The presented work introduces a new class of controllers for free-flying space manipulators liable to unknown/unstructured, adverse disturbing forces/torques imposed on the end effector. A novel approach for constructing the spacecraft desired trajectory based on a virtual space manipulator with maximal holonomic manipulability measure is also offered herein. Applying the accurately defined task-space nonsingular terminal sliding manifold as well as the Lyapunov stability theory, we offer a class of controllers based on the estimated, extended, transposed Jacobian matrix which also appear to be efficient in countering the unstructured disturbing forces/torques. The numerical calculations being carried out for a space manipulator that is composed of a spacecraft propelled by eight thrusters and a holonomic manipulator of three revolute kinematic pairs exemplify the performance of the recommended controller. Numeric comparison with other control algorithms, which are renowned in the literature, is made as well.