Meet Ramjet-X: The Mach-speed drone that launches from another drone
3 min read
The aerospace startup, Hermeus, has announced it is developing an expendable ramjet-powered autonomous vehicle to launch from its F-16-sized Quarterhorse drone called Ramjet-X. Ramjet-X is around 22 feet long and around seven feet wide.
A larger drone launching a smaller drone
The Ramjet-X will turn Hermeus’ flagship, the Quarterhorse Mk 3 into a mothership, while the Ramjet-X is to be a parasitic aircraft. The high speed of the Hermeus will provide the Ramjet-X with the high initial speed required for it to effectively initiate its ramjet engine.
The concept is for Quarterhorse to carry Ramjet-X under its wing pylons, allowing it to carry two on each mission.
Hermeus is currently testing the Ramjet-X’s ramjet engine at its HEAT facility in Jacksonville, Florida. The company is planning for integrated vehicle testing to commence in 2027.
America wins the high-speed race by putting hardware in the sky, learning fast, and flying again next week.
— Hermeus (@hermeuscorp) September 9, 2026
Today, Hermeus introduces Ramjet-X.
Air-launched directly from our Quarterhorse flight test program, Ramjet-X is a low-cost ramjet test platform engineered to break one… pic.twitter.com/3Y9vRlfzYQ
The release speed will be around Mach 3, which is the speed at which ramjets can start operating. Ramjet-X will then climb to around 100,000 feet and operate at around Mach 4. This will place it below the hypersonic threshold (considered Mach 5).
It’s also worth noting that Northrop Grumman’s subsidiary, Scaled Composites, recently announced its reusable Talon-A hypersonic test vehicle had successfully completed its tenth test flight.
Hermeus is one of the nine acknowledged vendors planning to compete for the Air Force’s Increment 2 Collaborative Combat Aircraft (CCA) programme.
While most CCA concepts are subsonic, Hermeus is an outlier in developing supersonic autonomous aircraft with eventual plans to produce hypersonic aircraft. It has said it plans to produce the fastest aircraft in history.
An affordable testbed high-Mach platform
The contractor says that its Ramjet-X will enable Hermeus to offer high-Mach Flight Test as a Service (FTaaS). This will expand access to flight environments that have “historically been costly and difficult to reach.”
It is unclear if Hermeus plans an operational military application for the drone.
Zach Shore, CEO of Hermeus, said, “High-speed flight testing is extremely expensive, and you don’t get many shots at it,” adding that Ramjet-X lowers the barriers to gathering extremely valuable data using a platform that offers speed, sustained flight, and scalability.
Ramjet-X will be able to integrate payloads, sensors, communications, autonomy, material samples, propulsion technologies, and other experimental hardware and software.
This will allow companies to have an affordable high-Mach experimental platform option. It is unclear if Ramjet-X will be reusable.
By utilizing its reusable Hermeus platform and the smaller Ramjet-X aircraft, it allows companies to experiment with a high-Mach platform without needing a bespoke test vehicle for every experimental flight.
The Cold War SR-71 (M-21) & D-21 redux
The concept of motherships carrying parasitic aircraft has been around since the 1930s, when the US Navy developed the Akron-class airships to carry Curtiss F9C Sparrowhawk biplanes.
But this particular Hermeus setup bears a striking visual resemblance to the M-21 (a variant of the SR-71 Blackbird) and its D-21 Tagboard supersonic spy drone. That said, Ramjet-X is considerably more compact than the D-21.
At the time, the D-21 was intended to be a reconnaissance drone that would take photos over a pre-programmed route before crashing into the sea to be recovered. That programme ultimately proved unsuccessful.
Underlying the two concepts is the fundamental problem that ramjets cannot provide useful thrust from a standing start or at low speeds.
The Ramjet-X also underscores that while most development effort is on stealthy subsonic platforms with increased endurance, there is also a significant amount of effort towards high-Mach and hypersonic aircraft and missiles.
The US, China, Russia, and various other countries are all racing to develop hypersonic systems.
