Passive Variable Heat Rejection Freeze-Tolerant Direct Condensation Heat Exchanger/Radiator

The ever-increasing processing power of spacecraft and satellites puts a tremendous demand on the thermal control subsystem (TCS) to acquire, transport, and reject large amounts of heat.nbsp; Consequently, the radiator surface needed to reject the anticipated highest amount of heat become large.nbsp; The TCS gets very cold in the nominal or part-load operations in the cold spacecraft attitudes.nbsp; Temperature control of the on-board payloads is essential for the optimal performance and long lifetime of the equipment.nbsp; nbsp;nbsp;Electrical power is often expended to maintain the payloads above the temperature limit, conceivably overwhelming the power subsystem.nbsp; The radiator temperatures may drop below the freezing point of the working fluid in the worst-case survival mode.nbsp; The existing ldquo;direct condensationrdquo; radiator technology does not allow the fluid to freeze, precluding the best available refrigerant ndash; Ammonia ndash; to be used for room-temperature applications.nbsp; The proposed Passive Variable Heat Rejection Freeze-Tolerant Direct Condensation Deployable Radiator offers an innovative method of (i) autoregulating the heat rejection just enough to condense the vapor load back to saturated liquid, (ii) allowing the heat transport loop to operate while the radiator fluid is frozen, and (iii) gracefully thawing out the radiator and return the loop to normal operation