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A World Class Team Develops Cutting-Edge Technology Yasuhiro Morita M-V Launch Vehicle Project Manager
In the half century since the pencil-rocket launch experiments, Japan's research on solid-propellant rockets has been making steady progress. Today, there are no better launch vehicles for scientific missions than Japan's M-V rockets. Their most distinctive characteristic is that they were developed in collaboration between space engineers who are experts in rocketry and space scientists who design satellites. We look forward to a successful launch of the M-V-8 (the M-V Launch Vehicle No. 8), carrying the infrared astronomical satellite ASTRO-F.
Solid-Propellant Rockets - The Most Appropriate for Scientific Satellites
The M-V rockets are the world's largest, best-performing multistage solid rockets. They are unrivalled in their ability to launch an explorer into an interplanetary orbit. The biggest benefit of solid rockets is their capability of launching at any time. This is very useful for scientific satellites that have limited launch windows, especially satellites with planetary missions. For example, because Mars and Earth have different periods of revolution, an opportunity to launch a satellite into a Mars orbit comes only once every two years, and it is not unusual that there is only a one-week launch window. In some cases, the window for launching a rocket can be as short as one minute; in fact, the asteroid explorer Hayabusa, launched in 2003, had a launch window of only 30 seconds. It is difficult to store full liquid-fuel rockets for long periods of time, so when a launch is postponed at the last minute, the rocket's fuel tanks must be emptied, and the rocket is not ready to launch for several days. Solid-propellant rockets, on the other hand, can be stored with their fuel, and can be ready to launch at any time, even the day after a cancellation. This is a significant issue for some scientific missions, which, if they miss a launch window, could have to wait several years for the next one.

The World's Best Guidance Technology for Solid-Propellant Rockets
Some countries have converted missiles built during the Cold War for use as solid-propellant rockets. These rockets, however, were not developed specifically for launching satellites, so they are not ideal for this purpose. For example, the sub-boosters of the United States' Titan rocket and the space shuttle's solid-rocket boosters can be used as back-up propulsion systems, but not for planetary exploration. Among multistage launch vehicles powered exclusively by solid-fuel propulsion, only M-V rockets are capable of putting an explorer into a planetary orbit.
One of the possible reasons for this is the complexity of the guidance control of solid-propellant rockets. The thrust of liquid-fuel rockets can be controlled during flight, while solid rockets follow a pre-determined flight path that cannot be changed after launch - once they are fired, the burn cannot be extinguished and lit again. In a figurative sense, if a liquid-fuel rocket were a car, you could increase the thrust by stepping on the accelerator, but you could also cut the engine. A solid-fuel rocket, on the other hand, is like a fully accelerated car that keeps running until its fuel runs out. You have no control over the power of the thrust when it is running, so you cannot change velocity or stop. Once a solid rocket is fired, it does not stop flying until the fuel is spent. This can cause great difficulty, because to make sure the rocket makes it to the designated orbit, we have to pack it with slightly more fuel than necessary, which means the rocket can easily overfly the orbit. To avoid this, we have to find a way to adjust the energy of the rocket during flight and guide it to its destination - a challenge in itself. And in addition, there is the difficulty that all scientific satellites have special needs and their designated orbits differ greatly. Given that control of rocket energy is limited, it is quite challenging to develop techniques that meet these widely varying demands.
A particularly sophisticated technique is required for the launch of ASTRO-F, which is carrying an infrared telescope, as it is going to be launched into a sun synchronous orbit that circles the Earth in a north-south direction. In addition, the satellite must be guided into this special orbit so it can fly over the day-night line on Earth. Finally, since hot celestial bodies emit a lot of infrared radiation, the telescope must be protected from the rays emitted by the sun and Earth. This is why ASTRO-F is designed to fly over the day-night line, always having the sun and Earth on a horizontal plane on opposite sides of the telescope. Japan's M-V launch vehicles are all-stage solid-propellant rockets that respond to complex guidance, and are capable of launching planetary exploration instruments. They are the best-performing solid rockets in the world.



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