Hypersonic aircraft company Hermeus hits engine test milestone

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Hypersonic aircraft company Hermeus hits engine test milestone - Aerospace Manufacturing

Hypersonic aircraft company Hermeus has demonstrated turbojet to ramjet transition within its engine, Chimera.

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HERMEUS

Hypersonic aircraft company Hermeus has demonstrated turbojet to ramjet transition within its engine, Chimera.


This is one of the most important technological feats to making operational hypersonic flight a reality, the company has said.

Chimera is a turbine-based combined cycle engine (TBCC) – which basically means it’s a hybrid between a turbojet and a ramjet. The ability to switch between these two modes allows Hermeus’ first aircraft, Quarterhorse, to take off from a regular runway and then accelerate up to high-Mach speeds.

The cost and speed at which the Hermeus team achieved this milestone is notable. Hermeus designed, built, and tested Chimera in 21 months for $18m.

“This achievement is a major technical milestone for Hermeus,” said CEO AJ Piplica. “But more than that, it’s a proof point that demonstrates how our small team can rapidly design, build, and test hardware with budgets significantly smaller than industry peers.”

The testing took place at the Notre Dame Turbomachinery Laboratory which provides heated air to simulate high-Mach temperatures and pressures.

“The Notre Dame facility allowed us to create conditions similar to what we’ll see in flight,” said CTO Glenn Case. “Completing this testing on the ground significantly de-risks our Quarterhorse flight test campaign which will begin late next year.”

At low speeds Chimera is in turbojet mode – just like any jet aircraft. But as the temperature and the speed of the incoming air increase, turbojets hit their performance limit. This happens at around Mach 2.

Chimera has a pre-cooler that reduces the temperature of the air coming into the turbojet. This allows Hermeus to squeeze out a bit more performance from the turbojet before transitioning to ramjet.

At around Mach 3, Chimera begins to bypass the incoming air around the turbojet and the ramjet takes over completely.

A ramjet is a simple propulsion system which “rams” the incoming high-pressure air to create compression. Fuel is mixed with this compressed air and ignited for thrust. Ramjets are optimal between Mach 3 and Mach 5.

Most hypersonic platforms are powered by a rocket engine. But this approach makes reusability much harder and inherently more dangerous for passenger flight.

By making a full-range air-breathing hypersonic engine that does not require a rocket to accelerate, Hermeus is setting the stage for operational hypersonic flight – meaning aircraft that can be rapidly re-used.

An additional benefit of this engine design is that it accommodates existing transportation infrastructure. Hermeus aircraft are designed to be operational at traditional airports.

This is important not just for hypersonic testing, but critical given Hermeus’ goal of radically accelerating passenger travel through hypersonic flight.

Building Chimera

An essential manufacturing principle at Hermeus is vertical integration.

Manufacturing in-house allows for a tight feedback loop between engineers and technicians which is key to the company’s ability to iterate quickly. Additionally, vertical integration eases reliance on outside vendors and allows for better control of the supply chain.

Another important factor in building Chimera is additive manufacturing. About 15% of the engine is 3D printed which enabled rapid development.

With mode transition successfully demonstrated, the Hermeus team is now racing to manufacture the first Quarterhorse aircraft that will begin flight testing in late 2023.

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Hermeus Acquires 3D Printers for Quarterhorse, Chimera

Velo3D is supplying its traditional Sapphire and large-format Sapphire XC to Hermeus for the Mach 5 Quarterhorse aircraft and its Chimera engine.

www.ainonline.com

(Photo: Hermeus)

 

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Turbojet to hypersonic ramjet: Hybrid Chimera engine shows its range

Atlanta company Hermeus has its sights set on Mach 4 next year, to beat the Mach 3.3 benchmark set by the SR-71 Blackbird way back in 1976. Watch its Chimera hybrid engine nailing the switch between low-speed turbojet mode and hypersonic ramjet mode.

newatlas.com

Turbojet to hypersonic ramjet: Hybrid Chimera engine shows its range​

Atlanta company Hermeus has its sights set on Mach 4 next year, to beat the Mach 3.3 benchmark set by the SR-71 Blackbird way back in 1976. Watch its Chimera hybrid engine nailing the switch between low-speed turbojet mode and hypersonic ramjet mode

Under US Air Force funding, the company is charging forth on its Quarterhorse project, a nuggety, dart-shaped, remotely-piloted UAV designed to sprint faster than any aircraft before it.

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

To get there, it needs an engine similar to what the Blackbird ran; a hybrid propulsion unit that can operate in two stages. When it's time for maximum thrust at hypersonic speeds, you need a ramjet. But ramjets rely on airflow to compress and heat air ready for combustion; they can't start you off on a runway, they produce basically zero thrust below Mach 0.5, and they don't become more efficient than a regular turbojet below somewhere around Mach 3.

Thus, the hybrid. Hermeus has designed and built an engine it calls the Chimera that runs a ramjet and a slower-speed turbojet in the same tube. The turbojet is functional even at a standstill, so it's capable of getting Quarterhorse down a runway and into the air, where it'll accelerate to Mach 3 before shutting off. The supersonic intake air will then be routed around the turbojet into the ramjet, which will compress it, ignite it, and blast the aircraft to its top speed.

The team took the Chimera engine to the Notre Dame Turbomachinery Lab last year, where it was mounted to a bench in a high-Mach test facility specially modified to deliver inlet air at speeds high enough to simulate Mach 4 flight. The engineers ran the jet in bursts, typically late at night to mitigate the insane electricity costs involved. The test campaign lasted a full five months before the Hermeus team was able to announce it had achieved a full and stable transition between the turbojet and ramjet stages in November.

“The Notre Dame facility allowed us to create conditions similar to what we’ll see in flight,” said Hermeus co-founder and chief technology officer Glenn Case in a press release. “Completing this testing on the ground significantly de-risks our Quarterhorse flight test campaign which will begin late [this] year.”


The Quarterhorse's stated goals are to break Mach 4, validate the Chimera engine, and break the 50-year-old airspeed record still held by the SR-71 Blackbird
Hermeus

NDTL director Joshua Cameron said, “We are pleased that Hermeus chose NDTL as their partner for this exciting test program.” Cameron, who is also a research assistant professor in Notre Dame’s Department of Aerospace and Mechanical Engineering, added, “I am also so proud of my team for developing the facility and executing a successful test campaign on a very aggressive schedule.”

Beyond Quarterhorse, Hermeus is planning a larger Darkhorse unmanned platform, which will run an enormous Pratt & Whitney F100 engine out of an F16 as its turbojet stage. This machine is targeted at delivering sustained hypersonic flight at Mach 5, a military capability no country has yet in its arsenal.

https://newatlas.com/aircraft/hermeus-chimera-hypersonic-test/#gallery:1
Hermeus has gone for a Pratt & Whitney F100 turbofan out of the F-16 for the turbine portion of the Chimera II engine that'll power its larger Darkhorse aircraft
Hermeus

But the end goal for Hermeus is not military. Its ultimate plan at this stage is to build a civilian, commercial, Mach 5 hypersonic airliner with a titanium-alloy body and a range around 4,600 miles (7,400 km), capable of ferrying up to 20 passengers across 125 different trans-oceanic routes. This "Halcyon" plane would blast you from Paris to New York in 90 minutes at a monster 90,000 ft altitude, higher than the legendary Blackbird was allowed to cruise.

Five times faster than any commercial aircraft on the market today, Halcyon frankly looks like a bit of a pipe dream at this stage, given that it's an exponentially harder thing to build, test and certify than a supersonic jet – and even those are proving critically difficult, with Florida company Aerion shutting down in 2021 despite more than US$10 billion in advance orders for its 50-passenger Mach 1.4 jet. Not to mention, it's a huge leap from developing military UAVs to getting a hypersonic airliner certified for commercial flight and into serial production, let alone cleared to fly at those speeds. Don't hold your breath on this one.

Still, Hermeus has made some pretty wild progress since it was founded in 2018. It's a young company, with a preternaturally young-looking team, working on some groundbreaking gear. They're shooting for the moon, who knows where they'll land? Check out the engine bench test in the video below, it's as awesome as you'd expect.