Weighing in at 139 tons and standing 30.7 meters high, the M5 is a three stage solid propellant satellite launcher with an optional kick motor for an extra fourth stage. Developed as the successor to the M3SII, which launched eight satellites, the M5 is more than a step beyond its predecessor. In fact its 1.8 ton to Low Earth Orbit payload capability is more than twice that of the M-3 SII.

Perhaps the most interesting feature of the new rocket is that the M-V adopts 'Fire in the Hole' (FIH) technology, in which the second stage is ignited at the same time as the first and second stage separation. In addition, the third stage rocket motor casing is a lightweight design filament wound casing made of Carbon Fiber Reinforced Plastic (CFRP). The third stage nozzle is extendible, which will be kept retracted just before third stage ignition. The rocket will also employ a fiber-optical gyroscope, says Prof. Yasunori Matogawa, Director of Japan's Kagoshima Space Center.

The M5 is going to be busy. The proposed launch schedule, which covers six launches over six years, is to be evenly divided between astronomical and planetary body research. On the astronomical side, the MUSES-B, ASTRO-E and IRIS satellites will observe radio, X-ray and infra-red resources respectively. "The main plan for the MUSES-B is to release a large antenna in space. It is also named the VSOP satellite after two professors had a long drinking session," Matogawa revealed.

Trips to the moon, Mars and 4660 Nereus, a near-earth asteroid which is believed to be one of the most primitive asteroids in the solar system, are planned from the LUNAR-A, PLANET-B and MUSES-C vehicles. Both LUNAR- A and MUSES-C are designed to take samples. Studying the structure and dynamics of the upper Martian atmosphere, especially its interaction with the solar wind, PLANET-B becomes Japan's first Mars mission.

The first flight was scheduled for Sept. 10, but has been put off to early next year. The delay came when the advanced gyroscope failed systems integration and vibration tests, Matogawa explains. "It was just a simple thing. It was an accident with the attitude control system involving the gyro and the internal signaling system. The inter-booster stage electronics systems also suffered problems. When the attitude sensing system was tested as single body it functioned perfectly, but in May we re-tested it in combination with all the other systems, and when the vibration test was taken, the linearity of the data didn't match," he said.

Matogawa also hinted that the M5 may prove under-powered for some future projects. Pointing out that planned upgrading to a three ton payload capability depends on further government funding, some might argue that the M5 is a waste of public money. An upgrade to three tons will, after- all, only equal the present capacity of NASDA's current launch vehicle, the H2. Matogawa agrees that there might be a problem asking for more money.

"I don't know what the attitude of the government people is. For further, more ambitious planetary missions to Venus and Mercury, it might be difficult to modify the M5 as the H2 is already a powerful vehicle, so we may have to use the H2," he said. Nonetheless, the M5 will meet ISAS's needs in the short term. "However any major lunar exploration will require the H2 or H2A," he added. While ISAS, anxious to maintain its autonomy from the commercial sphere, would prefer the extra money for an upgrade, he suggested, cooperation with NASDA may prove inevitable.

Also, the M5 doesn't come cheap. "Excluding development costs, building a single H2 rocket costs 1.9 billion yen, while each M5 costs 6 billion yen. We need to reduce costs and we will do this. But I think the important thing for ISAS is to maintain its integrity as a scientific institution set aside commercial considerations," he said.

Atsutaro Watanabe, Deputy Director, Launch Vehicle Systems Department, Office of Space Transportation Systems at the National Space Development Agency (NASDA) thinks that the M5 rocket may prove under-powered, but he considers it adequate to serve ISAS's needs, and may be of use to NASDA in terms of technical transfer. "Each rocket has its own perspective," he said, adding "I think that if the M5 is successful, NASDA will look very carefully at it and consider adopting its fiber casing technology in particular," he said.

Further, the M5 represents the fruition of ISAS's six-generation development of solid propellant booster development. "Our attitude at ISAS is that the solid propellant technology must be at the very highest level. From the standpoint of space technology, so we think it is our responsibility to promote solid propellant technology not only for commercial use, and not just for carrying payloads, but for scientific research," commented Matogawa.

Hiroshi Ikukawa, Deputy Director, Science and Technology Agency, Aeronautics and Space Development Division views the M5 as a valuable addition to Japan's family of rockets. "The development of the M5 rocket will contribute to the harmonious development of Japan's space activities between NASDA and ISAS. As the supervising agency, we would like to use three different types of rockets more effectively and efficiently for future space missions," he said.

In addition the M5 rocket program has been valuable as a whole in terms of technology transfer and has contributed to NASDA's program. "For example, the technology from the 'Mu' series rocket has been utilized in building the H2 rocket, particularly in the development of the solid booster technology," he said. Whether they like it or not, NASDA and ISAS would seem to be drawn closer.

08.05.96