Hermeus

Hermeus, founded in 2018 and headquartered in Atlanta, Georgia, is developing hypersonic aircraft capable of Mach 5+ speeds — targeting the potential to reduce transatlantic flight times to 90 minutes (New York to London) through a turbine-based combined cycle (TBCC) propulsion architecture that uses a standard jet engine at low speeds before transitioning to ramjet mode above Mach 3, then sustaining hypersonic cruise.

Hermeus' propulsion approach begins with a modified General Electric J85 turbojet that accelerates the aircraft to high supersonic speeds, then transitions to a proprietary pre-cooled precooled ramjet mode that can sustain Mach 5+ cruise. This TBCC architecture avoids the complexity of separate rocket boosters or scramjet-only approaches by maintaining turbomachinery-based low-speed operation while enabling hypersonic dash. The company's iterative development philosophy uses a series of increasingly capable vehicles: Quarterhorse (unmanned demonstrator, contracted with USAF for flight testing at Mach 4+), Halcyon (commercial passenger aircraft concept), and Darkhorse (DoD high-speed reconnaissance and strike platform).

The US Air Force Research Laboratory contracted Hermeus for the Quarterhorse Experimental program — a key validation that the DoD has both technical confidence in Hermeus' TBCC approach and strategic interest in hypersonic aircraft for time-critical surveillance and strike missions. The Darkhorse program targets a high-speed uncrewed aircraft for ISR (intelligence, surveillance, reconnaissance) missions requiring the dwell time reduction and speed-based survivability that hypersonic speeds provide versus sub-Mach ISR platforms.

Hermeus has raised over $100 million from investors including Khosla Ventures and Canaan Partners. The company competes with Boom Supersonic (Mach 1.7 commercial aviation), Reaction Engines (pre-cooling technology), and defense primes Lockheed Martin Skunk Works and Northrop Grumman in the high-speed flight sector.