text: In 1999, NASA initiated its Space Solar Power Exploratory Research and Technology program (SERT) for the following purposes:
  * Perform design studies of selected flight demonstration concepts.
  * Evaluate studies of the general feasibility, design, and requirements.
  * Create conceptual designs of subsystems that make use of advanced SSP technologies to benefit future space or terrestrial applications.
  * Formulate a preliminary plan of action for the U.S. (working with international partners) to undertake an aggressive technology initiative.
  * Construct technology development and demonstration roadmaps for critical space solar power (SSP) elements.
  SERT went about developing a solar power satellite (SPS) concept for a future gigawatt space power system, to provide electrical power by converting the Suns energy and beaming it to Earths surface, and provided a conceptual development path that would utilize current technologies. SERT proposed an inflatable photovoltaic gossamer structure with concentrator lenses or solar heat engines to convert sunlight into electricity. The program looked both at systems in Sun-synchronous orbit and geosynchronous orbit. Some of SERT's conclusions:
  * The increasing global energy demand is likely to continue for many decades resulting in new power plants of all sizes being built.
  * The environmental impact of those plants and their impact on world energy supplies and geopolitical relationships can be problematic.
  * Renewable energy is a compelling approach, both philosophically and in engineering terms.
  * Many renewable energy sources are limited in their ability to affordably provide the base load power required for global industrial development and prosperity, because of inherent land and water requirements.
  * Based on their Concept Definition Study, space solar power concepts may be ready to reenter the discussion.
  * Solar power satellites should no longer be envisioned as requiring unimaginably large initial investments in fixed infrastructure before the emplacement of productive power plants can begin.
  * Space solar power systems appear to possess many significant environmental advantages when compared to alternative approaches.
  * The economic viability of space solar power systems depends on many factors and the successful development of various new technologies (not least of which is the availability of much lower cost access to space than has been available); however, the same can be said of many other advanced power technologies options.
  * Space solar power may well emerge as a serious candidate among the options for meeting the energy demands of the 21st century.
  * Launch costs in the range of $100–$200 per kilogram of payload from low Earth orbit to Geosynchronous orbit are needed if SPS is to be economically viable.