The U.S. Department of War, through the Defense Advanced Research Projects Agency (DARPA), is launching an ambitious new program to design and develop a next-generation High Mach Gas Turbine (HMGT) engine aimed at powering future reusable hypersonic aircraft.
According to a solicitation released on September 24, the initiative—developed in partnership with the Air Force Research Laboratory (AFRL) and the Air Force Life Cycle Management Center’s Propulsion Directorate (AFLCMC/LP)—seeks to “jump start the development of a HMGT engine program compatible with the needs of future reusable hypersonic aircraft.”
The program’s first phase focuses on conceptual and preliminary design work, including identifying the engine’s core architecture, key subsystems, and a detailed technology roadmap to mature each component and the overall propulsion system. Phase 1 will also include subsystem and component testing to validate early design approaches.
DARPA says the HMGT program is designed to enable sustained airbreathing propulsion at hypersonic speeds for future aircraft operating at Mach 4 and beyond. Unlike rocket-based systems, airbreathing turbine engines could offer greater reusability, responsiveness, and affordability for military missions.
The effort underscores a broader Pentagon push to close critical capability gaps in high-speed flight and to expand options for long-range strike, intelligence, surveillance, and reconnaissance platforms in highly contested environments.
“This solicitation aims to identify the optimal HMGT engine architecture and subsystem technologies required to make reusable hypersonic aircraft viable,” DARPA said in its announcement.
The program is structured in multiple phases. Phase 1A will be funded with approximately $10 million, with Phase 1B expected to receive about $30 million in additional funding. Multiple awards are anticipated, and companies will need to submit an abstract to qualify for oral presentations and full technical and cost proposals.
DARPA officials confirmed that the “entire HMGT” is included in the design scope, and participants must propose complete engine system concepts rather than partial subsystems. The solicitation also specifies that only airbreathing turbine-based propulsion architectures will be considered; other engine types will not be accepted.
Ground test facilities capable of evaluating a full-scale HMGT across its operational speed and altitude envelope are expected to be available. However, DARPA clarified that flight testing using experimental X-plane platforms is beyond the scope of the current solicitation.
The HMGT program will also coordinate with other U.S. hypersonic technology efforts, such as the Air Force’s Combined-Cycle Rocket-Based Propulsion (CoRSAir) initiative, to ensure complementary development paths.
The HMGT concept represents a major shift in the Pentagon’s approach to high-speed propulsion. Whereas previous hypersonic efforts have largely relied on expendable rocket boosters or dual-mode scramjet demonstrators, a reusable turbine-based system could enable aircraft to operate repeatedly at hypersonic speeds, dramatically reducing launch costs and turnaround times.
The HMGT program is part of DARPA’s broader effort to accelerate propulsion innovation under its Advanced Propulsion Office (APO), which aims to integrate breakthrough propulsion technologies into operational platforms faster and more efficiently than traditional acquisition programs.