Abstract : An analysis of various thermal storage materials indicated that a eutectic mixture of lithium hydroxide and lithium fluoride would provide relatively high heat capacity for a closed-cycle thermal propulsion system for deep-running underwater vehicles. In contrast with other high-heat-capacity lithium compounds, this eutectic mixture undergoes practically no expansion during fusion. It has a low melting point of 800F. It does not react chemically with water, but does absorb small amounts of water if directly exposed to steam at high pressure. LiF-LiOH corrosion tests on samples of various metals, including 304 stainless steel and Inconel 600, indicated that corrosion may occur at random at temperatures above 900F. From 900F to 1200F, Inconel 600 indicated the least corrosion of any high-strength material tested.