Abstract. Digital radiator technology is one of several variable heat rejection techniques being investigated for future human-rated NASA missions.  The digital radiator concept is based on a mechanically pumped fluid loop with parallel tubes carrying coolant to reject heat from the radiator surface. A series of valves actuate to start and stop fluid flow to different combinations of tubes, in order to vary the heat rejection capability of the radiator by a factor of 10 or more.  Here we present some of the challenges associated with the technology and competing technologies, along with results from laboratory experiments demonstrating fluid evacuation techniques and qualitative testing of the freezing characteristics of several different candidate fluids, which show non-classical phase change behavior at low temperatures.

Silicon heat pipe technology provides a 2-dimensional heat spreader made entirely from silicon for cooling high power microelectronic devices.  The device uses a wicking structure resembling microscopic grass to generate the capillary forces that drive the heat pipe cycle.  This surface is manufactured using a cryogenic Deep Reactive Ion Etching technique, whereby passivation zones are randomly generated on a micron scale.  Here we present an overview of the manufacturing process along with preliminary results from laboratory testing experimental devices.