The U.S. Air Force is seeking proposals to develop and flight-test a combined-cycle rotating detonation rocket engine designed for future high-speed weapons. The program aims to advance the technology from an early proof-of-concept stage to a prototype demonstrated in a relevant environment over 36 to 48 months.The engine uses rotating detonations, in which combustion occurs through a continuous series of shockwave-driven explosions, as part of its propulsion process. The effort supports the development of High-Speed Affordable Mass Munitions (HAMM), with initial proposals due November 16, 2026.Air Force explores detonationThe U.S. Air Force Research Laboratory (AFRL) is seeking industry proposals to develop and flight-test a combined-cycle rotating detonation rocket engine designed for future high-speed weapons.The technology uses continuously propagating detonation waves to burn fuel and could offer an alternative to conventional rocket propulsion. The program aims to advance the engine from laboratory proof of concept to a prototype demonstrated in a relevant environment over 36 to 48 months.The effort is being managed by AFRL’s Rocket Propulsion Division at Edwards Air Force Base in California under the HERMES Broad Agency Announcement. Initial white papers are due November 16, 2026, and the program targets a flight demonstration the support HAMM development.Conventional rocket engines typically burn fuel continuously inside a combustion chamber to generate hot gases that produce thrust. Rotating detonation engines (RDEs) use a different combustion process, generating a detonation wave that travels around a ring-shaped chamber at supersonic speed.As the wave moves through the chamber, it ignites the incoming fuel and oxidizer mixture, sustaining a repeating series of detonations. This process uses the pressure generated by detonation rather than relying solely on conventional deflagration-based combustion.Researchers are investigating the technology because it could improve propulsion efficiency while reducing engine size and complexity. The rotating detonation process may also reduce the need for some conventional engine components, potentially allowing more compact propulsion systems. However, the practical benefits depend on the engine design and its operating conditions.Rotating rocket enginesThe AFRL program focuses on a combined-cycle configuration, designated the Rotating Detonation Rocket Engine-Combined Cycle (RDRE-CC). The design combines rocket propulsion with air-breathing operation, allowing the engine to use atmospheric oxygen during part of its flight rather than carrying all the required oxidizer onboard.This approach could help address the demands of high-speed flight, where propulsion systems must operate across different conditions. A combined-cycle engine must integrate the two operating modes while maintaining stable combustion and delivering the required performance throughout the flight profile.The planned development effort covers engine design, testing, and integration with a flight vehicle. Ground evaluations will include direct-connect tests, which examine engine operation using a connected test setup, and freejet tests that expose the propulsion system to simulated high-speed airflow.These tests are intended to assess the engine under conditions relevant to its intended flight environment before a demonstration vehicle is launched. The program is expected to conclude with a flight test in which a ground-launched sounding rocket boosts the engine-powered vehicle to the conditions needed to demonstrate its operation.AFRL intends to advance the technology from Technology Readiness Level 3, representing an early proof of concept, to Level 6, where a prototype has been demonstrated in a relevant environment.The solicitation requires participating companies to submit a proposed design, testing approach, schedule, and preliminary cost estimate. Selected applicants may then be invited to provide full technical and cost proposals, subject to funding availability.The program builds on ongoing U.S. military research into detonation-based propulsion. RTX’s Pratt & Whitney conducted rotating detonation engine tests in 2025 under DARPA’s Gambit program, which is pursuing air-breathing propulsion for future long-range weapons. AFRL researchers at Edwards have also tested rotating detonation rocket engines on ground-based test stands.