GoKawiilA ramjet, the technology at the core of the test, is a type of air-breathing jet engine that has no moving parts. The name is derived from the engine's reliance on rapid forward motion to "ram" and compress incoming air before mixing it with fuel and igniting it for thrust. The technology eliminates the need for heavy rotating compressors and allows them to operate at speeds that far exceed the capabilities of conventional turbofans. However, ramjets can't operate from a standstill: to function, they first need to be accelerated to supersonic speeds.
In the Japanese test, an experimental aircraft was mounted in a wind tunnel simulating conditions at around 25 kilometers of altitude, where the atmosphere is roughly one‑hundredth as dense as at sea level. At that elevation at Mach‑5, air around the nose and leading edges can reach temperatures exceeding 1,000 degrees Celsius (1,832°F), a challenge the U.S. Air Force has struggled to overcome with its own hypersonic jets.
To handle that level of heat, engineers constructed an advanced thermal‑protection system that maintained the aircraft's interior near normal operating temperature, allowing the onboard avionics and control electronics to function normally. Simultaneously, sensors mapped surface‑temperature distribution to verify thermal‑structure calculations, crucial for scaling up to a full‑size passenger vehicle.