In a breakthrough moment for experimental aerospace development, aviation startup Hermeus has completed the first flight of its Quarterhorse Mk 1—an uncrewed test aircraft representing a critical stepping stone toward hypersonic aviation. Conducted at Edwards Air Force Base in California, the test flight marks a tangible milestone in Hermeus’ mission to ultimately build a reusable aircraft capable of exceeding Mach 5 and breaking the airspeed record held by the SR-71 Blackbird.
Although the Mk 1 is not designed for supersonic flight, its successful maiden voyage underscores Hermeus’ ambitious, rapid development strategy. The company’s roadmap is nothing short of bold: beat the SR-71’s 1976 speed record of 2,193.2 miles per hour, master hypersonic propulsion, and eventually transform global aviation—both commercial and military.
According to Hermeus, the Quarterhorse Mk 1 “achieved stable flight and landed smoothly,” completing a brief but symbolically powerful sortie over the dry lakebed of Edwards. The aircraft, uncrewed and controlled remotely, is seen in company-released footage lifting off, flying a short distance, and landing with precision—an unassuming clip that may one day be viewed as the beginning of a new era in aviation.
This first flight was not about speed, altitude, or advanced maneuvering. Instead, it focused on validating the fundamental capabilities of an entirely new aircraft system: launch, flight stability, telemetry, and landing. Even the aircraft’s appearance—sporting a visibly rough and utilitarian finish—reflected Hermeus’ “build fast, test faster” ethos.
“Mk 1’s flight validated our rapid, iterative approach to airplane development and advanced our mission to radically accelerate aviation,” the company said in a statement.
Hermeus’ development process is deeply rooted in rapid prototyping and iteration, a model reminiscent of the fast-paced experimental aircraft programs of the 1950s and 1960s. Preceding the Mk 1 was the Quarterhorse Mk 0, a ground-based “dynamic iron bird” used to test major subsystems including propulsion, hydraulics, and avionics. Completed in just six months and thoroughly tested in only 37 days, the Mk 0 set the tone for what Hermeus describes as a “hardware-rich” development cycle.
The Mk 1, which went from concept to flight-ready in slightly more than a year, is the next rung on this ladder. Its role is clear: act as a proving ground for flight systems, command and control, flight termination systems, and basic airframe behavior. The aircraft is powered by a General Electric J85 turbojet—the same engine used in the T-38 Talon jet trainer—chosen for its reliability rather than thrust or speed.
Hermeus is not just building fast planes; it’s redefining how fast planes are built. The company refers to its approach as “hardware richness”—a development style in which multiple physical prototypes are constructed and tested quickly. This enables engineers to learn rapidly from real-world data rather than relying solely on simulation. It also allows for design evolution at a pace rarely seen in modern aerospace projects, where lengthy development timelines and cost overruns are more the norm than the exception.
By the time the Mk 3 aircraft is ready, Hermeus expects to demonstrate in-flight transitions from turbojet to ramjet propulsion—essential for sustained hypersonic flight. These complex transitions are the crux of turbine-based combined cycle (TBCC) engines, which combine traditional jet turbines with ramjet or scramjet elements to operate efficiently across a vast range of speeds.
While the Mk 1 remains subsonic, Hermeus’ roadmap is clearly structured for speed. The Mk 2, currently under construction in Atlanta, will be capable of flying at supersonic speeds below Mach 3. Roughly the size of an F-16 fighter jet, it will use a Pratt & Whitney F100 engine—the same powerplant used in many U.S. military aircraft.
If all goes as planned, the Mk 2 will take flight by the end of 2025. It will serve as a platform to validate the aerodynamics, materials, and avionics necessary to withstand high-speed flight and lay the groundwork for the much-anticipated Mk 3. That version is where the hypersonic ambitions truly come into play. Designed to exceed Mach 3 and break the SR-71’s record, the Mk 3 will be a full demonstration of Hermeus’ TBCC propulsion technology in flight—a feat that only a handful of programs have ever approached.
While Hermeus positions itself as a commercial startup—with goals of building “the fastest reusable aircraft in the world”—its ties to the U.S. military are extensive and growing. In 2021, Hermeus received $60 million in funding from the U.S. Air Force and private venture capital firms to advance the Quarterhorse program. That backing speaks volumes about the strategic interest in the company’s capabilities.
From reconnaissance missions to rapid cargo transport, the potential military applications of hypersonic and ultra-fast aircraft are vast. Hermeus has floated the idea of “mid-size autonomous aircraft” to fill these roles—offering quick-strike or rapid logistics capabilities with little notice and global reach.
Moreover, the Air Force’s broader push for “affordable mass” and rapid prototyping aligns perfectly with Hermeus’ development model. The notion of building multiple uncrewed aircraft quickly and affordably is gaining favor in defense circles, especially as geopolitical tensions drive demand for faster deployment cycles and adaptive technologies.
Hypersonic flight remains one of the most complex and elusive challenges in aerospace engineering. The environments involved—extreme temperatures, dynamic instabilities, and propulsion transitions at high speed—are unforgiving. Many hypersonic programs have stalled, failed, or been relegated to paper concepts and wind tunnel tests.
For Hermeus, the biggest challenge will be translating its fast, iterative development into reliable, scalable flight hardware. That’s a tall order, particularly when even modest supersonic passenger aircraft like the Concorde faced insurmountable economic and regulatory hurdles.
Competing startups, including those pursuing supersonic business jets or next-gen Concorde-style transports, have struggled to maintain momentum. Some have collapsed under the weight of technical and market realities.
What sets Hermeus apart is its more flexible market positioning. While commercial applications remain an end goal, the company is not tying its immediate success to an unproven market for supersonic travel. Instead, it is focusing on creating functional, fast, reusable platforms that could serve either commercial or defense applications.
The successful flight of the Quarterhorse Mk 1 doesn’t just demonstrate Hermeus’ engineering capabilities—it signals a changing attitude in aerospace innovation. By adopting a lean, aggressive development model, Hermeus is hoping to do what traditional programs have often failed to achieve: move from concept to airframe to breakthrough in record time.
The next milestone will be the first flight of the Mk 2, expected later this year. That aircraft will bridge the gap between subsonic testbeds and the fully capable hypersonic systems that Hermeus is ultimately chasing.
