How Hermeus’ Quarterhorse Mk 2.1 Is Closing in on the SR‑71 Record

On March 2, 2026, Hermeus successfully completed their first flight with the Quarterhorse Mk 2.1, lifting off from Spaceport America in New Mexico and flying over the White Sands Missile Range. From a base station, the team of operators maintained a tight eye on how the systems reacted, how well the plane operated under stress, and so on, basically to see if everything functioned as intended.

In terms of size and capability, the new bird is a beast, measuring nearly the same size as an F-16 fighter, weighing four times as much as the previous Mk 1 prototype, and being three times larger overall. It’s powered by a Pratt & Whitney F100 engine, similar to that used on F-15 or 16 fighters, with a new inlet precooler added to deal with the heat generated by pushing the envelope during later testing. The designers used a delta wing shape to boost performance once above subsonic speeds.

This flight was entirely for confirmation, as there was no need to set any land speed records just yet, hence it remained subsonic the entire time. The announcement did not include specific numbers for height, time, or velocity, but it did signal the beginning of a methodical plan to incrementally push the limits. Let’s not forget that Hermeus flew the Mk 1 for the first time in May 2025, so it’s been less than a year and they’ve already moved on to the next prototype, using the data from the previous one to improve the next.

The Mk 2 series is all about reaching supersonic speeds, and the team hopes that the Mk 2.2, which is set to arrive next, will rapidly dethrone the title of the world’s fastest unmanned aircraft. The Mk 3 will thereafter use a Chimera turbine-based combined-cycle engine that is meant to easily switch modes, i.e., from a turbine at low speeds to a ramjet at high Mach. Hermeus currently hopes to shatter the SR-71 Blackbirds’ air-breathing speed record of Mach 3.3 (about 2,193 miles per hour), set in 1976, and potentially even push it up to Mach 5.
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