DrSomnath999
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PLEASE note - this is a translated article from paralay.com pdf a russian article on work done on LOW OBservabilty in PAK-FA
the source is here
http://paralay.iboards.ru/download/file.php?id=18303
if any translation errors are there any russian member if here they should correct it if they are kind enough
REGARDS
PAK FA
Some areas of work in the part of invisibility
.
Air Intakes
It is believed that the air intake and the power plant make the largest contribution to the overall EPR aircraft. Further well-known correlation frequency characteristic fluctuations echo with some parameters low pressure compressor (number of blades, speed), this very phenomenon is called a compressor modulation
Consider how a system consisting of the actual intake and inlet guide vanes (IGV), and for some cases, and the entire power plant. At the beginning of the development considered and tested version of the S-shaped air intake, but later was abandoned. That has some basis, for the same F-22, despite the S-shaped channel radar blocker is still worth
Probably stopped for such an embodiment, the air intake. The air intake is considered as a waveguide, and the impeller load as BHA. This is the impeller and BHA is a radar-blockers. For some natural wave waveguide will impeller.
Nothing new, all known since the F-117, if not earlier, however, like everything else. In principle EOI penetrate waves with a length not more than two of the channel width. For the same F-22 in terms of danger OT wave length from 1.9 cm to 2 m. In the case of OT as a waveguide, the wave to easily penetrate impeller BHA through it but can not pass and is reflected from it, thus losing a significant part of the energy as the impeller RPM covered most effective for a given wavelength range, and then bouncing off the walls of the OT (and just as losing part of the energy) comes back. In the case of shorter waves, the wave goes on VZ reflected from the walls covered with RPM, naturally weakened, hit the impeller BHA,
which in this case the waveguide, and transmits it to the impeller and the motor, where it is repeatedly reflected, extinguished. Also inside the engine of the details have ceramic RPP. That part of the wave that is reflected from the BHA, numerous reflections from the walls of the OT and losing energy comes back.
In general, the question comes down largely to the quality of path computation various wavelengths in the OT, the calculation of the impeller BHA and availability of necessary materials. It should be understood that the principle of equal thickness of ¼ wavelength was justified just say for the first generation of RPM, high dielectric materials in this provision does not apply. Because F-22 on the coating thickness on the impeller BHA is about 1.6 mm per side. Currently the appropriate coating can be made thinner.
As part of the BHA "... in 3-cm wavelength range of choice of a suitable coating can be achieved by lowering the reflection BHA traditional design for 2-4 dB. Elongation of the chord-pillar (so that the total length of the BHA doubles) allows you to get an additional reduction by approximately 3 dB. Drastic reduction of the reflection from the first stage of the power plant by making possible BHA channel is S-shaped, which is associated with a simultaneous increase in length of the BHA. However, the same (two-fold) BHA elongation compared with the case of "direct" input section provides substantially more effective, allowing a reduction in the total design of the field reflected from the input of the engine by approximately 12 dB. "
Radar antenna
Along with the SU is one of the main sources of secondary (scattered) field in the forward hemisphere of the aircraft. Unmasking the antenna cover is due to scattering of the incident wave on the metal parts of the equipment installed in the bay and onto the antenna web. Electronic components or equipment in the usual hiding PRM, e.g., based on polyurethane
The most dangerous deviation antenna curtains within 30-60 degree when the diffraction maximum. To mask the antenna used fabric, usually screens are unmanaged and managed. The general principle - the frequency selective surface. Options control the screen
Electronic control pin diodes are used, in most cases, commercially produced. The initial loss of 0.5 dB (the screen in the open position) Minimum insertion loss and 20 dB (screen closed)
Plasma screen. The screen is effective for electromagnetic radiation at all frequencies below the plasma. These works were carried out in the USSR, and all the parameters have been optimized and the formation / quenching and energy. Prototypes have been tested for many years. It is likely that stopped on a plasma screen, as the site was gone, all information on this topic. Although there was a fairly detailed, indicating areas of required capacity, etc. In addition there was a message on awarding a group of scientists and engineers for their achievements in the implementation of plasma technology and aviation and rocket science.
Wing edges
Radar absorbing ceramic coating (engine)
To reduce the visibility of the aircraft when viewed from the rear hemisphere considered very efficient radar-absorbing coatings on the drawing elements of aircraft engine exhaust nozzle. The only material capable of withstanding the temperature at the same time (up to 1200 ° C) and mechanical stress that are characteristic for this part of the engine is ceramic. Developed multilayer ceramic coating sprayed onto the motor output elements by depositing molten metal microparticles and a dielectric or a semiconductor in the plasma arc discharge burning at atmospheric pressure. The main difficulty, which had to be overcome - the creation of a high adhesion between the layers rather thick metal-ceramic and metal surface. Furthermore, the temperature at which the coating should maintain its properties radiophysical varies widely - from 600 to 1200 ° C. Thus, it was necessary to develop materials, the permittivity and permeability which have not changed over a wide temperature range. This problem is partially solved.
Radio-absorbing coatings covered all the details that make a major contribution to the EPR
motor from the rear hemisphere. In addition the engine is deployed on 15 degree relative
axis. This is done primarily to facilitate the management in case of failure of one
motor, however the side effect deflection nozzle is good for stealth
(it was approximately the same and F-117, there is only the up and 10 degree)
Radio-designed ceramic coating with an operating temperature of 1000 degree Celcius
However, on the instructions of the need to cover an operating temperature 1200. Probably this
related that the above indicates that the problem is solved partially.
the source is here
http://paralay.iboards.ru/download/file.php?id=18303
if any translation errors are there any russian member if here they should correct it if they are kind enough
REGARDS
PAK FA
Some areas of work in the part of invisibility
.
Air Intakes
It is believed that the air intake and the power plant make the largest contribution to the overall EPR aircraft. Further well-known correlation frequency characteristic fluctuations echo with some parameters low pressure compressor (number of blades, speed), this very phenomenon is called a compressor modulation
Consider how a system consisting of the actual intake and inlet guide vanes (IGV), and for some cases, and the entire power plant. At the beginning of the development considered and tested version of the S-shaped air intake, but later was abandoned. That has some basis, for the same F-22, despite the S-shaped channel radar blocker is still worth
Probably stopped for such an embodiment, the air intake. The air intake is considered as a waveguide, and the impeller load as BHA. This is the impeller and BHA is a radar-blockers. For some natural wave waveguide will impeller.
Nothing new, all known since the F-117, if not earlier, however, like everything else. In principle EOI penetrate waves with a length not more than two of the channel width. For the same F-22 in terms of danger OT wave length from 1.9 cm to 2 m. In the case of OT as a waveguide, the wave to easily penetrate impeller BHA through it but can not pass and is reflected from it, thus losing a significant part of the energy as the impeller RPM covered most effective for a given wavelength range, and then bouncing off the walls of the OT (and just as losing part of the energy) comes back. In the case of shorter waves, the wave goes on VZ reflected from the walls covered with RPM, naturally weakened, hit the impeller BHA,
which in this case the waveguide, and transmits it to the impeller and the motor, where it is repeatedly reflected, extinguished. Also inside the engine of the details have ceramic RPP. That part of the wave that is reflected from the BHA, numerous reflections from the walls of the OT and losing energy comes back.
In general, the question comes down largely to the quality of path computation various wavelengths in the OT, the calculation of the impeller BHA and availability of necessary materials. It should be understood that the principle of equal thickness of ¼ wavelength was justified just say for the first generation of RPM, high dielectric materials in this provision does not apply. Because F-22 on the coating thickness on the impeller BHA is about 1.6 mm per side. Currently the appropriate coating can be made thinner.
As part of the BHA "... in 3-cm wavelength range of choice of a suitable coating can be achieved by lowering the reflection BHA traditional design for 2-4 dB. Elongation of the chord-pillar (so that the total length of the BHA doubles) allows you to get an additional reduction by approximately 3 dB. Drastic reduction of the reflection from the first stage of the power plant by making possible BHA channel is S-shaped, which is associated with a simultaneous increase in length of the BHA. However, the same (two-fold) BHA elongation compared with the case of "direct" input section provides substantially more effective, allowing a reduction in the total design of the field reflected from the input of the engine by approximately 12 dB. "
Radar antenna
Along with the SU is one of the main sources of secondary (scattered) field in the forward hemisphere of the aircraft. Unmasking the antenna cover is due to scattering of the incident wave on the metal parts of the equipment installed in the bay and onto the antenna web. Electronic components or equipment in the usual hiding PRM, e.g., based on polyurethane
The most dangerous deviation antenna curtains within 30-60 degree when the diffraction maximum. To mask the antenna used fabric, usually screens are unmanaged and managed. The general principle - the frequency selective surface. Options control the screen
Electronic control pin diodes are used, in most cases, commercially produced. The initial loss of 0.5 dB (the screen in the open position) Minimum insertion loss and 20 dB (screen closed)
Plasma screen. The screen is effective for electromagnetic radiation at all frequencies below the plasma. These works were carried out in the USSR, and all the parameters have been optimized and the formation / quenching and energy. Prototypes have been tested for many years. It is likely that stopped on a plasma screen, as the site was gone, all information on this topic. Although there was a fairly detailed, indicating areas of required capacity, etc. In addition there was a message on awarding a group of scientists and engineers for their achievements in the implementation of plasma technology and aviation and rocket science.
Wing edges
Radar absorbing ceramic coating (engine)
To reduce the visibility of the aircraft when viewed from the rear hemisphere considered very efficient radar-absorbing coatings on the drawing elements of aircraft engine exhaust nozzle. The only material capable of withstanding the temperature at the same time (up to 1200 ° C) and mechanical stress that are characteristic for this part of the engine is ceramic. Developed multilayer ceramic coating sprayed onto the motor output elements by depositing molten metal microparticles and a dielectric or a semiconductor in the plasma arc discharge burning at atmospheric pressure. The main difficulty, which had to be overcome - the creation of a high adhesion between the layers rather thick metal-ceramic and metal surface. Furthermore, the temperature at which the coating should maintain its properties radiophysical varies widely - from 600 to 1200 ° C. Thus, it was necessary to develop materials, the permittivity and permeability which have not changed over a wide temperature range. This problem is partially solved.
Radio-absorbing coatings covered all the details that make a major contribution to the EPR
motor from the rear hemisphere. In addition the engine is deployed on 15 degree relative
axis. This is done primarily to facilitate the management in case of failure of one
motor, however the side effect deflection nozzle is good for stealth
(it was approximately the same and F-117, there is only the up and 10 degree)
Radio-designed ceramic coating with an operating temperature of 1000 degree Celcius
However, on the instructions of the need to cover an operating temperature 1200. Probably this
related that the above indicates that the problem is solved partially.
