H-IIロケット失敗の原因とその教訓

抄録

H-II launch vehicle, the large Japanese launcher placing a 4000kg class satellite into GTO, failed in the two flights of No. 5 and No. 8, after the successful 29 flights from N-I to H-II. Both failures were caused by malfunction of the cryogenic engine, the second stage engine LE-5A or first stage engine LE-7, respectively. The incidents, the causes, and the corrective actions of these failures are reported in detail in this paper. The failures brought us the precious experiences and a lot of lessons and learn.
Important lessons are related with small amount of products such as a launch vehicle, which happen to fail for uneven quality by handcraft. To solve this problem, it is noted that critical manufacturing process should be distinguished to control very important characteristics of products, and that all specifications on critical processes should be determined on well-grounded technical data. In development phase, the design margin of important characteristics should be assured by testing the varied nature within defined specifications.
H-IIA flew successfully in its maiden flight on August 29, 2001 to put LRE (laser Ranging Experiment) into GTO precisely. The author believes that this success results from great efforts of many engineers and researchers who learned the precious lessons of H-II failures. Rocket technology will make progress to be matured by a lot of lessons and learn from failure.