Browsing by Author "Escobar, Christine"
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Item 1st International Space Ecology Workshop - Research Needs & Roadmap to the Future(2023 International Conference on Environmental Systems, 2023-07-16) Escobar, Christine; Grubbs, Patrick; Lantin, Stephen; Shevtsov, Jane; Taub, Frieda; Damlo, SherriSelf-sufficient life support systems will be crucial for meeting the physical and mental health needs of crew during long-term, deep space exploration missions and for maintaining a permanent human presence in space. Closing the material loop with food production and waste recycling is necessary to reduce reliance on Earth resupply. Closed ecological systems (CES) can utilize a combination of biological, ecological, and physicochemical processes to support human life. A space habitat can be considered an artificial ecosystem in which human beings exchange energy and material with other system components and their extraterrestrial environment. The inaugural International Space Ecology Workshop was held on October 22, 2022, to promote and organize CES research internationally and to reignite interest in the ecological systems approach to space life support. This workshop brought together engineers, space biologists, and ecologists to discuss the past, present, and future of CES that could enable indefinite, sustainable human exploration of space, as well as sustainable living on Earth. Specific workshop goals were to review research needs and knowledge gained to date, connect active professionals in the field, and plan next steps for closing knowledge and technology gaps. This paper summarizes the proceedings and a Space Ecology Roadmap for prioritizing and guiding future action.Item Capillary Provision of Water and Nutrients to Plants Grown in Microgravity(2020 International Conference on Environmental Systems, 2020-07-31) Nabity, James; Pitts, Ray; Rehmeier, Jacob; Weislogel, Mark; Escobar, Christine; Shaffer, Brett; Escobar, AdamPassive provision of water and nutrients for the growth of plants in microgravity environmental systems can effectively be accomplished through the exploitation of capillary forces in various geometries, such as a network of wetted open interior corners. Provided the Concus-Finn condition is satisfied, capillary flows may be established along conduits that consist of simple interior corners (or ‘wedges’). A numerical free surface solver tool was employed to predict capillary flow of water to inform the design and construction of test articles for use in drop tower experiments. In addition, single and parallel flow path configurations were investigated with consideration for harvesting duckweed, a micro-flowering plant, in a microgravity environment. We report the effects of material, surface conditions, and interior corner half-angle on capillary performance. Titanium, glass and polymeric materials with factory, machined, and shot peened surfaces were used in experiments with deionized water and duckweed. The results guided the advanced development of micro-plant growth beds.Item Defining ECLSS Robustness for Deep Space Exploration(47th International Conference on Environmental Systems, 2017-07-16) Escobar, Christine; Nabity, James; Klaus, DavidHuman exploration of deep space will require Environmental Control and Life Support Systems of increasing dependability as mission duration and distance from Earth increases. As crews travel to distant unexplored environments, designers will need heightened confidence in life support availability under increasing levels of uncertainty and risk. Variation in system performance, environmental conditions, resource consumption, waste generation, and even mission characteristics will lead to unexpected responses, increased likelihood of failures, and even design obsolescence. The cost of system failures will also rise, due to launch mass and volume constraints, time and cost of resupply, and reduced ability to abort to Earth. If not accounted for early in design, this increased risk and cost of uncertainty might preclude the economic feasibility of human deep space exploration. The choice of an ECLSS architecture will include many different combinations of technologies that fulfill the functions of atmosphere revitalization, waste removal, and the provision of food and water. The difficult question facing ECLSS designers is how to optimize for the system performance and cost effectiveness necessary for mission feasibility. How do we reduce mass, energy usage, and waste while also ensuring availability of critical life support functions? An optimal architecture must take into account many facets of system performance, such as quality, safety, reliability, and maintainability. Exploration life support systems must continue functioning under harsh conditions, for long durations, without support, and with limited resources or resupply. This review discusses sources of uncertainty in deep space ECLSS design and potential impacts on system functionality. The concept of robustness is proposed to characterize and improve ECLSS performance in off-nominal conditions and abnormal operation. The characterization of ECLSS robustness will lay the foundation for future work in identifying design features and practices for sustaining operation in the face of the uncertainty of deep space missions.Item Duckweed: A Tiny Aquatic Plant with Enormous Potential for Bioregenerative Life Support Systems(47th International Conference on Environmental Systems, 2017-07-16) Escobar, Christine; Escobar, AdamSelf-sufficiency of space life support systems is crucial for long-duration exploration missions. NASA’s Technology Roadmap states that this will be achieved through resource recovery, system closure, high-reliability, autonomous control, and minimal use of expendables. Regenerative space life support will undoubtedly require food production to recover nutrients and close the carbon loop. Biological plant based systems also provide multiple life support functions such as CO2 removal, oxygen production, water recovery, and waste recycling. Technologies that both treat waste and produce food with minimal resources (such as energy and water) enable sustainable agriculture on Earth, benefiting populations in water and nutrient scarce regions. Duckweed (Lemna minor) is a tiny flowering plant with enormous potential for bioregenerative space life support. This small angiosperm is gaining global recognition as a powerful and ecologically friendly means of absorbing nutrients and other pollutants from wastewater. In addition, duckweed has a very high protein content and very little fibrous material, making it a 100% edible food supplement for diets lacking in protein. This review explores the capacity of Duckweed to provide a food supplement for a spacecraft crew that is high in protein, while recycling nutrients from human metabolic waste, removing and reducing CO2 from the cabin air, providing oxygen, and purifying metabolic waste water for drinking (ridding of the need to process brine). The review also presents challenges in the safe implementation of a duckweed wastewater treatment and food production system with recommendations for possible solutions and future research.Item Effects of additive manufacturing on capillary-driven fluid flow for provision of water and nutrients to free floating plants(48th International Conference on Environmental Systems, 2018-07-08) Shaffer, Brett; Eble, Jonathan; Nabity, James; Escobar, ChristineAn autonomous environmentally controlled floating plant cultivation system needs robust water and nutrient delivery for use in microgravity. Passive fluid control in the microgravity environment can be accomplished through the exploitation of capillary forces in various geometries, such as a network of isolated interior corners. Capillary driven flow largely depends on the surface properties of the material. Due to the Concus-Finn condition, capillary flow designs using interior corners are limited to a range of contact angles and interior corner half-angles which meet this condition. Additive manufacturing – particularly through the fused deposition method – introduces a new dimension to this design space in that the surface structure of the additively manufactured system is axially dependent. The resulting anisotropy in surface properties due to the layer-by-layer deposition of material means that the contact between a fluid and a particular surface depends upon the surface's orientation with respect to the print axis. This study develops an empirically derived relationship between controllable variables in the additive manufacturing process (particularly, layer height and axial orientation) and their effects on capillary flow rates of water through given channel geometries constructed from plastic and metal materials. These rates are compared to the rate of evaporation and the uptake requirements for sustenance of duckweed, as well as those from established and validated modeling methods that simulate fluid surface interactions between the fluid and material for a diverse set of geometries in order to identify whether or not the empirical relationship is material agnostic.Item Influence of ECLSS Performance on Spacecraft Habitability(51st International Conference on Environmental Systems, 7/10/2022) Nabity, James; Laughton, Kathleen; Escobar, ChristineSpace habitats for human missions shall keep the crew alive, healthy, happy and productive. Together, these attributes inform habitability, "How well does the space habitat meet crew physiological, psychological, and resource needs throughout the mission?" First and foremost, the Environmental Control and Life Support System (ECLSS) must provide for crew metabolic inputs and manage their outputs. Sustenance of human life, i.e. "keep the crew alive", demands that these be met. ECLSS performance and efficacy also influence crew physical and behavioral health which in turn may affect productivity. For these reasons, habitability management requires active real-time assessment of ECLSS performance. In this paper, we define habitability parameters and organize them according to their categorical influence on "alive, healthy, happy and productive." Paramount among these are ECLSS design and operational parameters, factors affecting crew safety, and space habitat facilities and features that accommodate the crew. We discuss, assess and rank each for inclusion in a habitability index that will characterize the overall health of the space habitat. We then recommend a subset of habitability parameters to quantify ECLSS robustness.Item Past, Present, and Future of Closed Human Life Support Ecosystems - A Review(47th International Conference on Environmental Systems, 2017-07-16) Escobar, Christine; Nabity, JamesDuring the development of human space exploration, the idea of simulating the Earth’s biosphere to provide human life support led to the convergence of space biology and the field of ecology to develop closed manmade ecological systems. A space habitat can be thought of as an ecological system of human beings exchanging energy and material within a spacecraft. In order to understand and control material and energy exchange processes, one must combine basic ecological principles with the knowledge gained through Bioregenerative Life Support Systems (BLSS) research to date. Experimentation in closed manmade ecosystems for spacecraft life support began in the 1960’s and over the years has shown biological life support systems to be realizable. By building on lessons learned, we can identify and prioritize future research objectives. Future development should focus on improved reliability of mechanical components, autonomous ecosystem control, closure of the carbon cycle (food generation and waste recycling), and the maintenance of long-term stability and robustness. A common need identified throughout all closed ecological life support systems (CELSS) research is mass and energy exchange models that enable intelligent autonomous control and design optimization. To validate mass balance models, integrated system level experiments are needed, but full-scale tests are time consuming and expensive. Small closed experimental ecosystems (microcosms) could allow observation of stability limits and response to perturbation with repeated short duration experiments. However, they must have proper scaling to represent larger system dynamics. Thus, the definition of non-dimensional ecological parameters (or invariant system descriptions) that define similarity between biological life support systems of different temporal and spatial scales is a potentially critical yet little studied research area that will enable prediction of mass and energy exchange for various system configurations and operating scenarios.Item Quantifying ECLSS Robustness for Deep Space Exploration(49th International Conference on Environmental Systems, 2019-07-07) Escobar, Christine; Nabity, James; Escobar, AdamHuman exploration of deep space will require Environmental Control and Life Support Systems of increasing robustness as mission duration and distance from Earth increases. As crews travel to distant unexplored environments, designers will need heightened confidence in life support availability under increasing levels of uncertainty and risk. Variation in system performance, environmental conditions, resource consumption, waste generation, and even mission characteristics will lead to unexpected responses, increased likelihood of failures, and even design obsolescence. The cost of system failures will also rise, due to launch mass and volume constraints, time and cost of resupply, and reduced ability to abort to Earth. If not accounted for early in design, this increased risk and cost of uncertainty might preclude human deep space exploration. We have previously defined ECLSS robustness as “the ability to maintain habitable conditions for crew survival and productivity over the mission lifetime under a wide range of conditions.” This wide range of conditions includes ordinary usage, finite occasional environmental disturbances or disruptions, and sustained changes in the system or mission context. ECLSS robustness must be quantifiable for design evaluation, comparison, improvement, and optimization. A robustness metric must quantify the system’s ability to maintain consistent performance (i.e. conditions necessary for crew productivity) in time, under perturbation of state, and in the event of system disturbance (failure or other shock). A robustness metric should address spacecraft habitability, not just crew survival; apply to all levels of system abstraction; apply to all design phases or levels of fidelity; be practical for use, relevant, and objective; and be compatible with existing assessment tools and all technology types. In this paper we assess several potential robustness metrics with respect to these criteria. Finally, an ECLSS robustness metric is proposed and discussed for future use in design evaluation and improvement.Item Supported Ionic Liquid Membrane for Selective CO2 Capture(50th International Conference on Environmental Systems, 7/12/2021) Nabity, James; Tata, Bharath; Armstrong, Isaac; Escobar, ChristineIn situ utilization of carbon dioxide (CO2) from the Mars atmosphere provides a critical element for on-surface crop production. The atmosphere management system for the MarsOasis� growth chamber provides CO2, recovers water and oxygen, and removes ethylene to maintain a hospitable atmosphere for the crops. A supported ionic liquid membrane (SILM) can selectively provide CO2 while rejecting carbon monoxide (CO) back to the Mars atmosphere. The SILM comprises an ionic liquid infiltrated into the pores of a thin physical membrane support such as polyethersulfone or nylon. Ionic liquids are most promising for their negligible vapor pressure, low melting points (many remain liquid below 0�C), thermal stability up to 100�C or greater, and solubilities (especially for water and/or acid gases) that depend upon the cation and anion that comprise the IL. The negligible vapor pressure means that fluid will not be lost from the membrane, a common problem with other liquid sorbents. The physical processes of sorption and solution-diffusion through the membrane are enhanced; in part, because the supported liquid membrane can be made much thinner than a purely physical membrane without blowing liquid out of the support or losing it to vaporization. Then, amine-, fluorine-, or nitrile-functionalized groups in the IL can further facilitate the highly selective transport since these compounds chemically interact with CO2 to increase its uptake and rate of diffusion. In this paper we report experiments to characterize a SILM for selective CO2 capture from surrogate atmospheres.Item μG-LilyPond™: Preliminary Design of a Floating Plant Pond for Microgravity(2020 International Conference on Environmental Systems, 2020-07-31) Escobar, Christine; Escobar, Adam; Power, Gabriel; Nabity, JamesVersatile, reliable, and efficient space crop production systems can provide nutritional supplementation and a psychological benefit to the crew, while potentially reducing the mass of food provision for long duration space exploration missions. Aquatic plants have enormous potential to provide atmosphere regeneration, edible biomass production, biofuel generation, and even metabolic wastewater treatment, but been little studied as potential food crops for space applications. μG-LilyPond™ is an autonomous environmentally controlled floating plant cultivation system for use in microgravity. The system expands the types of crops able to grow in space to include aquatic floating plants. μG-LilyPond™ is designed to have low maintenance, increased reliability with passive water delivery, volume efficiency, full life cycle support via vegetative propagation, close canopy lighting, and crop versatility. Through a NASA STTR Phase I project, Space Lab and the University of Colorado at Boulder established feasibility of floating aquatic plant cultivation in microgravity and developed the growth chamber system concept. In Phase II, the project team is developing a fully functional engineering demonstration unit (EDU) that will be used to verify and validate the µG-LilyPond™ design. The EDU will demonstrate low-TRL technologies (water transport, nutrient medium recycling, harvesting, close canopy PAR delivery, and radiant heat dissipation), as well as extensibility to support higher rooted plants. Finally, the µG-LilyPond™ water transport and harvesting capabilities will be tested in a relevant microgravity environment via a Blue Origin suborbital flight. This paper reviews the µG-Lilypond™ growth chamber system concept, performance predictions, and prototype demonstrations to date.