Low-cost ramjet-powered vehicle that can fly at high-Mach speeds could inspire efficient propulsion

A Los Angeles-based company is developing a low-cost, expendable ramjet-powered vehicle designed for launch from its Quarterhorse aircraft. Called Ramjet-X, the Hermeus’ vehicle can fly at high-Mach speeds.Hermeus revealed that Ramjets require significant initial speed before they can operate effectively. Instead of relying on a large, expensive, expendable booster for every test, Hermeus will use its reusable Quarterhorse aircraft to carry Ramjet-X to the speed and altitude required for launch. Once released, Ramjet-X will commence ramjet-powered flight, while Quarterhorse returns for future flight test missions. High-speed flight testing is extremely expensive “High-speed flight testing is extremely expensive, and you don’t get many shots at it,” said Zach Shore, CEO of Hermeus. “Ramjet-X gives us a way to put new systems into sustained high-Mach environments without building an expensive one-off test program every time. Bringing speed, sustained flight, and scalability all into one system lowers the barriers to gathering extremely valuable data from these conditions and accelerates programs for both us and our customers.”Ramjet-X will also enable Hermeus to offer high-Mach Flight Test as a Service (FTaaS), expanding access to flight environments that have historically been costly and difficult to reach. Customers and partners will be able to integrate payloads, sensors, communications and compute systems, autonomy, material samples, propulsion technologies, and other experimental hardware and software onto Ramjet-X for testing in representative sustained high-Mach conditions. By providing a repeatable platform, launch architecture, and flight-test infrastructure, Hermeus can allow customers to focus on the technology being evaluated rather than developing a bespoke high-speed flight vehicle and test program for every experiment, according to a press release. High-temperature structures are in development Development of Ramjet-X is already well underway. Hermeus is testing Ramjet-X’s ramjet engine at its HEAT facility in Jacksonville, Florida, while high-temperature structures are in development at its headquarters in El Segundo, California. Integrated vehicle testing is currently planned for 2027. High-Mach flight presents engineering challenges that go far beyond simply making an aircraft travel faster.At extreme speeds, aerodynamic heating becomes a major concern. Structures, sensors, propulsion systems and other components must operate while exposed to temperatures and pressures that are substantially different from those encountered by conventional aircraft.Propulsion is another major challenge. Ramjets, for example, do not operate efficiently from a standstill. They depend on the forward motion of the vehicle to compress incoming air before fuel is introduced and burned. This means a ramjet-powered vehicle needs to reach a sufficiently high speed before its propulsion system can become effective.Hermeus’ approach is to solve that problem by using another aircraft as the accelerator. Ramjet-X is also closely connected to Hermeus’ work on air-breathing high-speed propulsion.The company is developing turbine-based combined-cycle propulsion technology in which different propulsion modes are used at different stages of flight. Hermeus’ Chimera engine, for example, combines turbine and ramjet concepts, allowing the propulsion system to operate across a wider range of speeds.At lower speeds, a turbine engine can provide the necessary thrust. As the aircraft accelerates and the conditions become suitable for ramjet operation, airflow can be redirected so that the ramjet becomes the primary source of propulsion.This is important because a purely ramjet-powered aircraft cannot simply take off from a runway and accelerate from zero to its optimal operating speed. It needs an initial boost.Ramjet-X effectively approaches the problem from another direction: rather than asking the test vehicle to provide all of its own acceleration, a reusable aircraft can provide the initial speed.Get the latest in engineering, tech, space & science - delivered daily to your inbox.Prabhat, an alumnus of the Indian Institute of Mass Communication, is a tech and defense journalist. While he enjoys writing on modern weapons and emerging tech, he has also reported on global politics and business. He has been previously associated with well-known media houses, including the International Business Times (Singapore Edition) and ANI.