The Development of Structure and Mechanisms for Mu-3SII

Abstract

This paper describes newly developed structures and mechanisms of Mu-3SII launch vehicle, the process of development and some design features. Although Mu-3SII is a version of Mu-launch vehicles, most of the structural and mechanical items were newly developed or redesigned from it predecessor. A second stage motor casing made of newly developed maraging steel and two types of spherical motor casings made of Ti-4A16V were developed. An open-petal directly-fastening inter-stage joint, an open-petal marman-clamp joint and a marman clamp joint with light CFRP lattice structure are also described. The joints and jettison mechanism for strap-on boosters were designed so that brace push away the boosters from the core motor utilizing the acceleration of the core motor, resulting in a collision-free jettison. A unique clamp and jettison mechanism was developed for the nose-fairing, which clamps the halves of the fairing with each other at many points along the split line and releases by an action of a small number of initiators. The fairing is capable of collision-free jettison under an acceleration of up to 5 G. The tail cylinder and tail fins were redesigned from those of the preceding version of Mu-vehicles.