Hiller "Six Pack" Pulse Reactor Engine

Prototype pulse reactor; 6 horseshoe-shaped combustors; designed for V/STOL applications; called "Six Pack"; side shields missing.

In the early 1960s, under U.S. Navy contracts, Hiller Aircraft Company developed a pulse reactor lift engine for vertical/short take-off and landing (V/STOL) applications that would be competitive with turbojets, but with reduced complexity and cost. Simplicity of the concept was that it had no moving parts, and could operate near the ground without sustaining foreign object damage.

Consisting of package of six pulse reactor tubes, the Hiller engine was a pulsating combustion type with a pulse rate of approximately 100 cycles per second. Following operation on a Navy variable attitude stand under various conditions, it was concluded that the engine was not suitable for use as a V/STOL engine because it would neither start nor operate in a nose-up position (exhausting into the wind) at elevated air velocities; and maximum thrust was approximately 5 percent below that obtained by Hiller. The 0.71 thrust/weight ratio was also considered unsatisfactory for V/STOL aircraft.