High-thrust engine makes a grand debut! Kyushu Rocket's "Longyun" liquid oxygen-methane engine successfully completes its semi-system thermal test evaluation!

　　Recently, Longyun, the next-generation high-thrust liquid oxygen-methane engine developed by Jiuzhou Yunjian, successfully completed a semi-system hot test evaluation. During the test, parameters such as turbine pump speed, post-pump pressure, gas generator chamber pressure and temperature, as well as ignition system pressure, remained stable throughout the entire process and aligned precisely with the pre-set values.

The successful semi-system hot testing of the Longyun engine marks:

　　I. For the first time in China, breakthroughs have been achieved in the technology of vortex pump gas bottle spin-up combined with torch-type electric ignition for starting a high-thrust liquid oxygen-methane engine, and the multiple-start capability has been preliminarily verified.

II. For the first time domestically, a multi-condition semi-system thermal test run was successfully conducted, enabling early assessment of the Longyun engine's adaptability to deep thrust variation under semi-system conditions.

III. Longyun Engine is set to undergo a full-system hot test evaluation this year.

Video of Longyun Half-System Hot Testing

What is a semi-system?

　　The semi-system refers to the bypass system combined with the main pipeline valves of an open-cycle liquid rocket engine. The bypass system primarily includes components such as the ignition system, gas generator, turbopump, auxiliary control valve, vent valve, solenoid valve, and check valve. Meanwhile, the main pipeline valves consist mainly of the main valve and throttling elements. As the most complex and critical component in an open-cycle liquid rocket engine, the semi-system plays a vital role in energy conversion, propellant delivery, and thrust regulation. Ultimately, whether an engine can start and shut down smoothly depends entirely on the proper coordination and integration of all components within this semi-system.

Footage of the Longyun Engine Half-System Hot Test

　　What does the semi-system test involve?

　　The semi-system test primarily evaluates the feasibility and operational compatibility of the gas generator and turbopump—key components of the liquid rocket engine—as well as the engine's start-up and shutdown characteristics. It also aims to acquire essential parameters required for the full system's operation. After completing the semi-system test, the engine will be just one step away from the ultimate "big test" of the entire system.

　　The technical head of Kyushu Cloud Arrow Engine stated:

　　The most critical aspect of this round of Longyun engine semi-system testing was the use of real propellants to evaluate in advance the seamless coordination between the gas generator and the turbopump, laying a solid foundation for predicting the engine's overall system performance, assessing startup and shutdown characteristics, defining timing sequences, and developing variable-thrust evaluation plans. In particular, for the pump-fed gimbal engine, the successful completion of this semi-system test with real propellants signifies that the Longyun engine has already achieved more than 70% of its full development milestone.

Dragon Cloud Engine Assembly Blueprint

　　Introduction to Longyun Engine

　　Longyun Engine is an 80-ton-class liquid oxygen-methane engine, representing the second-generation liquid oxygen-methane engine developed by JiuZhou YunJian. It is also China's first large-thrust engine equipped with a non-pyrotechnic ignition system, offering user-friendly operational conditions. This engine boasts a high thrust-to-weight ratio and can be configured in a layout of five engines arranged along a 3.35-meter diameter. Additionally, it features deep thrust modulation capabilities ranging from 30% to 110%, enabling multiple restarts. As such, it is ideally suited for use as the recoverable ground stage or second stage of medium- to large-scale reusable rockets.