The Age of Space Science ---- Mu Rockets

Then came the age of the M (Mu) rocket. ISAS has proceeded step by step by improving the launch performance of the Mu rocket series. The history of Mu reflects the process by which Japanese space science has established its position in the global academic society.

The first generation was the four-stage M-4S type. The M-4S adopted the gravity-turn method as a payload injection scheme, and stabilized the attitude by tail fins and spin. Following the launch of a technological test satellite TANSEI in February 1971, ISAS succeeded in orbiting two full-fledged scientific satellites, SHINSEI and DENPA, in September 1971 and August 1972, respectively by means of the M-4S.

The second generation, M-3C, had three stages. Both 2nd and 3rd stages were newly developed, with the 2nd stage incorporating SITVC (secondary injection thrust vector control) and SJ (side jet) systems to improve orbit-injection accuracy. The M-3C sent three satellites into orbit: TANSEI 2, TAIYO and HAKUCHO in February 1974, 1975 and 1979 respectively.

ISAS next developed the third generation, M-3H, by extending the length of the first stage motor with improved propellant to achieve a greater payload capability. The M-3H carried three satellites into orbit around earth: TANSEI 3, KYOKKO, and JILIKEN in February 1977, February 1978, and September 1978 respectively.

The fourth generation of Mu vehicle named the M-3S introduced a thrust vector control (TVC) system to the 1st stage, too, to improve the launch accuracy and ease restrictions on launch conditions. The M-3S successfully launched four satellites: TANSEI 4, HINOTORI, TENMA and OHZORA in February of 1980, 1981, 1983 and 1984 respectively.

The Challenge of Japan's First Satellite INDEX Reorganization of ISAS and New Launch Vehicles