Description:

A rotating detonation rocket engine improves performance over a conventional rocket engine by harnessing the increase in pressure provided by detonative combustion for thrust generation. The detonation wave propagates in an annular combustor and runs transverse to the flow direction at very high speeds, often requiring only a few inches to accomplish propellant mixing and combustion. RDRE combustors are also attractive because they can be very short, allowing for improved integration with vehicles, such as upper stages or landers. RDRE's have been shown to operate with a wide variety of propellants, including hypergolic propellants, and can operate over a wide throttling range. Operation with cryogenic propellants has also been demonstrated. Regeneratively cooled chambers have been demonstrated with run times up to several minutes at a time. Current research is focused on injector technology to prevent coupling of the pulsed combustor flow with the propellant supply manifolds, developing optimized combustor contours, and nozzles optimized for unsteady flow. All of these technical challenges will need to be addressed in order to achieve full theoretical performance. Related technologies include high heat flux combustor cooling concepts, advanced instrumentation for high speed oscillatory flows, and advanced computational modeling tools and techniques. This last area includes specialized combustion kinetic models that simultaneously capture detonative and deflagrative behavior correctly, assessments of required numberical accuracy and grid density, wall heat transfer modeling in an unsteady environment, and the development, demonstration, and validation of lower order models that can be incorporated into higher fidelity simulations for parameters such as skin friction loss and heat transfer to reduce model run times.

Benefits: Improved specific impulse and decreased propulsion system length are the primary benefits. Specific impulse benefit can be on the order of 10%, with advanced multi-phase detonation concepts significantly higher. Combustor length has been demonstrated to be at least 40% shorter than a standard rocket, with the potential to be as much as 80% shorter. The annular combustor design also enables the development of shorter optimum nozzles. The RDRE concept can benefit any mission utilizing chemical propulsion. First use is expected to be for in-space propulsion. Additional benefits can include decreased pump supply pressure, decreased risk of unexpected combustion instability and decreased system weight. These benefits can be traded off to provide an optimal propulsion solution for a given mission. A recent vehicle level study showed the ability to close the design of a Mars Ascent Vehicle with an RDRE, when the design would not close with a conventional rocket engine, with the primary benefit arising from weight reduction.