1. Department of Materials Science and Technology, Faculty of Industrial Science and Technology, Science University of Tokyo, 264, Yamazaki, Noda, Chiba 278, Japan
2. Research Division of Space Propulsion, Institute of Space and Astronautical Science, 3-1-1, Yoshinodai, Sagamihara, Kanagawa 229, Japan
3. Department of Mechanical Engineering, Waseda University, 3-4-1, Okubo, Shinjuku, Tokyo 169, Japan
4. Ishikawajima-Harima Heavy Industries Co. Ltd., 3-5-1, Mukodai, Tanashi, Tokyo 188, Japan