PURPOSE: To provide a rotary mechanism for a space vehicle having a stacking means not requiring an operation device by a pyrotechnics by releasing a stacking means to prevent relative rotation between an inside part and an outside part during a launching stape by an excess of phase change temperature of a member made of a shape memory material.

CONSTITUTION: A rotary mechanism is furnished with ball bearings 14, 14' and furnished with stacking systems 32, 32' to stack two parts of the rotary mechanism which must not be rotated each other during a launching stage. After completion of the launching stage, the stacking systems 32, 32' are released by heating shape memory material members 46, 46'. It comes to be possible to arrange the stacking systems 32, 32' at a position adjacent to the ball bearings 14, 14' by using the shape memory materials 46, 46'. Consequently, force generated by launching is transmitted from the one part of the rotary mechanism to the other part without applying a load on balls of the bearings, and it is possible to minimize dimensions and weight of the bearings.