As part of a funded effort under the Game Changing Development Program of the National Aeronautics and Space Administration (NASA) carbon nanotubes (CNT) are being studied for their potential usage in Nuclear Thermal Propulsion (NTP) structural elements, as a replacement for metals and carbon fiber composites. In order to conduct a credible systems analysis to determine the benefits of using this emerging material system in that application, radiation resistance data are required. This unique set of data is not available for these CNT materials at this time, and can be obtained by piggybacking on tests of NASA prototype nuclear fuel compositions being conducted this summer/early fall at the Idaho National Lab. Exposure of these CNT materials to conditions in those experiments will provide data on the effect on the performance of structural CNT composites of radiation exposure (1016 neutrons/cm2) through various thermal cycles that mimic the environment around the NTP engine. In this proposal, we seek to characterize CNT mechanical behavior and morphological changes, post-irradiation, as compared to unirradiated CNT, and other NTP candidate structural materials. The materials of interest will include high strength CNT yarn which are now available in kilometer quantities, CNT fabric woven from these yarns, CNT yarn composites and CNT fabric composites where the CNT reinforcement comprises about 80% of the composite. Early work on this set of materials indicates the potential for this material to outperform aerospace composites currently in use so that significant mass savings can be realized to enable alternative aerospace vehicle designs. The tests that will be conducted this summer/early fall can provide insight on material performance that will be used to assess where on the NTP design concept this material can be used to enable lightweight structures that ultimately contribute to reduction in the cost of space exploration. The expected period of performance is the time period that aligns with the NTP fuel testing this summer/early fall plus up to 3 weeks of time for post-irradiation characterization at ORNL LAMDA test facilities.