Molten salt reactors are a subtype of reactor that uses nuclear fuel dissolved in a molten salt liquid medium (such as LiF-BeF2-UF4) as both fuel and coolant. The fuel is constantly circulating through the reactor core and other reactor systems. Molten salt reactors are an appealing technology for space because of their high temperature and low pressure operation, controllability, and high fuel burn up, among other features. The proposed research will investigate how molten salt reactor technology can be used to power sub-100 kWe reactors for science missions and for MWe class reactors for human exploration. Both of these applications are cited as relevant to current US goals in space in NASAs Draft 2010 Space Power and Energy Storage Roadmap, and will greatly assist in space exploration. Specifically, sub-100 kWe reactors are a potential solution to the Pu-238 shortage, and molten salt reactor technology can address the issue of controlling small reactors. MWe class reactors require large amounts of fuel and benefit greatly from operating at high temperatures. A MWe molten salt reactor is capable at operating at high temperatures and would require less fuel than its traditional solid fuel counterpart. Terrestrial MSRs have been recognized as a potential long term solution to Earths energy needs. Molten salt reactors have the ability to efficiently utilize thorium. Thorium is an alternative nuclear fuel that is roughly 4 times as abundant as uranium. In addition, the thorium fuel cycle produces comparatively little waste and has many proliferation resistant features compared to fuel cycles using uranium. Development of the MSR for space could result in spin-off technology to aid in the development of terrestrial MSRs. Specifically, the development of advanced multiphysics tools for MSRs, like those proposed here, will aid in the study, design, and licensing of future terrestrial MSRs. The research will use Monte Carlo nuclear simulation codes (MNCPX) and multiphysics simulations to explore to the role molten salt reactors can play in the exploration of the solar system. Design studies for various applications and organized trade studies for individual systems will be conducted. Key values such as specific mass, technology readiness levels, and possible development costs, will be produced. In addition, a number of specific technical questions, such as what power ranges in which EM pumps would be suitable for molten salt reactors, will be investigated.