Abstract
In this paper, the Liquid Rocket Engine Development Planning and Expectation in Japan are described based on LE-5/ LE-7 Development Results and Actual flight Results. In USA Apollo era, Design Criteria was prepared synthesizing their enormous Failure Experiences and was published in general. For the next development, Design Criteria or Failure Limits have to be prepared at our own efforts. It is important to take up Failure Investigation, Simulation or both merging effort in early phase, to realize the rational and optimum Design.
