Spacecraft thermal control systems typically perform three key functions — heat acquisition, heat transport, and heat rejection — in addition to those of insulation, heat generation, and heat storage. In a typical pumped fluid-loop spacecraft thermal control system, heat is acquired from heat-generating equipment via coldplates, transported via pumps and cooling lines, and rejected to space via radiators, evaporators, and/or sublimators. Combining all three of these functions into one hardware component can provide system mass savings by combining multiple pieces of hardware into a single piece, and providing additional fault tolerance without the need for redundant hardware.
This invention, the Passive Integrated Sublimator Driven Coldplate (ISDC-P), provides cooling to equipment in a manner similar to a standard flow-through coldplate. However, rather than supplying cooling via a pumped cooling loop, the ISDC-P collects energy via a passive heat pipe plate that transports waste heat to a sublimator where the heat is rejected to a low-pressure environment.
The key to the ISDC-P is the combination of the coldplate and the sublimator into one piece of hardware. The thermal energy from the heat-generating device can now be rejected directly to space via sublimation in the ISDC-P.
The ISDC-P has several layers. The mounting surface consists of an HiK™ plate on which heat-generating components such as avionics boxes are attached. This heat is transferred via a series of longitudinal heat pipes to the sublimator mounting position. A second layer of transverse heat pipes distributes the heat evenly over the sublimator interface surface to optimize its performance. The sublimator consists of an interface surface under which is a feedwater layer, followed by a porous sublimator surface. Heat is transferred from or across the feedwater layer to the sublimator surface. The feedwater layer may contain interstitial material such as metal foam or fins to enhance heat transfer across the feedwater layer. The porous sublimator surface provides a substrate on which the feedwater freezes and subsequently sublimates to space. The resulting vapor flows out of the device through an exhaust path. One or more ISDC-P units can be supported by a single set of tanks and valves to initiate feedwater flow to support one or more avionics locations.
Due to the benefits for short-duration missions, this could directly impact the upper stages of small, medium, and heavy launch vehicles, including the targeted Space Launch System (SLS), as well as boost stages for high-altitude orbits or other systems requiring peak load thermal management. Many of the planned technology demonstration missions will require simple, safe, and reliable platforms in which the ISDC would assist in reducing the weight and complexity.