Future manned spacecraft venturing into deep space will require sophisticated thermal control systems to protect against extreme environments ranging from direct illumination by solar radiation to complete darkness. To manage these extremes, heat exchangers composed of phase change materials, which can expand and contract without causing structural damage, will be essential. NASA is seeking non-toxic heat transfer fluids with transition temperatures between 8 and 12 (deg)C with heat of fusion >200 kJ/kg. Specifically, the fluids must have suitable thermal conductivity, high heat capacity, and low viscosity to enable flow with negligible volume expansion. Changes are also needed to reduce the existing heat transfer unit size and weight. InnoSense LLC (ISL) plans to develop new modified ionic liquid-based phase change materials heat exchangers. ISL, in collaboration the University of Nevada, will synthesize salt additives to modulate the operating temperatures, and the thermal and flow properties of the ionic liquid based eutectic phase change material with negligible volume change during phase change. In Phase I, ISL will formulate and test heat transfer formulations in a laboratory environment to demonstrate feasibility. During Phase II, ISL will scale-up synthesis and test fluid performance in a larger experimental apparatus and a wide range of working environments.