The dynamic characteristics of a hydrostatic thrust air bearing with an actively controlled orifice restrictor are investigated theoretically and experimentally. Theoretical results show that the dynamic stiffness and damping coefficients can be increased simultaneously when the restrictor area is controlled with appropriate phase-lag to the change of air film thickness, that is, plate vibrations. Consequently stability of the bearing can be improved. Experimental results show fairly good agreement with theoretical ones.

In order to predict the flammability limit of thin materials in microgravity environments without conducting microgravity experiments, we developed a simplified model for flame spread in an opposed flow by introducing two non-dimensional parameters which represent radiative quenching and blow-off extinction. Thin PMMA sheet and NOMEX HT90-40 fabric were used as the sample. For predicting the blow-off limiting curve, the pre-exponential factor and the activation energy are required, however, these properties are hardly available in the literature. Hence, we proposed a novel blow-off test in a forced flow to obtain empirical parameters which reproduce the actual blow-off phenomena correctly. Although the properties of NOMEX are unknown, the limiting curves of NOMEX with these empirical parameters well agreed with the results of the parabolic flights, and the obtained minimum oxygen concentration was also close to the experimental value.

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The flammability map of a thin PMMA sheet with an opposed flow in microgravity environment was investigated with varying the thermal properties of the ambient gas. We also developed a new model to predict the limiting oxygen concentration (LOC) in 1g, minimum limiting oxygen concentration (MLOC) and critical opposed flow velocity, Vcr, at which MLOC was observed. We compared the predicted results with the experiment results by changing the gas-phase properties to validate the model. As the balance gas, nitrogen, carbon dioxide, and argon were used. It was found by experiment that LOC, MLOC, and Vcr significantly changed for each balance gas. These differences were reasonably predicted by the scale analysis which included the effects of radiation and kinetics on the suppression of the flame spread.