Core technology upgraded again! Jiuzhou Yunjian's "Lingyun" engine completes large-scale continuous variable-thrust hot firing tests.

　　Recently, Jiuzhou Yunjian's "Lingyun" 10-ton-class liquid oxygen-methane rocket engine successfully completed a large-scale, continuous variable-thrust hot firing test. This test was conducted at Jiuzhou Yunjian's independently built, 100-ton-class dual-test-bed facility, marking a complete success for the experiment.

　　This experiment has the following characteristics:

　　① Following its pioneering completion of variable-thrust hot testing in 2019, Lingyun Engine has significantly increased both the duration and number of thrust variations during this latest test.

　　② Lingyun Engine achieved a thrust regulation range of 100% to 38% in this test, demonstrating a leading-edge adjustment capability on a global scale.

　　③ This test covers the flight test mission profile requirements for the target rocket.

Large-Scale Continuous Thrust Variation Hot Test of Lingyun Liquid Oxygen-Methane Engine

(Starts reducing thrust after rated operation for 100 seconds)

　　What is wide-range thrust regulation in liquid rocket engines?

　　Vertical recovery of launch vehicles can significantly reduce launch costs while also offering promising prospects for a wide range of derivative applications. Currently, the key bottleneck hindering the development of China's vertical recovery rockets lies precisely in the liquid rocket engines. For a rocket to achieve vertical recovery, its engine must not only be capable of performing more than three ignition cycles but also needs to enable extensive thrust modulation prior to landing—essentially "applying full braking" to bring the engine's operating conditions down to extremely low levels, ensuring a smooth and stable touchdown. If the engine's thrust modulation range fails to reach at least 60% of its nominal capacity, it becomes exceedingly challenging to guarantee safe rocket landing. Conversely, the wider the engine's thrust modulation range and the better its responsiveness, the higher the "margin of error" during the rocket recovery process. The Lingyun engine has demonstrated the ability to throttle down to as low as 20% of its rated power under actual testing conditions. This particular test involved continuous thrust modulation across a range from 100% to 38%, further validating the engine's variable-thrust capability and reliability.

Before-and-after footage of the Lingyun liquid oxygen-methane rocket engine operating at 100% and 38% thrust levels.

　　What is the difference between this test run and the deep thrust vector control test conducted in 2019?

　　Lingyun Engine had already achieved breakthroughs in deep thrust modulation technology as early as 2019 and was the first in China to conduct extensive variable-thrust hot tests. However, due to the limitations of the testing conditions at that time, both the range of testable thrust levels and the duration of the tests were relatively limited. In 2020, Kyushu Yujian initiated the independent construction of an intelligent engine test facility, designed specifically to provide stable and reliable hot-testing conditions for both the Lingyun and Longyun engines. The facility boasts a thrust capability spanning up to the hundred-ton scale, making it well-suited to support comprehensive testing of these two engine models. This recent large-scale, continuous variable-condition hot test was successfully carried out at the independently built test site. Notably, both the duration of the test and the number of thrust modulation cycles far exceeded those of the 2019 trial, thereby enabling a more effective evaluation of the reliability and performance of Lingyun Engine's advanced deep-thrust modulation technology.

Footage of the 2019 Lingyun Engine's Deep-Thrust Thermal Test Run

　　The "Lingyun" engine will continue to undergo various assessments, including reliability accumulation and extreme-condition testing, ensuring solid advancements in both engine technology innovation and operational reliability. Additionally, technologies such as multiple engine startups, advanced thrust modulation capabilities, and cost-effective, rapid maintenance procedures will significantly accelerate the development of the reusable "Longyun" engine. Currently, the "Longyun" engine has successfully completed semi-system thermal tests, and full-system trials are expected to commence later this year.