Quarterhorse: The Air Force is Getting a Mach 5 Monster

The hypersonic aircraft Quarterhorse,  is poised to join “the world’s fastest aircraft” at an astonishing speed of Mach 5. That’s right, five times the speed of sound. 

Hermeus is the brains behind the $60-million joint project with the US Air Force, an Atlanta-based aerospace developer of hypersonic aircraft to accelerate the global transportation network. 

The startup’s multimillion aircraft projects connect global cities on regional timescales, reducing flight times and increasing safety for long-haul and business-class air travel. 

With the said multimillion contract award from the Air Force, Hermeus is developing three uncrewed aircraft, with Quarterhorse as its forerunner superjet project.

Quarterhorse, a remotely-piloted hypersonic aircraft, is set to smash the almost 50-year-old airspeed records held by the SR-71 Blackbird. NASA records show that the Air Force retired the Blackbird in 1990, reactivated it for funding in 1995, then used it as a research platform and for crew training until 1997.

“Hypersonic travel has the potential to add more than $4 trillion of global GDP growth per year by radically accelerating the speed of commerce and cultural exchange,” Hermeus says in a statement.

 Milestone  With Hermeus’ Hypersonic Engine

More than just media hype, Hermeus’ hypersonic dream is now a reality, with proven tests on its hybrid turbojet-ramjet engine called the “Chimera.”

Hermeus founder and CEO AJ Piplica is ecstatic.

“This is one of the most important technological feats to making the operational hypersonic flight a reality.  This achievement is a major technical milestone for Hermeus.  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 flight tests were held at the  Notre Dame Turbomachinery Laboratory,  providing heated air to simulate high-Mach temperatures and pressures.

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

Other team members also celebrated the recent milestone, validating Chimera as a hypersonic powerhouse.

Senior propulsion engineer Jordan Fisher shared that their initial testings on the Chimera “proves that all of these operating modules were possible,” with the flight test results validating its hypersonic performance. 

Fellow senior propulsion Engineer Weston Schlack called the Chimera milestone “a huge deal.”

“We had done it back in the seed round with a small-scale engine.  Chimera is the actual engine that will be flying on Quarterhorse using the  (repurposed) J-85 turbojet engines .”

Building Chimera

Hermeus stressed that an essential manufacturing principle  in the company 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.

With “additive manufacturing,” Hermeus scores another essential factor in building its hypersonic engine.

“About 15% of the engine is 3D printed, which enabled rapid development,” the company added.

The Chimera Explained

Hermeus’ Chief Technology Officer and founder Glenn Case explains that for an aircraft to hit hypersonic speeds, it needs a specific type of hybrid engine, a turbojet and a ramjet combined. This is why Hermeus’ Chimera was born.

“To hit hypersonic speeds, you need to fly at  Mach 5, that’s over 3836 miles per hour. Turbojets just can’t go that fast, but ramjets can, “ Case explains.

“But the problem is ramjets only work when you’re going really fast, like Mach 3. So taking off on a regular runway to go to Mach 5, you must operate with both turbojet and ramjet. And that’s what our engine is. Chimera is our hybrid turbojet-ramjet engine.”

Traditional turbojet engines max out around Mach 3 ( three times faster than the speed of sound ). On the other hand, a ramjet engine operates at high speeds as it uses air to pressurize air and fuel in the combustion chamber. This allows them to reach Mach 5 speeds (five times faster than the speed of sound). 

Also, Hermeus is designing its aircraft with an adjustable wingspan capability to fly more efficiently at different speeds.

Hypersonic Flights  

Hypersonic flight is best achieved via the use of a ramjet engine. 

However, ram jet engines cannot operate at slower speeds; they can only run from Mach 3 to Mach 6. This is because a ramjet has no fan, compressor, or moving parts. Instead, ramjets rely on a simple setup of heavy air pressure flowing into the inlet and around a cone for compression.

After compression, this air is ignited to produce thrust. Immense pressure only occurs at speeds greater than Mach 3, so ramjets cannot be used at slower rates. 

However, the default speed of aircraft is not Mach 3; it’s Mach 0. This means that ram jets cannot power aircraft to hypersonic speeds, at least not alone. So there is a need to team up with a different type of engine, which is a turbojet engine.

Turbojet-Ramjet Hybrid for Chimera

A turbojet engine, generally used in fighter jets today, has a fan that sucks in incredible volumes of air. Turbojets squeeze that air with a compressor. The compressed air is then mixed with fuel and ignited, similar to how a piston compresses the air-fuel mixture in a car. 

The ignited air-fuel mixture pushes out the back of the engine as propulsion and powers a turbine in the process. 

This mechanical function of a fan, a compressor, and a turbine enables a turbojet engine to thrust a jet from a stationary position. The compressor produces the high-velocity air required to create compressed air.

In an interesting twist of fate, a turbojet engine loses efficiency at speeds approaching Mach 3. This is the same speed at which a ramjet begins to operate efficiently, like a match made in heaven. 

Hermeus engineers discovered that a turbojet-ramjet fusion thrusts an aircraft from a stationary position up to Mach 5 + speeds. This combination forms a new turbine-based combine cycle (TBCC) engine, a hypersonic hybrid now known as Chimera.

More Hypersonic Flights With Dark Horse And Halcyon 

Hermeus’ other hypersonic aircraft include the Dark Horse, dubbed by its creators as its hypersonic uncrewed aerial system (UAS) with multi-mission flexibility designed for defense and intelligence clients. 

The company brands the Dark Horse as its hypersonic flight representing its “major technological leap …. (with a) capability that no other country in the world has.”

Halcyon, meantime, is Hermeus’ passenger aircraft designed to cruise through more than 125 transoceanic routes bursting at hypersonic speeds. That translates to a 90-minute flight from New York to Paris—five times faster than the current fastest commercial aircraft. 

The Future Of Modern Aviation With Hermeus

Hermeus,  with its forerunner project Quarterhorse ,  expressed optimism that its “world’s fastest aircraft” will usher in a new era of skyrocketing hypersonic flights.

The company’s groundbreaking superjets, namely the Quarterhorse, Dark Horse, and Halcyon prototypes, are revolutionary on their own accord, powered by the hypersonic Chimera geared on full throttle at Mach 5. 

Analysts observe that Hermeus could be the first to achieve these hypersonic feats, with full operational flights by 2029. Yet, their multimillion projects can also be surpassed by other aviation companies.

While Hermeus works on its TBCC engines, other aircraft developers and aerospace experts are also working on their hypersonic engines, keeping the Atlanta-based company on its toes.