PURPOSE: To prevent movement of a center of gravity by the uniform feed of a propellant from a plurality of auxiliary rockets to the main rocket side before separation and obviate the need for precooling of a main rocket piping, in a rocket constituted to simultaneously separate a plurality of the auxiliary rockets.

CONSTITUTION: In a rocket wherein a plurality of auxiliary rockets 10 and 10 are simultaneously separated away from a main rocket 1 and a repellent is fed from the auxiliary rockets 10 and 10 to the main rocket 1 before separation, the propellant tanks 12, 12, 13, and 13 of a plurality of the auxiliary rockets 10 and 10 are interconnected through manifolds 20 and 21. The manifolds 20 and 21 are connected to the propellant tanks 2 and 3 of the main rocket 1.