Hypersonic flight: Jaxa tests Mach 5 engine

The Japanese space agency Japan Aerospace Exploration Agency (Jaxa) has tested a Mach 5 class engine in an experimental aircraft during a ground test, as The Mainichi reports. The hydrogen-powered ramjet engine's combustion was tested in conjunction with the entire airframe. Such an engine could be used in the future as a drive for hypersonic aircraft in aviation and could significantly shorten long-haul flights, for example.

The tests of the approximately two-meter-long model of the Mach 5 ramjet engine already took place in April 2026 in a test facility for ramjet engines at Jaxa's Kakuda Space Center in the Japanese prefecture of Miyagi. Waseda University, the University of Tokyo, and Keio University were involved. The testing of the engine is part of a cooperatively designed research program focusing on the integrated control of airframes and propulsion systems of hypersonic aircraft.

A Question of Temperature

The scientists simulated flight conditions on the test rig that can occur during Mach 5 flights. Under these flight conditions, high temperatures of up to about 1000 °C occur around the airframe. Jaxa reportedly succeeded in developing an airframe in which the internal temperatures could be maintained at almost “normal temperatures.”

The heat shield ensured that the entire avionics were not affected by the heat development and functioned smoothly, The Mainichi writes. The researchers measured the distribution of surface temperatures on the airframe to obtain data that could provide information about the thermal-structural design. The scientists intend to improve the designs of future hypersonic aircraft with this.

The researchers also evaluated the temperature distribution of the ramjet engine's exhaust gases. With this, they want to test to what extent the hot emissions impact flight stability at different flight speeds up to the high-speed range. Because, unlike conventional aircraft, with hypersonic aircraft at supersonic speeds, there is a mutual influence between airflow and propulsion activity. The shock waves that form around the aircraft directly impact the airflow entering the engine. However, this airflow is crucial for ramjet engines, as the airflow generated by the high flight speed is used to compress the air and keep the combustion in the engine going. At the same time, there are effects from the thrust generated by the engine on the aircraft's aerodynamics. Accordingly, the propulsion system and airframe must be considered as a complete system that must be developed together as a unit.

Shorter flight times possible

Jaxa now plans, after further improvements, to launch the experimental aircraft into the air with a carrier system, such as a high-altitude rocket, to gradually approach a real demonstration flight in the Mach 5 range. The technology could be used in civilian hypersonic passenger aircraft in the future. According to The Maichini, Jaxa states that flight times could be drastically reduced as a result: for example, for the route between Japan and the USA to around two hours.

(olb)