Endothermic fuel (EF) has extreme cooling capability and is useful for removing large heat flux. In particular, it has attracted attention as a fuel for hypersonic vehicles. Compared to liquid hydrogen, endothermic hydrocarbon fuels have some advantages from a practical viewpoint; they are not cryogenic fluids and have a higher density. In this study, the pyrolysis characteristic of methylcyclohexane (MCH) as a model compound of EF was experimentally investigated with Ni, Ni/SiO₂ and Pt/Al₂O₃ as catalysts. It was found that an effective endothermic reaction was promoted at 500--600K with Pt/Al₂O₃. Ni/SiO₂ also promoted endothermic reaction at a higher temperature (>600K). A simple analysis on a regenerative cooling of a rocket engine showed that a small amount of MCH with a Pt/Al₂O₃ catalyst effectively cooled a rocket chamber.

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This paper proposes a new concept of a noise reduction nozzle and describes the sensitivity analysis of the nozzle's acoustic and thrust characteristics. The proposed concept envisages a variable nozzle that enables a change in cross-section and reduction of noise by a single mechanism. Under takeoff conditions, the nozzle has a convergent shape with teeth and slots similar to those of a spline hub, which enables noise reduction. On the other hand, under cruise conditions, the shape of the nozzle can be altered from convergent to a clean convergent-divergent configuration. This concept has been validated by scale model tests in a jet noise facility, and the sensitivity of the acoustic and thrust characteristics has been analyzed using numerical analysis. The analysis revealed that the acoustic benefit depends on the depth of slot, and its frequency characteristics depend on the number of slot. Thrust loss strongly depends on the nozzle throat position and weakly depends on the number of slot. The proposed concept has the potential to provide significant acoustic benefits relative to the thrust loss, and the results of the sensitivity analysis enable us to design appropriate nozzle geometry.

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This paper is concerned with the design problem of preview altitude controller for Unmanned Airplane for Radiation Monitoring System\nobreakspace {}(UARMS) to improve its control performance. UARMS has been developed for radiation monitoring around Fukushima Dai-ichi nuclear power plant which spread radiation contaminant due to the huge tsunamis caused by the Great East Japan Earthquake. The monitoring area contains flat as well as mountain areas. The basic flight controller has been confirmed to have satisfactory performance with respect to altitude holding; however, the control performance for variable altitude commands is not sufficient for practical use in mountain areas. We therefore design preview altitude controller with only proportional gains by considering the practicality and the strong requirement of safety for UARMS. Control performance of the designed preview controller was evaluated by flight tests conducted around Fukushima Sky Park.

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The deformation of the bow-shock and the pressure fluctuation inside of a simplified model of the supersonic parachute canopy were investigated. As a result, for the time-averaged characteristics in the reconstruction mode, the deformation of the canopy-bow-shock is decreased and the time-averaged pressure inside of the canopy is increased monotonously with the increase in the distance between the capsule and the canopy. These time-averaged characteristics were explained on the basis of simple analytical models. On the other hand, time-varying characteristics are more complicated. In the Separated mode, there was a peak around at the frequency of 2kHz in the spectral of the pressure fluctuation. In the reconstruction mode, the fluctuation of the pressure decreased with the distance between the capsule and the canopy. The distinguishing non-Gaussian probability-distribution-functions were found in the Separated mode and also in the reconstruction mode when the suspension lines were inserted between the capsule and the canopy models. These experimental data of the statistical characteristics in the pressure fluctuation will play an important role to evaluate the numerical methods for the Fluid-Flexible-Structure-Interference (FFSI) phenomena.

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A time-spectral, or reduced-frequency method for the CFD is developed in place of a time-marching method for simulations of periodically unsteady flows around oscillating bodies. The efficiencies and accuracies of the method are validated through comparisons with transonic-flow experiments for two- and three-dimensional wings. For the case of a three-dimensional viscous flow, the computation time to obtain the same periodic flow with a time-marching solution of a sufficiently fine time step was about 1/18 in the time-spectral method. The method is expected for applications to calculating dynamic derivatives of aircrafts or wing-flutter problem where the flow responses to small-amplitude oscillations are used to judge the stability.

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A Hall thruster system for in-space propulsion has been developed as a part of a Japanese collaborative research and development project aiming at practical use of a high power anode layer type Hall thruster. Its thrust was measured at the ISAS/JAXA vacuum chamber facilities using a dual-pendulum thrust stand developed at the University of Tokyo. In the low specific impulse mode operation, thrust efficiency of 64% and thrust to power ratio of 80mN/kW were achieved. In the high specific impulse mode operation, the thruster was successfully operated at the acceleration voltage of up to 1,000V.

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A benchmark problem, acoustic scattering analysis around a circular cylinder, is solved in order to show the applicability of lattice Boltzmann method (LBM) for a direct simulation of sound propagation with reflection, diffraction and interference. First, compressible Euler equation with sound source term is derived from lattice Boltzmann equation with sound source term in order to show the consistency between the equations. Next, the benchmark problem is analyzed using linearized version of lattice Boltzmann method (LLBM). The effects of physical viscosity and grid resolution on the directivity pattern of the sound pressure are evaluated. In order to investigate the independent effect of the grid resolutions at the propagation region, the body surface region and the sound source region, hierarchical Cartesian grid is developed on LLBM. It is found that grid resolutions at all three regions are important for the accurate acoustic simulation. By setting sufficient grid resolution at each region, good agreement is observed between the numerical result and the exact solution.

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This study proposes a power management method for a spacecraft with Variable Speed Control Moment Gyro/Integrated Power and Attitude Control System (VSCMG/IPACS) and Lithium-ion battery, considering the lifetime of the battery. The proposed method achieves the attitude control of the spacecraft through the steering law of the VSCMGs, while the IPACS and battery realize the required power, suppressing the degradation mode of the battery. In the proposed power management method, the total required power is distributed into two references, which should be realized by the battery and the IPACS. In case the thresholds of the state of charge (SOC) or C-rate of the battery are exceeded, the IPACS assists the power output and charging of the battery while considering the saturation of the wheel speed of the IPACS.

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