Quarterhorse Mk 2 will fly with this precooler-F100 engine combination and be capable of hitting speeds greater than Mach 2.5. The entire Chimera engine, which includes a ramjet, will power Hermeus' following aircraft, Quarterhorse Mk 3. This aircraft will reach speeds close to Mach 4 and pave the way for future Hermeus aircraft that will fly at hypersonic speeds.

The 2026 Quarterhorse Mk 3 prototype will fly to Mach 3.3 and beyond and get high altitude like the SR-71 then it will have a controlled dive to get towards mach 5 as it switches to the ramjet. The ramjet is not efficient in until speeds are near mach 5. Previous hypersonic designs have involved three engines. Hermeus will only use two engines. They will pre-cool the regular engine to get up to mach 3.3 or more then they use gravity to bridge the inefficient gap to get up to efficient ramjet speeds.

The planned, controlled dive is explained in this video by the technical lead of Hermeus.

Quarterhorse Development Timeline:

Mk 1: The first flyable version of Quarterhorse, Mk 1, is set for flight tests later in 2024. These tests will focus on high-speed takeoffs and landings

Mk 2: Scheduled for 2025, Mk 2 will be powered by a Pratt and Whitney F100 engine, enabling supersonic flight. This version will serve as a precursor to the full hypersonic capabilities planned for future iterations

Mk 3: Expected to be developed by 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, supporting Defense Department testing.