Hiroaki Kobayashi

化石燃料の代替エネルギーとして水素利用が検討されている。水素は、気体よりも液体の方が密度が大きく利用しやすい。そこで、タンク内の液体水素の残量を高精度に連続的な測定が可能な液位センサが必要とされている。液体水素の大気圧下沸点は約20 Kであり、臨界温度が約39 KのMgB₂超電導体が液体水素用の液位センサとして応用できる可能性がある。よって、SUS/FeシースMgB₂線材を用いて超電導式液面計を試作し、その動作特性を実験的に評価した。

First flight testing of Balloon-based Operation Vehicle (BOV) was carried out in 2006 and succeded. Second flight testing with a wing-body configuration will be done by a high-altitude balloon and dropped in September, 2006. Various types of onboard experiments such as a microgravity experiment and a demonstration of a supersonic engine are planned during flights for the third, fourth, and fifth flights. The aerodynamics load and characteristics of BOVs have been obtained by the CFD simulations as well as by the wind tunnel testing in ISAS. In this paper, the numerical simulations for BOV are presented and the results showed that the non-linear interaction between the wings, body, and engine exists for high angle of attack.

For an application of PDE to hypersonic air-breathing engines, thrust performances of air-breathing PDEs are estimated analytically in this study. Thrust/weight ratio of the engine decreases with increasing flight speed because of a low density of atmospheric air. In order to improve this disadvantage, new concept air-breathing PDE is proposed. By closing the exit of the PDE combustion chamber during a filling phase, ram pressure of the intake can be utilized effectively. Furthermore, by cooling the intake exit air by the cryogenic fuel, flight range can be extended for M 0.5. After system analysis of the air-breathing PDE, PDRJE (Pulse Detonation Ram Jet Engine) with air precooler is proposed. Size of PDRJE is 0.3 m in cowl inlet diameter. Engine thrust and weight are estimated to be 4.6x10³ N and 74 kg respectively. To evaluate the basic performances of the PDE, firing test of the scaled model was performed using GH2 and GOX. Heat flux of the combustion chamber was approximately 5 kW/m²/Hz.

An accurate comprehensive optimization method of the TSTO spaceplane has been developed. A new aerodynamics model bases on the data obtained by accurate CFD simulations. Strong aerodynamic interaction occurs between the Booster and the Orbiter in the CFD simulations, and it indicates the importance of the accurate aerodynamics model. The optimization using the new aerodynamics model results in the heavier gross take-off weight compared to the result using the conventional aerodynamics model. Furthermore, multi-objective optimization, in which the gross take-off weight and the time at separation should be minimized, is also implemented. It indicates that the propulsion parameter which control the flow rate of captured air during supersonic flight plays an important role in the trade-off relation between these objectives.