Browsing by Author "Klaus, David M."
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Item Characterization of Potassium Superoxide and a Novel Packed Bed Configuration for Closed Environment Air Revitalization(44th International Conference on Environmental Systems, 2014-07-13) Holquist, Jordan B.; Klaus, David M.; Graf, John C.Potassium superoxide (KO2) has been used in environmental control and life support systems (ECLSS) ranging from early Soviet spacecraft to self-contained self-rescuer devices for mine safety. By reacting with moisture carried in an air flow, KO2 releases oxygen and absorbs carbon dioxide. Because KO2 performs multiple functions required in closed environments (humidity removal, oxygen provision, carbon dioxide removal), and its reactions are triggered by a metabolic waste product (respired moisture), KO2 can be used as a basis for a simple, passive, and compact air revitalization system. The performance of KO2, lithium hydroxide, and silica gel with respect to carbon dioxide adsorption, oxygen release, and humidity control is reviewed. The operation of these granular chemicals was characterized in sequentially layered, plug-flow, packed beds with both steady state and transient (feedback controlled) inlet conditions for durations of up to 10 days. Because the output of these chemical beds in a symmetric layering configuration either exceeded or fell short of metabolic requirements at different times, an alternative packing configuration was desired. As a result of this research, a proposed system concept of an asymmetrically packed granular bed was developed to provide constant output environmental control utilizing KO2, lithium hydroxide, and silica gel. Such a system can be initially designed to meet an expected metabolic loading profile for a given duration. In this way, a reliable and volumetrically efficient air revitalization system can be provided for applications including mine rescue shelters, military vehicles, and human space transportation vehicles for durations of up to 10 days.Item Characterizing the Effect of Gravity on a Freezable Water Heat Exchanger with Respect to Flow Orientation(45th International Conference on Environmental Systems, 2015-07-12) Nabity, James A.; Holquist, Jordan B.; Milanese, Matthew J.; Klaus, David M.Water-based freezable heat exchangers hold promise to simplify spacecraft thermal control systems through self-regulation of heat rejection as some of the flow channels within the device become blocked with ice. This Phase Change Material (PCM) based heat exchanger approach also adds endothermic heat storage capacity to a thermal control system as the water freezes when the radiator rejects heat to cold thermal environments. It then reduces the net heat load to the radiator by melting the solid-phase coolant during periods of high cabin temperatures or when the spacecraft is in a hot thermal environment. Unfortunately, these heat exchangers are susceptible to catastrophic damage if the volumetric expansion during water freeze is not accommodated. Solving this design challenge is complicated when using ground-based experiments to predict the freeze-thaw behavior and performance of PCM heat exchangers in microgravity, since the fluid behaves differently in space than on Earth. Buoyancy-induced convection and stratification of the flow are absent in microgravity, and thus the fluid momentum and interfacial phenomena dominate the flow behavior and heat exchanger performance. For these reasons, the design and setup of laboratory experiments that provide insight into the effects of gravity on freezable heat exchangers are important. Herein, we describe a test rig that allows us to vary the orientation of the heat exchanger relative to the gravity vector and obtain the data needed to quantify heat exchanger performance and operational behavior under different flow configurations. We present and discuss key results from the freeze-thaw experiments.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 Incorporating Bioastronautics into an Engineering Curriculum(44th International Conference on Environmental Systems, 2014-07-13) Klaus, David M.The discipline of Bioastronautics can be summarized as addressing biological, behavioral and medical aspects governing humans and other living organisms in a space flight environment; and includes the design of payloads, spacesuits, spacecraft habitats and life support systems. In short, it spans the study and support of life in space. Interestingly, however, this captivating field of study is not a typical component of an engineering curriculum. This paper lays out a foundation for incorporating different aspects of human spaceflight through a series of courses that can be adopted as part of an undergraduate or graduate engineering program, or used as a guide for adding select material to existing traditional courses.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.