The big potential of humanoid robots is not restricted to the ground, but these versatile machines can be successfully employed in unconventional scenarios, e.g. space, where contacts are not always present. In these situations, the robot's limbs can be used to assist or even generate the angular motion of the floating base, as a consequence of the centroidal momentum conservation. In this paper, we propose to combine, in the same whole-body motion control, visual servoing and centroidal momentum conservation. The former dictates a rotation to the floating humanoid to achieve a task in the Cartesian space; the latter is exploited to realize the desired rotation by moving the robot's articulations. Simulations in a space scenario are carried out using COMAN, a humanoid robot developed at the Istituto Italiano di Tecnologia.