Forum: Technology

Russian Stealth Research Revealed
Russia shows solid progress in a variety of low-observable technologies
by Bill Sweetman
Jan. 1, 2004

Russian research into low-observable (LO) technology has remained largely secret, despite the collapse of the Soviet Union and the semi-privatization of the aircraft industry. However, a newly published paper from the Institute for Theoretical and Applied Electromagnetics (ITAE) at the Russian Academy of Sciences (Moscow, Russia), presented at the International Quality and Productivity Center's conference on stealth, held in London in October 2003, shows that Russian researchers have made solid progress in key technologies for LO aircraft and have test-flown some technologies – such as the use of plasmas to protect targets from radar – that are not known to have been studied in the West.

In the paper, entitled "Stealth Technology: Fundamental and Applied Problems," Russian stealth researchers claim to have reduced the head-on radar cross-section (RCS) of a Sukhoi (Moscow, Russia) Su-35 fighter by an order of magnitude, halving the range at which hostile radars can detect it. The research group has performed more than 100 hours of testing on a reduced-RCS Su-35. According to other reports, the ITAE has demonstrated similar technology on a MiG-21bis, and it has been offered to India as part of a MiG-21 upgrade package. Similar modifications have been made to Western aircraft (such as the Have Glass package developed for the F-16), but it is not known whether they claim the same level of performance.

Russian investigators certainly have the basic scientific knowledge to apply stealth to aircraft. Some of the basic mathematical and optical theories that underlie stealth originated in Russia (such as Ufimtsev's theory of edge diffraction), and some of the most significant early work on reducing the RCS of military vehicles was carried out by Russian warship designers. The Kirov-class battlecruisers – with a 22° "tumblehome" angle imposed on normally vertical bulkheads, screens, and skirts to shield high-RCS components from radar, along with extensive use of radar-absorbent material (RAM) – were remarkably stealthy despite their size. "If you saw a big wake with nothing in front of it," British marine LO expert Peter Varnish has said, "you knew you'd found the Kirov."

There is also an LO strand in Russian aircraft design. The Tupolev (Moscow, Russia) Tu-160 Blackjack bomber is a reduced-signature design reminiscent of the B-1 Lancer. Sukhoi has designed a series of supersonic bombers with low-profile, highly blended configurations. In early 2000, Russian military leaders considered that a new, stealthy medium bomber would be the next major Russian military aircraft project, to replace the Tu-22M.

Most current Russian military aircraft show little evidence of stealth in their design, but that is not surprising, given that they were defined in the early 1970s. The more recent MiG 1.42 and Sukhoi S-32 fighter prototypes were designed as details of US stealth projects became known and, thus, represent a compromise solution. They carry their primary weapons internally, and the Vympel R-77 missile – which corresponds to this generation of aircraft – is designed for internal carriage. However, they do not reflect features found on US designs, such as the careful organization of wing, tail, and inlet edges along a few common alignments. They look like aircraft in which aerodynamics dominate the basic shape, and materials are used to eliminate RCS hotspots – very much the same as the technology described in the ITAE paper.

The dominant contributors to the Su-35's head-on RCS are the inlets, which the ITAE researchers call "a huge problem." With a straight duct that provides direct visibility to the entire face of the engine compressor, the inlet might have been designed to advertise the fighter's presence at the greatest possible range. (Lockheed stealth pioneer Alan Brown's comment on straight ducts is that "the energy comes romping out like a lighthouse beam.") The ITAE, though, has developed a high-performance, ferro-magnetic RAM for the compressor face and duct walls. The material has to be thin, because it cannot constrict airflow or impede the operation of anti-icing systems, and must withstand high-speed airflows and temperatures up to 200°C. The ITAE team has developed and tested coating materials which meet these standards. A layer of RAM between 0.7-mm and 1.4-mm thick is applied to the ducts, and a 0.5-mm coating is applied to the front stages of the low-pressure compressor, using a robotic spray system. The result is a reduction of 10-15 dB in the RCS contribution from the inlets – more than halving the RCS.

Like the Have Glass F-16, the modified Su-35 also has a treated cockpit canopy that reflects radar waves. The ITAE has developed a plasma-deposition process to deposit alternating layers of metallic and polymer materials, creating a durable coating that blocks radio-frequency (RF) waves and does not trap solar heat in the cockpit. The plasma-coating process is carried out in a vacuum chamber by a robotic tool.

The ITAE and its partners use plasma technology for applying ceramic coatings to the exhaust and afterburner. Multi-layer coatings formed from microparticles of dielectric, metal, or semi-conductor material are deposited by an arc-discharge plasma under atmospheric pressure. Challenges include the need to keep the ceramic bonded to the metal structure over a wide temperature range (600°C to 1,200°C), despite the fact that the materials have widely different thermal-expansion characteristics. The coating materials also need to maintain constant electrical characteristics in the face of widely varying temperatures. Researchers describe this problem as "partially solved," and engines treated with ceramic RAM have already been flight-tested.

Video at the conference also showed the use of hand-held sprays to apply RAM to R-27 air-to-air missiles. There is no point, researchers say, in reducing the RCS of the airframe unless the reflectivity of external weapons can be reduced as well.

The ITAE has flight-tested a unique and exotic technology to mask the Su-35's huge 35-inch radar antenna: the use of a low-temperature, "plasma-controlled screen." The screen is mounted in front of the antenna and is transparent to radar when switched off; it may be similar to a plasma TV screen, comprising cells filled with neon or xenon gas, which is excited by an electrical current. (Video shows a clearly defined luminous panel in front of the antenna.) When activated, the screen absorbs some incoming radar energy and scatters the rest in safe directions, over all RF bands lower than the frequency of the plasma-generation system. The screen switches on and off in tens of microseconds, according to the ITAE, thanks to years of intensive development of the gas mixture and plasma-generation system.

In principle, this is the same as the "plasma stealth" system that was reportedly developed by the Keldysh Scientific Research Center (also part of the Academy) in 1999. At the time, it was claimed that the system, using a 100-kg generator, could reduce the RCS of any aircraft by two orders of magnitude, or 20 dB. The ITAE has not attempted to develop a whole-aircraft system, which would use plasma-generating antennas to ionize the air flowing over the aircraft – an artificial version of St. Elmo's fire – but researchers expressed the view that it would be difficult to apply except to a high-altitude, relatively slow aircraft, because the airstream would dissipate the plasma faster than it could be generated.

The ITAE paper gave some indications of the direction of stealth technology for future aircraft. Test facilities developed in Russia include compact, indoor RCS ranges for large-scale models and outdoor, ground-level ranges with short pylons, which can be used to test full-size aircraft (rather than the models used for US pylon tests). In future designs, one emphasis is on large, complex skin panels, reducing the number of gaps and mechanical fasteners in the skin. The ITAE paper showed an example of a single, 23-ft., monolithic fuselage panel, without indicating for which aircraft it was intended. However, it might form part of the upper fuselage of the S-32 Berkut prototype.

Russia's ability to achieve an order-of-magnitude reduction in the RCS of a non-stealthy aircraft is significant for two reasons. First, it makes the Sukhoi family more competitive with Western aircraft, particularly in the case of export variants that may not feature LO modifications such as Have Glass. Second, it points to an ability to design low-maintenance, stealthy combat aircraft, missiles, and UAVs in the future.

"Stolen" seems like something of an unfair word. It's probably more correct to say that aerodynamic structures and design principles like strakes, VG inlets and wing-body blending are "discovered" more than they are "invented".

Going by that, one could say that the United States "stole" the flying wing design from the Germans with the B-2 and the swept wing design for the F-86. Everybody is influenced by everyone else. Society is more efficient that way.

The Russian version, first flight…never. However designed after the STS. Is there even anything different besides the fact that it’s larger and heavier? Must have been hard to figure out how to get all the systems to fit when you don’t have those schematics to copy as well…never fear, if we just make it bigger we can get them to fit!

First things first, I have no problem admitting that the Americans stole the swept wing design from the Germans. Following WWII, the U.S. was heavily influenced by German scientists and engineers who came to America. I will agree that some design features are merely generational, and thus are seen in many airframes from the same era. However, if you look at the aircraft that Russia developed over the last 40 years, they are extremely similar to American designs that came first, even though for some reason the Europeans were able to develop unique aircraft while still incorporating generational design features. But let’s take a look at just a few examples and I’ll illustrate what I mean.

F-111, first flight 1964

Not seen in this picture, but the “football” at the base of the tail was for EA.

Su-24, first flight 1967. The football at the base of the tail is for…nothing. Russia thought there was an aerodynamic principle for it, and thus incorporated it.



A-9 (lost the fly-off to the A-10), first flight 1972


Su-25, first flight 1979


B-1, first flight 1974


Tu-160, first flight 1981. The first models could not get the avionics to fit, so the pilots’ seats were moved aft. However the panels that jettison for ejection were kept in the B-1’s location, so had the pilots ejected they would have ejected into the ceiling (clearly would not have been this way had Russia developed it from the ground up).


F-4, first flight 1958. Its inlet has a strake for cutting through Bak barrier ropes during emergency carrier landings.
http://farm1.static.flickr.com/23/31331632_051754351e.jpg?v=0

MiG-23, first flight 1967. F-111 maybe…yeah, yet single engine...but I digress. It has never landed on a carrier, most likely never will, and certainly was not designed to…but Russia had no idea what the strake was for, just that the F-4 inlet design worked.
http://123.55.252.122:8080/www.afwing.com/images/airshow/shenyang/j8II04.JPG?MT=1225574104

My personal favorite, the Space Shuttle, first flight 1977


The Russian version, first flight…never. However designed after the STS. Is there even anything different besides the fact that it’s larger and heavier? Must have been hard to figure out how to get all the systems to fit when you don’t have those schematics to copy as well…never fear, if we just make it bigger we can get them to fit!


And now, full circle so as not to get too far off topic. The F-22, first flight 1990.


PAK-FA, T-50…whatever, first flight yet to be determined (I’m guessing not in 2009 though). Is there any doubt what it’s going to look like? Probably the most wide spread preliminary design.


I’m guessing the actual design is either going to be much more similar to the F-22 than it already is, or it’s going to be a hybrid of the F-22 and F-35.

You're not swallowing that magical plasma stuff hook line and sinker are you? Must be ten years now that stuffs been floating around the net and still no sign of this mythical 'I-win' button... just slightly sceptical

You didnt read it well. Read again. This time carefully

Not to nit-pick, but the Buran DID fly one unmanned flight. It is different from the Shuttle in that there are no launch engines on the Buran. All the thrust for launch was provided by the Energia booster. It could carry 5 tons more payload to orbit than the Shuttle. It's max crew size at launch was 10 vs 8 in the shuttle. There are no OMS pods on the tail of Buran as the de-orbit engines are where the SSME are in the Shuttle.

There is speculation that there was espionage involved in acquiring the technical drawings of the shuttle, but there was a lot of publicly available data on the shuttles at the time that could have been used to design the Buran and the Soviets did have a lot of talent in the their design bureaus at the time to be able to fill in the blanks. Both programs were fighting the same physics problems and many of the best solutions were already in place on from the shuttle, so there was no need to re-invent the wheel on Buran.

I'm honestly not sure which angle you are coming at me from with your post, I have read the article carefully many times thanks, not just here but for the last god knows how many years on other internet sites where it's normally found to have been posted by breathless Sukhoi or RuAF fans trying to score credibility points.
"Much different" or not then the old plasma tech or not the point still stands that like the PAK-FA this stuff is pretty much mythical and the article/ Russian propaganda is really grasping at staws trying to present this as a 'gamechanger' , I mean even if this stuff did work as advertised it'd take perhaps 30 years before Russia will have it in mass production, perhaps never. Like I say, grasping at straws.

It doesn't really matter if the info was public or not, the point is that Russia couldn't design it on their own, they had to copy an American design. Flying an unmanned flight doesn’t count, that’s not what it was designed to do, orbiting the Earth and bringing a payload with it was the goal. Also, take a look at the boosters and fuel tank required to get "Buran" into orbit...it's not like is was going to be able to do it with the same amount of thrust and propellant. And finally, the stats are all what it was SUPPOSED to do, it never actually did it. They could have promised that it would take a crew to Jupiter for all I care, it never actually took a payload 5 tons heavier or a crew of 10 into orbit, so who really knows if it was possible for the Buran to accomplish it. Especially since Russia has grown a reputation for exaggerated promises that don’t deliver, and when the facts become public they promise that “it’s only a few years away.”


sorry for the

On the subject of copying. is it really true that the CIA executed a plan to let the KGB steal a fulty set of plans to the Concorde? This was said to be the cause of the crah of the Soviet Concordeski years late. Is this just a myth or is there some truth to it?