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Radiator stagnation is being explored to design single loop thermal control systems using Galden HT170 for heat rejection systems requiring large turn-down ratios. A previous Small Business Innovation Research (SBIR) Phase 1 studied sequential stagnation in a system of different length tubing. As part of a follow-on Phase 2, tests were performed to study the effects of adding a facesheet in a manner consistent with typical spacecraft radiator effectiveness. Onset of stagnation for different tubes was demonstrated for a given inlet temperature by lowering mass flow rate. Temperature and/or mass flow rate were increased to investigate stagnation recovery. A Thermal Desktop® model was built to simulate the test. Test results and modeling comparisons are presented.

Paragon Space Development Corporation is developing a single-loop, non-toxic, active pumped thermal control design for robust, reliable operation near stagnation regimes as experienced in low power/cold environments. This research uses a safe fluid named Galden® HT170, manufactured by Solvay Solexis that has lower temperature stalling characteristics over typical space-based radiator fluids such as propylene glycol/water (PGW). A test bed and stagnation test article were designed, built and then modeled using Thermal Desktop® software to explore tube stagnation using Galden. Tube stagnation was sequentially controlled in each tube in a predictable manner, while collecting data to validate models. The data compared well to the modeling results. Fluid-compatibility results also showed no degradation to the fluid or to the aluminum tubing and weld materials and structures

Paragon Space Development Corporation has created the only privately developed and owned Environmental Control and Life Support Systems Human-rating Facility (EHF) for spacecraft ECLSS system testing in a dynamic flight environment. The facility allows for simulating the very stressing dynamic changes in pressure, altitude and operating conditions for human spaceflight, including suborbital and orbital flight profiles as well as Mars and lunar environments. Testing of space suits, pressure suits and ECLS systems can be performed for failure scenarios not able to be duplicated during flight testing. The facility allows for testing of ECLSS hardware before integration with the spacecraft, lowering ECLSS development cost and time, thereby reducing program risk. This paper describes the detailed design and setup of the EHF as well as the various capabilities.

Suborbital flight provides unique design considerations for Environmental Systems. The comparison of an aircraft like flow through system and a spacecraft like closed environmental system is presented. Considerations for safety aspects associated with pressure control and redundancy are also addressed.