[2] In March 2022, the company raised a $100 million series B investment round led by Sam Altman.

[4] The company claims to have designed, built, and successfully tested a Mach 5 engine prototype in only 9 months.

The engine to be used in the Hermeus aircraft adds a precooler to a standard Pratt & Whitney F100[clarification needed].

[13] In 2021, Hermeus secured $60 million in funding from the U.S. Air Force and from venture capital sources to support the Quarterhorse flight test program.

A non-flying Quarterhorse MK 0 prototype will be used to validate systems including electrical, hydraulic, pneumatic, aviaonics, steerinng and propulsion.