宇宙開発におけるＬＨｚ研究の現状と将来

Abstract

Although wide industrial use of liquid hydrogen is anticipated in the future, its present application in Japan is almost entirely limited to the space program. The combination of liquid oxygen and liquid hydrogen (LOX/LH2) gives the highest performance among the propellants now used for space launch vehicles. LOX/LH2 engines were used for the huge rocket, Saturn, which sent astronauts to the moon, and are to be used for the first reusable launch vehicle, Space Shuttle of the United States.A program to develop a LOX/LH2 engine is being carried out also in Japan by the National Space Development Agency of Japan (NASDA). The engine which develops 10ton thrust in vacuum is to be used as the second stage of the future Japanese launch vehicle, H-I.The final configuration and the development plan of the H-I launch vehicle is now being discussed, and might be settled before the end of FY 1979. For the time being, develoment efforts will be concentrated on the second stage with a LOX/LH2 engine and inertial guidance system.A combination of the newly developed second stage and the first stage of the N-II launch vehicle, which is an improved version of the present N-I, is called Test Vehicle (tentative) and will be developed as a first step of the H-I program. The main objective of the first flight of the Test Vehicle, which is scheduled for late FY 1984, is to verify the integrity of the second stage. The Test Vehicle is a two stage vehicle and can launch a satellite into low earth orbit. If a third stage is added, it can place a payload of more than 500kg into geostationary orbit.The second stage is the core of the Test Vehicle. It consists of a LOX/LH2 engine, tank, inertial guidance system, control system, and others. The LOX/LH2 engine is the key element to improve the capability of the launch vehicle.NASDA has conducted the development tests of the major components of the engine since FY 1975, in cooperation with the National Aerospace Laboratory (NAL) and the Institute of Space and Aeronautical Science (ISAS) of the University of Tokyo. When the tests were initiated, use of liquid hydrogen in Japan was very limited. NASDA had to start from basic tests using liquid hydrogen produced by a small pilot plant. A large commercial plant was constructed in FY 1978, and now tests of full scale components are conducted on regular schedule.Topics covered in this paper are;(i) LOX/LH2 engineFollowing a brief description of rocket engine fundamentals, characteristics of liquid hydrogen as a rocket propellant will be stated. LOX/LH2 engines developed and being developed in the United States and European countries will be shown as examples.(ii) Development of a LOX/LH2 engine in JapanAn outine of the H-I program will be described. Main characteristics and development tests of the second stage will be stated, laying stress on the LOX/LH2 engine.