抄録
On the occasion of the first flight of H-IIA launch vehicle (TF#1), the dynamic motion of liquid hydrogen aboard the upper stage was observed with a CCD camera. The visualized images and the other outputs from the sensors indicated that the injected gas for the pressurization penetrated deeply into the liquid phase under low-gravity condition during the coasting flight before the second ignition (SEIG2). To avoid the gas penetration in the second flight (F#2), the configuration of the diffuser, which introduce the pressurized gas into the tank, was modified and its performance was both experimentally and numerically investigated in advance. To grasp the detail of liquid motion driven by the injected gas, the flow field including free-surface was simulated with newly developed code, called CIP-LSM. In the computation, the gas penetration was successfully reproduced with the old diffuser and the improved performance of the modified diffuser was also confirmed
