Propulsion systems are the most important part of space transportation. As can be seen with the LE-5 and LE-7 rocket engines, Japan's hydrogen propulsion system is among the most advanced in the world, and we have been building related technologies in Japan. It is important that we proceed with this project with the objective of further enhancing reliability. On the other hand, recent research has made us recognize that improved performance can be achieved by combining a hydrogen propulsion system with a liquid natural gas (LNG) propulsion system. This is due to LNG's high propulsion force density, relatively high specific impulse, low cost, great reusability, strong storability in space, high safety and other such factors. Particularly promising are the prospects for booster stages and space tugs by taking advantages of the low cost and high density of LNG, and the greater safety and low evaporativity of hydrogen. To further develop our propulsion technology, it is vital that we deal not only with hydrogen propulsion systems but also with other systems, including LNG ones, so we can address diversified and universal future space activities. In addition, the world's first practical application of an LNG propulsion system will enable us to lead the world in this field rather than follow other countries. We will demonstrate the feasibility of an LNG propulsion system by conducting two flight experiments with the GX rocket, the first one to be developed by private initiative. After that, it will be commercialized as the second-stage propulsion system of that GX rocket. The main driving force behind our future space development will be joint projects with the private sector. We have been striving to be the pioneer of similar future projects by successfully overcoming the various kinds of unprecedented difficulties inherent in this project. Furthermore, I believe that LNG, given its merits, is the most promising propulsion system for interplanetary flights to planets - including Mars - and for Japan's first manned flight. It can contribute to the diversification and evolution of space development not only in Japan but all over the world. MORE >>