In this paper with the use of theory of variable mass systems and dynamic analysis, rotary motion of variable mass cylinder has been evaluated. Effects of angular rates, the methods of mass reduction and propellant burn, the shape and measurement of geometrical elongation in direction of symmetry axis of cylinder have been known in stability of the system. The results of this paper lead to understand unexpected and sudden changes in angular velocities of spin-stabilized rockets which in some of them is happened near the end of motor burn and has made problems in control and stability of the system. In this paper the equations of motion have been derived from the methods of analytical dynamicsâKane's formalism.
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