Turbojet to hypersonic ramjet: hybrid Chimera engine shows its range

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Atlanta-based Hermeus is targeting Mach 4 next year to beat the Mach 3.3 benchmark set long ago by the SR-71 Blackbird in 1976.

Funded by the US Air Force, the company is rushing ahead with its Quarterhorse project, a chunky, arrow-shaped, remote-controlled UAV designed to sprint faster than any aircraft before it.

With funding only awarded in 2021, the pace of development on this one is pretty wild, and Hermeus claims it’s still on track to break the all-time land speed record for air-breathing aircraft next year.

To get there you need an engine similar to the Blackbird; hybrid drive unit that can be operated in two stages. When it’s time for maximum thrust at supersonic speeds, you need a ramjet. But traffic jam jets cannot function without the pressure and temperature of flight speeds at least three times the speed of sound.

The turbojet takes you from zero to Mach 3, then the ramjet kicks in and the real part begins


So the hybrid. Hermeus designed and built an engine called the Chimera that powered a ramjet and a slower turbojet in the same tube. The turbojet is also functional while stationary, allowing it to take Quarterhorse along a runway and into the air, where it accelerates to Mach 3 before shutting down. The supersonic intake air is then directed around the turbojet to the ramjet, which compresses it, ignites it, and propels the aircraft to its top speed.

The team brought the Chimera engine to the Notre Dame Turbomachinery Laboratory last year, where it was mounted on a workbench in a high-mach test facility that was specially modified to deliver the -inlet air at speeds high enough to produce one Mach -4 flight to simulate. . Engineers ran the jet at once, usually late at night, to mitigate the insane energy costs involved. The test campaign lasted a full five months before the Hermeus team could announce in November that they had achieved a complete and stable transition between the turbojet and ramjet stages.

“The facility at Notre Dame allowed us to create conditions similar to what we will see on the plane,” said Glenn Case, Hermeus co-founder and chief technology officer, in a press release. “Completion of these ground tests will significantly reduce the quarter horse flight test campaign, which will start late [this] A year.”

The Quarterhorse’s stated goals are to break Mach 4, validate the Chimera engine, and break the 50-year-old air speed record still held by the SR-71 Blackbird.


NDTL Director Joshua Cameron said, “We are delighted that Hermeus has chosen NDTL as a partner for this exciting testing program.” so proud of my team who developed the facility and ran a successful test campaign on a very aggressive schedule.”

In addition to Quarterhorse, Hermeus is planning a larger Darkhorse unmanned platform that will power a giant Pratt & Whitney F100 engine from an F16 as the turbojet stage. This engine is designed to enable sustained hypersonic flight at Mach 5, a military capability that no country currently has in its arsenal.

Hermeus selected a Pratt & Whitney F100 turbofan from the F-16 for the turbine section of the Chimera II engine that will power its larger Darkhorse aircraft.


But the ultimate goal for Hermeus is not military. The ultimate plan at this stage is to build a civilian, commercial, hypersonic Mach 5 aircraft with a titanium alloy body and a range of approximately 4,600 miles (7,400 km) capable of carrying up to 20 passengers on 125 routes different transoceanic. This plane “Halcyon” would blast you from Paris to New York in 90 minutes at a monster altitude of 90,000 feet, higher than the legendary Blackbird was allowed to fly.

Five times faster than any airliner on the market today, the Halcyon honestly seems like a pipe dream at this point, which is exponentially harder to build, test and certify than a supersonic jet – and even those they are proving critically difficult considering that based in Florida. the Aerion company will shut down in 2021 despite more than $10 billion in pre-orders for its 50-passenger Mach 1.4 jet. Not to mention it’s a big leap from the development of military UAVs to a hypersonic aircraft approved for commercial flight and in mass production, let alone cleared to fly at those speeds. Don’t hold your breath on this one.

Still, Hermeus has made some pretty wild moves since its inception in 2018. It is a young company with a preternaturally young looking team working on innovative equipment. They are shooting for the moon, who knows where they will end up? Check out the dyno test of the engine in the video below, it’s as great as you’d expect.

Hypersonic Engine test milestone

Source: Hermeus

Source: newatlas.com

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