Yoshifumi Inatani

Experimental and Numerical Study of Pyrolysis Gas Pressure in Ablating Test Piece

The pyrolysis gas pressure and temperature inside ablator pieces are measured in an arc-heated wind tunnel. The obtained pressure and temperature data are compared with the computed results that account for unsteady ablation. In the calculation, the motion of pyrolysis gas is determined by solving the mass and momentum conservation equations assuming a finite permeability determined in our previous study. Though a quantitative agreement is not yet reached, the observed trend in pressure showing an initial increase, a decrease, and eventually reaching a plateau is reproduced qualitatively by the present calculation. It is suggested from the experimental data and the computed result that delamination of the ablator likely occurs at the region where the ablator is not fully charred but partially pyrolyzed, which results in a smaller porosity and higher pyrolysis gas pressure in the region.

Thermal Response of Ablative Test Piece in Arc-Heated Wind Tunnel

A two-dimensional version of the super charring materials ablation code is developed for the purpose of studying thermal response of ablative test piece that is put into the arc-heated airflow. The calculated pyrolysis gas pressure and temperature profiles within the ablative test piece are compared with those obtained by one-dimensional calculation, and also with experimental data. The effect of ply angle on pyrolysis gas pressure inside of ablative test piece is examined. It is found that the maximum pressure value along the centerline of the ablative test piece becomes 1/3 of that obtained by the one-dimensional calculation. It is also indicated in this study that the maximum pressure value can be further reduced if carbon-cloths are properly tilted with respect to the ablating surface.

Numerical Analysis of Shock Wave with Precursor Heating

A coupled numerical analysis of flow and radiation is done to predict the magnitude and characteristics of the precursor of the strong shock wave. This numerical analysis uses a model which includes thermochemical nonequilibrium, accounts for detailed radiative absorption and emission using SPRADIAN, and utilizes mass rate of production and vibrational-electronic energy rate for the photoionization reaction. Several numerical results indicate that there is some productions of ions and electrons ahead of the shock wave due to radiative absorption. Comparison of the present results with shock tube data shows the same tendency. However, the precursor has negligible effect on behind the shock wave in this case.

Aerodynamics of Vertical Landing Rocket Vehicle with Engine Thrust in Landing Phase

A vertical take-off and vertical landing rocket is one of the future space transportation vehicle expected as fully reusable system. In the landing phase of vertical lander, the vehicle is decelerated by the main engine thrust and lands softly to the ground site. Then its aerodynamic characteristics are affected by the interaction between the engine plume and the subsonic free-stream against the vehicle. In order to investigate the influence of such interaction, wind tunnel tests were conducted. The aerodynamic forces and surface pressure were measured by using scale model of the Reusable Vehicle Testing (RVT) which is a small vehicle built for flight tests in ISAS/JAXA. Flowfield around the vehicle model was visualized by using Particle Image Velocimetry (PIV) method. As a result, the drag force and pitching moment acting the vehicle were affected by the change of pressure distribution due to the jet/free-stream interaction.

Parachute deployment experiment for a small capsule dropped from a balloon

In order to verify the entire functions of a parachute deployment system, applicable to a small space capsule, and to examine the transonic dynamics of the capsule with a blunt nose, a free fall capsule experiment was successfully conducted using a balloon with 30,000 m in volume in September, 1996. The capsule weighed approximately 26 kg, and its configuration was 40 cm in diameter and 20 cm in height. The capsule was released from the balloon gondola at 36 km in altitude, and the maximum descent speed was 1.1 in Mach number 45 seconds after the release. As the velocity increased to supersonic, the capsule pitching amplitude was enlarged due to the dynamic instability, and the angle-of-attach was approximately 30 degrees at maximum. On the other hand, the velocity decreased to subsonic, the oscillation was little damped. The single stage cross-type parachute was directly pulled out by the parachute cover, using newly developed pyrotechnical cover openers. The opening shock was 24 G, and it corresponded with the opening shock coefficient of 1.3. The flight results well met the estimation based on the ground test results, except for the less damping efficiency. This paper presents the outline and the flight results of the balloon-borne drop test. Comparison with wind tunnel tests is also described. Penetrator. In MUSES-C (Mu-rocket Space Engineering Spacecraft #C) mission, which will launch a spacecraft towards a small asteroid, Nereus, in the early 2002, a reentry capsule will be applied so as to bring the asteroid material back to the ground. The current capsule design is tentatively as such the weight of the capsule is 18 kg, and the diameter is 40 cm. Besides, the capsule is covered with the relatively thick ablator materials of 2 to 3 cm in thickness. Thus, inside volume for equipments is quite severe. The capsule is not so heavy that the parachute enables to be a single-stage without a drogue nor a pilot chute. This simplification can reduce both weight and volume. Furthermore, the parachute is rigged in the torus-shaped container, so as to keep the maximum space for measurement and transmission instruments at the center of the capsule. Thus, the parachute is equipped in looping around the instruments, and it is directly pulled out by the cover of the parachute container. Therefore, it should be carefully discussed whether the rigid cover can generate the enough aerodynamic force to pull stably the parachute out in the back stream of the forebody. The shape of the capsule is conventional, which has a spherical nose of 20 cm in radius and a conical body of 45 degrees in half-cone-angle. Therefore, the dynamic instability should be carefully investigated. Capsule Configuration