M-4S
The first generation of the Mu series was the four-stage M-4S rocket. It utilized a gravity turn for its orbital insertion, and stabilized its attitude with tail fins and spin. It could send a 180 kg satellite into low earth orbit.
The Japanese technological test satellite, Tansei, was launched by the Institute of Space and Aeronautical Science, University of Tokyo, from the Kogoshima Space Center. The satellite was a 26-sided body measuring 71.2 cm in diameter across the flat sides. Technological data were recorded by an onboard data recorder and sent back by radio command. The transmitter was operated by chemical batteries and was designed for an estimated lifetime of 1 week. The tracking beacon transmitted continuously, with real-time telemetry.
The Earth Environment Observation Satellite “DENPA” aimed to conduct observation of plasma waves, plasma density, electron flux, electromagnetic waves, geomagnetism, etc. to study plasma filling the entire solar system. After the satellite’s insertion into orbit by M-4S-4 on August 19, 1972 , the antennas for scientific observation, magnetometers and electron temperature sensor were confirmed to be extended. All the observation instruments and onboard systems were operable and power output of the solar cells was also as planned. At 09:04 on August 22, three days after launch, ground commands were transmitted but no response from the satellite was received. It was thought that the satellite's power-supply circuit malfunctioned causing discharge that eventually damaged semiconductor components such as transistors vulnerable to overvoltage.
The vehicle M-4S-1 is described as follows
| 1st st. | SOB | 2nd st. | 3rd st. | 4th st. | ||
|---|---|---|---|---|---|---|
| Total length | m | 23.557 | 5.794 | 10.595 | 5.860 | 1.838 |
| Maximum diameter | mm | 1410.0 | 310.0 | 1410.0 | 860.0 | 786.0 |
| Weight (ig.) | kg | 43710 | 4166 | 13211 | 3273 | 509.4 |
| Weight (b.o.) | kg | 19118 | 1482 | 6052 | 1282 | 140.5 |
| Propellant weight | kg | 20522 | 2696 | 7146 | 1986 | 368.6 |
| Mass ratio | 2.2031 | 2.1808 | 2.5491 | 3.6235 | ||
| Specific impulse | sec | 219.0 | 219.0 | 261.0 | 265.0 | 270.0 |
| Center of gravity (ig.) | % | 61.98 | 63.74 | 56.74 | 60.60 | |
| Center of gravity (b.o.) | % | 46.10 | 52.53 | 43.72 | 45.82 | |
| Ix (ig.) | kg.m.sec2 | 1610.1 | 329.82 | 34.89 | 3.445 | |
| Ix (b.o.) | kg.m.sec2 | 660.41 | 152.73 | 12.74 | 0.8464 | |
| Iy (ig.) | kg.m.sec2 | 134206 | 7181.5 | 563.05 | 7.8630 | |
| Iy (b.o.) | kg.m.sec2 | 62307.6 | 4873.3 | 329.85 | 3.9039 | |
| Net payload | kg | 49.4 | 62.2(SA) | |||
| Gross payload | kg | 148.2 | 68.9 | |||
| Nozzle expansion ratio | 5.94 | 3.57 | 20.0 | 17.36 | 19.9 | |
| Nozzle exit diameter | m | 0.8626 | 0.0716 | 0.7595 | 0.3758 | 0.0745 |
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