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AbstractIn response to government and industry needs for greater space lift capability, greater space mobility, and more affordable spacecraft, the Air Force Research Lab has been researching advanced technologies that include solar thermal propulsion and solar thermionic based power systems. Efforts over the last ten years have focused on feasibility, design, and fabrication issues of the various components.Recent programs have progressed to the point of ground based demonstrations of major subsystems. Because solar thermal based concepts are designed to make use of the 0-g space environment, the validation of several key issues can only be accomplished with a space flight experiment. These issues include the long duration containment and acquisition of two-phase hydrogen, stability and dynamic control of large solar concentrators, exhaust plume impingement, and autonomous multi-impulse orbit raising.In an effort to validate these issues, a conceptual design of a space experiment has been created which includes basic layout and design drawings, performance predictions, and subsystem requirements. The design was produced using a design to cost approach. This paper gives a basic overview of the conceptual design as well as a description of the drivers and rational behind the design. The DTC method shows to be a valuable tool for defining low cost technology experiments although the results must be considered in the light of the driving factors.