In this paper, the dynamics and control problems of free-floating space manip- ulator systems are studied. It is verified that the dynamic equations of free-floating space manipulator systems can be linearly dependent on a group of inertial parameters. Based on the results and with the augmentation approach, an adaptive control scheme for space manipulator systems with unknown payload parameters to track the desired trajectory in joint space is developed. The control scheme proposed above is structurally and computationally simple, because of an effective exploitation of the system dynamics. In particular, it requires not the measuring of the position, velocity and acceleration of the base. A simulation study of two-link planar space manipulator system is presented; it is shown that the control scheme proposed is feasible and effective.