heat pipe was below the melting temperature of potassium (85°C). However, start-up was rational and well-behaved, and was accomplished without any special adjustments. A similar start-up test at full power of 1900 W was performed with the pipe initially at room temperature (frozen K) with no evidence of heat pipe malfunction or evaporator burnout. We have taken a molybdenum-lithium heat pipe from room temperature (frozen lithium) condition to 1900°C in 90 s. The conduction and sonic fronts visibly propagate down the heat pipe until they reach the end of the condenser, where upon the heat pipe temperature rises isothermally to the desired operating condition. New Materials In an effort to reduce the mass of the heat rejection radiator subsystem, alternate materials of construction are constantly being evaluated. Cursory analyses [8, 9] have shown that by simply integrating the new composite materials which are available into existing radiator designs, mass reductions of over 50% are achievable. The unique properties of these new materials also make revolutionary design configurations feasible, in turn bringing order of magnitude mass reductions within reach. Current radiator systems exhibit mass densities on the order of 0.5-1 g/cm2 of radiator area. If the radiator is hardened against potential military threats, or even severe space debris threats, the mass value quickly approaches 2-3 g/cm2. Objectives are to reduce this number to 0.05-0.10 g/cm2 (hardened or unhardened). To meet these demanding objectives, new materials are being investigated. The leading advanced material contender is carbon-carbon. Carbon-carbon offers the potential of (i) exhibiting intrinsic hardness against space debris threats as well as hostile military threats (ii) having very low mass and (iii) being optimized, both thermally and mechanically, through specific orientation of its fibers. In order to enlist this material for use as a heat pipe envelope, a method must be identified to form a
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