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The Essence of the Failure
      Mamoru Endo
Space Tranceportation Program Manager/ Director,Program Management and Integration Dept.
Office of Space Flight  and Operations ,Japan Aerospace Exploration Agency H-IIA F6 was not the first Japanese launch vehicle to fail. Japan's large-scale rocket development began with H-II, and progressed to H-IIA. H-II F5 and H-II F8 failed due to problems with their liquid-fuel rocket engines. That technology was first obtained from the United States. Later, Japan developed H-II as its primary rocket system, and completed the evolution of liquid-fuel technology with the transition to H-IIA.

At the same time, since the launch of the Pencil Rocket in 1955, Japan's domestic rocket technology had focused on solid-fuel engines, and it was such an engine that caused the H-IIA F6 accident. Although that type of engine had previously been used in the H-I, M-V, and H-II launch vehicles, it had failed only once before, with M-V-4 in 2000.

The M-V-4 accident happened near the beginning of the transition from H-II to H-IIA. At that time, H-IIA's engine design and development were considered to be complete, but the failure of M-V-4 clearly indicated an unfounded overconfidence in Japan's solid-rocket technology.
That failure was followed by great efforts to make the whole system more sophisticated. We reduced the number of parts, improved reliability, and cut costs in half. H-IIA's rocket boosters became more compact and more powerful, ending up with a very different design from the H-II series.
Solid Rocket Booster (SRB-A) static firing test
Solid Rocket Booster (SRB-A) static firing test

H-IIA's solid rocket boosters doubled the combustion pressure of previous designs. To the three ground tests originally scheduled, two more were added after the ablation of nozzle insulation proved to be greater than expected. Once all five tests were completed, we concluded that the ablation would not create a hole in the nozzle, that cause the failure, and thus finally H-IIA F1 was launched. That was the first of five successful H-IIA launch vehicles, and we believed that the technology had been validated. The F6 accident was a rude shock. Studying its causes has reminded us of the difficulties of space development.


Almost all other types of technology - automobiles, aircraft, electrical appliances, etc. - can be thoroughly tested on the ground or in the air, where they are intended to be used. Rockets, on the other hand, are designed to go into space, and ground tests alone cannot prove their reliability. After all possible ground testing has been completed, the final - and most important - test is the actual launch.

It costs a fortune to launch a rocket, so it's a fact of life that improvements have to be made based on a very limited number of launches. Some people might wonder why a satellite that costs billions of yen has to be launched under such uncertainty. However, for modern life, space infrastructure such as artificial satellites has already become an absolute necessity. No matter what the financial risk, we have to accept the uncertainty in order to continue to make progress. As long as we are capable of launching rockets, we should try to meet the needs of modern life.

LE-7A rocket engine firing test
LE-7A rocket engine firing test

With Japan's level of space technology today, it's as if we have to stretch upward on our tiptoes to stand eye-to-eye with the rest of the space-faring world. In order for Japan to be world-class with feet firmly planted, we must gain more experience and develop more skills. In the lead-up to the H-IIA F6 accident, there was once again overconfidence in Japan's technology, and this was probably one of the reasons the problem was overlooked.

Japan's space sector is still growing. To be successful, we must gain more experience, and develop a wider range of knowledge and technology for new large-scale systems. The ability to detect problems in advance can be learned only with experience - as demonstrated by the success in space of the United States and Russia. It is that strength that has enabled them to build solid space development programs.

In order to improve reliability, Japan's space program has to broaden its range of technology, train its staff to think comprehensively, and learn through experience to better foresee potential problems.

The failure of H-IIA F6 has turned out to be not just a big trial for our space program, but also a valuable lesson towards further progress. Now it is time to learn from this experience, improve our technology, and gain experience, in order to achieve top-class reliability in our rocket technology.

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