JAXA, Waseda University, the University of Tokyo, and Keio University announced on April 16 that they had completed Japan’s first successful Mach 5 combustion ground test for a hypersonic experimental aircraft. The roughly two-meter-long vehicle was mounted inside the ramjet engine testing facility at JAXA’s Kakuda Space Center in Miyagi Prefecture, which simulates flight conditions at five times the speed of sound and an altitude of approximately 25 kilometers — nearly double the cruising altitude of current commercial airliners. At those speeds, aerodynamic heating drives air temperatures around the airframe to roughly 1,000°C (1,832°F). According to JAXA, the vehicle’s thermal protection system successfully maintained near-normal interior temperatures throughout the test, allowing onboard avionics and control electronics to operate normally. The team also measured surface temperature distribution and exhaust temperature from the hydrogen-fueled ramjet to validate thermal-structure analysis methods and collect data on potential environmental effects of future hypersonic propulsion.
The test is a significant milestone for the project — which has been in development since 2013 — but remains well short of a flight demonstration. The immediate next step is to mount the experimental aircraft on a sounding rocket and attempt an actual Mach 5 flight, gradually working toward a full-scale demonstration. JAXA’s long-term roadmap targets commercial hypersonic passenger service by the 2040s, with a Mach 5 aircraft capable of completing the Tokyo–Los Angeles route in roughly two hours rather than the current ten. The agency also envisions the same propulsion and thermal-management technology enabling spaceplanes capable of reaching altitudes approaching 100 kilometers. Ramjets require no moving compressor parts but cannot operate from a standstill and must be accelerated to supersonic speed by a separate propulsion system before igniting.
BGR （原始声明来源：早稻田大学 / JAXA，2026年4月16日）