Takanobu Kamiya

Fundamental investigation of a superconducting level sensor for liquid hydrogen with MgB2 wire

The feasibility study of a superconducting level sensor for liquid hydrogen with a magnesium-diboride (MgB2) wire is carried out from an experimental point of view. The sample wire consists of a mono-cored MgB2 superconductor and a cupronickel sheath, and several potential taps are attached to it at even intervals in order to understand the position of a threshold between the superconducting and resistive states roughly. The fabricated sensor is vertically located in a glass dewar vessel with an infill of liquid hydrogen, and the position of a preselected potential tap is adjusted by eye and hand to liquid level before starting a new measurement. Simulated operations with constant currents finally yield the future possibilities as the level sensor for liquid hydrogen with MgB2 wire although the fabricated sensor has a few problems at present. In order to improve the performance of the sensor, the specifications required for MgB2 wires will be reported elsewhere by applying the stability theory in superconductor composites and by simulating the operation with a numerical code.

PRESSURE DROP REDUCTION OF SLUSH NITROGEN IN TURBULENT PIPE FLOWS

Slush fluid such as slush hydrogen and slush nitrogen is a two-phase (solid-liquid) single-component cryogenic fluid containing solid particles in liquid, and consequently its density and refrigerant capacity are greater than for liquid state fluid. Experimental tests were performed with slush nitrogen to obtain the frictional pressure drop flowing in a 15 mm internal diameter, 400 mm long, horizontal, stainless steel pipe. The primary objective of this study was to investigate the pressure drop reduction phenomenon with changes in velocity and solid fraction. From the experimental results, the pressure drop correlation between the friction factor and the Reynolds number was obtained and an empirical correlation was derived. Flow patterns for slush nitrogen inside a pipe and the behavior of solid particles were also observed using a high speed camera.

Development Status of H-IIB Launch Vehicle Propulsion system

H-IIB launch vehicle is the latest most powerful Japanese rocket which is developed by JAXA and MHI. Development of H-IIB is based on the heritage of H-IIA in order to minimize risks and save resources. There are only two major items to be newly developed, which are the 5.2m-diameter propellant tanks and the main engine cluster technology. The overview of the clustered propulsion system of H-IIB and its development plan are described in this paper.