High-altitude simulation tests of the LOX/LH2 engine LE-5

The LE-5, under development since 1977 to power the second stage of the next Japanese launch vehicle, is an oxygen/hydrogen gas generator cycle engine with a thrust of 10.5 tonf at a chamber pressure of 36.8 kgf/cm and a 140:1 area ratio nozzle. Flight-type engine tests were conducted under simulated altitude conditions. Engine specific impulse at a mixture ratio of 5.5 reached 448 s. The engine started smoothly and reliably with the tank head, fuel bleed start. Problems due to ice formation were solved by purges and heating.