Task: to find stealth
Despite the long history research and development in the field of stealth, the number of practical methods used in practice is not so great. So, to reduce the probability of detecting an aircraft using radar, it must have specific hull and wing circuits that minimize reflection of the radio signal towards the radiating antenna, and also, if possible, absorb some of this signal. In addition, thanks to the development of materials science, it became possible to use radio-transparent materials in the structure, which do not reflect radio waves. As for stealth in the infrared range, in this area all solutions can be counted on fingers. The most popular method is to create a special nozzle for the engine. Due to its shape, such a unit is capable of significantly cooling reactive gases. As a result of applying any of the existing methods of reducing visibility, the detection range of an aircraft is significantly reduced. At the same time, the complete invisibility in practice is unattainable; only a decrease in the reflected signal or the radiated heat is possible.
It is the remnants of radio and thermal radiation that are the “hooks” that can make it possible to detect an aircraft made using stealth technology. In addition, there are techniques that allow to increase the visibility of a stealth aircraft, without resorting to very complex technological solutions. For example, it is often proposed to use their own main feature against unobtrusive airplanes - the dispersion of incident radio waves. In theory, it is possible to separate the transmitter and the radar receiver at a sufficiently long distance. In this case, the “distributed” radar station will be able to easily capture the reflected radiation. However, despite its simplicity, this method has several serious drawbacks. First of all, it is the difficulty of ensuring the operation of the radar with a transmitter and receiver separated by a considerable distance. Some kind of communication channel is required, connecting the various blocks of the station and having sufficient characteristics of speed and reliability of data transmission. In addition, in this case, special difficulties will be caused by great complexity or even the inability to make two rotating antennas, synchronize the operation of systems, etc.
All the complexities of remote radar equipment do not allow such systems to be used in practice. However, a similar principle is used in electronic intelligence systems, which can also be used to detect enemy aircraft. Last year, the European concern EADS announced the creation of a so-called. passive radar, which only works to receive and processes incoming signals. The principle of operation of such a system is based on the reception of signals from third-party emitters - tele- and radio towers, cellular substations, etc. Some of these signals can be reflected from a flying aircraft and fall on the antenna of a passive radar, the equipment of which analyzes the received signals and calculates the location of the aircraft. The main difficulty in designing this system was reportedly the creation of an algorithm for the computing complex. The electronics of the passive radar is designed to extract the necessary signal from all available radio noise and its subsequent processing. There is information about the creation of a similar system in our country. Receipt of passive radar in the troops should wait no earlier than 2015 year. At the same time, the prospects of these systems are not completely clear, although the manufacturers, in particular the EADS concern, already now feel free to make loud statements about the guaranteed detection of any unobtrusive flying equipment.
An alternative to bold new solutions like antenna diversity or passive radar is a method that actually represents a return to the past. The physics of propagation and reflection of radio waves is such that as the wavelength increases, the main indicator of the object's visibility — its effective scattering surface — increases. Thus, by returning to the old long-wave emitters, you can increase the probability of detecting a stealth aircraft. It is noteworthy that the only currently confirmed case of the destruction of an inconspicuous aircraft is associated with this method. 27 March 1997 was shot down by an American F-117A strike aircraft over Yugoslavia, discovered and attacked by a calculation of the C-125 anti-aircraft missile system. One of the main factors that led to the destruction of the American aircraft was the working range of the detection radar, which worked in conjunction with the C-125 complex. The use of meter-range waves did not allow the aircraft’s stealth technologies to prove themselves, which led to a subsequent successful attack by anti-aircraft gunners.
Of course, the use of meter waves is far from a panacea. Most modern radar stations use shorter wavelengths. The fact is that as the wavelength increases, the range increases, but the accuracy of determining the coordinates of the target decreases. As the wavelength decreases, the accuracy increases, but the detection range falls. As a result, the centimeter range was recognized as the most convenient for use in radar, which gives a reasonable combination of detection range and accuracy of determining the location of the target. Thus, a return to older radars with a longer wavelength will necessarily affect the accuracy of determining the coordinates of the target. In some cases, this feature of long waves can be useless or even harmful for a radar or air defense system. When changing the operating range of the radar, it is also worth considering the fact that promising stealth planes are likely to be created in the future, taking into account the possible countermeasures of the most common radar stations. Therefore, such a development is possible when the designers of the radar will change the radiation range, trying to balance the range, accuracy and requirements for countering stealth solutions of aircraft designers, and those in turn will change the design and appearance of aircraft in accordance with current trends in development of detection tools.
The experience of previous years clearly shows that the protection of any object requires several anti-aircraft complexes and several detection tools. There is a concept of so-called. integrated radar system, which, according to its authors, is able to provide reliable protection of covered objects from air attacks. An integrated system implies “overlapping” of the same area by several radar stations operating at different ranges and frequencies. Thus, an attempt to fly unnoticed by an integrated system's radar will result in failure. A part of the reflected signal from these stations can get on to others, or the aircraft will give out its side projection, which, for obvious reasons, is poorly adapted for dispersing the radio signal. This technique allows fairly simple methods to detect stealth aircraft, but it has a number of drawbacks. For example, it is difficult to maintain and attack targets. For effective missile guidance, you will need to create an effective data transmission system from the “side” radar to the control systems of the air defense system. This need is preserved when using radio-command missiles. The use of missiles with radar seeker - active or passive - also has its own characteristics, which partially impede an attack. For example, the effective capture of a target by a homing head is possible only from a number of angles, which does not increase the combat effectiveness of the rocket.
Finally, the integrated air defense system, as well as other systems using radio waves, are subject to attacks by anti-radar missiles. In order to prevent the destruction of a station, a short-term activation of the transmitter is usually used in order to have time to detect the target and not let the rocket be aimed at it. However, another method of countering anti-radar missiles is also possible, associated with the absence of any radiation. Theoretically, the detection and tracking of stealth aircraft can be carried out using systems that capture the infrared radiation of the engine. However, such systems, firstly, have a limited detection range, which, moreover, depends on the direction to the target, and secondly, they significantly lose their effectiveness when radiation levels decrease, for example, when using special engine nozzles. Thus, optical-location stations are unlikely to be used as the main means of detection with the required efficiency of existing and prospective aircraft made using stealth technology.
Thus, at present, several technical or tactical decisions can be considered at once as a measure of countering stealth technologies. At the same time, they all have both pros and cons. Due to the lack of any means capable of finding stealth planes guaranteed, the most promising option for the further development of all detection technologies looks like a combination of various techniques. For example, the system of an integral structure, in which radars of both centimeter and meter range will be occupied, will have good opportunities. In addition, the further development of optical-location systems or combined complexes looks quite interesting. The latter can combine several principles of detection, for example, radar and thermal. Finally, recent work in the field of passive location allows us to hope for the soon emergence of practically applicable complexes operating on this principle.
In general, the development of aerial target detection systems does not stand still and is constantly moving forward. It is possible that in the near future any country will present a completely new technical solution designed to counter stealth technology. However, we should not expect revolutionary new ideas, but the development of existing ones. As we see, existing systems have much to develop. Yes, and the development of air defense will necessarily entail the improvement of the technology of hiding aircraft.
On the materials of the sites:
http://airwar.ru/
http://ausairpower.net/
http://paralay.com/
http://vivovoco.rsl.ru/
http://pvo.guns.ru/
http://rbase.new-factoria.ru/
http://vpk-news.ru/
http://janes.com/
http://popmech.ru/
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