To provide a low radar visibility of the aircraft, widely used plasma technologies, especially plasma-vacuum, with which to create the scattering coating on the lamp cockpit. Normal windows folding lamp is transparent to electromagnetic waves, so if the electromagnetic wave is incident on a plane from the upper hemisphere, hollow cabin makes significant contribution to the ESR of the observation angles. One solution to the problem of low radar visibility plane is fairly obvious: Metallizing glazed cabin. Reflected from the metallized lamp electromagnetic wave will not be returned to the radar receiver, to be rather, the value of the ESR cab, averaged over some small sector of angles of observation, significantly reduced. However, the metallization should not worsen optical properties of glass cockpit, which imposed extremely stringent requirements. Thus, the reflection coefficient of glass lantern Cabin in the microwave should be close to unity, and in the optical - to zero. But in this case the requirements for coverage, not exhausted. There is a problem overheating pilot in the cockpit, used in tropical countries. Power conditioning in the cabins of many foreign aircraft, however, as and a number of our people, not enough for a comfortable state of the pilot, therefore, requires certain steps for the selection of the infrared spectrum.
Generally speaking, This problem arises in the creation of selective energy-saving glass in the construction industry. At the Institute of Theoretical and Applied Electrodynamics RAS proposed and patented the so-called energy-saving glass. They are produced in large vacuum chambers, where the glass surface is applied multi-layer coating by magnetron (probably - magnetron - VV ), sputtering. To achieve the best optical, infrared and microwave characteristics are used coatings consisting of alternating films of various metals and their oxides thickness of approximately 100 A. Abroad, established powerful industry of manufacture of such glasses in Russia, mass production, usually based on the export (probably - Import - VV ), equipment.
However, folding of the canopy all aircraft made not of glass, polymer, and, moreover, its surface has double curvature. Polymer base canopy pilots periodically subjected to strain. For materials scientists involved in the process of spraying, the technological challenge of essentially reduced to the deposition of thin hard coating thickness in fractions of micrometers ... a soccer ball with the requirement of durability of this thin coverage. We all know that during the game thin film on the surface of the ball covered with countless number of cracks. Nevertheless, this problem could be solved by magnetron sputtering in a vacuum metal to produce metallic island films. These films are alternated with polymer layers caused by Plasma-chemical method. The quality of multilayer coatings can be significantly improved if they are understood and predicted by the end of many plasma- reactions occurring during the deposition of polymer films in low-temperature plasma discharge.
It is well known that by changing the discharge regime and composition of hydrocarbon and fluorinated gases, which burn level, we can obtain a wide range of properties of the deposited film - from the polycrystalline diamond to the polymer. And although we do not have complete fundamental knowledge in this field, developed a stable plasma-chemical technologies, implemented in a large vacuum chamber with a volume of 22 m 3 with a pressure of 4 x 10 -5 mmHg The camera is equipped with a computer-controlled robot, which moves the magnetron, and computer-controlled gas inlet system and discharge control. In this chamber, and coated on a variety of optically transparent airplane parts.
To reduce the ESR aircraft under the supervision of its rear hemisphere is first necessary to reduce the ESR cavity of the engine exhaust nozzle. In addition to special affirmative action, which must be provided for the establishment of new engines, effective application of radar absorbing coatings found on the elements exhaust nozzle. The only material capable of withstanding both the temperature (1200 ° C) and mechanical stress typical for this part engine, is ceramics. Developed multi-layer ceramic coating is deposited on the weekend engine components by applying melted microparticles dielectric and metal or semiconductor plasma arc discharge burning at atmospheric pressure. The main difficulty that had to be overcome - the creation of high adhesion between the relatively thick layers of metal-ceramic and metal surface. As is known, ceramics and metal core aircraft structure have significantly different coefficients of thermal expansion. In addition, the temperature at which the coating must maintain radiophysical their properties vary over a very wide range - from 600 to 1200 ° C. Thus, it was necessary to develop materials, dielectric and magnetic permeability which should not be changed in a wide temperature range. This problem is partially solved: motors with radio absorbing ceramic coatings are on board the aircraft and tested in various flight regimes.
The fundamental problem is to reduce reflection from the nose fairing aircraft. Due to the fact that under the dome is a system of radar, but because it is often the system of units with equipment, providing the antenna, contribution to the antenna unit in the ER aircraft can greatly exceed the contribution of all other elements of its design. In that case, if the mirror antenna is directed orthogonally to the line locator, the EPR may reach several tens or more square feet. This means that all the other tricks that were invented to reduce the radar visibility of the aircraft, become meaningless. However, if you turn the mirror of the antenna, pointing it, for example, up can significantly alter the EPR along the axial direction.
This - a trivial and well-known solution, and it is widely used. But in some cases, this procedure is not effective enough.
proposed several solutions to this problem. We consider only those associated with the use of controlled screens, the more so because such screens can be used on new aircraft and the modernization of existing ones. Let's start with the version that appears most straightforward in terms of technical solutions.
deposited on the inner surface of the fairing radiotransparent semiconductor film, arranged so that under the action of the optical or ultraviolet radiation, it can change the conductivity by many orders of magnitude. Then, putting under the fairing of the sources of optical radiation (Fig. 5 a), we might, depending on our desire to translate the surface of the fairing of the state, fully transparent to microwaves, fully reflecting the state, if the impact of radiation sources that are above the dome, the conductivity reaches high values. Metallized fairing will reflect the incident electromagnetic wave at him, and his ESR for observation angles other than from orthogonal to the axis of the aircraft will be low. Naturally, at that time own radar aircraft can not work.
 | Fig. 5. circuit the reflection of electromagnetic waves from the fairing with the semiconductor driven shield (a), the change in resistance of semiconductor films depending on the light (b) scheme and the reflection of electromagnetic waves from the dome with controlled screen (a) On the chart: the dark rectangle corresponds to the conductivity of the films, ensuring the transparency of the screen, a gray box - the level of conductivity, providing surface metallization PLF-1 - the resistance of existing semiconductor films, 2 - the resistance of the hypothetical film, which will implement the idea of a semiconductor Managed screen |
Generally speaking, the resistance of semiconductor doped films CdSn or CdS varies by many orders of magnitude at quite a reasonable level of illumination (curve 1 in Fig. 5, b). However, they are not suitable for the implementation of the above technical solutions. Necessary the film with other dynamic properties (curve 2 in Fig. 5, b), but as they do not yet very clear.
Another technical solution - installing front radar screen, on the surface of which there are so-called frequency-selective structures - a system of periodic openings of some form, configured in such a way that they are free to pass in both directions, an electromagnetic wave in a narrow band of natural frequencies of radar and fully отражают электромагнитные волны других частот. Вводя в эти специальным образом организованные отверстия, которые, по существу, представляют собой открытые резонаторы, управляющие полупроводниковые системы, можно при желании "закрыть" экран, сделав его непрозрачным для всех частот.
Проблеме частотно-селективных surfaces is an extensive literature from which we can draw conclusions about the peculiarities of their application. We have developed numerical methods for calculating the frequency-selective screens, possess the appropriate technology and produced a working model of managed screens. Depending on the specific design of the antenna can be used as a frequency-selective screen and plasma. It is mounted inside the fairing the same way as the frequency-selective screen, but it принцип действия несколько другой. При отсутствии сигнала управления, который может подаваться пилотом самолета или его станцией обнаружения внешнего exposure, the screen turned off and transparent at all frequencies. When the signal goes to the screen voltage is applied, it ignited the low-temperature collisional plasma, as a result of the radiation is partially reflected from the screen in the directions shown in Figure 5, and is partially absorbed in the screen. The screen is effective для электромагнитного излучения всех частот, меньше плазменной. Значение плазменной частоты в таких системах может быть очень большим. Многолетние исследования processes occurring in low-temperature plasma, allowed to find optimal parameters for gas composition, plasma generators, and optimize high-speed system of plasma generation needed to respond to rapidly changing external environment. Flight tests demonstrate the high efficiency of the proposed decisions aimed at reducing the radar visibility of the antenna cover.
control so many radio physical and electrical parameters individual layers that make up the coating, and the optimization results of individual fragments of the aircraft is carried out in the radio-physical experiments. To study the macroscopic parameters of the substances, the behavior of frequency dispersion of dielectrics, ferromagnetic materials, fine particles, made from ferromagnetic alloys, semi-thin island films used laboratory equipment, which must satisfy all the requirements of the modern physical laboratories in the electrodynamics of continuous media. In addition, special Materials Research and Chemical Equipment designed to study the properties of the composites.
Fragments of the aircraft covered with radar absorbing and dispersing coatings investigated in the so-called anechoic chambers. In these simulated conditions, realized in the space of the real situation, when which an object falls flat electromagnetic wave, and no reflections from the underlying surface. Creating anechoic chamber with a low noise requires skilful work skills which Russian scientists speak in such a degree that exporters of these cameras in industrialized countries. After as the main fragments of the aircraft will be tested in an anechoic chamber, introduced the amendment process, if necessary, and shall complete technological cycle of work on the aircraft. In the process it is the continuous monitoring of Radio.
All of the above technological developments implemented in our country, and in advanced foreign countries. Demonstrate the global trend of radar visibility of supersonic maneuverable aircraft (Fig. 6). If in the 1980's aircraft such as F-15 had ESR greater than 10 m 2 then modernized aviation system EPR is 1-1.5 m 2 , and a promising fifth-generation aircraft systems, such as the F-22, JSF, - 0.3 m 2 . Still lower value of the EPR in a modernized national MiG-21.
| Fig. 6. Trends in radar visibility of supersonic aircraft |  |
Interventions to reduce the visibility of the aircraft to be agreed with the opportunities and requirements of electronic countermeasures. Reducing visibility, of course, reduces the power consumption of electronic countermeasures, but more importantly, the use of subtle means of electronic countermeasures aircraft provides a significant advantage in the air.
In foreign literature You can find estimates of the probability of loss of aircraft depending on the EPR (Fig. 7). Decrease in ESR to 10-15 m 2 - values typical of the heavy fighters of the fourth generation of up to 0.3 m 2 can fundamentally reduce the losses of aircraft in combat. This effect is enhanced if simultaneously with the aircraft, having a low ESR, apply modern means of electronic countermeasures (Fig. 8).
 | Fig. 7. loss of the aircraft in overcoming the defense, depending on their effective surface scattering |
| Fig. 8. Effect of joint use of radar counteract and reduce radar visibility for the loss of aircraft |  |
should be remembered that at the first stage of construction new aircraft, you must decide whether we are prepared to put as the problem number 1 is possible to obtain a small value of ESR at the expense of many other properties of the aircraft or shall we endeavor to keep up the good aerodynamics in achieving a low level of its radar visibility. Examples of the first approach - This aircraft the F-117 and B-2, whose shape is optimized to achieve low ESR at the expense of their aerodynamic properties, examples of the second approach - it's a plane F-22 JSF and several others.
Obviously, when you create a new aircraft with low ESR are required design-technological measures to optimize form of an airplane: To ensure a smooth transition between the elements of the airframe, the exclusion of external load of weapons - carry weapons inside the fuselage. In turn, This requires longitudinal stiffness fuselage input into the construction of additional hydro units, security start-up and discharge of weapons, and even change targeting algorithm.
One of the technological methods that reduce the visibility of the aircraft - the use of large panels of complex forms as elements of fuselage (Fig. 9). Having established such a panel can significantly reduce the number of joints of casings on the surface of the aircraft and the number of riveted and bolted joints, which are elements reflected in the forward hemisphere at various angles.
After performing all the activities aimed at reducing the radar visibility is required optimization of complex avionics. Unmasking symptoms caused by his work, become significant at background of low radar visibility plane. Minimization of operating time on-board equipment in raioelektronnogo radar radiation, the use of bistatic radar mode. Wanted covert methods of communication for aircraft that are in the group. Two aircraft are in pairs, and one of them emits a signal, while the second operates in passive mode and can not be detected by the locator of the enemy. Using computational capabilities of the onboard equipment, maps and a variety of other methods allows radio silence to determine the position of the aircraft and combat missions.
is necessary to ensure the effectiveness of all the activities. Naturally, the most objective criterion of efficiency would participate in a real conflict, which, fortunately, in recent years trying to avoid most of the countries. But the process of test aircraft from the point of research on their radar visibility is required and has a number of specific features. Detection probability is proportional EPR is a statistical measure and depends on many factors, including weather conditions and, naturally, the plane off course with respect to radar.
flight tests precede the ground, when conducted surveillance aircraft from various angles. Ground measurement complex (Fig. 10) allows you to get pie charts of the EPR in a wide range of wavelengths. Measurements can be performed with the engine running, which is important to determine the EPR in the rear hemisphere. There is also an opportunity to assess the contribution of individual elements in the ER aircraft. Then, the EPR plane measured in terms flight with simultaneous evaluation of the detection range. For a set of statistics to a large number of experiments on the ground and in flight. In particular, during works to reduce the radar visibility of the fourth generation aircraft such as Su-27 for a set of statistics, it took more than 100 hours of continuous operation radar stations on the ground and stand over 30 hours - in flight. In some cases, comparisons were paired flights, in which участвовали малозаметный и обычный самолеты.
Рис. 10. Самолет на поворотной платформе наземного измерительного комплекса
Подводя up, we can say that as a result of research and solve a number of fundamental and applied problems stele technology: created computational and experimental methods and complex technologies to reduce the visibility, refined and tested fourth-generation aircraft such as Su-27, proposed radio-absorbing materials that are not inferior in its characteristics best foreign specimens. We believe that this area requires further development to strengthen the country's defense. Stealth technology can be used in aircraft modernization, standing on the arms, and creating advanced aircraft systems.
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