A Chinese university has successfully flown its Feitian 2 hypersonic vehicle at a site in northwestern China, according to an announcement on the Northwestern Polytechnical University (NPU) website on Monday.
The research team said the test represented the first successful acquisition of real-flight data for a rocket-based combined cycle (RBCC) engine using a kerosene-hydrogen peroxide propellant. The university鈥檚 statement said the test flight proved key capabilities, including variable-geometry intake operation, thrust-varying acceleration and autonomous flight with variable angle of attack.
NPU led the project with participation from the Shaanxi Province Aerospace and Astronautics Propulsion Research Institute. It follows a flight test of the Feitian 1 prototype in July 2022 that showed the engine鈥檚 ability to achieve stable transitions at different speeds.
Notably, NPU is subject to US sanctions and requires specific US Commerce Department approval to buy sensitive US-made research equipment and components. Undergraduate students from NPU also face significant hurdles in obtaining US study visas.
In September 2022, Chinese authorities publicly accused the US National Security Agency鈥檚 (NSA) Tailored Access Operations (TAO) unit of carrying out extensive cyberattacks against the university.
Hypersonic vehicles sometimes operate outside the atmosphere or in extremely thin air, preventing them from using atmospheric oxygen such as in air-breathing engines. Consequently, they must carry both oxidiser and fuel on board.
Traditional hypersonic propellants include liquid oxygen with kerosene, or liquid hydrogen with liquid oxygen. The US X-51A scramjet employed hydrocarbon fuel for its lower cooling demands and Feitian 1 showed that kerosene could effectively be used as fuel for the propulsion system.
Feitian 2 advances this by using a kerosene and hydrogen peroxide propellant.
Although it is less efficient at converting propellant to thrust than liquid hydrogen, this mixture eliminates the need for complex cryogenic systems, allowing pre-fuelling and long-term standby readiness.
The Feitian 2 exterior has been modified from its predecessor, including the addition of wings near the rocket head, and visibly larger and longer tail fins.
The RBCC engine represents a revolutionary concept, integrating the benefits of traditional rocket engines and air-breathing ramjets within a single system. Its core objective is to maximise the use of atmospheric oxygen as the oxidiser during atmospheric flight, drastically reducing the oxidiser weight the vehicle must carry, thereby significantly boosting the payload capacity and fuel efficiency.
But a fundamental challenge for all combined-cycle engines is achieving smooth transitions between operational modes, particularly from ejector mode, in which a rocket provides initial thrust, to ramjet mode where thrust from the ejector rocket decreases before the ramjet effect fully establishes sufficient thrust.
The 鈥渢hrust-varying acceleration鈥 mentioned in this experiment suggests the researchers found a way to bridge the gap, ensuring smooth and continuous acceleration.
To meet other challenges, Feitian 2鈥檚 flight test is likely to have validated its 鈥渧ariable-geometry intake鈥 that would allow the engine to change its inner structure on the go, adjusting to varying conditions for peak efficiency and stability at different speeds.
Additionally, its 鈥渁utonomous flight with variable angle of attack鈥 would enable the vehicle to autonomously adjust its angle of attack based on the flight environment and mission requirements to optimise performance.
Observers noted that the design progression from Feitian 1, which focused on engine validation, to Feitian 2 showing a controllable vehicle, reflected a deliberate, state-strategy-driven two-step approach.
This evolution signalled that China鈥檚 RBCC development path had entered the engineering phase.