The Mu rocket project began with the development of a sounding rocket for probing the outer Van Allen belt. From there, it has developed into a satellite for scientific satellite launching, culminating in the production of the M-V rocket (illustrated below).
The first generation Mu rocket was the four-stage M-4S, which was used to launch satellites in 1971 and 1972. The second generation was the M-3C, a three stage rocket. This was used for the launch of Tansei 2 in 1974, Taiyo in 1975 and Hakucho in 1979. The M-3H was the third generation rocket, and was used for launches in the late 1970s. The M-3S was the next development, and was successfully used for the launch of Tansei 4, Hinotori, Tenma and Ohzora in the early 1980s.
The fifth generation rocket was the M-3SII. It used the first stage of its predecessor and newly developed second and third stage motors and strap-on boosters to enhance the payload capability. The first two launches with the M-3SII were the first Japanese interplanetary probes, Sakigake and Suisei, both launched in 1985 to encounter Halley's Comet. Since then, Ginga, Akebono, Hiten, Yohkoh and ASCA have all been launched with the M-3SII. The last scheduled M-3SII launch was EXPRESS, which was launched in January 1995.
In 1990, funding was approved for the M-V rocket. The M-V is a three stage, solid fuel, rocket (with an additional kick-motor), which is capable of placing an 1800kg payload into low Earth orbit, or an 800kg payload into a MUSES-B type orbit. The M-V contains as much fuel in its first two stages as the M-3SII carried in total. Successful tests of the M-V rocket stages have taken place at the Noshiro Testing Center during 1994 and 1995.