The "Lingyun" liquid oxygen-methane engine successfully completes thermal testing and evaluation.

In July 2019, Kyushu Yunjian (Beijing) Space Technology Co., Ltd. successfully completed multiple deep-throttle thermal tests of its independently developed "Lingyun" 10-ton-class variable-thrust liquid oxygen-methane engine, with all tests achieving full success.
A key technical prerequisite for liquid rockets to achieve widespread application in the commercial space market is their ability to be recovered and reused. Through recycling and reuse, the cost of a single launch can be significantly reduced, making commercial applications feasible. The technological foundation enabling this recovery and reuse lies in three critical capabilities: the engine's reusability, multiple ignition capabilities, and advanced deep-throttle control technology.
As China's first liquid oxygen-methane engine that truly achieves reusability, multiple ignition capabilities, and deep thrust-vectoring control, the "Lingyun" engine has undergone a series of bold yet challenging explorations and trials during its development phase. These efforts focused on key areas such as low-cost, rapid deployment, and maintenance of the engine; its ability to perform multiple ignitions; advanced technologies for wide-range thrust modulation; sophisticated control systems; and the adaptability of critical component assemblies. The successful completion of this round of hot-fire tests marks a significant milestone for Jiuzhou Yunjian's "Lingyun" engine, representing multiple effective breakthroughs in overcoming long-standing technological bottlenecks associated with pump-fed cryogenic liquid rocket engines in China.
(1) Filling the domestic gap in deep thrust regulation technology for pump-fed liquid rocket engines, achieving a minimum throttling condition of 20%, fully meeting the variable thrust requirements during rocket recovery, and reaching an internationally leading level in throttling capability.
(2) For the first time domestically, a dual-channel torch-type electric ignition system has been successfully implemented, completely eliminating the traditional gunpowder-based ignition method. This breakthrough significantly enhances the engine's ignition reliability and durability, effectively meeting the multiple ignition requirements during rocket recovery operations. Additionally, this innovative approach eliminates the need for pyrotechnic components throughout the entire engine assembly, thereby improving the convenience of engine storage and transportation.
(3) For the first time in China, we have successfully developed and mastered the full-nitrogen gas-based maintenance technology for liquid rocket engines. Compared to the traditional cryogenic rocket engines that rely on helium gas for maintenance, this breakthrough significantly reduces the operational and maintenance costs of the engines.

Video One: 30% Thrust Variation Test

Video Two: 20% Deep Thrust Variation Test

Video Three: 20 Consecutive Continuous Thrust Tests

In addition, this round of testing also completed the adaptability assessment of the combustion device and the coaxial turbopump under large reduction ratio conditions, as well as the robustness test of the turbopump operating throughout the entire cavitation state at low chamber pressure during engine startup.
During this round of testing, the engine's parameters closely matched the preset values. The reliability of the ignition system has been repeatedly verified through multiple tests. Furthermore, the turbopump speed, head, and efficiency were all in excellent agreement with the design expectations. The thrust chamber pressure remained stable, demonstrating high combustion stability even under ultra-low operating conditions. Additionally, both the thrust regulating valve and its associated control system functioned normally under engine vibration conditions, ensuring accurate thrust modulation and meeting the design requirements for response characteristics. To address potential box-pressure deficiency scenarios during rocket recovery, a robustness test was conducted to evaluate the engine's ability to initiate operation under extremely low box-pressure conditions. Remarkably, the turbopump continued to operate effectively despite the significantly reduced inlet pressure. Throughout the test, key performance parameters such as overall chamber pressure and thrust remained highly stable.
The "Lingyun" engine has successfully demonstrated its reusable capabilities, multiple ignition functions, and advanced deep-thrust vector control technology. These validated technologies will be directly integrated into the high-thrust "Longyun" engine without requiring additional development efforts, enabling Jiuzhou Yunjian to offer a comprehensive portfolio of commercial, recoverable liquid oxygen-methane engines tailored for rocket customers.