The development program of the H-II Rocket has been initiated in 1985, and now engineering model test is being progressed. The H-II Rocket is a new expendable launch vehicle to meet a demand of space activities in the 1990's, with capability of placing a 2 ton class satellite into geostationary earth orbit (GEO). After trade-off studies, LOX/LH2 propulsion system with a single main engine (LE-7) of staged combustion cycle has been selected for the 1st stage of the H-II Rocket, considering its high performance and the accumulated experience in cryogenic propulsion system technology through development of the 2nd stage (LOX/LH2) of the H-I Rocket, of which the first test flight was successfully launched in August, 1986. And the 2nd stage propulsion system will be developed by upgrading modification (tank volume increase and engine thrust up) of the H-I Rocket 2nd stage. This paper shows an outline of the propulsion systems of H-II Rocket 1st and 2nd stages, and the technical problem including the technics which was gained in the development of H-I 2nd stage propulsion system.
Concerning computer simulation of serration at very low temperatures, calculation procedure and its several applications have been mentioned. Simulation methods by other researchers have several shortcomings, for instance, deformation beeing unreasonably considered to occur homogeneously. Using the present author's method, characteristics of serration and the accompanied phenomena can be simulated very well, and the effects of many factors on serration can be clarified.
A new method for producing a step-like change of magnetic field has been developed by using magnetically-coupled two superconducting coils and two superconducting switches. In this method, since the change of the magnetic field occurs as a transition from a stable persistent-current state to another, no power supply is required in the two states to keep the magnetic fields constant. Also in this method, no unstable transient phenomenon is generated in principle, and a sharp step-like change of magnetic field is produced. A step magnetic-field change of 2.1T was experimentally obtained in a time interval of about 600ms without any unstability. It is expected that the time constant of the transition can be reduced more than two orders of magnitude when the characteristics of the superconducting switches are improved. The present method is especially useful in obtaining a large change of high magnetic field.
The dynamic stabilization method was proposed in Part I and Part II of this paper in order to achieve high current density in large scale magnets. To demonstrate the feasibility, a model coil with a stored energy of 25MJ and a central field of 8T was designed at an overall current density of 100A/mm2: The conductor was 1mm×50mm, Cu-Nb3Sn-Cu tape and it was needed to grade the thickness of Nb3Sn to meet the requirement of dynamic stability. These procedures clarified the design criteria of dynamically stabilized magnets. The quench analysis was performed to identify problems peculiar to high current density magnets. The maximum temperature rise was found to be relatively high, 420K. The protection by external resistor is enough to suppress the temperature rise down to 100K. These results indicate that the dynamically stabilized tape conductor can attain high overall current density in large scale magnets and that the method is applicable for emerging materials.