Aerospace startup Hermeus has taken another step toward challenging the Lockheed SR-71 Blackbird’s legendary supersonic speed record as the company’s uncrewed Quarterhorse Mk 2.1 lifted off from Spaceport America in New Mexico on March 2, 2026 for its maiden flight.
One of the legends of the Cold War, the Lockheed SR-71 Blackbird reads like something out of a spy thriller. Designed by Clarence “Kelly” Johnson at Lockheed’s Skunk Works, it was a jet-black aircraft built largely from titanium, with giant engines and sweeping lines that would not look out in a futuristic sci-fi movie.
It was also extraordinarily fast – so fast that out of more than 4,000 missiles fired at SR-71s by hostile forces, not a single one hit because none could catch the aircraft. With a cruising speed beyond Mach 3, it could simply outrun anything fired at it. The Blackbird still holds the record as the fastest air-breathing aircraft ever built, reaching an official top speed of Mach 3.32.
And that was in 1976, 50 years ago.
Today, Hermeus aims to surpass that record with its Quarterhorse aircraft, which is being developed as a precursor to an even more ambitious reusable Darkhorse hypersonic aircraft intended for defense and national security applications.
To achieve this, Hermeus is not building Quarterhorse as a single airframe. Instead, its strategy is to accelerate development by fielding a series of prototypes, each designed to address a specific phase of flight. The first, Quarterhorse Mk 0, was built solely for taxi tests to validate integrated systems. It was followed by the Mk 1, which flew in May 2025 and focused on validating high-speed takeoffs and landings.
Now the Mk 2.1 is flying over the White Sands Missile Range in New Mexico in a subsonic maiden flight intended to validate the uncrewed aircraft’s systems. If successful, the plan is to gradually expand the flight envelope before moving to the Mk 2.2, which will attempt to break the sound barrier.
This cautious approach is standard practice for supersonic aircraft development because of the complex aerodynamic forces that occur as an aircraft transitions from subsonic to transonic and then to supersonic speeds. A mistake during this phase can quickly turn a prototype into very expensive debris.
The Quarterhorse Mk 2.1 is roughly the size of a General Dynamics F-16 and is the first in the series to use a delta-wing configuration optimized for supersonic aerodynamics. It is powered by a modified Pratt & Whitney F100 jet engine fitted with a proprietary precooler in the air inlet to prevent overheating at high speeds. For the hypersonic Mk 3, this engine will be replaced with Hermeus’ Chimera turbine-based combined-cycle (TBCC) engine as the company attempts high-Mach flight and a challenge to the SR-71’s air-breathing speed record.
"Speed is the fundamental requirement for our flight systems and for our company," said AJ Piplica, CEO and Founder of Hermeus. "We’re building and flying aircraft on timelines that match the urgency of the world we’re in. Today’s flight kicks off a critical flight test campaign that will ultimately get us to supersonic speeds, bringing the United States closer to having the high-speed capability it needs now, not decades from now."
Source: Hermeus
