Hot-Fire Testing and System Analysis of the LUMEN Liquid Upper Stage Demonstrator Engine

The German Aerospace Center (DLR) has successfully completed hot-fire testing of the Liquid Upper Stage Demonstrator Engine (LUMEN), reaching a major milestone in the development of DLRs first rocket engine. LUMEN is an expander-bleed cycle rocket engine that uses liquid oxygen (LOX) and liquefied natural gas (LNG) as propellants and generates 25 kN of thrust. With this achievement, LUMEN is now fully operational and available as a testbed for the development of advanced technologies such as intelligent control and health monitoring. This paper presents the results of two hot-fire test campaigns demonstrating key capabilities such as stable combustion over a wide throttling range of 38 bar to 78 bar, a long duration test of 248 s and intelligent control. LUMEN also successfully replicated an Apollo lunar module thrust profile, demonstrating its potential for precise, mission-like thrust modulation. Finally, an EcosimPro model of LUMEN is being compared to experimental data and used to study the operational envelope.