Large space solar-power systems have intermittently been a topic for consideration during the past 30 years. However, the last major studies in the United States on these concepts were conducted in the late 1970s. After two decades of relative inactivity, large-scale space solar power (SSP), including the generation of solar power in space for transmission to terrestrial markets, has recently reemerged as a potential energy option. This occurrence is timely because global energy demand continues to grow dramatically while environmental concerns increase. Demand for power in space is also likely to increase during the same time frame. A wide range of technology advances would be needed to enable such systems. In addition to very low cost space transportation and highly efficient and high voltage solar arrays, significant developments must also take place in technologies such as wireless power transmission, large space structures, robotic assembly and maintenance, and others. However, recent NASA studies and focused research and development progress in a number of key areas suggest that such systems are technically feasible. This paper presents an overview of the subject of space solar power, including results of recent NASA activities.