小林 弘明

<p>The payload capacity of launch vehicles must be increased in order to allow the exploration and development of space to be extended from low-Earth orbit into the solar system. A propellant system using a cryogenic fluid must reduce the amount of unusable propellant due to evaporation and boiling. However, in space exploration and development, where safety and reliability of missions are critical, predictions of the boiling heat transfer of current technology are not sufficiently reliable for thermal management design due to a lack of knowledge and relevant research. Therefore, the objective of this research is to understand and accurately predict boiling heat transfer by developing numerical simulation tools for two-phase flows that consider phase change. In this paper, recent research activity toward the development of chill-down process simulation technology is presented.</p>

The research and development conducted regarding fully superconducting motors for liquid-hydrogen transfer pumps using MgB&lt;sub&gt;2&lt;/sub&gt; monofilamentary wires are gathered into this paper. Synchronous rotation without slip can be realized using squirrelcage-type rotor windings composed of quasi-superconducting loops soldered between MgB&lt;sub&gt;2&lt;/sub&gt; wires, thereby enabling superconducting motors with low loss and high efficiency to be achieved. The use of MgB&lt;sub&gt;2&lt;/sub&gt; wires for stator windings also enables the primary winding loss to be reduced drastically compared to conventional copper winding. The transfer of liquid hydrogen from a metal cryostat containing the fabricated MgB&lt;sub&gt;2&lt;/sub&gt; motor to a glass Dewar vessel for visual monitoring is demonstrated successfully.&lt;tt&gt; &lt;/tt&gt;

In this paper is presented a microgravity experiment system utilizing a high altitude balloon. The feature is a double shell structure of a vehicle that is dropped off from the balloon and a microgravity experiment section that is attached to the inside of the vehicle with a liner slider. Control with cold gas jet thrusters of relative position of the experiment section to the vehicle and attitude of the vehicle maintains fine microgravity environment. The design strategy of the vehicle is explained, mainly referring to differences from the authors' previous design. The result of the flight experiment is also shown to evaluate the characteristics of the presented system.

The Japan Aerospace Exploration Agency launched the S-310-43 sounding rocket from the Uchinoura Space Center on Aug.04, 2014 for the purpose of investigating such behavior as boiling and flow of cryogenic liquid rocket propellant in an environment simulating coasting flight on orbit by using the sounding rocket&#039;s sub-orbital ballistic flight. In the low-gravity state, the cryogenic fluid (liquid nitrogen) was introduced into the test sections of similar shapes to the flow channels in the cryogenic propulsion systems. The boiling of liquid nitrogen inside the test-sections and the transition of flow regimes from gas/liquid two-phase flow to liquid mono-phase flow were visualized. The temperatures, pressures and void fractions of each channels were measured as well. Development of the experimental equipment for S-310-43 sounding rocket is described in this paper.