With the advancement in space technology, the leading countries in this field are on the trend to rely more heavily on cryogenic propellants for upper stage propulsions for which storable propellants have been most commonly utilized. Enhanced demands for the liquid oxygen and liquid hydrogen propellant combination in the space program of the U.S. that have been evident since 1957, have been a constant stimulus to induce rapid progress in its liquid hydrogen production technology. The successful launch of the Engineering Test Sattelite (ETS-II) in February 1977, enabled Japan to become the world's third country capable of orbiting a geo-stationary sattelite, demonstrating that the country had embarked on its space program in full earnest. As the space program becomes more advanced and requires payloads of greater weight, the need to develop the propulsion system utilizing liquid oxygen and liquid hydrogen becomes urgently emphasized. Currently the production of liquid hydrogen in this country is confined within laboratory scale. Therefore, in order to provide sufficient quantity of liquid hydrogen for rocket engine development testing, it is necessary to establish some substantial manufacturing plants in the beginning. To realize efficient supply of liquid hydrogen, a comparative analysis was made whether to centralize manufacturing plants and to transport their products to local users, or to distribute the plants on user's sites. It was concluded that for rocket applications the centralization of liquid hydrogen production plants would be superior in all respects covering facility cost, safety, and influence on other non-aerospace industries to utilize liquid hydrogen. The Japanese liquid oxygen/liquid hydrogen rocket engine development will be programmed to be in line with the liquid hydrogen supply from the centralized production facilities. The target is 1984 for completion of the first flight type engine.
The critical current of superconductors was measured by an inductive method. The experimental set-up consisted of a superconducting magnet into which a one turn, short-circuited sample was inserted. During the external field rise, the current will be induced in the sample. When this induced current rises up to the critical current, they will collapse. By the voltage taps attached on the sample and a pick-up coil, the quenches of the induced current was measured. The critical current can be calculated using the values of the external field currents, their sweep rate and the quenching time. The critical current of the multifilamentary superconductors was measured by this method and compared with that measured by the usual method of current and voltage measurements. They agreed well each other. This inductive method is very useful to induce the large currents in the superconductor without potential leads and power sources.