Cassidian, the defence and security division of EADS, has developed what is known as "passive radar" that can locate even difficult-to-detect flying objects such as stealth aircraft and that itself is practically undetectable. In contrast to conventional radar, passive radar doesn't emit any radiation, but instead analyses radiation reflections from other emitters, such as radio and television stations, to detect objects.
China has recently tested its stealth fighter jet. The tests went well, although a question remains as to why Chinese engineers still use the previously popular technology. The stealth technology has been repeatedly proved ineffective experimentally.
It has long been known that the aircraft survivability in combat can be provided not only through armored plates installed on the body of the aircraft. It is possible to achieve the desired goal by duplicating its control systems, raising the speed and ensuring its invisibility - i.e. by masquerading aircraft against the earth and the sky. However, one can not say that it is the aviation industry that pays special attention to camouflage. For example, on the eve of World War II, Soviet fighter aircraft would be painted blue on the bottom, and green on the top. These colors used to be considered as camouflage.
However, Soviet aircraft used to be varnished. Therefore, fighter jets were shining like candy in the sky and could be seen very well. SB bombers used to be colored with silvery paint. The losses of the USSR in aircraft on 22 June 1941 were not surprising at all. Combat experience made engineers use speckled and striped camouflage with matte surface, and this form of protective coloration became the commonplace technology of passive protection.
Print version Font Size Send to friendThe protection was useless against enemy radars, of course. The British came up with a different idea. They offered to drop strips of metal foil from airplanes, with the length of the strips corresponding to the length of enemy radar radiation. A bright spot would thus be displayed on the screen instead of separate pixels. This technology would give really hard times to air defense forces. After all, such a cloud on the screen could be created by both one and hundreds of aircraft at the same time.
The technology to protect aircraft from radars appeared about 30 years ago, when U.S. intelligence came across an article penned by the Russian physicist Pyotr Ufimtsev. The article said that the aircraft of the "flying wing" type made of certain materials, with specially profiled surfaces and appropriately colored, could turn out to be virtually invisible to radar. US military showed great interest in the work, and the United States decided to build and test such an airplane.
The Americans had all opportunities for that. During that time, the Pentagon was developing a program to create a new generation of aircraft - a high-altitude spy plane and a high-altitude interceptor. The aircraft was supposed to be out of reach to enemy's means of detection and destruction. In the mid-1970s, the U.S. Air Force received the first-class spy plane SR-71, which was peculiar for its unusual aerodynamic shape and special paint to reduce the radar visibility of the aircraft.
There is information saying that on the aircraft of this type, Soviet missile engineers produced more than a thousand of S-75 anti-aircraft missiles, but none of those planes had ever been downed! Encouraged with their success, the Americans moved on and began to develop new types of invisible aircraft based on the ideas of the Russian physicist. The project became known as "stealth" technology.
However, the attempts to create the "stealth aircraft" were not bringing any results for a long time. Only 20 years ago, the U.S. showed the world a miracle of defense technology. The aircraft looked like a bat or an alien combat aircraft in two modifications at once: F-117 fighter-bomber and B-2 strategic bomber. The new bomber planes were used in the war against Iraq. A little later, stealth fighter F-22 went into operation.
Outwardly, the F-117 was similar to the flying wing in a span of 13.2 meters. Except for the special shape, the entire design of the aircraft was developed with the best possible use of radar-absorbing materials that reduced the level of signals the aircraft was reflecting.
The flying and technical qualities of the F-117 are not the best in the world, to put it mildly.
However, the whole stealth technology was designed for the use of S-band enemy radars, for which these "invisible" aircraft are really hard to notice. However, Russia, and air defense forces of other countries now have VHF-band radars for which it does not matter whether it is a "stealth" or a normal plane.The news of the invisibility of stealth planes for only one type of radar caused a scandal in the U.S. government. The development of stealth aircraft cost billions of dollars, and it turned out that their combat effectiveness could be even lower than that of older aircraft.
However, it seems that the problem has not reached military organizations of all countries. Recently, news agencies reported that a prototype of the Chinese J-31 fighter, developed by AVIC Shenyang Aircraft Corporation took off successfully. The flight took place on October 31, 2012, lasted for about 10 minutes and ended with a successful landing.
The J-31 (J-21/F-60) is a second Chinese fighter made with the use of stealth technology. It was developed in record time - in only 19 months. In contrast to J-20, the J-31 is smaller and probably cheaper than the J-20. It can become a very popular aircraft in the arms market. Chinese aircraft designers did not hesitate to borrow US design solutions that had been tested on F-22 and F-35 fifth-generation fighters.
Experts note that the wings, nose cone, air intakes and cockpit canopy of the J-31 almost completely reproduce the contours of similar parts of the aforementioned U.S. aircraft. This is probably the result of the work of Chinese intelligence. In particular, there was a scandal in the United States in 2009 connected with the theft of drawings from six American aerospace contractors, including those involved in the development of the F-35 fighter.
For the time being, it just so happens that the Chinese fighter will compete on the international arms market with more simple and cheap modifications of Russia's Su-27 and MiG-29, rather than with the complex and expensive F-35. Currently, the Chinese have quite modern electronic equipment, including phased antenna array radar stations.
The situation with modern jet engines of Chinese development is more complicated, although China has some progress in building its own digital control engines. The J-31 has two of them, and most likely, they are either Russian RD-93 engines, which China bought from Russia, or their Chinese copy WS-13. The J-31 has a wingspan of about 11.5 meters, which means that the plane is smaller than the American F-22.
The "Chinese miracle" may have some commercial success in the arms market, but the real value of such military aircraft today is questionable. The growing number of satellites in Earth's orbit makes it easy to detect any number of any type of aircraft from space to subsequently destroy them.
The meeting of wavelengths between radar and aircraft causes resonation between the two, significantly raising an aircraft's reflection in the radar spectrum, making it much more visible.
VHF radar has been incorporated into the Russian military's 1L119 Nebo SVU, its first VHF-band active electronically steered array (AESA); although detailed analysis of this vehicle-mounted array, Russian sources report it has achieved excellent results in spotting stealth aircraft.
