If you thought the US had completely lost interest in supersonic airliners, think again. Supersonics is one of the areas NASA is pursuing under its revitalised aeronautics research program, and the US agency is tying up with its Japanese counterpart JAXA to study ways to reduce the sonic boom.
NASA has near-, mid- and long-term research under way aimed at three generations of supersonic transport: N+1, a Mach 1.6-1.8 business jet that could be available by 2015; N+2, a small, 35- to 70-passenger supersonic airliner for service around 2020; and N+3, a 100- to 200-passenger, 6,000nm-range, low-boom airliner capable of speeds up to Mach 2.0.
Aiming for entry into service in 2030-35, N+3 is getting back to the size of aircraft envisaged under NASA's High Speed Civil Transport program, which was cancelled in 1999 after Boeing merged with McDonnell Douglas and lost interest in supersonic airliners. HSCT was designed to carry 300 passengers across the Pacific at Mach 2+, but could not fly supersonically over land because of its sonic boom.
NASA's new work is aimed at reducing the boom enough the enable supersonic flight over land, opening up new markets. It also needs to reduce airport noise so that an SST can be as quiet as subsonic airliners of the same timeframe. Neither is an easy task.
The tie-up with JAXA will give NASA access to Japan's planned Silent Supersonic Technology Demonstrator (S3TD, or "S-Cube"). This is an unmanned aircraft planned to fly in 2012 to demonstrate, relative to Concorde, a 3dB reduction in take-off noise through engine shielding and a 50% cut in sonic-boom intensity through airframe shaping.
The 13m-long vehicle will take off and land autonomously and cruise at Mach 1.2-1.4 and 20,000-40,000ft for about 5 minutes while an array of ballons measure its sonic boom. While NASA is funding low-boom research by Gulfstream and Lockheed Martin, there are no plans for a flight demonstrator. So the tie-up with JAXA is significant.
To see a video about S-Cube, check this JAXA website on the project.