The US Air Force may have decided to stay subsonic for its ultra-stealthy Next Generation Bomber, but it has not lost interest in high speed for long-range strike. Air Force Research Laboratory officials speaking at the AIAA aerosciences meeting in Orlando (Jan. 5-8)'say they are windtunnel-testing stealthy tailless supersonic designs with embedded engines. The combination has never been done before, they say, and the technology needs to be matured before it will be seriously considered by the Air Force.
The key technology is active flow control, which is used to improve the efficiency of'the serpentine inlet and exhaust ducts for the embedded engines and for'stability and'control of the tailless aircraft. The above model of a Lockheed Martin design has been tested in the 4ft transonic tunnel at AEDC to compare the effectiveness of a jet-effects spoiler (lower wing) and a conventional solid spoiler (upper wing) for yaw and roll control.
Supersonic designs, manned and unmanned,'were evaluated in the analysis of long-range strike alternatives that led up to the selection of a manned subsonic platform for the Next Generation Bomber, A key factor was technology maturity, as the NGB is intended for service-entry in 2018 and has to be low-risk. Broadband all-aspect stealth requires a tailless configuration, and the risk with a supersonic design was too high, says AFRL.
Artwork: Northrop Grumman
With a subsonic platform selected, the Air Force is looking at high-speed weapons that could be carried by the NGB. AFRL, Air Combat Command and Pacific Command are evaluating long-range strike weapon alternatives under a project called Trespass/Trespals - an acronym no-one seems able to explain. Options include a missile derivative of the scramjet-powered X-51 hypersonic demonstrator."