PURPOSE: To obtain optimum thrust force × time, by arranging in the axial direction a combustion control member, which is installed partially in the circumferential direction of grains loaded in a rocket chamber and which has a portion closed toward the periphery.

CONSTITUTION: A combustion control member 3, which is installed in the circumferential direction of grains 1 loaded in a rocket chamber 4 and which has a portion closed toward the periphery, is arranged in the axial direction. Thereby the web according to the inner-surface combustion system will become a one having substantially a diameter 2W3 times as large as the grains' 1, to cause substantial increase of the combustion progressive web. The combustion pattern thus obtained will transfer from the combustion initial face 1a to the combustion progressive face A one after another, wherein a comparatively large thrust force is obtained in the initial stage, while a comparatively small, approx. constant and stable thrust force is obtained continuously after passage of a certain period of time. This provides effectiveness for launching an aeronautical body in vertical position to a high altitude, as well as the reach can be stretched even in launching aslant.