【摘要】 本文在多级火箭理想末速度公式的基础上，推导了可延伸喷管有效比冲增益的计算公式，并对某三级固体运载火箭进行计算，得到了三种状态下可延伸喷管的有效比冲增益更多还原

【Abstract】 A calculation method is prsented to determine the effective gain of specific impulse,when the extendible exit cones(cone)are(is)used in upper stages(stage)of the launching vehicle. The formulations of this method are developed by the ideal velocity eguations of multistage rocket. A certain solid rocket motor missile is analysised by this calculation method. The effective specific impulse gains of the extendible exit cones(cone)are calculated under three conditions.更多还原