Last month, the race to develop reusable hypersonic aircraft heated up as GE Aerospace unveiled a groundbreaking advancement in high-speed jet engine design, potentially enabling conventional aircraft to reach speeds exceeding Mach 10. According to GE’s press release, the company achieved a world-first hypersonic dual-mode ramjet (DMRJ) rig test with rotating detonation combustion (RDC) in a supersonic flow stream. This breakthrough leverages rotating detonation combustion, a highly efficient power production method, within a dual-mode ramjet/scramjet engine.

Ramjets and scramjets are air-breathing jet engines that excel at high speeds, typically from around Mach 3 up to Mach 5 and beyond, but are less effective at lower speeds. GE’s achievement represents a significant step towards developing dual-mode ramjet/scramjets with extended range, especially when combined with a turbine-based combined cycle (TBCC) propulsion system.

GE had previously disclosed its collaboration with the Defense Advanced Research Projects Agency (DARPA) and the Air Force Research Lab (AFRL) on an RDC-equipped TBCC engine in June of the same year.

The TBCC engine, as explained by GE Aerospace Military Engines CEO Amy Gowder, combines four different types of air-breathing jet engine technologies into a single system. This system allows an aircraft to take off and land using conventional turbofan power while achieving hypersonic speeds under scramjet power during sustained flight. GE’s design, distinguished by the incorporation of Rotating Detonation Combustion, promises to be more compact and efficient than previous efforts, making hypersonic flight a more practical endeavor.

A functional TBCC engine has long been sought after for reusable hypersonic aircraft, as current propulsion systems for hypersonic weapons are single-use and cannot operate at the low speeds necessary for aircraft landing. Other firms, such as Hermeus, Leidos, and Lockheed Martin, have made strides in TBCC engine development, but GE Aerospace’s inclusion of Rotating Detonation Combustion may prove to be the most promising and efficient combined cycle hypersonic propulsion system to date.

GE Aerospace’s rapid progress in this program, which began only a year ago, is attributed in part to the company’s acquisition of Innoveering LLC, a hypersonic-focused organization with expertise in high-speed inlet designs. These inlets play a crucial role in jet engine function, especially in dual-mode scramjets where precise and adjustable inlets are essential for managing shockwaves at different flight speeds.

GE Aerospace anticipates demonstrating this cutting-edge engine system as early as next year.

But what exactly is a Rotating Detonation Engine, and how does it work? In its simplest form, an RDE is a propulsion system that offers greater efficiency than traditional air-breathing jet engines due to a more effective means of ignition.

A rotating detonation engine builds upon the principles of Pulse Detonation Engines (PDEs) and Pulsejets. Pulsejets operate by mixing air and fuel within a combustion chamber and igniting the mixture in rapid pulses. Pulse detonation engines, on the other hand, utilize detonation—a form of rapid combustion that occurs at supersonic speeds. Detonation engines are more efficient and produce more thrust than traditional jet engines that rely on deflagration (subsonic combustion).

A rotating detonation engine takes this concept further. Instead of ejecting the detonation wave as propulsion, it circulates the wave around a circular channel within the engine itself. Fuel and oxidizers are introduced into the channel through small openings, where they are ignited by the rotating detonation waves. This process results in continuous thrust, combining the efficiency of detonation combustion with continuous power output.

GE Aerospace’s achievement in incorporating Rotating Detonation Combustion into a dual-mode ramjet/scramjet engine offers the potential for high-speed, efficient, and reusable hypersonic aircraft propulsion.

In addition to GE Aerospace, other aerospace companies are actively working on TBCC engines to power hypersonic aircraft, aiming to bridge the gap between low-speed turbofan power and high-speed scramjet propulsion. The development of efficient combined cycle engines is seen as a crucial step in the pursuit of practical hypersonic flight.

By Impact Lab