A year of ground testing saw the engine generate 13,000 lb of thrust with over an hour of sustained combustion under various hypersonic flight conditions.

Hypersonic technology is regarded as one of the great game changers in 21st century warfare. Just as supersonic flight rendered all previous warplanes and anti-aircraft defenses all but obsolete overnight, aircraft and missiles that can fly at over five times the speed of sound would require an equally great advance in radar, data processing, air defenses, and even artificial intelligence to counter.

However, one major challenge is finding a way to make a craft maintain hypersonic velocity. Currently, most test vehicles are actually hypersonic gliders, which are dropped from a mothership at high altitude, then accelerated to above Mach 5 (3,709 mph, 5,969 km/h) either by rocket or by going into a dive to build up speed. That's fine for a test program, but for something practical, gliding has its limitations – not least of which is restricted range and the inability to operate at lower altitudes.

The approach of the AFRL-Aerojet Rocketdyne team to maintain flight is to use a scramjet. A decade ago, they produced the first hydrocarbon-fueled and cooled air-breathing hypersonic flight test with the Air Force's X-51A Waverider. Now they are working on an 18-foot (5.5-m) Generation-3 version, which can propel a vehicle 10 times the size of the X-51 to hypersonic speed. The new engine is claimed to have increased performance at a lower price.