Performance of Expansion-Deflection Nozzles for Rotating Detonation Rocket Engines

Rotating detonation combustion (RDC) has seen substantial research and development in recent years. Pressure-gain in RDC engines due to the detonation mode of combustion enables greater extractable energy potential, generating thrust more efficiently than conventional combustion engines. This increased efficiency is critical for both hypersonic air-breathing applications, where RDC can be coupled to ramjets to enable high-speed, long-range flight, and for in-space propulsion which benefits from the increased delta-v and compact geometry of rotating detonation rocket engines (RDRE). Exhaust nozzle design determines the overall performance at the design point, contributes significantly to the total engine weight, and can affect the stability of the detonation, yet it remains an under-researched aspect of RDREs. An expansion-deflection (ED) nozzle is proposed herein as a solution to maximize the thrust potential of RDREs operating in vacuum conditions. High fidelity CFD simulations of candidate RDRE experimental configurations will be conducted to identify performance trends and transient forces and heating on the combustor surfaces. A reduced-order modeling (ROM) approach will be adapted to provide more rapid evaluation of candidate nozzle contours, and a novel shock-tracking numerical approach will be tested to enable more efficient CFD simulations. In Phase II the ED nozzle designs will be prototyped and tested experimentally to validate the performance trends identified in the CFD. The ROM approach will be further developed to optimize the nozzle contours for increased thrust and reduced weight and length. Additionally, the feasibility of active thrust control through moving the center body pintle will be explored.

The potential performance gain and mass and length reduction afforded by ED nozzles would significantly enhance missions to the Moon, Mars, and other planetary bodies within the solar system. Ongoing research and design of RDREs at NASA, such as the recently demonstrated 3D-printed engine developed in collaboration with IN Space LLC, would immediately benefit, and there is potential for insertion into programs including Artemis and beyond. The proposed nozzle technology could enhance the stability and performance of rotating detonation engines, including hypersonic air-breathing engines such as GE Aerospace’s recently demonstrated dual-mode ramjet with rotating detonation combustion and conventional RDREs such as the one recently developed by Venus Aerospace in collaboration with DARPA.

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