To link "space development" into our future lives as an essential item, we must reduce related costs markedly. One way of accomplishing this is to realize the reusability of the rocket. As part of this effort, Japan Aerospace Exploration Agency (JAXA) R&D is working on the reusable engine for a sounding rocket. Japanese researchers have set two major objectives in producing a reusable rocket engine. One is to turn the engine into a durable one, usable for multiple flights. The other is to develop a fault tolerance system, meaning an engine which can be stopped immediately and safely even if an engine fault occurs during flight. To realize the latter, the engine condition must be accurately monitored, with the fault being detected as soon as possible upon occurrence. This process is known as "Health Monitoring System" (HMS). Since I am focusing on HMS in rocketry, especially for the reusable rocket engine, I chose the JAXA endeavor as the theme for my master's course at School of Engineering, Tohoku University. Currently I am drawing up plans for a reusable rocket engine system and a HMS by carrying out studies on past JAXA activities. At Kakuda, ten firing tests for a reusable rocket engine have already been conducted and many more firing tests are to be performed during this academic year. I hope my research concerning data from these tests will help make the reusable rocket engine possible. I look forward to continued involvement in this R&D field.