A High-Speed Response LOX/LH 2 Full Expander Cycle Engine with Deep Throttling Capability

For a flight test campaign of reusable vehicle, 10 kN class small LOX/LH 2 propulsion systems have been developed. They are regenerative cooling engines with a continuous throttling capability for making vertical landing possible. Current phase of the campaign is to demonstrate an entire sequence of full-scale operation with a vehicle equipped with turbopump-fed engine, following the three-generation vehicles with pressure-fed engine had successfully performed in repeated flight operation tests between 1999 and 2003. From a result of primary system analysis, we decided to build an expander cycle engine by refurbishing a pair of turbopumps, which had been build for another research program, and putting them into a new engine developed in the present study. A combustion chamber with long cylindrical portion adapted to the engine cycle was also newly made. Three captive firing tests were conducted to verify functional suitability for the vertical landing flight. In the last two tests, a deep throttling capability down to 28 % and a high-speed response over 5 Hz of the propulsion system were successfully demonstrated with newly developed thrust control system. The fourth-generation vehicle powered by the full expander cycle engine is now under development.