# Hermeus

Hermeus Corporation is an American startup company designing a hypersonic airliner.

## History

The company was founded in 2018 with initial funding led by Khosla Ventures.
In March 2022, the company raised a $100 million series B investment round led by Sam Altman. Other investors included Founders Fund, In-Q-Tel, and existing investors Khosla Ventures, Canaan Partners, and Bling Capital.

## Products

The aircraft under development is planned to fly at Mach 5 with a range of 4,600 miles (7,400 km). The company claims to have designed, built, and successfully tested a Mach 5 engine prototype in only 9 months. In August 2020, Hermeus received a $1.5 million contract from the United States Air Force to develop their proposed aircraft and function as a possible Air Force One.
They are building the supersonic Quarterhorse Mk 2 with an advanced engine based on the Pratt & Whitney F100. Quarterhorse Mk 2 is expected to hit speeds greater than Mach 2.5.

## Design

The engine to be used in the Hermeus aircraft adds a precooler to a standard Pratt & Whitney F100. The precooler lowers the temperature of incoming air, preventing the melting of engine parts and allowing the engine to be more efficient.
The next-generation Chimera engine includes a ramjet, which was successfully tested in November 2022. It will power the Quarterhorse Mk 3, which will reach speeds close to Mach. Until reaching sufficient speed, Chimera routes incoming air around the turbojet and the ramjet takes over.

### Versions
#### Quarterhorse

Hermeus is initially focused on the Quarterhorse design program:
The Quarterhorse development schedule has four stages:
* MK 0: A non-flying prototype to validate all major aircraft subsystems in a real-world environment.
* Mk 1: The first flyable version of Quarterhorse.
* Mk 2: Scheduled for 2025, Mk 2 will be powered by a precooled Pratt & Whitney F100 engine, enabling supersonic flight.
* Mk 3: In 2026, Mk 3 will incorporate Hermeus' Chimera II propulsion system, which includes a modified F100 engine. This version aims to achieve speeds faster than Mach 3.3.

#### Darkhorse

Next comes Darkhorse, an uncrewed hypersonic military jet intended for mass production. After Darkhorse, the plan is to create Halcyon, a hypersonic passenger jet.

#### Chimera

Chimera is a pre-cooled, full-range, air-breathing, turbine combined cycle (TBCC) hypersonic engine combining a pre-cooled turbine with a ramjet. At low speeds Chimera operates as a turbine, while at higher speeds the engine transitions to ramjet mode. The precooler helps bridge the gap between these modes increasing the performance of the turbine. Chimera begins to bypass the incoming air around the turbojet at around Mach 3, and the ramjet takes over completely. Hermeus demonstrated achieving this in tests in November 2022.

## Testing

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, avionics, steering and propulsion. In August 2024, Hermeus completed low-speed taxi tests. The testing was completed in 37 days from the time the MK 0 prototype arrived at the test facility.