Browsing by Author "Massina, Christopher J."
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Item Evaluation of Heat Transfer Strategies to Incorporate a Full Suit Flexible Radiator for Thermal Control in Space Suits(44th International Conference on Environmental Systems, 2014-07-13) Massina, Christopher J.; Klaus, David M.; Sheth, Rubik B.Traditionally, thermoregulation of space walking astronauts has been achieved by the sublimation of water to the vacuum of space. Future missions call for the need to achieve robust closed-loop thermal control to reduce or eliminate extravehicular activity (EVA) burden on consumables. The current leading concept to achieve closed-loop thermal control is the Space Evaporator-Absorber-Radiator (SEAR). The SEAR is nearly capable of achieving the desired non-venting capability; however, carried water mass for evaporation will still be comparable to a sublimator-based system. Evolution from systems which leverage sublimation or evaporation of water as the primary heat rejection mechanism to a system which directly leverages the local radiation environment may provide another means of achieving robust closed-loop space suit thermal control at a reduced system mass. Previous EVA thermal control investigations that utilize radiation have generally limited radiator surface area to the available size of the portable life support system backpack: about 0.85 m2. The utilization of a full suit flexible radiator increases this area by a factor of ~4 for traditional gas pressure suits and ~2 for the advanced mechanical counter pressure suit concept. Radiator heat dissipation capacity is also dictated by radiator temperature, radiator surface properties (e.g. emissivity, absorptivity) and the local thermal environment. As such, suit radiator surface temperature should be maximized to the extent possible for the flexible radiator architecture to be feasible under most circumstances. Here we present radiator surface temperature guidelines for the full suit flexible radiator architecture in steady-state environments. Results identify favorable thermal environments in which a full suit flexible radiator can reject a nominal 300 W metabolic heat load produced within a space suit.Item Modeling the Human Thermal Balance in a Space Suit using a Full Surface, Variable Emissivity Radiator(45th International Conference on Environmental Systems, 2015-07-12) Massina, Christopher J.; Nabity, James A.; Klaus, David M.Space suit thermoregulation has traditionally been achieved by sublimating water to space. Incorporation of a full suit radiator using variable emissivity electrochromic devices is one proposed alternative for reducing or eliminating the water mass loss incurred for cooling by sublimation. This concept allows the majority of a space suit’s outer surface area to operate as a radiator, while the electrochromic’s controllable surface properties enable variable heat rejection rates. Internal heat loads are balanced to the total radiated energy by selecting the emissivity of the electrochromic surfaces. Steady-state evaluations of this concept indicate that high metabolic loads and/or hot lunar surface locations can exceed the radiative heat dissipation capacity, however, the net impacts of dynamic internal and external environments on an astronaut’s thermal condition have not yet been fully considered for this application. Here we present an evaluation method for determining transient environmental thermal impacts on a simulated human in a space suit using variable radiative cooling. Four test scenarios are used to illustrate the utility of the method for an astronaut in a simplified lunar pole environment. The scenarios considered were chosen such that comfort requirements could be maintained throughout the duration of each of the simulations. Overall, the approach described here can be used in future investigations to advance the characterization of the electrochromic suit radiator architecture’s working environment envelope.