A megawatt-class space power installation based on a mirror solar radiation collector and an magnetohydrodynamic (MHD) generator is considered. Probable decisions for the construction of a mirror system and a radiation heat receiver are proposed. The analysis of mass characteristics shows that the level of specific power of 600 W/kg can be reached. An MHD generator with nonuniform gas-plasma flow, being the most suitable type of this type of device for the space use, is examined with respect to questions of nonequilibrium plasma kinetics, efficiency of energy conversion, and two-dimensional (2-D) instability of flow. It is shown that the two-dimensional structure of plasma layer remains stable during the time of fly through the MHD channel due to turbulent viscosity. Two-dimensional effects do not cause a significant decrease of energy conversion efficiency, which makes the considered scheme usable in space energy installations.