and fast to be able to bypass radar by its altitude and speed. The Blackbird was developed primarily for the Cold War between the United States and the U.S.S.R. SR-71 Aircraft is shown in figure3.1.

Fig 3.1. SR-71 BLACK BIRD



Then in 1982, the first F-117A (Fig 3.2) was delivered. It is world’s first operational aircraft designed to exploit low observable Stealth Technology.

Fig 3.2. F-117A NIGHT HAWK

Then world’s most advanced Stealth fighter, B-2 delivered by1988. A B-2 Spirit multi-role bomber is shown in figure 3.3.

Fig 3.3. B-2 SPIRIT MULTI-ROLE BOMBER



4. HOW DOES STEALTH TECHNOLOGY WORK?

The idea is for the radar antenna to send out a burst of radio energy, which is then reflected back by any object it happens to encounter. The radar antenna measures the time it takes for the reflection to arrive, and with that information can tell how far away the object is.

The metal body of an airplane is very good at reflecting radar signals, and this makes it easy to find and track airplanes with radar equipment. The goal of stealth technology is to make an airplane invisible to radar.

There are two different ways to create invisibility:1 The airplane can be shaped so that any radar signals it reflects

are reflected away from the radar equipment.

2 The airplane can be covered in materials that absorb radar signals.

REQUIREMENTS TO BE STEALTHY:

To make a stealthy aircraft, designers had to consider six key ingredients: 1. They need to reduce the imprint on the radar screen.2. Turn down the heat of its infrared picture.3. They need to reduce muffling noise.4. They need to reduce the turbulence.5. Making the plane less visible.6. Stifle radio emissions.



4.1) RADAR ECHO REDUCTION

4.1.1 Scattering The airplane can be shaped so that any RADAR signals it reflects are deflected away from the RADAR equipment. Most conventional aircraft have a rounded shape. This shape makes them aerodynamic, but it also creates a very efficient radar reflector. The round shape means that no matter where the radar signal hits the plane, some of the signal gets reflected back:

Fig 4.1 Conventional Aircraft-Very efficient radar reflector

A stealth aircraft (fig3.3), on the other hand, is made up of completely flat surfaces and very sharp edges. When a radar signal hits a stealth plane, the signal reflects away at an angle, like this:

Fig.4.2. Stealth Aircraft-Radar signal reflect away at an angle



In addition, surfaces on a stealth aircraft can be treated so they absorb radar energy as well. The overall result is that a stealth aircraft like an F-117A can have the radar signature of a small bird rather than an airplane. The only exception is when the plane banks -- there will often be a moment when one of the panels of the plane will perfectly reflect a burst of radar energy back to the antenna.

4.1.2 Reduction by RAM: A second way of stopping RADAR reflections is by coating the plane with material that soaks up Radar energy. Radar absorbing coatings can be applied to the surface of the body, which effectively drain the energy of the radar signal. For example, Radar Absorbent Material (RAM), coatings designed to suck in and dissipate the electromagnetic energy of radar wave instead of reflecting it back tothe source.

Radar Absorbent Material (RAM) As its name implies, RAM is intended to reduce the scattered signal by absorbing some part of the incident radiation. Microwave energy is converted into heat energy with hardly any noticeable temperature rise because the energies involved are extremely small. Various kinds of materials can be made to absorb microwave energy by impregnating them with conducting materials such ascarbon and iron. Mainly, there are two currently used kinds of absorbers , called di-electric RAM and magnetic RAM. Addition of carbon products in an insulating material introduces electric resistance and changes the electrical properties. Hence carbon-based absorbers are called dielectric RAM. The most familiar examples are pyramidal absorbers found in anechoic chambers. Dielectric RAM is usually too bulky and fragile and not attractive where space is limited and severe mechanical vibrations exist. Magnetic RAM uses iron products such as carbonyl iron and iron oxides called ferrites. Iron effectively dissipates radar waves and has been used in aircraft paint. It is quite effective against the high frequency radars used in modern fighters. Unlike dielectric RAM, magnetic RAM is compact, thin and of adequate strength to withstand loads and an abrasive environment. Nevertheless, its thickness does rob volume from volume limited aircraft. Some important RAM’s used today are:

(a)Salisbury Screen:

Its construction consists of a conductive carbon coated “lossy”fabric, separated from a conductive ground plane by a low dielectric foam core.



(b)Foam Materials:

Different foam materials are:

a) single layer foam b) multi layer foam-made of 3 single layers c) reticulated foam d) weather proof foam

(c)Magnetic Absorbers:

The magnetic absorbers are electrometric moulded sheets loaded with magnetic filler. The use of the magnetic filler provides the best performance at the minimum thickness.

Different magnetic absorbers are: a) tuned frequency magnetic absorbers b) surface wave absorbers c) multiband absorbers

(d)Core Material:

Core material is a broadband microwave absorbing honeycomb core. Normally uses either aramid or fiberglass honeycomb core and applies a lossy coating to it.

(e)PIFRAM (Poly Crystalline Iron Fibre RAM):

It is the only electromagnetic Radar Absorbing Material that may be retrofitted to existing material because of its low weight and very low thickness.

4.2) ECHO CANCELLATION

Metal component such as the engine, which produces significant radar reflections, can be shielded using a metal and plastic sandwich whose layers are spaced in such a way as to create a standing wave, canceling out any radar reflections.



4.3) HEAT RADIATION REDUCTION

Infrared radiation (heat) should be minimized by a combination of temperature reduction and masking. The main body of the airplane has its own radiation, heavily dependent on speed and altitude, and the jet plume can be a most significant factor, particularly in after burning operation. The engines are buried deep in the fuselage These have got shallow ‘platypus’ exhausts, whichcool and deflect the exhaust gases upward to minimize heat emissions.

4.4) TURBULENCE DETECTION REDUCTION

By optimizing the aerodynamics of the stealth plane, the eye visible turbulence trail in the air, can be kept to a minimum. This way it becomes harder for the very special laser equipment to detect the trail and trace it back all the way to the plane which created it.

4.5) VISUAL DETECTION REDUCTION

4.5.1 Hiding smoke contrails (jet wake)

Reducing smoke in the exhaust is accomplished by improving the efficiency of the combustion chambers. Tests have been done using exotic chemicals to be inserted in to the engine outlet gases to modify infrared signature as well as to force water molecules in the exhaust plume to break up in to much finer particles, thus reduce or even eliminate contrails. One of the chemicals used for this was chloro-fluoro-sulphonic acid.

4.5.2 Low Visibility

An aircraft at low to medium altitudes tends to be a black dot against the background of the sky. To avoid this, the plane is given a special medium gray color. The gray, when combined with light scattering at low to medium altitudes ensures about as low observability as can be possible or a reduction to 30% in visibility.

4.5.3 Low Level Flight

Another technique used by aircraft to avoid radar is to fly at very low levels where there is a great deal of ‘ground clutter’…radar reflections given off by buildings and other objects. Low level aircraft can go undetected by most radar systems.



5. PLASMA STEALTH TECHNOLOGY:

5.1) HISTORY OF PLASMA STEALTH TECHNOLOGY

For a number of years Russia has conducted a research and development effort aimed at utilizing non-conventional hypersonic technologies to achieve a significant breakthrough in hyper sonic flight. The Russian program, known as Ajax, has the goal of building a Mach 12 or greater aircraft based on the integration of three novel subsystem technologies: plasma-aerodynamic shock-wave modification, endothermic fuel conversion, and magnetohydrodynamic (MHD) power generation. If successful, the integration of these technologies into the development of a hypersonic vehicle would revolutionize air and space flight. The experiments have verified two major Russian claims: (1) that plasmaaerodynamic effects can cause "anomalous relaxation" of a bow shock wave, resulting in a major reduction in drag, and (2) that plasma effects can cause the speed of a shock wave to increase, the shock structure to disperse, and the shock wave amplitude to dissipate. Although verified experimentally, the phenomena are not understood. If these effects can be controlled and made tooccur in an efficient, large-scale way, there is potential for high-payoff, both commercially and militarily. In addition to reducing drag, the same plasma system could offer a fundamentally different type of stealth technology. It may be possible that aircraft can be made invisible to radar by creating plasma clouds around them. Several phenomena occur as the plasma cloud interacts with theelectromagnetic waves. The waves are partly absorbed by the plasma as they interact with the charged particles in the cloud and transfer some of their energy to them. Electromagnetic waves also tend to bend around the plasma formation. Both these phenomena cause either a sharp decrease in signal reflection, or produce a number of false echoes that make it extremely difficult to determine the speed of the aircraft and its location.

Fig:5.1 Russian made Plasma stealth aircraft



5.2) HOW PLASMA RESISTS RADAR?Russian scientists approach the issue from the other direction. They proposed to create a plasma formation around protected object, which prevents radars from seeing it. Thus, aerodynamical characteristics of the plane itself do not suffer. Without interfereing with technical characteristics the artificially created plasma cloud surrounding the plane guarantees more than hundred times decrease in its observability.

The physics of plasma protection can be described as following. If an object is surrounded by a cloud of plasma, several phenomenas are observed when the cloud interacts with electromagnetic waves radiated by enemy radar. First, an 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. Both of these phenomenas results in dramatic decrease of the reflected signal.

Static and flight experiments proved the effectiveness of this technology. The first generation devices, producing plasma field surrounding an aircraft and decreasing reflected signal were created in the Center. Later, a possibily of creating second generation advanced systems (capable of not only decreasing reflected signal and changing its wavelength, but also producing some false signals) was discovered. Such systems significantly complicate determination of actual aircraft's speed, its location and leads to development of completely new approaches to LO provision, unachievable to conventional Stealth technology. Furthermore, the weight of the systems developed in Russia do not exceed 100 kg, and power consumption ranges from kilowatts to tens of kilowatts



5.3) ABSORPTION OF EM RADIATIONS BY PLASMA

When electromagnetic waves, such as radar signals, propagate into a conductive plasma, ions and electrons are displaced as a result of the time varying electric and magnetic fields. The wave field gives energy to the particles. The particles generally return some fraction of the energy they have gained to the wave, but some energy may be permanently absorbed as heat by processes like scattering or resonant acceleration, or transferred into to other wave types by mode conversion or nonlinear effects. As mentioned previously, the plasma aids in absorbing the radar signals. The absorption takes place when the electromagnetic waves encounter a charged particle. During this encounter, a portion of the electromagnetic wave’s energy is transferred to the charged particles. A plasma can, at least in principle, absorb all the energy in an incoming wave, and this is the key to plasma stealth.

The central issue here is frequency of the incoming signal. A plasma will simply reflect radio waves below a certain frequency (which depends on the plasma properties). This aids long-range communications, because low-frequency radio signals bounce between the Earth and the ionosphere and may therefore travel long distances. Early-warning over-the-horizon radars utilise such low-frequency radio waves. Most military airborne and air defense radars, however, operate in the microwave band, where many plasmas, including the ionosphere, absorb or trasmit the radiation (the use of microwave communication between the ground and communication satellites demonstrates that at least some frequencies can penetrate the ionosphere). Plasma surrounding an aircraft might be able to absorb incoming radiation, and therefore prevent any signal reflection from the metal parts of the aircraft: the aircraft would then be effectively invisible to radar. A plasma might also be used to modify the reflected waves to confuse the opponent's radar system: for example, frequency shifting the reflected radiation would frustrate Doppler filtering and might make the reflected radiation more difficult to distinguish from noise.

Control of plasma properties is likely to be important for a functioning plasma stealth device, and it may be necessary to dynamically adjust the plasma density, temperature or composition, or the magnetic field, in order to effectively defeat different types of radar systems. Radars which can flexibly change their transmission frequency might be less susceptible to defeat by plasma stealth technology. Like LO geometry and radar absorbent materials , plasma stealth technology is probably not a panacea against radar.


http://en.wikipedia.org/wiki/Radar_absorbent_material

http://en.wikipedia.org/w/index.php?title=LO_geometry&action=edit

http://en.wikipedia.org/w/index.php?title=Mode_conversion&action=edit

http://en.wikipedia.org/w/index.php?title=Mode_conversion&action=edit

http://en.wikipedia.org/wiki/Electromagnetic


6. PLASMA AND ITS' PROPERTIES:

A plasma is a quasineutral (total electrical charge is close to zero) mix of ions (atoms which have been ionized, and therefore possess a net charge), electrons, and neutral particles (possibly including unionized atoms). Not all plasmas are fully ionized. Almost all the matter in the universe is plasma: solids, liquids and gases are uncommon away from planetary bodies. Plasmas have many technological applications, from fluorescent lighting to plasma processing for semiconductor manufacture.

Plasmas can interact strongly with electromagnetic radiation: this is why plasmas might plausibly be used to modify an object's radar signature. Interaction between plasma and electromagnetic radiation is strongly dependent on the physical properties or parameters of the plasma, most notably, the temperature and density of the plasma. Plasmas cover a wide range of values in both temperature and density; plasma temperatures range from close to absolute zero and to well beyond 109 kelvins (for comparison, tungsten melts at 3700 kelvins), and plasma may contain less than one particle per cubic metre or be denser than lead. For a wide range of parameters and frequencies, plasma is electrically conductive, and its response to low frequency electromagnetic waves is similar to that of a metal: a plasma simply reflects incident low frequency radiation. The use of plasmas to control the reflected electromagnetic radiation from an object (Plasma stealth) is feasible at higher frequency where the conductivity of the plasma allows it to interact strongly with the incoming radio wave, but the wave can be absorbed and converted into thermal energy rather than reflected.

Plasmas support a wide range of waves, but for unmagnetised plasmas, the most relevant are the Langmuir waves, corresponding to a dynamic compression of the electrons. For magnetised plasmas, many different wave modes can be excited which might interact with radiation at radar frequencies.


http://en.wikipedia.org/wiki/Kelvin

http://en.wikipedia.org/wiki/Electron

http://en.wikipedia.org/wiki/Atom

http://en.wikipedia.org/wiki/Ion

http://en.wikipedia.org/wiki/Electrical_charge

http://en.wikipedia.org/wiki/Plasma_(physics)


6.1) PROPERTIESPlasma properties are strongly dependent on the bulk (or average) parameters. Some of the most important plasma parameters are the degree of ionization, the plasma temperature, the density and the magnetic field in the plasma region. We explain these parameters, and then describe how plasmas interact with electric and magnetic fields and outline the qualitative differences between plasmas and gases.

6.1.1 Degree of ionization

For plasma to exist, ionization is necessary. The degree of ionization of a plasma is the proportion of atoms which have lost (or gained) electrons, and is controlled mostly by the temperature. Even a partially ionized gas in which as little as 1% of the particles are ionized can have the characteristics of a plasma (i.e. respond to magnetic fields and be highly electrically conductive). The degree of ionization, α is defined as α = ni/ (ni + na) where ni is the number density of ions and na is the number density of neutral atoms.

6.1.2 TemperaturesPlasma temperature is commonly measured in Kelvin or electron volts, and is (roughly speaking) a measure of the thermal kinetic energy per particle. In most cases the electrons are close enough to thermal equilibrium that their temperature is relatively well-defined, even when there is a significant deviation from a Maxwellian energy distribution function, for example due to UV radiation, energetic particles, or strong electric fields. Because of the large difference in mass, the electrons come to thermodynamic equilibrium among themselves much faster than they come into equilibrium with the ions or neutral atoms. For this reason the ion temperature may be very different from (usually lower than) the electron temperature. This is especially common in weakly ionized technological plasmas, where the ions are often near the ambient temperature.

Based on the relative temperatures of the electrons, ions and neutrals, plasmas are classified as thermal or non-thermal. Thermal plasmas have electrons and the heavy particles at the same temperature i.e. they are in thermal equilibrium with each other. Non thermal plasmas on the other hand have the ions and neutrals at a much lower temperature (normally room temperature) whereas electrons are much "hotter".

Temperature controls the degree of plasma ionization. In particular, plasma ionization is determined by the electron temperature relative to the ionization energy (and more weakly by the density) in accordance with the Saha equation. A plasma is sometimes referred to as being hot if it is nearly fully ionized, or cold if only a small fraction (for example 1%) of the gas molecules are ionized (but other definitions of the terms hot plasma and cold plasma are common). Even in


http://en.wikipedia.org/wiki/Saha_equation

http://en.wikipedia.org/wiki/Ionization_energy

http://en.wikipedia.org/wiki/Ionization_energy

http://en.wikipedia.org/wiki/Ambient_temperature

http://en.wikipedia.org/wiki/Electron_temperature

http://en.wikipedia.org/wiki/Electric_fields

http://en.wikipedia.org/wiki/UV_radiation

http://en.wikipedia.org/wiki/Distribution_function

http://en.wikipedia.org/wiki/James_Clerk_Maxwell

http://en.wikipedia.org/wiki/Thermal_equilibrium

http://en.wikipedia.org/wiki/Electron_volts

http://en.wikipedia.org/wiki/Kelvin

http://en.wikipedia.org/wiki/Degree_of_ionization

http://en.wikipedia.org/wiki/Ionization


a "cold" plasma the electron temperature is still typically several thousand degrees. Plasmas utilized in plasma technology ("technological plasmas") are usually cold in this sense.

6.1.3 DensitiesNext to the temperature, which is of fundamental importance for the very existence of a plasma, the most important property is the density. The word "plasma density" by itself usually refers to the electron density, that is, the number of free electrons per unit volume. The ion density is related to this by the average charge state . The third important quantity is the density of neutrals n0. In a hot plasma this is small, but may still determine important physics. The degree of ionization is ni / (n0 + ni).

6.1.4 PotentialsSince plasmas are very good conductors, electric potentials play an important role. The potential as it exists on average in the space between charged particles, independent of the question of how it can be measured, is called the plasma potential or the space potential. If an electrode is inserted into a plasma, its potential will generally lie considerably below the plasma potential due to the development of a Debye sheath. Due to the good electrical conductivity, the electric fields in plasmas tend to be very small. This results in the important concept of quasineutrality, which says that it is a very good approximation to assume that the density of negative charges is equal to the density of positive charges over large volumes of the plasma .

It is, of course, possible to produce a plasma that is not quasineutral. An electron beam, for example, has only negative charges. The density of a non-neutral plasma must generally be very low, or it must be very small, otherwise it will be dissipated by the repulsive electrostatic force.

In astrophysical plasmas, Debye screening prevents electric fields from directly affecting the plasma over large distances (ie. greater than the Debye length). But the existence of charged particles causes the plasma to generate and be affected by magnetic fields. This can and does cause extremely complex behavior, such as the generation of plasma double layers, an object that separates charge over a few tens of Debye lengths. The dynamics of plasmas interacting with external and self-generated magnetic fields are studied in the academic discipline of magneto hydrodynamics.

6.1.5 Magnetization

A plasma in which the magnetic field is strong enough to influence the motion of the charged particles is said to be magnetized. A common quantitative criterion is that a particle on average completes at least one gyration around the magnetic field before making a collision (ie. ωce / νcoll > 1 where ωce is the "electron


http://en.wikipedia.org/wiki/Magnetohydrodynamics

http://en.wikipedia.org/wiki/Academic_discipline

http://en.wikipedia.org/wiki/Magnetic_field

http://en.wikipedia.org/wiki/Debye_length

http://en.wikipedia.org/wiki/Magnetic_field

http://en.wikipedia.org/wiki/Debye_length

http://en.wikipedia.org/wiki/Electric_field

http://en.wikipedia.org/wiki/Electric_field_screening

http://en.wikipedia.org/wiki/Astrophysical

http://en.wikipedia.org/wiki/Electrostatic_force

http://en.wikipedia.org/wiki/Debye_sheath


gyrofrequency" and νcoll is the "electron collision rate"). It is often the case that the electrons are magnetized while the ions are not. Magnetized plasmas are anisotropic, meaning that their properties in the direction parallel to the magnetic field are different from those perpendicular to it. While electric fields in plasmas are usually small due to the high conductivity, the electric field associated with a plasma moving in a magnetic field is given by E = -V x B (where E is the electric field, V is the velocity, and B is the magnetic field), and is not affected by Debye shielding.

6.2) PLASMAS ON AERODYNAMIC SURFACES

Plasma layers around aircraft have been considered for purposes other than stealth. There are many research papers on the use of plasma to reduce aerodynamic drag. In particular, electrohydrodynamic coupling can be used to accelerate air flow near an aerodynamic surface. It considers the use of a plasma panel for boundary layer control on a wing in a low speed wind tunnel. This demonstrates that it is possible to produce a plasma on the skin of an aircraft. However, it is not clear whether the plasmas generated in these aerodynamics experiments could be used to reduce radar cross-section.


http://en.wikipedia.org/wiki/Electrohydrodynamic

http://en.wikipedia.org/wiki/Drag_(physics)

http://en.wikipedia.org/wiki/Debye_shielding

http://en.wikipedia.org/wiki/Debye_shielding

http://en.wikipedia.org/wiki/Anisotropic


7. GENERATION OF PLASMA ON AIRCRAFTS:

7.1) PLASMATRON-THE SIMPLE METHODPlasmatron is a perfectly new plasma device fit out with a special oxide cathode to incorporate such features as high performance characteristics and simplicity of design.

The device uses no consumable electrodes capable of preventing the pinch effect by scattering electrons in plasma of arc discharge. Prevention of the pinch effect is possible due to minimal rate of movement of electrons in plasma of arc discharge and, correspondingly, minimal magnetic interactions between electrons. This results in formation of wide anode spot (not a thin beam of electrons) on the surface being heated (up to 40 mm in diameter at current of 250-750 A).

The plasmatron is very simple in design and does not need any special installation that makes it highly reliable, easy and convenient in use.

Figures of plasmatron devices



8. ADVANTAGES OF PLASMA STEALTH TECHNOLOGY:Plasma stealth technology has three major advantages.

1) The first is that the RAM painting is not necessary when a plasma cloud is used. This means that the cost and maintenance of RAM coatings are avoided.

2) Second, plasma clouds also provide a heat shield that separates the plane from super heated air.

3) Lastly, the plasma cloud would smoothen airflow across the fuselage of the aircraft making it more aerodynamic.

9. DISADVANTAGES:

Plasma stealth technology also faces various technical problems. For example, the plasma itself emits EM radiation. Secondly, plasmas (like glow discharges or fluorescent lights) tend to emit a visible glow: this is not necessarily compatible with overall low observability. Furthermore, it is likely to be difficult to produce a radar-absorbent plasma around an entire aircraft traveling at high speed.Another shortcoming with plasma stealth technology is that the plasma layer that would surround the plane would also block the pilot’s radar. According to the designers of the Russian SU-35 tested a plasma generator similar to the one mentioned previously. In this model the generator switched frequently to let its own radar out at a set interval. Probably the best solution to this problem is to use a different type of stealth technology on the antenna itself and eliminate the presence of plasma around the radar antenna.

Another drawback is that when the ions neutralize they will give off light and not all ions will neutralize either. These left over ions will neutralize later creating a visible path that points directly to the plane. This visual path is called a plasma trail and can also be used to lock on planes but this can be overcome by either flying very high or by operating only during the day. The plasma trail shown is normal to space shuttle reentry. It is caused by the super heating of air around the space shuttle which ionizes the surrounding gas. This gas then neutralizes behind the space shuttle and gives off light.

Disadvantages aside, this exact technology is being implemented in the Russian “AJAX” hypersonic aircraft project.



CONCLUSION

Imagine you can electronically change the color of a given surface in such a way it can match the terrain below it. Looking from above, the surface appears to match the terrain. Fly over forest, and the surface takes on a green like hue. A cloudy day adds clouds to match what sensors see underneath and the aircraftbecomes a chameleon and disappears. This may sound like science fiction, but then think of the LCD display of notebooks and it may not seem so far fetched all of a sudden. This is not a new idea; in fact several military fiction writers have already come up with the idea, in one particular instance having the aircraft continually modifying top and bottom like a magician’s mirror box making the aircraft totally invisible. More technologies are currently under development and will be closely monitored. But likewise the F-117, we may not hear about that until the first smart bomb coming out of nowhere has made a successful hit!

The advancements in the field of stealth technology has seen staggering heights. Plasma Stealth technology is just one of the advancements that we have seen. In due course of time we can see many improvements in the field of military aviation which would one-day even make stealth technology obsolete.



BIBLIOGRAPHY & REFERENCE

1. Ray Whiteford, Designing For Stealth in Fighter Aircraft, Cranfield University. 2. Electronics for you.

3. Introduction to Radar systems, Merril l Skolnik.

www.aeronautics.ruwww.milnet.comwww.airforce-technology.orgwww.air-attack.comwww.f-22raptor.com
