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NASA's proposed lunar lander, Altair, will be exposed to vastly different external temperatures following launch till its final destination on the moon. In addition, the heat rejection is lowest at the lowest environmental temperatures (0.5 kW @ 4K) and highest at the highest environmental temperature (4.5 kW @ 215K). This places a severe demand on the radiator design to handle these extreme turn-down requirements. A radiator with digital turn-down capability is currently under study at JPL as a robust means to meet the heat rejection demands and provide freeze protection while minimizing mass and power consumption. Turndown is achieved by independent control of flow branches with isolating latch valves and a gear pump to evacuate the isolated branches. A bench-top test was conducted to characterize the digital radiator concept. Testing focused on the demonstration of proper valve sequencing to achieve turn-down and recharge of flow legs.

The current regenerative CO, Removal System (RCRS) is a two sorbent bed, vacuum pressure swing, CO, adsorption/desorption system. While one bed is removing CO, and moisture from cabin air, the other bed is vented to space vacuum so that the CO, and water can be desorbed off the bed. To guard against the possibility that cabin air can be vented directly to space, 11 valves and a series of mechanical linkages control the flow paths. The RCRS has one set of adsorption beds, one fan, one compressor, and two redundant controllers. A single failure could cause a loss of function; so a contingency CO, removal system must, and is flown. A new sorbent material has been developed that greatly decreases the required size of the sorbent bed. A new valve design is proposed that replaces the complex series of valves and linkages with one moving part. Using the new bed material and new valve design, system size and weight can be cut approximately in half.

In a crewed spacecraft environment, atmospheric carbon dioxide (CO2) and moisture control are crucial. Hamilton Sundstrand has developed a stable and efficient amine-based CO2 and water vapor sorbent, SA9T, that is well suited for use in a spacecraft environment. The sorbent is efficiently packaged in pressure-swing regenerable beds that are thermally linked to improve removal efficiency and minimize vehicle thermal loads. Flows are controlled with a single spool valve. This technology has been baselined for the new Orion spacecraft, but additional data was needed on the operational characteristics of the package in a simulated spacecraft environment. One unit was tested with simulated metabolic loads in a closed chamber at Johnson Space Center during the latter part of 2006. Those test results were reported in a 2007 ICES paper.

Research into increased capacity solid amine sorbents has found a candidate (SA9T) that will provide enough increase in cyclic carbon dioxide removal capacity to produce a fully redundant Regenerative Carbon Dioxide Removal System (RCRS). This system will eliminate the need for large quantities of backup LiOH, thus gaining critical storage space on board the shuttle orbiter. This new sorbent has shown an ability to package two fully redundant (four) sorbent beds together with their respective valves, fans and plumbing to create two operationally independent systems. The increase in CO2 removal capacity of the new sorbent will allow these two systems to fit within the envelope presently used by the RCRS. This paper reports on the sub-scale amine testing performed in support of the development effort. In addition, this paper will provide a preliminary design schematic of a fully redundant RCRS.

The International Space Station Alpha Electrical Power System has a thermal control system to remove heat from the batteries and power distribution electronics. A major subsystem of this thermal loop is the Pump and Flow Control Subassembly (PFCS) which functions as an ammonia fluid distribution and control subsystem. This paper will detail the development, construction and operational performances of the PFCS hydraulic elements operating with an ammonia fluid. These elements include flow meter, accumulator, flow control valve, and pumps. The electronics which are utilized to operate these hydraulic elements will also be described. The combination of these hydraulic and electronic elements form a subassembly to safely control a hazardous, low viscosity fluid.