US Air Force’s Next Hypersonic Aircraft ‘Quarterhorse’ Takes a Big Leap

Defence Industry

New Delhi: Few planes can arouse passions of aviation aficionados quite like the SR-71 Blackbird. From its stealthy design to its secretive history, the Blackbird is indeed cool as it’s the fastest air-breathing crewed aircraft in human history.

The aircraft SR-71 which is capable of flying in excess of Mach 3.2 (around 2,200 mph), has been the pinnacle of aviation speed for nearly half a century, but soon it will have a little competition from the Atlanta-based aviation company Hermeus. The company’s vision of hypersonic flight (meaning speeds faster than Mach 5) isn’t one reserved for clandestine spy missions, however. That’s because Hermeus wants to bring hypersonic airliners to an airport near you.

In 2021, the US Air Force awarded Hermeus a $60 million contract to develop three uncrewed concept aircraft, including the hypersonic “Quarterhorse.” Late last year, Hermeus passed a major milestone by successfully firing a turbojet-ramjet hybrid engine, known as “Chimera.”

The air-breathing monster behind the powerful SR-71 is a Pratt & Whitney J58 turbojet engine, which maxes out at speeds around Mach 3. In Hermeus’ hypersonic design, a ramjet, which can only operate at high speeds as it uses this air to pressurize air and fuel in the combustion chamber, kicks in and carries the theoretical Quarterhorse aircraft to Mach 5 and beyond. For any plane hoping to dethrone the Blackbird, its engine needs to somehow seamlessly transition between turbojet, ramjet, and back to turbojet—and Hermeus has already pulled off that delicate piece of aviation engineering.

“We just demonstrated a mode transition, which means we went from turbojet mode to ramjet mode,” Hermeus co-founder and CTO Glenn Case said in a recent video. “This is probably the most critical challenge in unlocking hypersonic flight.”