Experimental Investigation of Rotating Detonation Rocket Engines for Space Propulsion

The performance (specific impulse, ) of a modular, -class rotating detonation rocket engine (RDRE) was measured with three gaseous fuels (methane, ethane, and ethylene) and gaseous oxygen over a wide range of flow rates and equivalence ratios. All tests exhausted to sea level backpressure and were conducted using a calibrated thrust stand and Coriolis mass flow meters. Configurations tested included a straight, open annulus, as well as several converging/diverging annular nozzles. Throughout testing, wave numbers observed via high-speed video varied from 5 to 8 waves, whereas wave speeds varied from 60 to 72% of ideal Chapman–Jouguet velocities. Measured performance ranged from 68 to 85% of ideal liquid rocket engine (deflagration engine) sea-level performance, based on comparisons to ideal NASA Chemical Equilibrium with Applications performance estimates. Additionally, an altitude compensating aerospike nozzle increased performance by 10–13%. Several constricting annular exits were also tested, and yielded increased with decreasing flow area. Direct detonation upset tests revealed remarkable combustion stability, and extended pulse-mode firings demonstrated the potential for RDREs as attitude control thrusters.