ISAS's new launch vehicle for science use

The M-3SII rocket, developed by Japan's Institute of Space and Astronautical Science as the latest version of the Mu rocket family, is described. The medium-sized M-3SII was developed primarily for the Halley's Comet mission. A novel movable nozzle system was introduced, and the control system was digitalized to increase control logic design flexibility. The vehicle is a three-staged solid rocket with two strap-on boosters; a kick stage is added optionally for high-energy missions such as interplanetary flights. It can lift 700 kg of payload into a 250-km circular orbit with medium inclination. Attitude reference is given by three rate-integrating gyros mounted on the second stage, and two gyros on the first stage provide damping signals for the first-stage pitch and yaw control. The instrumentation system includes equipment for ground monitoring of the subsystems during prelaunch checkout and countdown, telemetry monitoring of flight performance, radar beacon tracking, and command-destruct information.