The problem of detection of aircraft such as stelc

The problem of detecting aircraft type "stelc"

(According to gaze foreign military professionals)

The U.S. military would persist in their efforts to achieve military advantages over the Russian Union, making an unusual bet on new types of equipment and instruments. In today's criteria as between the USSR and the United States signed contract on the Elimination of Intermediate-Range and the lower, negotiated a 50 per cent reduction in strategic offensive weapons in the Pentagon's plans strategists increasingly prominent place given to subtle aircraft (LA). Since 1983, the South American programm "Stelc" aimed at the development of the technology stealth aircraft, the least coverage in the Western press. On the first place in popularity came Strategic Defense Initiative. Yet incarnation applets "Stelc" lasts quite highest rate. According to the views of zabugornyh military professionals, the results gained in the process of its implementation will have a strong influence on the kind of promising aircraft. It is believed that the decrease in visibility will be leading the trend in military aircraft 90s. Proof of this are the development of higher-priority programs from the aircraft of different classes, with low visibility property. These aircraft include the B-2 bomber, promising tactical fighter ATF, ACM cruise missile.

Decrease the visibility of the aircraft is carried out in different parts of electric ranges, radar, optical, infrared and acoustic. Most attention is paid to reduce the radar cross section, as at the present time the main means of detecting aircraft in air defense systems are radar stations. Known and technical ways reduce radar visibility LA: improving aerodynamic shapes, the use of new construction materials and coverings, the decrease in the number of antennas, etc. Judging by zabugornoy printing, advanced technology, made by programmke "Stealth", can reduce the effective size of the scattering (EPR) aircraft almost 70 percent. compared with conventional aircraft schemes. With all of this detection range of such stealth aircraft will be reduced to the third part, because the detection range is proportional to the fourth power of the ESR values.

Predicting the total receipt for service in the 90s stealth aircraft, zabugornye military agencies deployed a wide range of studies on problems of combating such aircraft. The focus for all this dilemmas spetsy pay increase range radar stealth aircraft, believing that the implementation of the results in almost all will determine the type of radar 90s.

Ongoing research and development at the current time conventionally divided into two groups. The first group of research conducted within the framework of the usual approach to solving the puzzles increase the range of the radar target detection. Namely, we study the ability of the growth of the energy potential of radar, increasing the sensitivity of the radar receiver. The corresponding feature of these operations is that in the process of actually recorded specificity type aircraft "Stealth" as radar targets. The results of the work is meant for use in the main upgrade existing radar.

The second group of research and development a huge variety of different thoughts and directions of research. It presents a completely new approaches, and known in the theoretical ideas of radar, which for various reasons have not been implemented before. Common is the desire of researchers to use for the growth of the detection range of special features for stealth aircraft (for example, the relevant forms). As a result of these R & D generally, the necessity of the creation of fundamentally new systems and equipment.

The problem of detecting stealth aircraft associated with effective scattering area whose magnitude is dependent on many factors: the size, shape, spatial position of the aircraft, the material from which it is made, the frequency, polarization and form the illuminating signal. However, even petty change at least some of the causes of naming can lead to a substantial (and more than an order of magnitude) change in the value of the EPR. Because when you specify the value of the EPR certain aircraft must be precisely defined the conditions under which they were obtained. But zabugornyh publications devoted subtle aircraft, this rule is often bullied. So, speaking of the value of the ESR unobtrusive LA usually lead its value during irradiation apparatus in the front hemisphere, although the adopted measure is the average value of EPR aircraft irradiated from all directions. Thanks to the similar "little tricks" in Western publications devoted to stealthy aircraft, there is a value of the ESR equal to 10.2 m2.

Foreign military experts at note that most of the founders of publications about the stealth aircraft are specifically related to their development. Because these articles are usually subtle highlights the advantages of the aircraft, but about the shortcomings or controversial issues mentioned. Common in calculations of the detection range of stealth aircraft is the introduction of features available air defense radars. Improving the ability of the radar, and the configuration parameters that affect the EPR objectives are not usually considered, although the spices in the field of radar on the basis of an impartial analysis of the features stealth aircraft and the dependence of the EPR features of radar have led to a promising way to increase the detection range of the objectives of this type.

Classical methods of increasing the range of detection based on the increase of the energy potential of radar and enhancing the properties of signal processing. The first may rise due to the increase in transmitter power and antenna directivity factor acts radar. In the future, expected to occur generating devices that will increment power radar transmitters at 2-3.
Increasing the act directed, usually associated with an increase in the geometric size of the antennas. The possibility of the creation of the 'Aircraft distant radar conformal antennas based on phased array antennas. Antennas of this type will be part of the skin of the aircraft, which will allow them to locate, for example, along the fuselage or the front edge of the wing. So Makarov, it becomes possible to increment the geometrical dimensions of the antenna to the limits determined by the size of an aircraft carrier. But, as the calculations show, even the size of the antennas to increase the limit values provide increased detection range of only 60-70 percent., That will allow to fill reduction target RCS is 10 dB. In connection with this zabugornye experts at turning their attention to the fact that the newly growing role of ground radar systems, antennas, which have virtually no restrictions on the geometric dimensions.

The increase in properties of the radar receivers will reach first by analyzing the structure of the narrow signals on the basis of the implementation of digital filtering algorithm on a computer. In this regard, great hopes are pinned on the introduction of high-speed integrated circuits and integrated circuits integral microwave and millimeter-wave bands. To perform certain operations on signal processing are charge-coupled devices that also use the surface acoustic wave.

To increment range detecting stealth targets, U.S. Air Force plans in the first half of the 90s to upgrade AWACS radar planes and management of E-3 AWACS (see color insert), in other words to make better quality digital signal processing by a computer. It is believed that after the
modernization range target acquisition will increase significantly due to the increase of the signal level by 10-13 dB, and increased reliability and noise immunity radar. Improvements will also affect other electronic equipment E-3 aircraft. It is planned, that is, to establish a specific electronic intelligence systems for passive detection of enemy aircraft, apperaturu NAVSTAR satellite navigation system and terminals 2nd class integrated tactical system disk imaging rassredotachivaniya DZHITIDS.

A well-known technique to increase the detection range is to increase the time of coherent clusters of echoes. Based on this principle, a method of inverse synthetic aperture. It uses techniques, working in modes that are used in synthetic aperture radar and allow to obtain detailed images of ground targets on the basis of the analysis of Doppler frequency signal. The distinguishing feature of this method is that the accumulation signal is due to motion target and the radar antenna is not as in the ordinary synthetic aperture.

The method of inverse synthetic aperture has been tested in ground-based measuring systems (using radar on about. Kwajalein radar signatures were obtained gallakticheskih objects), and the early 80's and has been implemented in the radar, which took flight tests. The first production aircraft stations, in which this method is used, the radar was AN/APS-137, designed to determine the tasks and organize offshore facilities. It is set on the deck antisubmarine aircraft S-3B «Viking" and the base patrol P-3 "Orion". Drawback of this method is the need for knowledge of the target range and speed of its movement. Errors in the determination of these characteristics lead to a deterioration of accuracy hell radar operation with the introduction of the method of inverse synthetic aperture.

To the usual methods of increasing the detection range stealth aircraft conditionally include those that are based on the rational choice of operating frequency range of the radar. Known to the current time means reducing the visibility effective only in a limited frequency spectrum. It is believed that the lower limit of the range of 1 GHz, and the upper — 20 GHz. In this case, reduction of visibility in all the designated spectrum can only be achieved through an inclusive use of different means and methods. Taken separately means even more narrow-band. Range 1-20 GHz elected not the case. In 1-x, it works most of the existing air defense radar, because the designers tend to reduce the per-metnost LA is in this range. In 2-x, a number of fundamentally physical constraints to reduce the visibility of the aircraft is part of the spectrum.

At the basis of rational choice of operating frequencies of the spectrum is the dependence of the EPR radar aircraft on the frequency of the illuminating signal. For example, the EPR fighters conventional schemes with decreasing frequency (higher wavelengths) of the probe signal grows by law close to the line. For stealth aircraft such dependence is even stronger — ESR is proportional to the square of the wavelength of the probe signal. Calculations demonstrate that the detection range in free space in an unobtrusive plane 1-2 GHz range 1.75 times greater than the range 2-4 GHz, and 2.2 times more than the 4-8 GHz range. In this regard, note the experts at zabugornye increased interest in the radar VHF and UHF. In several decades, one of the leading trends in the development of radar was more high-frequency ranges, which was justified by the possibility of obtaining more of the highest resolution possible. The emergence of new stealth aircraft to interested professionals in the VHF and UHF spectra.

The principal direction of reducing the visibility of the aircraft is the use of radar absorbing coatings. It is believed that if the air defense system will be used radar different ranges of make effective radio-absorbing coating for aircraft will be virtually impossible. Ferrite comparable narrowband radio-absorbing materials. Thus, materials known under the name ekkosorb, thickness 5-8 mm provide 99 percent absorption. incident wave energy in the band of approximately 300 MHz. It is noted that to reduce the visibility of the aircraft in a wider range should be applied to multilayer coatings. But given the fact that the specific gravity of modern ferrite coating is almost two times more than duralumin, it is hardly realizable. Coatings based dielectrics have the lowest mass, but their thickness is in direct proportion to the frequency of the absorbed waves. For example, to counter the probing signals radar clocked at 1 GHz, it is necessary that the thickness of the coating was about 300 mm, which is, of course, unacceptable for aviation.

If the wavelength of the probe signal Nala is commensurate with the size of the target, the reflection will be resonant in nature, caused by the interaction of the direct wave and the reflected wave, envelops the target. This phenomenon contributes to the formation of strong echoes. The resonance phenomenon can appear on the elements of the design objectives. Thus, in the resonance region AWACS radar aircraft E-2C "Hawkeye", working at frequencies around 400 MHz (wavelength 0.75 m) fall stabilizers and wingtips. The command of the U.S. Navy plans to quit plane "Hawkeye" in service after regular equipment upgrades.

The possibility of use of 2-band configuration and frequency of the signal in accordance with the form of goals is the main idea in the development of a promising AWACS aircraft ASTARA (Atmospheric Surveillance Technology Airborne Radar Aircraft), which is designed specifically to detect stealth aircraft. The implication is that it will add an E-3 AWACS. Flight tests of the new aircraft are scheduled for 1991.

Creating the-horizon radar in the United States began a long time before the organization works to counter stealth aircraft. But the fact that such stations are operating in the VHF spectrum of waves, now the South American spice gives reason to consider them as one of the principal means of detecting stealth aircraft. For further development and tests are carried out over the horizon radar, taking into account the performance of the newest features. The development of trans-horizon radar back-and-tilt sensing experts at the U.S. Air Force engaged since 1975. It is planned to build four radars, which should provide detection targets approaching the North American continent with all directions except north. The latter can not be covered due to the unbalanced distribution of temper short-range signals in high latitudes.

In 1988, the U.S. Air Force conducted the first test-horizon radar to detect small targets imitating cruise missiles. Assessed its ability to detect targets in the air space between Fr. Puerto Rico and Bermuda you. Radars operating in the spectrum of 5-28 MHz. Due to the influence of the ionosphere during the day used a highest frequency of the spectrum, and the lower NIGHT MODE. Cruise missiles, unmanned aircraft simulated AQM-34M, which were launched from the aircraft carrier NC-130, Their flight took place at different altitudes (150, 4500, 7500 m) at a rate of 650-750 km / h As the representative of the U.S. Air Force, the tests confirmed the possibility of detecting small targets over the horizon radar at a range of up to 2,800 km. According to their results, the decision to increment the size of the receiving antenna radar, built on the West Coast of the United States, from 1500 to 2400 meters, which will allow to double the sensitivity of the radar receiver. Complete the deployment of 4-horizon radar is planned for 90 years.

U.S. Navy developing transportable-horizon radar ROTHR, the main advantage of which is the possibility of its transfer in a relatively short period in the early prepared positions. This station provides detection of aircraft at a range of 925-2700 km in the sector of 60 °. Its electrical equipment located in 30 vans
. Where possible war zones are created antenna field, which in the event of crisis situations will be transported vans with equipment. According to the representative of "Raytheon" has already experienced the standard radar is located at the position in the state of Virginia, in the next time it is scheduled to relocate to the Aleutian Islands. Other items for the radar yet selected, but it is understood to deploy more than 9 radar at first on sea (ocean) theater, where they will use, camping, along with the aircraft AWACS E-2C "Hawkeye" and the E-3 "Sentry".

In order to increase the properties of the functioning of the horizon radar experts at the U.S. Air Force will explore the possibility of creating artificial ionospheric mirror. In their opinion, it will contribute to a more focused reflection of the probing signals, increasing the resolution and will allow to detect targets at ranges least 500 km.

Even the most ardent supporters of the-horizon radar recognize the characteristic them severe shortcomings: a low resolution and rather weak immunity. Yet, according to the views of foreign experts, the-horizon radar — this is the only type of system that could potentially go into service a number of states in the West and to detection stealth aircraft. All other types of systems, whatever advantages they may possess, are on the early stages of development.

The above approach to a good selection of the spectrum was aimed at increasing the wavelength of the probing signals in comparison with the applicable modern air defense radars. In the foreign press and discusses the other way is to switch to range millimeter waves. Since it is believed that at the present time there are no radio-absorbing materials, which are more effective in the millimeter range, because radar operating in the millimeter-wave spectrum can be an important element of promising anti-aircraft systems. The development of millimeter-wave spectrum is the highest rate. Already fulfilled element base and principles of systems operating at frequencies of 30-40 GHz and 85-95, also created standards with operating frequencies close to 140 GHz.

Unconventional methods of increasing the detection range of the aircraft with low ESR are based on new approaches to solving the problem — the time-frequency and space. As part of a time-frequency approach explores methods of forming and processing of complex new radar signals.

The use of probing signals compatible with the shape of a target, can significantly enhance the echoes. This method is similar to the matched filter used in modern radars. Formation of probing signals is carried out on the basis of the pulse target property, depending on its configuration, the spatial position and motion dynamics. In practice, the signal conditioning required to nanosecond pulse duration. Personal case of such pulses are non-sinusoidal signals in the fundamental properties of which is an ultra-wideband. In the foreign literature considered as an example of signals that occupy a strip of 0.5-10 GHz and having a duration of 0.1-1 ms. Their implementation can range resolution within 0,15-0,015 m With all of this reflection from the target are the totality of the echo signals from multiple point reflectors distributed over the surface of the target, allowing you to build a model of reflections on the particular aircraft, which is coordinated and form of probing signals. Calculations show that the weakly ferromagnetic materials absorb energy from the radar of non-sinusoidal signals.

Since the information about the configuration of the aircraft can be used to increase the detection range of the aircraft with low ESR zabugornye military experts at considering the possible measures to conceal. These are classified following: placing the aircraft in shelters, the best choice and locations of the restriction of training flights during the day to reduce the likelihood of photo reconnaissance aircraft by different means, improving training systems and the transfer of the center of mass training of flight personnel on exercise equipment, equipment stealth aircraft devices , enlarging and distorting the EPR plane, because during training flights in the area act radar air traffic control systems civilian aviation possible opponent could provide useful information about the actual EPR.

By the time-frequency methods of detecting stealth aircraft and the use of radar is a multi-frequency signals. The aim in this case is irradiated by several continuous signals at different frequencies. Reception and processing of echo signals are performed using a multichannel receiver, each of the channels which are formed a pair of signals on nearby frequencies, and then is blocked, and multiplies the integration or Doppler filtering. The advantage of multi-frequency radar is the ability to select the totality of frequencies, providing the highest detection range. As in the past, the method of determining the parameter configuration is the goal.

To increase the detection range of the aircraft with low ESR also study the possibility of using the effect of "nonlinear radar." The effect is that the objects by irradiation techniques not only reflects incident waves, and generate harmonics on reradiation. From time to time, this phenomenon is referred to as the effect of "rusty bolt" because the source of generation at the harmonics are, namely, the compound iron parts. But a similar property owned and semiconductors. The last event is the enthusiasm of researchers in connection with equipment LA functional active phased array antennas, in which you plan to use the elements gallium arsenide. The level of radiation with increasing harmonic number is dramatically reduced. That is why practical interest are the only radiation at the second and third harmonics.

According to reports in the Western press, all methods of time-frequency are still in early stages of theoretical and experimental research and development and implementation because they will likely only in the long term.

As part of the spatial approach to improve the detection range stealth aircraft developed methods and tools based on the dependence of the EPR of the aircraft from the direction of illumination. Usually, the designers of these devices can reduce the value of the ESR priemuschestvenno irradiation in the frontal hemisphere.

In recent years increased enthusiasm professionals referred to as multiport radars which represent a system of multiple cooperating transmitters and receivers spaced. Simple multiposition radar comprising transmitter 1st and 1st receiver, called bistatic. Principles of construction of multi-position radars were known in the early days of radar, but some technical difficulties, such as providing data for synchronization of transmitters and receivers that are not found in those years of satisfactory solutions. For the future development of radar has gone towards improving single-position systems.

The fundamental parameter of bistatic radar is the angle between the directions on the purpose of the transmit and receive position — so called bistatic angle. Increased attention is given to research bistatic radar with an angle equal to 180 °, in other words when the aircraft is detected on the line connecting the transmitter and receiver. In this case, the aircraft is very EPR (at 10's decibel) is increasing as a result of an effect known under the title "forward scatter". In the first approximation EPR "forward scattering" is the ratio of the square of the irradiated area to the square of the aircraft radar transmitter wavelength multiplied by a factor of 12. Since the ESR "forward scattering" is not depending on the material from which the aircraft is made, the effect of the introduction of unobtrusive aircraft composites and radar absorbing coatings to be neutralized. ESR value "forward scattering" with decreasing bistatic angle decreases, and at an angle of 165
° is still substantially greater than that of monostatic radar.

In zabugornoy printing are different variants of multi-position radar, which differ by the organization priemuschestvenno irradiation purposes. As the transmitting stations can be used AWACS radar systems and reconnaissance-strike complexes, the radar-based gallakticheskogo or even broadcast television stations. We also consider the possibility of introducing a multi-mode radar and existing building on their radar-based networks.

The use of radar builds on and gallakticheskogo. tion will allow the aircraft to irradiate the top. With all of this EPR aircraft is expected to grow due to the growth of the irradiated area. In the current time of spices United States, Britain and Canada made the creation of a joint programm gallakticheskogo radar-based, created for the detection of early warning and raid bombers and cruise missiles. At the same time, the requirements of each of the states to gallakticheskoy system, have their own characteristics.

Specialists England believe that radar-based gallakticheskogo should also provide tracking and maintenance of onshore and offshore facilities, including in the field. According to their estimates, tracking of marine sites is not severe technical problems, but the ability to implement the tracking of targets on the battlefield will be holding a huge amount of research. More suitable type of plants to be placed on gallakticheskom medium is synthetic aperture radar.

Canada is involved in a number of joint projects with the United States to ensure the defense of the American continent, including the modernization of the network of ground radar, the creation of trans-horizon radar, the expansion of areas under the control of the E-3 aircraft. But representatives of the Ministry of Defence of Canada said radar gallakticheskogo based only tool which can provide tracking of the entire country with the surrounding air space and marine areas. Apart from solving the basic tasks, taka'ya station, in their opinion, should make the function search and rescue, navigation and air traffic control. Original plan to launch low polar orbit 4 — 10 satellites equipped with radar. To increase the survivability of experts at the U.S. Air Force are considering the creation of a distributed radar gallakticheskogo home. Co-operation "constellation" will allow the satellite to embody a very huge total aperture of the system. As crotch put forward proposals to deploy the radar in airships or balloons that provide lifting payloads weighing up to 1 ton to a height of 25 km.

Along with the development of radar in the United States is preparing to withdraw experience Infrared Telescope into orbit as a means of detection, which has a passive mode of operation and more than the highest resolution. Deliver Telescope into orbit was planned in March 1986 by gallakticheskogo reusable spacecraft "Shuttle", but the tragedy of the ship "Challenger" delayed the holding of the experience for a couple of years.

Assessing the dilemma of increasing the detection range stealth aircraft as a whole, say experts at zabugornye that saturated the theoretical and experimental works are held in all possible directions. Individual results can be achieved and the coming term, after obtaining reliable disk imaging what ways and means of reducing the visibility went out and brought practical implementation on the aircraft 90s. Specialists in the field of radar optimistic, because the history of technology shows that the radar has always had the dignity to counter means, and this situation will continue, of course, and in the foreseeable future.

As for the task of fighting aircraft of the "stealth", it is least concerned about foreign military professionals. It is believed that with a reliable detection and tracking, they can be destroyed with a given probability as the existing anti-aircraft missile systems and promising.

The problem of detecting aircraft type "stelc"
Foreign Military Review July 1989 number P.37-42

PS: Please pay attention to the date of publication — 1989.
Even then, for many professionals, it was clear that the massively promoted the concept of invisibility, a panacea "invulnerability" can not. And time has proved it — all the F117 made by stealth technology to the detriment of aerodynamics, hastily, to end of life, retired.
The same is true of the subsequent products of advertisers — F22.
And the songs of praise that our designer in the creation of the T-50, did not go on this ruinous path …

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