Concept for the next-generation supersonic civil transport

Currently, airplanes fly at about Mach 0.8, which is markedly slower than the speed of sound. Japan is distant from Europe and the United States. It takes more than 12 hours to fly the distance. If we could fly faster than sound, for example, at twice its speed, then the time for flying would be halved and the flight time from Japan to Europe or the United States would be about 6 hours. If the travelling time were shortened, economic activities would be bolstered through increased opportunities for business and tourism. Moreover, measures against disaster could be taken quickly, thereby ushering in a safer and more affluent society. If the flight time were cut to less than 6 hours, then the increasing frequency of hazards, nuisances, and ailments such as economy-class syndrome could be prevented. Perhaps most importantly, everyone would be able to enjoy travel more comfortably than ever. These airplanes that enable high-speed transportation, flying faster than the speed of sound, are called supersonic civil transport.
Although realization of hypersonic airplanes is highly anticipated, supersonic civil transport successors to the Concorde, which was retired in 2003, have not emerged. Nevertheless, momentum for the development of business jet class supersonic civil transport increased considerably in the 2010s. The International Civil Aviation Organization (ICAO) began deliberation of international standards for sonic booms.
For Japan to establish a firm footing in the design and production of next-generation supersonic civil transport developed through international joint development, JAXA will demonstrate the high technical potential of aircraft technology owned by Japan through presentation of a unique airframe concept and verification of specialty technologies.

Concept image of small supersonic civil transport

We aim at the accomplishment of technical targets, which play key roles in the realization of small supersonic passenger aircraft (Mach 1.6, 36–50 passengers, 70 ton class takeoff weight, cruising distance greater than 3,500 nm (about 6,300 km)) and the presentation of the airframe concept.

Overall length	47.8 m
Breadth	23.6 m
Total height	7.3 m
Area of main wing	175 m²
Aspect ratio	3.0
All-up weight	70 ton
Engine	15 ton twin-engine
Number of passengers	36–50
Cruising speed	Mach 1.6
Cruising distance	More than 3500 nm

Technology objectives

We will accomplish the following technology objectives before the end of fiscal 2014.

1. Attain supersonic flight over land by sonic boom reduction (half the sonic boom strength of the Concorde)
2. Meet noise level standards applied to current subsonic passenger aircraft during takeoff and landing (In compliance with ICAO Chap. 4)
3. Reduce air resistance to reduce fuel consumption and to lengthen the cruising distance (cruising lift–drag ratio: higher than 8.0)
4. Reduce structural weight to reduce fuel consumption and to lengthen the cruising distance (15% of the structural weight of the Concorde)

Sonic boom

When an airplane is flying at supersonic speed, impact waves generated at every part of the airframe are integrated as they propagate long distances through the atmosphere, which is observed on the ground as type N pressure waveform causing two sudden pressure fluctuations. Human ears recognize them as an instantaneous explosive sound: a "sonic boom". Concorde, which was retired in 2003, was not allowed to fly over land at supersonic speeds because of sonic booms, and supersonic flight was restricted to transoceanic flights. Sonic booms are therefore a daunting technical challenge hindering the realization of future supersonic civil transport.
At present, ICAO is working on deliberation of international standards for sonic booms. JAXA now intends to contribute to this activity using data obtained from the D-SEND project and from evaluation tests using sonic boom simulators to assess how humans sense them and how buildings are affected.

Sonic boom simulator

With a sonic boom simulator, a large speaker for low frequency (low-pitch sound) provided on the wall in a small box type room reproduces changes in acoustic pressure to simulate an actual sonic boom. JAXA's sonic boom simulator produces a simulated sonic boom sound using eight large speakers for low frequencies (four speakers at the front and rear) and four small speakers for high frequencies. Using this simulator, listeners are requested to listen to various sonic booms and to report their evaluations. Human tolerance of sonic booms can thereby be investigated.