U.S. Tests Advanced Hypersonic Engine With No Moving Parts

American aerospace giant GE Aerospace is testing a hypersonic engine with no moving parts.

The main advantages of a scramjet (supersonic combustion ramjet) are its minimal moving components and its ability to reach hypersonic speeds above Mach 5. GE Aerospace is now running flight trials of its Atmospheric Test of Launched Airbreathing System (ATLAS), equipped with the new scramjet engine.

One of the biggest engineering challenges remains accelerating an aircraft to hypersonic speeds. At those velocities, incoming air floods the engine at extreme pressure and heats the combustion chamber to several thousand degrees, potentially melting it.

The ATLAS program avoids the use of liquid fuel. Instead, the inner surface of the engine is coated with a solid hydrocarbon material that resembles rubber. This layered “fuel cake” burns as incoming air passes through, igniting the material in stages, layer by layer.

For testing, the prototype scramjet was mounted on an F-104 fighter jet that had been converted into a flying testbed capable of speeds up to Mach 2.2 — since no wind tunnel can truly simulate hypersonic flight. At this stage, however, the engine itself was not ignited; the goal was to validate aerodynamic performance.