STEPPED-UP STEALTH
Unmanned aircraft projects are emerging as the main drivers for European low-observable technology investment.
As part of this trend, EADS is completing work on a radar measurement facility that should allow it to boost the stealth characteristics of future systems. Research also is ongoing to improve aircraft visual signatures.
The company’s focus is not just on UAVs, though. For example, researchers have applied radar-absorbing material to a single Tornado strike aircraft to reduce its radar cross section (RCS). The treatment has been affixed selectively to areas that provide radar return spikes.
The goal was not to turn a Tornado into a stealth aircraft, but to reduce the RCS enough to improve the effectiveness of its towed-decoy. Developers here believe spending money on the selective use of the technology will be a cheaper way to make Tornados more survivable than fitting the aircraft with a higher power decoy.
A 10-dBsm. signature improvement can be generated with these techniques at the cost of about 80 kg. (176 lb.) of additional weight, developers suggest.
Other aircraft could similarly benefit from this approach, with the Eurofighter Typhoon a likely candidate. EADS has a half-scale model of the fighter to conduct detailed signature analysis and identify possible radar energy scatter points that could be treated.
But the more far-reaching improvements in stealth technology are being envisioned for unmanned aircraft. EADS’s German unit already is building a classified stealth UAV for the German military, called Barrakuda (AW&ST Mar. 21, p. 26). This is only one of a large number of classified and unclassified unmanned aircraft programs the country has on the agenda.
The next acknowledged step will likely be the Unmanned Reconnaissance Air Vehicle (URAV), a demonstration program being discussed by EADS and the German government. The effort would likely run from 2005-10, says Peter Gutsmiedl, EADS military aircraft senior vice president for programs. A full-fledged unmanned combat air vehicle (UCAV) project isn’t expected to emerge until 2020-25, he adds.
The German program is being undertaken with an eye on meeting future air force and navy tactical reconnaissance requirements, including replacement of the Cl-289 fast drone and the Tornado’s tactical recce system. The type of sensor with which the URAV would be equipped hasn’t been determined, but it would likely use several as part of the technology evaluation process. The URAV would be a modular system, Gutsmiedl says, to allow changing out of various elements.
Work on future UCAVs would be supported by the new signature measurement facility that EADS is building at Lemwerder, north of Bremen. The building can accommodate vehicles sized up to 12 meters (39 ft.) and is to be completed in November. Initially, it will support vehicles weighing up to 2,250 kg. (4.950 lb.), although that should grow to 5,000 kg., says Jurgen Kruse, an EADS signature technology expert.
The 48 X 31 X 15-meter facility will include an adjustable height antenna up to 13 meters to take different measurements, as well as walls within walls to ensure that wind doesn’t cause wall warping, distorting signature assessments. Measurements will range from 0.5-100 GHz.
The new site is deemed critical to achieving a step-change in aircraft signatures, with a target of reaching a level on the order of 10-3 sq. meter from the current 10-2 sq. meter. Developers hope to beat the F/A-22’s performance by 10 dB. on future systems.
For unmanned aircraft, engineers believe signatures on the order of 10-4 sq. meter can be achieved. Lower observability can be achieved on unmanned aircraft, because they don’t have to accommodate a canopy; keeping the radar reflectivity low where the fuselage and canopy interface has proven difficult for designers.
The new RCS facility, while designed largely for work in Germany, will be made available to others on a contractual basis. Kruse notes that to keep personnel costs down and be competitive with similar facilities in the U.K. and U.S., the site will rely heavily on automation.
Additionally, EADS is working on a government contract to devise “tunable” optical signatures. Aircraft are often too dark and stand out; by illuminating the surface, the aircraft brightness can be adapted to the sky to blend in. The project essentially tries to adapt modern flat-screen TV technology to aircraft skins. A demonstration of the technology is to begin in the near future. Developers believe the power requirements for such subsystems and their weight are now small enough for airborne use.
EADS IS PURSUING both the near-term efforts on current aircraft and UCAV thrust because “we have to think in terms of products that contribute to our business while not forgetting about our future,” adds Gutsmiedl.
EADS foresees military users fielding a variety of unmanned aircraft with different survivability levels–high-end, extremely stealthy systems with visual, infrared and radar reductions and advanced sensors, alongside more affordable, “less decked out” UCAVs.
Some of these efforts are also underway in other countries. Russia, for example, is believed to have the know-how to selectively add stealth material to its combat aircraft, and it may be exporting that capability. One concern out of this development would be that when allied aircraft encounter a treated fighter, its signature return would no longer match threat databases, making target identification more difficult.
http://aviationnow.ecnext.com/free-scripts/comsite2.pl?page=aw_document&article=100305p06
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October 5, 2005 at 6:03 am