ALBERT

Description: The Advanced Exploration Systems (AES) Program's Atmosphere Resource Recovery and Environmental Monitoring (ARREM) Project have been developing atmosphere revitalization and environmental monitoring subsystem architectures suitable for enabling sustained crewed exploration missions beyond low Earth orbit (LEO). Using the International Space Station state-of-the-art (SOA) as the technical basis, the ARREM Project has contributed to technical advances that improve affordability, reliability, and functional efficiency while reducing dependence on a ground-based logistics resupply model. Functional demonstrations have merged new process technologies and concepts with existing ISS developmental hardware and operate them in a controlled environment simulating various crew metabolic loads. The ARREM Project's strengths include access to a full complement of existing developmental hardware that perform all the core atmosphere revitalization functions, unique testing facilities to evaluate subsystem performance, and a coordinated partnering effort among six NASA field centers and industry partners to provide the innovative expertise necessary to succeed. A project overview is provided and the project management strategies that have enabled a multidiscipinary engineering team to work efficiently across project, NASA field center, and industry boundaries to achieve the project's technical goals are discussed. Lessons learned and best practices relating to the project are presented and discussed.

Description: A subsystem architecture derived from the International Space Station's (ISS) Atmosphere Revitalization Subsystem (ARS) has been functionally demonstrated. This ISS-derived architecture features re-arranged unit operations for trace contaminant control and carbon dioxide removal functions, a methane purification component as a precursor to enhance resource recovery over ISS capability, operational modifications to a water electrolysis-based oxygen generation assembly, and an alternative major atmospheric constituent monitoring concept. Results from this functional demonstration are summarized and compared to the performance observed during ground-based testing conducted on an ISS-like subsystem architecture. Considerations for further subsystem architecture and process technology development are discussed.

Description: To support continued manned space exploration, the development of atmosphere revitalization systems that are lightweight, compact, durable, and power efficient is a key challenge. The systems should be adaptable for use in a variety of habitats and should offer operational functionality to either expel removed constituents or capture them for closedloop recovery. As mission durations increase and exploration goals reach beyond low earth orbit, the need for regenerable adsorption processes for continuous removal of CO2 and trace contaminants from cabin air becomes critical. Precision Combustion, Inc. (PCI) and NASA Marshall (MSFC) have been developing an Engineered Structured Sorbents (ESS) approach based on PCI s patented Microlith technology to meet the requirements of future, extended human spaceflight explorations. This technology offers the inherent performance and safety attributes of zeolite and other sorbents with greater structural integrity, regenerability, and process control, thereby providing potential durability and efficiency improvements over current state-of-the-art systems. The major advantages of the ESS explored in this study are realized through the use of metal substrates to provide structural integrity (i.e., less partition of sorbents) and enhanced thermal control during the sorption process. The Microlith technology also offers a unique internal resistive heating capability that shows potential for short regeneration time and reduced power requirement compared to conventional systems. This paper presents the design, development, and performance results of the integrated adsorber modules for removing CO2, water vapor, and trace chemical contaminants. A related effort that utilizes the adsorber modules for sorption of toxic industrial chemicals is also discussed. Finally, the development of a 4-person two-leg ESS system for continuous CO2 removal is also presented.

Description: Photocatalytic oxidation (PCO) is a maturing process technology that shows potential for spacecraft life support system application. Incorporating PCO into a spacecraft cabin atmosphere revitalization system requires an understanding of basic performance, particularly with regard to partial oxidation product production. Four PCO reactor design concepts have been evaluated for their effectiveness for mineralizing key trace volatile organic com-pounds (VOC) typically observed in crewed spacecraft cabin atmospheres. Mineralization efficiency and selectivity for partial oxidation products are compared for the reactor design concepts. The role of PCO in a spacecraft s life support system architecture is discussed.

Description: Engineered structured (ES) sorbents are being developed to meet the technical challenges of future crewed space exploration missions. ES sorbents offer the inherent performance and safety attributes of zeolite and other physical adsorbents but with greater structural integrity and process control to improve durability and efficiency over packed beds. ES sorbent techniques that are explored include thermally linked and pressure-swing adsorption beds for water-save dehumidification and sorbent-coated metal meshes for residual drying, trace contaminant control, and carbon dioxide control. Results from sub-scale performance evaluations of a thermally linked pressure-swing adsorbent bed and an integrated sub-scale ES sorbent system are discussed.

Description: Exploring the frontiers of deep space continues to be defined by the technological challenges presented by safely transporting a crew to and from destinations of scientific interest. Living and working on that frontier requires highly reliable and efficient life support systems that employ robust, proven process technologies. The International Space Station (ISS), including its environmental control and life support (ECLS) system, is the platform from which humanity's deep space exploration missions begin. The ISS ECLS system Atmosphere Revitalization (AR) subsystem and environmental monitoring (EM) technical architecture aboard the ISS is evaluated as the starting basis for a developmental effort being conducted by the National Aeronautics and Space Administration (NASA) via the Advanced Exploration Systems (AES) Atmosphere Resource Recovery and Environmental Monitoring (ARREM) Project.. An evolutionary approach is employed by the ARREM project to address the strengths and weaknesses of the ISS AR subsystem and EM equipment, core technologies, and operational approaches to reduce developmental risk, improve functional reliability, and lower lifecycle costs of an ISS-derived subsystem architecture suitable for use for crewed deep space exploration missions. The most promising technical approaches to an ISS-derived subsystem design architecture that incorporates promising core process technology upgrades will be matured through a series of integrated tests and architectural trade studies encompassing expected exploration mission requirements and constraints.

Description: The Advanced Exploration Systems Program's Atmosphere Resource Recovery and Environmental Monitoring (ARREM) project is working to mature optimum atmosphere revitalization and environmental monitoring system architectures. It is the project's objective to enable exploration beyond Lower Earth Orbit (LEO) and improve affordability by focusing on three primary goals: 1) achieving high reliability, 2) reducing dependence on a ground-based logistics resupply model, and 3) maximizing commonality between atmosphere revitalization subsystem components and those needed to support other exploration elements. The ARREM project's strengths include using existing developmental hardware and testing facilities, when possible, and and a well-coordinated effort among the NASA field centers that contributed to past ARS and EMS technology development projects.

Description: Photocatalytic oxidation (PCO) is a candidate process technology for use in high volumetric flow rate trace contaminant control applications in sealed environments. The targeted application for PCO as applied to crewed spacecraft life support system architectures is summarized. Technical challenges characteristic of PCO are considered. Performance testing of a breadboard PCO reactor design for mineralizing polar organic compounds in a spacecraft cabin atmosphere is described. Test results are analyzed and compared to results reported in the literature for comparable PCO reactor designs.

Description: Toxic chemical release into the cabin atmosphere is one of the three major emergency scenarios identified on the International Space Station (ISS). The release of anhydrous ammonia, the coolant used in the U.S. On-orbit Segment (USOS) External Active Thermal Control Subsystem (EATCS), into the ISS cabin atmosphere is one of the most serious toxic chemical release cases identified on board ISS. The USOS Thermal Control System (TCS) includes an Internal Thermal Control Subsystem (ITCS) water loop and an EATCS ammonia loop that transfer heat at the interface heat exchanger (IFHX). Failure modes exist that could cause a breach within the IFHX. This breach would result in high pressure ammonia from the EATCS flowing into the lower pressure ITCS water loop. As the pressure builds in the ITCS loop, it is likely that the gas trap, which has the lowest maximum design pressure within the ITCS, would burst and cause ammonia to enter the ISS atmosphere. It is crucial to first characterize the release of ammonia into the ISS atmosphere in order to develop methods to properly mitigate the environmental risk. This paper will document the methods used to characterize an ammonia leak into the ISS cabin atmosphere. A mathematical model of the leak was first developed in order to define the flow of ammonia into the ISS cabin atmosphere based on a series of IFHX rupture cases. Computational Fluid Dynamics (CFD) methods were then used to model the dispersion of the ammonia throughout the ISS cabin and determine localized effects and ventilation effects on the dispersion of ammonia. Lastly, the capabilities of the current on-orbit systems to remove ammonia were reviewed and scrubbing rates of the ISS systems were defined based on the ammonia release models. With this full characterization of the release of ammonia from the USOS TCS, an appropriate mitigation strategy that includes crew and system emergency response procedures, personal protection equipment use, and atmosphere monitoring and scrubbing hardware can be established.

Description: Atmospheric Revitalization (AR) is the term the National Aeronautics and Space Administration (NASA) uses to encompass the engineered systems that maintain a safe, breathable gaseous atmosphere inside a habitable space cabin. An AR subsystem is a key part of the Environmental Control and Life Support (ECLS) system for habitable space cabins. The ultimate goal for AR subsystem designers is to 'close the loop', that is, to capture gaseous human metabolic products, specifically water vapor (H2O) and Carbon dioxide (CO2), for maximal Oxygen (o2) recovery and to make other useful resources from these products. The AR subsystem also removes trace chemical contaminants from the cabin atmosphere to preserve cabin atmospheric quality, provides O2 and may include instrumentation to monitor cabin atmospheric quality. Long duration crewed space exploration missions require advancements in AR process technologies in order to reduce power consumption and mass and to increase reliability compared to those used for shorter duration missions that are typically limited to Low Earth Orbit. For example, current AR subsystems include separate processors and process air flow loops for removing metabolic CO2 and volatile organic tract contaminants (TCs). Physical adsorbents contained in fixed, packed beds are employed in these processors. Still, isolated pockets of high carbon dioxide have been suggested as a trigger for crew headaches and concern persists about future cabin ammonia (NH3) levels as compared with historical flights. Developers are already focused on certain potential advancements. ECLS systems engineers envision improving the AR subsystem by combining the functions of TC control and CO2 removal into a single regenerable process and moving toward structured sorbents - monoliths - instead of granular material. Monoliths present a lower pressure drop and eliminate particle attrition problems that result from bed containment. New materials and configurations offer promise for lowering cabin levels of CO2 and NH3 as well as reducing power requirements and increasing reliability. This chapter summarizes the challenges faced by ECLS system engineers in pursuing these goals, and the promising materials developments that may be part of the technical solution for challenges of crewed space exploration beyond LEO.