A collaborative project between Oregon State University and Auburn University is proposed on the topic of heat rejection. A unique and innovative method of phase-change heat rejection (condensation) suitable for microgravity environment is proposed. The overall objective is to characterize the effects of surface microstructures on film dynamics and heat transfer rate by variation of the microstructure size or surface conditions. The key innovation lies in the surface microstructure design of the condenser, which is in the form of repeating asymmetric ratchets. Together with an innovative evaporator design that is being currently developed by the PIs, the condenser will result in a phase-change thermal management loop that is capable of removing moderate heat fluxes, is passive with no electrical input or moving parts, is self-regulating, reliable and lightweight. The proposed technology is expected to exit the project period at TRL 2.