October 14, 2021 (JST)

National Research and Development Agency
Japan Aerospace Exploration Agency (JAXA)

The Japan Aerospace Exploration Agency (JAXA) has teamed up with the National Aeronautics and Space Administration (NASA) and the Boeing Company (Boeing) on joint research to validate the low sonic-boom design of X-59, NASA’s low boom flight demonstrator^*1.

Supersonic aircraft^*2 are currently restricted to fly supersonically only overwater due to sonic booms^*3, the loud noise caused by the shockwaves they generate. Discussions on en-route sonic boom standards for commercial aircraft to fly supersonically over land have been underway at the International Civil Aviation Organization (ICAO) since the early 2000s. JAXA supports these discussions through its research and development activities^*4. This joint research is a mutual opportunity for NASA, Boeing and JAXA to share expertise to improve respective capabilities within the overall objective of helping the development of sonic boom standards for future supersonic transport.

The joint research uses a 1.62%-scale model of the X-59 to conduct wind tunnel tests at both NASA and JAXA facilities. The test results will be exchanged for comparison and cross-validation of sonic boom characteristics of the model. Boeing and JAXA will conduct numerical analyses of the model through computational fluid dynamics (CFD) ^*5, then all three parties will exchange and compare simulation results with wind tunnel tests. This collaboration would be an opportunity for NASA to validate the X-59’s low sonic boom design with various test and simulation results, and for JAXA to improve its sonic boom prediction technologies by utilizing NASA's wind tunnel test results and Boeing's CFD analysis results.

JAXA contributes to the development of new international sonic boom standards by joining forces with domestic and international partners, and by making use of the findings through this collaborative research.

*1 NASA X-59 low boom flight demonstrator
The X-59 is NASA's supersonic experimental aircraft, or Low Boom Flight Demonstrator (LFBD), designed to reduce loud sonic booms to a quiet thump. The full name of the X-59 experimental aircraft is the X-59 QueSST which stands for "Quiet SuperSonic Technology".
https://www.nasa.gov/X59 External Link

*2 Supersonic aircraft
The cruising speed of today's subsonic airliner is about Mach 0.8, and flight between Japan and US or Europe can take more than 12 hours. With supersonic aircraft that are capable of flying faster than the speed of sound, this travel time could be reduced, for example halved to around six hours by doubling the flying speed while over land.

*3 Sonic Booms
Sonic boom is a phenomenon that occurs when an aircraft travels through the air faster than the speed of sound. Shock waves generated from various parts of the airframe propagate in the atmosphere and merge together, causing two sudden changes in pressure that extend to the ground. It is recognized as an explosive sound to the people on the ground.

*4 JAXA supersonic transport technology research
JAXA has been conducting various research and development into quiet supersonic transport technology. Major technologies developed to date include the following:
a) Low sonic boom design technology (to reduce environmental impact)
To validate low sonic boom design technology, JAXA conducted the flight demonstration project named D-SEND#2. Flight testing was conducted in 2015 at the Esrange Space Center in Sweden using a supersonic experimental airplane designed based on JAXA’s original concept to reduce sonic booms. The results showed that JAXA’s unique sonic-boom reduction design technology can halve the sonic boom of the Concorde.
b) Drag reduction technology (to improve fuel efficiency and economic efficiency)
The low-drag design technologies were validated by flight testing the NEXST-1, a small supersonic experimental aircraft designed to improve fuel efficiency. Flight testing was conducted at the Woomera test range in Australia in 2005. The effectiveness of the design in reducing supersonic drag was confirmed from the test data. The project achieved a reduction in Drag Reduction of 13% as compared to the Concorde.
https://www.aero.jaxa.jp/eng/research/frontier/sst/

*5 Computational Fluid Dynamics (CFD)
Computer-based simulation to analyze airflow around aircraft numerically.