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 engine
Following 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 Japan
An 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.

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This paper presents the results of a study on the pressure drop and the film boiling heat transfer for a two-phase flow of hydrogen in a horizontal tube.
Experiments were made on two types of tube; two pieces of vacuum insulated straight tubes of 4m long, inside diameters of which are 18.4 and 23.9mm, respectively; Anuninsulated tube of 8m long with 90 degree bends at two locations, inside diameter of which is 12.3mm.
Experimental conditions were as follows; Flow rate (l/min.); 5 to 50 Vapor quality; 0.01 to 0.90 Pressure (bar); 1.4 to 5.8 Conclusions obtained from the experiments are summarized below.
1) The frictional pressure drop of two-phase flow of hydrogen for a straight tube is well related to a modified Lockhart-Martinelli (L-M) curve, that is, L-M pressure ratio parameter, φl multiplied by 0.8, for both adiabatic and diabatic conditions. More than 90% of data fell within the scatter band of ±20% from the modified L-M curve.
The pressure drop for a bend was also correlated by using parameters analogically introduced from L-M parameters for a straight tube.
2) As for the heat transfer by forced-convection film boiling, the following relationship was established based on the method proposed by Ellerbrock.
(Nu_f/Nu_fm)⋅Bo^-0.4=9.46X_tt^-0.131
More than 90% of data obtained were in agreement with the the expression shown above with no more than ±20% error.
In this study, it was known that the heat transfer for two-phase flow of nitrogen as well as hydrogen follow Ellerbrock's theory.

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Liquid hydrogen had been used only on a laboratory scale until 1976, but the demand for liquid hydrogen was considerably increased as a result of development of rocket engines.
consequently, it became necessary to have large facilities for reception of liquid hydrogen as well as for its production and transportion. To meet the requirements, we manufactured LH₂ storage tanks of 50, 000 liters capacity in September 1978, and those of 11, 000 liters capacity in March 1979.
This paper presents the details of design and construction of these huge-scale storage tanks.

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The development of LH₂/LOX rocket engine is being conducted in Institute of Space and Aeronautical Science, University of Tokyo. This paper describes the liquid hydrogen turbopump for rocket engine. The turbopump was designed to feed liquid hydrogen into the thrust chamber of 7, 000kg thrust level, and has the capabiliites of head rise of 5, 900m and flowrate of 2.90kg/sec at the rated rotational speed of 44, 000rpm. The pump is a single-stage, centrifugal-flow type with a helical inducer and a single volute casing. The impeller of the pump, 130mm in diameter, consists of 24 blades with a discharge angle of 90 degrees. The axial thrust loaded on pump shaft is balanced by decreasing the pressure behind the impeller to an adequate level with the aid of 24 small radial vanes. The pump is driven by a single-stage impulse turbine.
Tests were performed in Noshiro Testing Center of ISAS since August in 1977 and the performance characteristics and the functions of the pump were verified through 14 runs up to date. The tests showd that the pump satisfied the design specifications. The results are summarized as follows;
(1) the head coefficient of the pump is 0.64 at the rated flowrate,
(2) the distribution of pressure in the volute is less than 10% of the mean value,
(3) the pump works without stall under the condition of negative NPSH, although the performance is deteriorated to some extent.

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On September, 1978, Hydrogen Liquefaction Unit was established with a new plan to distribute customers by an industrial larger scale more than ever the way it had been applied. By this inovation caused in hydrogen distribution system, new chance was developed for the people who have not any knowladge and experience on the use of the liquid hydrogen.
Accordingly, it is naturally requested to master the way of Liquid Hydrogen Safety Handring. This point will be guidance for people, operater and designer to easy handling the liquid hydrogen in the future.

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