Abstract: Presents a space motion model (SMM) of multiple rigid bodies with varying mass for the description of the intercept problem of homing missiles with roll stabilization. The SMM is more accurate and comprehensive than those previously published, such as the plane model and space article model. The SMM includes descriptions of the following critical and often neglected missile characteristics: space dynamics of a missile which is considered as a combination of a varying-mass rigid body and other rigid bodies, space dynamics of a homing seeker and relative space motion between a missile and a target. In addition, the general simulation program of the SMM is discussed