WASHINGTON DC – Few planes ignite the awe-inspiring passions of aviation nerds quite like the SR-71 Blackbird. From its stealthy design to its secretive history, the Blackbird simply screams cool—and it also helps that it’s the fastest air-breathing (a.k.a. “not a rocket”) crewed aircraft in human history.
- Aviation company Hermeus successfully demonstrated mode transition between turbojet and ramjet engines for the Air Force’s Quarterhorse hypersonic aircraft, a major hypersonic flight milestone.
Capable of flying in excess of Mach 3.2 (around 2,200 mph), the SR-71 has been the pinnacle of aviation speed for nearly half a century, but the Atlanta-based aviation company Hermeus thinks it’s time for a little competition. 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 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’s 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.
