The Status of the Research and Development of LNG Rocket Engines in Japan

This chapter reports the status of research and development which have been carried out to realize a liquefied natural gas (LNG) rocket engine with higher performance in Japan. As a fuel of rocket engine, LNG has better characteristics, i.e., longer storage, lower cost, and nontoxic; hence, LNG rocket engines have been investigated among many countries. However, LNG rocket engines have never been used for actual flight application in Japan, even in the world. The reason is that the performance and characteristics of the current LNG rocket engines do not have enough advantages compared with other liquid rocket engines. For example, if it would apply to a future reusable liquid rocket booster, the specific impulse (Is) of LNG rocket engine should be higher than 360 s in order to get more advantages than other liquid rocket engines. The Is of the current LNG rocket engines in Japan is between 310 and 350 s, falling short of the target level of 360 s. Therefore, continuous research and development have been conducted for the purpose of extending the advantages and promoting the practical use of LNG rocket engines in Japan.