Browsing by Author "Chen, Thomas"
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Item Analysis of Crew Quarters � ECLSS Interactions for Improved Temperature Control and CO2 Mitigation(50th International Conference on Environmental Systems, 7/12/2021) Chen, Thomas; Ewert, MichaelCrewmembers spend a substantial amount of time within their crew quarters (CQ) as a source of heat and CO2. Currently, CQs on-board the International Space Station (ISS) exchange air with the cabin aisle to provide a comfortable space, i.e. satisfactory temperature, humidity, and CO2 levels. However, limited temperature and CO2 concentration differences between the cabin and CQ necessitates high air exchange rates to achieve suitable CO2 washout and thermal control. Exploration spacecrafts may try to leverage the various air revitalization streams to improve upon the current configurations. Interaction between the Environmental Control and Life Support System (ECLSS) and the CQ have been analyzed to understand the effect on CO2 washout and thermal efficiencies. Both the direct delivery of conditioned air from the Temperature and Humidity Control (THC) and low CO2 air delivery from the Carbon Dioxide Removal Assembly (CDRA) have been studied. Independent delivery from these sources are inadequate to effectively control both temperature and CO2 levels below thresholds of 72.4 �F and 2 mm Hg, respectively. Conditioned THC air can control temperature with significantly lower air flow rates; however, poor CO2 washout leads to its accumulation. In contrast, CDRA air delivery can effectively lower CO2 concentrations which would reduce crewmember exposure to elevated CO2 levels; however, the hot CDRA air is poor at controlling temperature. A combination of both strategies, i.e. THC + CDRA air delivery, are able to provide crew comfort and reduce CO2 concentrations while significantly reducing air flow rates by ~75% even in the worst-case scenario (95th percentile crewmember and maximum CDRA air temperature). Additionally, this design implements a Nafion membrane prior to air delivery to pre-condition the CDRA air to provide a stable air temperature. This study illustrates the analysis of different ECLSS-CQ configurations and the trade-offs to utilizing different air revitalization streams.Item Benefits of Trash-to-Gas versus Jettison of Waste via Trash-Lock for Mars Transit(2023 International Conference on Environmental Systems, 2023-07-16) Chen, Thomas; Ewert, MichaelHuman exploration missions to Mars pose difficulties due to the significant waste that will be generated during transit, which will need to be carried along or disposed of in some fashion. Waste removal from the spacecraft decreases the spacecraft’s mass as well as the associated logistic items necessary for storing the waste. A mission propellant analysis was performed to highlight the mass benefits that may be accessed via waste removal. The propellant mass savings were determined for different waste removal rates (2.9 – 11.6 kg/day) with the highest removal rate leading to the greatest propellant savings of 7,785 kg for an 850-day round-trip mission. Due to these benefits, two methods for waste reduction were studied for the 850-day Mars mission: Trash-to-Gas (TtG) and physical jettison via a trash-lock. The trash-to-gas methods considered were combustion, steam reforming, and pyrolysis, which convert waste into ventable gases (e.g., CO2, CO, CH4, etc.). Combustion and steam reforming require a co-reactant (O2 and/or H2O). Therefore, additional processing units or integration with the spacecraft’s environmental control and life support system (ECLSS) are required to facilitate recycle of the pertinent species. In contrast, pyrolysis is a purely thermal degradation process, which can operate as a standalone system; however, a lower percentage of waste is gasified with pyrolysis. The study herein compares standalone TtG (e.g., Advanced Organic Waste Gasifier, Plasma Pyrolysis, etc.), integrated TtG-ECLSS (e.g., Orbital Syngas Commodity Augmentation Reactor, Incineration/Gasification, etc.), and physical jettison. Each system’s mass, volume, power, and cooling requirements were compared via an equivalent system mass (ESM) analysis to ascertain potentially promising technologies that can achieve efficient waste removal while minimizing their own spacecraft load. This study highlights the advantages and disadvantages the different waste management technologies and provides recommendations on the promising technologies based on the ESM metric and propellant mass savings.Item Design of a Jettison System For Space Transit Vehicles(51st International Conference on Environmental Systems, 7/10/2022) Sepka, Steve; Ewert, Michael; Lee, Jeff; Chen, Thomas; Venigalla, ChandrakanthMany options to re-use waste are currently being developed by NASA. These include combustion, compaction, torrefaction, and converting waste materials to an easily stored base polymer for future use. Human exploration missions require large amounts of supplies such as food, clothing and spare parts. A many-month journey to Mars will still result in the generation of a substantial amount of problematic waste products. It is thought that this waste must be discarded to enable a Mars transit mission. The most cost-effective, reliable, and safest method to address this problem may be to simply jettison these materials from the spacecraft. The ability to jettison requires a multi-component integrated system design. Major components include a launcher, airlocks, trash bags, and tracking system. Depending upon mission requirements, a jettison dedicated airlock may be necessary. In other cases, the crew airlock might be all that is needed. This paper will discuss these design issues and give guidance to a pathway forward.Item Trade Study Analysis of a Cryogenic Oxygen Architecture for Lunar Outpost Life Support(51st International Conference on Environmental Systems, 7/10/2022) Chen, Thomas; Sweterlitsch, JeffreyA trade study was performed to compare the use of cryogenic liquid oxygen (LOX) with high pressure gaseous oxygen (GOX) and electrolysis approaches for Lunar outpost life support, which consists of a surface habitat and pressurized rover. This analysis presents the relevant mission details pertaining to a Lunar outpost architecture, discusses the viable concept of operations (ConOps) for each architecture, and compares the equivalent system mass (ESM) of the cryogenic LOX, high pressure GOX, and electrolysis approaches across different parameter trades, e.g. mission duration or extravehicular activity (EVA) frequency, for the single and 10-year mission architectures. For a single nominal mission, high pressure GOX is favored for short missions (< 50 days); cryogenic LOX is favored for a wide-range of mission durations (50 � 270 days); and the electrolysis approach is favored for long missions (> 270 days). However, when considering a 10-year mission architecture, each additional resupply negatively impacts cryogenic LOX due to the additional replacement tankage. Thus, over a 10-year mission, an electrolysis approach, which can provide all life support O2 needs utilizing solely recovered H2O, appears to be favored over cryogenic LOX. However, a real electrolysis system may need resupplied H2O due to incomplete closure of the air revitalization loop. Thus, the cryogenic LOX approach was compared with the electrolysis approaches utilizing 100% resupplied or 100% recovered H2O to approximate the resupplied to recovered H2O ratio, i.e. the degree of loop closure, where one approach trades over the other. Additionally, gaps were identified, which are expected to affect the viability and trade of LOX. These include the development of cryogenic pumps and vaporizers to generate high pressure GOX from LOX as well as understanding payload limitations which can affect O2 resupply. This analysis highlights the possible viability and favorable trade of cryogenic LOX depending on mission parameters.