Anthony J. Hanford

Testing of Commercial Hollow Fiber Membranes for Spacesuit Water Membrane Evaporator

Three commercial-off-the-shelf (COTS) hollow fiber (HoFi) membrane evaporators, modified for low pressure, were tested in a vacuum chamber at pressures below 33 pascals as potential space suit water membrane evaporator (SWME) heat rejection technologies. Water quality was controlled in a series of 25 tests, first simulating potable water reclaimed from waste water and then changing periodically to simulate the ever concentrating make-up of the circulating coolant over that is predicted over the course of 100 EVAs. Two of the systems, comprised of non-porous tubes with hydrophilic molecular channels as the water vapor transport mechanism, were severely impacted by the increasing concentrations of cations in the water. One of the systems, based on hydrophobic porous polypropylene tubes was not affected by the degrading water quality, or the presence of microbes. The polypropylene system, called SWME 1, was selected for further testing. An inverse flow configuration was also tested with SWME 1, with vacuum exposure on the inside of the tubes, provided only 20% of the performance of the standard configuration. SWME 1 was also modified to block 50% and 90% of the central tube layers, and tested to investigate performance efficiency. Performance curves were also developed in back-pressure regulation tests, and revealed important design considerations arising from the fully closed valve. SWME 1 was shown to be insensitive to air bubbles injected into the coolant loop. Development and testing of a full-scale prototype based on this technology and these test results is in progress.

Systems Analysis of Life Support for Long-Duration Missions

Work defining advanced life support (ALS) technologies and evaluating their applicability to various long-duration missions has continued. Time-dependent and time-invariant costs have been estimated for a variety of life support technology options, including International Space Station (ISS) environmental control and life support systems (ECLSS) technologies and improved options under development by the ALS Project. These advanced options include physicochemical (PC) and bioregenerative (BIO) technologies, and may in the future include in-situ resource utilization (ISRU) in an attempt to reduce both logistics costs and dependence on supply from Earth. PC and bioregenerative technologies both provide possibilities for reducing mission equivalent system mass (ESM). PC technologies are most advantageous for missions of up to several years in length, while bioregenerative options are most appropriate for longer missions. ISRU can be synergistic with both PC and bioregenerative options.

Hollow Fiber Space Suit Water Membrane Evaporator Development for Lunar Missions

The Space Suit Water Membrane Evaporator (SWME) is the baseline heat rejection technology selected for development for the Constellation lunar suit. The Hollow Fiber (HoFi) SWME is being considered for service in the Constellation Space Suit Element (CSSE) Portable Life Support Subsystem (PLSS) to provide cooling to the thermal loop through water evaporation to the vacuum of space. Previous work described the test methodology and planning to compare the test performance of three commercially available hollow fiber materials as alternatives to the sheet membrane prototype for SWME: 1) porous hydrophobic polypropylene, 2) porous hydrophobic polysulfone, and 3) ion exchange through nonporous hydrophilic modified Nafion. Contamination tests were performed to probe for sensitivities of the candidate SWME elements to organics and non-volative inorganics expected to be found in the target feedwater source, i.e., potable water provided by the vehicle. The resulting presence of precipitate in the coolant water could plug pores and tube channels and affect the SWME performance. From this prior work, a commercial porous hydrophobic hollow fiber was selected to satisfy both the sensitivity question and the need to provide 800 W of heat rejection. This paper describes the trade studies, the design methodology, and the hollow fiber test data used to design a full

Key Gaps for Enabling Plant Growth in Future Missions

Growing plants to provide food or psychological benefits to crewmembers is a common vision for the future of human spaceflight, often represented in media and in serious concept studies. The complexity of controlled environment agriculture, and plant growth in microgravity have and continue to be the subject of dedicated scientific research. However, actually implementing these systems in a way that will be cost effective, efficient, and sustainable for future space missions is a complex, multi-disciplinary problem. Key questions exist in many areas: human medical research in nutrition and psychology, horticulture, plant physiology and microbiology, multi-phase microgravity fluid physics, hardware design and technology development, and system design, operations and mission planning. This paper describes key knowledge gaps identified by a multi-disciplinary working group within the National Aeronautics and Space Administration (NASA). It also begins to identify solutions to the simpler questions identified by the group based on work initiated in 2017. Growing plants to provide food or psychological benefits to crewmembers is a common vision for the future of human spaceflight, often represented in media and in serious concept studies. The complexity of controlled environment agriculture, and plant growth in microgravity have and continue to be the subject of dedicated scientific research. However, actually implementing these systems in a way that will be cost effective, efficient, and sustainable for future space missions is a complex, multi-disciplinary problem. Key questions exist in many areas: human medical research in nutrition and psychology, horticulture, plant physiology and microbiology, multi-phase microgravity fluid physics, hardware design and technology development, and system design, operations and mission planning. This paper describes key knowledge gaps identified by a multi-disciplinary working group within the National Aeronautics and Space Administration (NASA). It also begins to identify solutions to the simpler questions identified by the group based on work initiated in 2017.