Bolstered by a $60 million Air Force-backed contract, Hermeus is working toward developing the full-scale flight engine for its Quarterhorse concept aircraft as the aerospace start-up barrels toward a potential first flight test of the platform within the first half of 2023.
Known for its goal to develop a Mach 5 passenger jet, the Georgia-based company in late July won a deal to boost hypersonic development from the service and a group of venture capital firms. Some four months later, in November, Hermeus unveiled a ground prototype of the Quarterhorse, firing its engine at maximum afterburner power in front of a group of military and government officials, investors, researchers and others.
In the weeks since, Hermeus co-founder and CEO AJ Piplica told Inside Defense in a December interview that officials have been operating on two parallel tracks, working on vehicle-level development in advance of two wind tunnel tests planned for mid-2022 while proving out the core technology for the engine in an integrated fashion, a push set to culminate around March, before seeking to log their first flight test the following year.
Behind the schedule is the start-up’s latest agreement with the Air Force, something Piplica described as “a huge accelerant for us.” With it, he said, Quarterhorse will be able to enter flight testing “a year or two ahead of what we originally laid out in plans.”
Hermeus’ new contract builds on a previously awarded $1.5 million AFWERX deal to explore how the company’s in-development Mach 5 aircraft technology could feed into the future Presidential and Executive Airlift fleet.
Piplica noted from the company’s outset, its founders were aware of the importance of “bringing private capital to bear” on various technology problems. But the other component of that, he said, is involving the Defense Department as a partner.
Being able to leverage “more of a public-private partnership model to solve a lot of these modernization challenges is incredibly important,” he said.
The $60 million contract has allowed the start-up to grow its team from around a dozen at the beginning of 2021 to nearly 50 now, with personnel likely to “double again by the end of 2022.” The deal is also fostering investments in facilities as the company works to advance further vertical integration, he added, rather than “relying solely or exclusively on an external supply chain” in certain areas.
In addition, the agreement helps Hermeus “be very hardware-rich in how we go through this development process,” given the company’s plans to build three reusable Quarterhorse aircraft, rather than just one, within three years. That in turn, he said, gives officials the go-ahead “to take a lot more risk in our flight-test program than you normally would be able to.”
For example, rather than waiting to book wind tunnel time to allow for a full, free-jet test on the ground, as he said was typical when developing a high-speed engine or vehicle, officials can use the baked-in flexibility to “basically push that risk into flight” and thus move faster.
Central to Hermeus’ Turbine-Based Combined Cycle engine configuration is the General Electric J-85, which powers the aging T-38 trainer and is used in the Quarterhorse for low-speed operations before transitioning to a ramjet at higher speeds, around Mach 3.
The configuration helps aircraft jump what Piplica called a “real cliff” between Mach 1.5 and Mach 3, the space in which he said turbojet engines struggle to operate due to rising temperatures and ramjets lack the right amount of pressure. TBCC’s solution involves cooling down the incoming air before it hits the turbojet, allowing platforms “to bridge that gap between the two systems.”
From a military operations perspective, the setup provides a platform that can operate from a runway, loiter at low speeds for shorter periods and integrate with other aircraft, he said.
Once it reaches Mach 5, Piplica continued, the aircraft could then “conduct an operation in a contested environment where you’re really relying on physics for survivability -- so speed, altitude and maneuverabilty.”
Looking ahead, Piplica declined to share specifics on what may come between developing the Quarterhorse and Hermeus’ end goal of creating a commercial Mach 5 aircraft toward the end of the decade, though he said more details are likely to come “sometime next year.”
One of the gaps in between the two efforts, he noted, centers around the scale of the engine. The company, he said, needs to build a larger engine for a passenger transport aircraft while simultaneously buying down the risk for long-duration, high-speed flights.
“Quarterhorse really just kind of gets up to high speed and altitude and then comes back down,” he said. “So it’s just a sprinter. We don’t get thermal equilibrium, we don’t really stress the system from a thermal standpoint. So those types of things really need to be demonstrated … We’ll probably do that with another system that’s in the roadmap to demonstrate that before we move onto the passenger transport aircraft.”
As Hermeus continues to work with the Air Force and defense officials more broadly, Piplica stressed the need for officials to build the partnership to the point where “we’re actually able to deliver capability out into the field at scale,” something he noted few other venture-backed companies have been successful at doing.
While he acknowledged the Air Force is likely the “place where the majority of this capability will live” once it’s developed, he said components will probably be leveraged by others in the defense realm. In preparation, the company has worked to make inroads with the Army, Navy and special forces community, he said.
“Really understanding what some of those use cases are, what some of those requirements are beyond just the Air Force is actually quite important to us early on, and we do spend a good deal of time understanding those so that we ensure that when we do get a capability out there in the field, that it’s useful, it does what it needs to do,” he said.