For decades, engine development has set a pretty clear limit on what a plane or missile can do in the air. Achieving hypersonic speeds does not depend only on materials or aerodynamic design, but on solving a much more complex problem: how to maintain a stable propulsion system from takeoff to beyond Mach 6. China has been working in this direction since the mid-nineties, and now claims to have completed a prototype that seeks to cover that entire range without resorting to switching between propulsion systems in mid-flight.
That goal takes shape in what researchers describe as a “counter-rotary ramjet engine,” an air-breathing engine designed to operate continuously from startup to speeds above Mach 6. The team, linked to the Chinese Academy of Sciences (CAS) and led by Xu Jianzhong, maintains that the prototype has already been completed and experimentally verified after more than three decades of work. Even so, the development is in a preliminary phase: the next steps involve adapting it to different platforms and subjecting it to real flight tests that allow its behavior to be validated outside the laboratory.
The engine that can mark a before and after in defense
The traditional solution to high-speed and hypersonic flight typically combines two propulsion systems: a turbine engine for speeds up to around Mach 3 and a ramjet for higher speeds. On the one hand, turbine engines cover takeoff and the first phases of flight, while ramjets can only operate when the device is already moves at high speed. This division of labor solves part of the problem, but introduces other complications. As the researchers explain, the system drags unnecessary mass when one of the engines is inactive and adds technical complexity when changing regimes, a process that can become unstable in demanding phases of flight.
The Chinese team’s proposal introduces changes on several fronts, but the core is in its compressor. Unlike conventional designs, it uses two sets of blades that rotate in opposite directions, one for high pressure and the other for low pressure, this configuration reduces centrifugal forces on the components. It would also improve rotation efficiency. Added to this is an unusual approach: instead of minimizing shock waves, the design takes advantage of them to compress the air flow, which would reduce its size and weight.
The road to this prototype has not been quick. According to SCMP, Xu Jianzhong began focusing on hypersonic propulsion in the mid-1990s and by 2000 he had outlined the concept of a counter-rotating compressor. For years, the project progressed until en 2009 obtained institutional supportwhich made it possible to build experimental platforms from scratch. From there, the team spent nearly a decade resolving technical bottlenecks, especially in blade cascade design, before reaching the experimental verification now announced.
If this architecture were to be transferred to operational systems, its implications would be direct in the design of hypersonic aircraft and missiles. Reducing the weight of the engine in this type of weapon opens the door to increasing the amount of fuel, payload or range, in addition to improving maneuverability. For reusable aircraft, a single propulsion system would simplify integration and reduce the risks associated with mid-flight mode changes. Even so, these advantages are presented for now in potential terms, awaiting validation in real conditions.
Despite the scope of the announcement, development is still in an early phase when viewed from an operational point of view. The tests carried out so far have been limited to experimental settings. The next challenge, according to the researchers, will be precisely that, adapting the engine to real aircraft or missiles and checking its behavior outside the laboratory.
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