The World's Most Secretive 737 Is America's Key To Better Stealth Tech
Tyler Rogoway
Filed to: testbeds2/19/15 11:45am
The World's Most Secretive 737 Is America's Key To Better Stealth Tech
Nobody knows exactly where "Rat 55" lives or precisely what technology it uses to accomplish its mission, but it sure is an exotic beast. The USAF's secretive NT-43A testbed is a highly modified 737-200 that goes far beyond ground-based radar and infrared signature testing on stealthy aircraft by plying its trade high up in the sky in their target aircraft's natural operating environment.
The aircraft's massive radomes and structural modification were said to have been designed by Lockheed's Skunk Works and were installed by the Goodyear Aerospace plant in Arizona around the turn of the century. Before that, USAF serial number 73-1155 lived its life as a humble T-43A navigational training aircraft from 1974 to 1997. It was then retired to the boneyard and stored there for over two years before being chosen for its new unique role. The aircraft's first flight in its monstrous NT-43A form was on March 21, 2001.
The World's Most Secretive 737 Is America's Key To Better Stealth Tech
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According to Globalsecurity.com, the NT-43A's genesis may have deep roots dating back to the origins of stealth technology itself. It seems that the company behind the project has direct links to the creator of the famous Skunk Works' ECHO-1 software program that resulted in the stealthy 'Hopeless Diamond' which eventually turned into the Have Blue demonstrator and then the famous F-117A Nighthawk:
In mid-2000 the Lockheed Martin Advanced Prototype Center, part of the Advanced Development Programs' (ADP) organization, handed over its first major deliverable — a flight-worthy composite structure — on the center's first design and fabrication contract. The structure, a 19-foot long, 6.2-foot diameter fairing and bulkhead assembly, was delivered to customer DENMAR Inc. The prime contractor Denmar is a company specializing in stealth technology. The "Den" stands for President Denys Overholser, the former Skunk Works engineer credited with devising the shape of the first stealth aircraft. The assembly provides an aerodynamic transition from the existing aft fuselage of a T-43 aircraft, a modified Boeing 737-200, to an oversized radome. The aircraft serves as a Radar Test Bed (RTB) for future Air Force programs. The design, fabrication and machining of the structure's components were all performed at Palmdale. The structure is made of a 90-percent carbon epoxy/honeycomb sandwich material, with machined aluminum parts, and houses an airborne radar assembly. The contract with DENMAR also included the design and fabrication of three radomes for the RTB aircraft. Each radome is more than 6.5 feet in diameter and 9 feet in length.
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The NT-43A radar aircraft testbed (probably where the "Rat" call-sign comes from) is most likely the last stop in advanced low-signature testing and validation for new stealthy aircraft, new radar absorbent coatings and heat mitigation technologies, as well as exotic and stealthy structural modifications to existing aircraft. In other words, whether it be a whole new aircraft or just a new radar absorbing material applied to an existing stealthy aircraft, the NT-43A evaluates it under realistic flight conditions with its powerful radars and infrared energy detecting devices. Even repairs and depot-level work on existing stealth aircraft may be validated in flight via the NT-43A.
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The NT-43A's massive radars are most likely able to take incredibly detailed synthetic aperture 'pictures' of their target aircraft, as well as collecting sensitive 'raw' radar measurements and associated data. Its front and rear pods that give the jet such an ungainly appearance allow it to collect radar and infrared data (the IR sensors sit atop the radar fairings) from every angle around the target aircraft in flight without having to fly at oblique angles towards and away from it. The radar system may have some bistatic capabilities when both front and back arrays are used in conjunction with one another.
Beyond evaluating a design's low observable qualities in flight, data collected by "Rat 55" is most likely also used to better understand a stealthy aircraft's strengths and weaknesses. For instance, an aircraft may have very little radar signature head-on, but at certain angles its radar cross section grows significantly. Once these intricacies are very well documented, the performance of enemy radars, infrared search and track systems and anti-air missile systems can be better theorized. This allows for a much more accurate understanding of how close a 'stealth' aircraft can get to different threats without being detected or without being engaged. Mission planners can then build elaborate routes around known enemy air defense systems and give crews good advice on how to present the best aspect of their aircraft to unplanned for 'pop-up' threats so that they have the best chance of surviving a mission. This route of lowest possible detection and greatest possible survival is known as the 'Blue Line' among stealth aircraft attack crews.
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