48th International Conference on Environmental Systems ICES-2018-276 8-12 July 2018, Albuquerque, New Mexico

The Next Steps for Environmental Control and Life Support Systems Development for Deep

Mark Jernigan1 NASA Johnson Space Center, Houston, TX 77058

Robyn Gatens2 and Jitendra Joshi3 NASA Headquarters, Washington, D.C. 20546

and

Jay Perry4 NASA Marshall Space Flight Center, Huntsville, AL 35812

Throughout the life of the International Space Station (ISS), NASA has developed, deliv- ered and operated a suite of progressively more capable environmental control and life support system (ECLSS) components and assemblies. These efforts have resulted in substan- tially reducing the supply chain necessary to sustain crews in flight and garnering invaluable lessons for sustained long term operations of the equipment. Currently, the ISS provides a unique platform for understanding the effects of the environment on the hardware. NASA’s strategy, already underway, is to evolve the ISS ECLSS into the Exploration ECLSS and perform a long-duration demonstration on ISS in preparation for deep space missions. This includes demonstrations of upgrades and/or new capabilities for waste management, atmos- phere revitalization, recovery, and environmental monitoring. Within the Advanced Exploration Systems Program under the Next Space Technologies for Exploration Partner- ships (NextSTEP) model, NASA intends to revise the architecture developed for ISS to make the systems completely independent of the Earth supply chain for the duration of a deep space crewed mission by increasing robustness, including prospective system monitoring to anticipate failures, designing for maintenance, repair and refurbishment, reducing spare part count through use of common components, and grouping subsystems into modular pal- lets to minimize interfaces and reduce complexity. The NextSTEP ECLSS will be a partnership between NASA and a competitively selected team of industry partners to pro- duce a closed loop long duration test capability to establish confidence that the systems will be able to work properly in the deep space environment for extremely long missions.

Nomenclature AR = atmosphere revitalization BAA = Broad Agency Announcement BPA = brine processing assembly DRA5 = Design Reference Architecture 5.0 DSG = Deep Space Gateway DST = Deep Space Transport ECLSS = environmental control and life support system EVA = ISS = International Space Station

1 NextSTEP GFE ECLSS Lead, Human Health and Performance Directorate, Mail Stop SA311. 2 Deputy Director, International Space Station Division, Mail Stop CJ000. 3 Lead for Technology Integration, Advanced Exploration Systems, Mail Stop CQ000. 4 Lead Engineer-Environmental Control Systems, Space Systems Dept., Mail Stop ES62. LSS = life support system NASA = National Aeronautics and Space Administration NextSTEP = Next Space Technologies for Exploration Partnerships PPE = personal protective equipment UWMS = universal waste management system WRM = water recovery and management MPa = mega-pascal psia = pounds per square inch absolute

I. Introduction HE environmental control and life support system (ECLSS) deployed aboard the International Space Station T (ISS) has provided the National Aeronautics and Space Administration (NASA) with valuable experience on functional deployment and long-term systems operations that will serve as a reference basis for future crewed space exploration beyond low-Earth orbit. In addition to this experience, the ISS affords a unique environment in which to demonstrate improved process technologies and logistics management concepts in preparation for these future mis- sions. Realizing future crewed exploration objectives1 builds on the foundation of nearly two decades of in-flight ECLSS operations experience gained aboard the ISS. Yet, to reach the next crewed exploration destinations requires advancing core ECLSS technologies to address obsolescence, improve logistics management and in-flight maintain- ability, and develop methods to increase and water recovery percentages. The initial life support systems delivered to ISS in the U.S. Laboratory Module, Destiny, included an open-loop four-bed molecular sieve (CO2) removal assembly, trace contaminant control assembly, temperature and humidity control systems, and stored oxygen and water replenished via -based logistics support. This system was adequate to support the initial crew of three; however, in order to increase the crew size to six without making resupply prohibitive, additional regenerative life support functions were required. To address this need, regenerative ECLSS hardware was delivered to the ISS in 2007 and 2009. This equipment included urine and potable water processing that recovers approximately 90% of crew urine and humidity condensate, and a water- electrolysis-based oxygen generation system. A functional scar was included in the oxygen generation system rack to accommodate a future CO2 reduction assembly. Initially installed in Destiny, this regenerative ECLSS hardware was moved permanently to Node 3 (Tranquility). In 2010, a Sabatier-based CO2 reduction system was installed in the oxygen generation subsystem rack. This addition allowed CO2 that was initially being vented overboard to be processed with H2 from the oxygen generation unit to produce water which is recycled. With this process in place, nearly 50% of the oxygen could be reclaimed from CO2. Although these systems had been in development since the early 1990s, they were still considered somewhat ex- perimental when deployed aboard the ISS. Over the past decade of operation, many lessons have been learned regarding the performance and reliability of these systems in the ISS microgravity environment. Though the current system is adequate to support long duration missions, its basic design and operations take advantage of the proximi- ty of the ISS to Earth and the ability to frequently resupply spare parts and consumable items. Therefore, improvements must be made to evolve the ISS ECLSS functionally into the system needed for deep space explora- tion. Given the resources needed to mature developmental systems into reliable operational systems, wholesale changes from the ECLSS state-of-the-art may be prohibitive as a strategy to achieve exploration goals. Instead, a strategy consisting of a combination of state-of-the-art component upgrades, new technologies, and targeted sup- plemental capabilities may yield results more rapidly and economically. The capability gaps by function that the current exploration ECLSS development and test campaign is addressing via using the ISS as a testbed have been defined. The following is an overview of each ongoing and planned activity.

II. ISS ECLSS Maturation The evolution of the ISS ECLSS into the Deep Space Exploration ECLSS is in and will continue through the early 2020s. Figure 1 provides an overview of developmental activities and flight demonstrations planned to be executed aboard the ISS by NASA and ISS international partners. Vertical arrows indicate when a flight demonstration or upgrade of a current system is planned aboard the ISS, while diamonds represent decision points or down-selection between alternate technologies. By 2021, the majority of down-selections and individual flight demonstrations will have been conducted, allowing NASA to begin a long- duration integrated test of the resulting Exploration ECLSS system. At the same time, these Exploration ECLSS technologies will become the baseline for the Deep Space Transport (DST) design work beginning in the early 2020s.

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Figure 1. ECLSS development roadmap to enable deep space exploration. While the testing aboard the ISS will be conducted in parallel with the initial DST design and development, there will be an opportunity to incorporate lessons learned prior to completion and launch of the DST to cis-lunar space in the late 2020s. Thus, the development and testing of the Exploration ECLSS aboard the ISS is a critical risk reduction step. Although the systems will not be packaged as they will in the DST module or integrated with the DST power, data, and thermal systems, the long-duration systems testing aboard the ISS allows performance and reliability to be evaluated in the unique cabin and microgravity environments that cannot be duplicated in ground-based testing facili- ties. NASA’s plan includes flight demonstration of at least three CO2 removal technologies. The best of these three CO2 removal approaches will be included in an integrated atmosphere revitalization system along with upgraded oxygen generation and trace contaminant control assemblies as well as a new CO2 reduction assembly capable of recovering >75% of the oxygen from CO2. A high pressure, high purity oxygen (O2) capability will also be developed to refill the 20.7 MPa (3000 psi) oxygen tanks used for extravehicular activity (EVA) and to provide contingency medical-grade oxygen. The current ISS urine and water processor assemblies will be upgraded to improve reliability and reduce consumables, and a new brine processor assembly (BPA) will be added to recover water from the urine processor brine. These improvements will result in >98% water recovery for the Exploration ECLSS water system. For solid waste management, a new universal waste management system (UWMS), or toilet, will be demonstrated aboard the ISS as well as deployed on board the Orion crew vehicle. Technologies to compact, stabilize, and recover useful resources from trash will also be demonstrated, along with possible fecal processing technologies. The current environmental monitoring approach aboard the ISS will be upgraded from time-intensive, limited methods that require sample return to ground-based laboratories for analysis to fully on-board, near real-time monitors that address the most important analytical targets and provide for data transmission to identify non-target substances. These include an atmosphere composition monitor that will measure major and trace gas constituents in the cabin, a contingency environmental monitor for fire by-products and other constituents measured by four different sensors aboard the ISS today, a water monitoring suite for measuring organic and inorganic contaminants in water, a microbial monitor, a particulate monitor, and an acoustic monitor. It is the goal that by the early 2020s, the ISS will

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transition to fully on-orbit environmental monitoring operations via either eliminating sample return for ground-based analysis or using these samples for validation checks of the on-orbit monitors and research purposes.

III. The NextSTEP Activities NASA initiated the Next Space Technologies for Exploration Partnerships (NextSTEP) Habitation Broad Agency Announcement (BAA) activities as a method to stimulate public-private partnership investment in conceptual designs for the habitats needed for deep space exploration missions. Phase I was completed at the end of fiscal year 2015, and consisted of conceptual designs for habitation concepts and an approach for an evolvable ECLSS suite of hardware sized to support the mission needs of the deep space missions. The ensuing phase II work calls for the construction of prototypes to conduct physical assessments of the attributes and characteristics of the phase I concepts to inform the requirements and constraints for the Deep Space Gateway (DSG) and DST flight development program. Five Industry teams were selected to produce ground based prototypes of a and to reduce overlap in design work. NASA decided to consolidate the ECLSS work into one effort to provide the conceptual designs for all of the teams. United Technologies was awarded a phase II contract to mature their phase I concept, and NASA is planning to use the outputs of that work as the foundation for making sure that each of the other phase II concepts are capable of accommodating the equipment and providing the needed services for it to operate. For the ECLSS development ef- forts under phase II, the primary objectives the following:  To advance the form, fit, and functional interfaces necessary to accommodate an evolvable ECLSS capability.  To investigate the application of smart monitoring systems to identify potential component failures.  To investigate an ECLSS physical layout that enables Earth-independent in-flight maintenance and repair. The success of these investigations with help enable technical advancement toward a highly-regenerative ECLSS for use in the NextSTEP cis-lunar habitat concepts which will inform the gateway and transport flight hardware development. These objectives are to be accomplished within the context of the five habitation provider prototype developments, and within a NASA reference implementation. However, it is noted that the habitat providers may elect to produce unique ECLSS concepts, process technologies, and components. In those exceptions, where unique ECLSS-related content offerings that complement NASA-sponsored exploration ECLSS developmental efforts are proposed by individual habitat providers, NASA’s goal is to support those activities with in-kind contributions (e.g. Government labor equivalents, loaned equipment) where possible. The goal of the refinement of ECLSS architecture is to enable deployment aboard multiple provider-developed habitat concepts.

IV. Key Architecture Attributes Although it is likely that most of the suite of equipment will be similar to components used aboard ISS in terms of process technologies and parts to take advantage of the long duration heritage and lessons learned through operations and the test campaign, the future crewed deep space exploration missions will require significant updates to the architecture to address areas of technology obsolescence, to become more independent from Earth for logistics sup- port, and to provide functional flexibility.2, 3 Advances in process technologies, changes among component and part suppliers, and changes in the market avail- ability of adsorbents, catalysts, and materials used in some ECLSS components used aboard the ISS present challenges relating to technology obsolescence. Given mission time horizons spanning over a decade, addressing ob- solescence will be a recurring challenge as has been experienced by the ISS Program. This challenge must be overcome for the future exploration-class ECLSS design by identifying key areas for obsolescence that may occur over the exploration program life cycle, identifying several suitable alternatives, preparing generalized technology specifications, and cultivating multiple suppliers. Like the ISS, the ECLSS for deep space exploration will likely need to be deployed incrementally due to launch mass and volume constraints, fiscal constraints, and evolving mission demands to reduce resupply of atmospheric gases, water, and other supplies as mission durations and the distance from Earth increases. Achieving an appropriate degree of ECLSS mass closure is a key component to becoming logistically Earth-independent. As well, designing the ECLSS to be maintainable in flight thus eliminating reliance on Earth-based maintenance depots is another key component to becoming Earth-independent for mission durations that may exceed 1000 days. Many ECLSS assem- blies and components that have been used successfully aboard the ISS will need to be redesigned to improve accessibility for maintenance, to reduce the number and mass of spare parts, and to improve system availability. The hardware design changes to provide for in-flight maintainability are expected to be substantial in order to allow for access to components for easy repair and replacement while striving to reduce the equipment part count and to make 4 International Conference on Environmental Systems

Figure 2. A simplified ECLSS block flow diagram illustrating functional evolution. maintenance activities achievable within the limited resources the crews will have during the mission. Investigation into smart systems technology may facilitate meeting this need by prospectively identifying which components require crew intervention before the failure actually occurs. The future ECLSS must provide operational flexibility and enable capability evolution across a number of explo- ration mission operational concepts as illustrated by Fig. 2. The functional capability aboard the DSG begins with an open loop core capability consisting of CO2 removal, trace contaminant control, temperature and humidity control, total atmosphere monitoring, and contingency atmosphere monitoring. Similar to the early ISS, the atmospheric gases and water will be resupplied. The intent for the initial capability provided by the DSG is to meet four crewmembers’ support needs for at least 30 days independent of the Orion crew transport vehicle. Capabilities independent of Orion provide maximum mission flexibility and allow the systems aboard Orion to retain optimum consumables to ensure margin for the crew’s safe return to Earth. This initial capability, shown in gray in Fig. 2, will evolve toward a future fully regenerative ECLSS end state ca- pable of supporting at least four crewmembers for mission durations of at least 1000 days as described in the Design Reference Architecture 5.0 (DRA5) described in 2009 and updated in 2014.4-6 The future ECLSS’s capacity, while sized to support four crewmembers, should provide functional margin to accommodate additional crewmem- bers wherever practical because current mission needs are soft and redesign is costly. Current deep space mission architectures feature long periods of quiescent operations when the crew is absent; therefore, the ECLSS must possess the resilience to handle these quiescent periods and return to full functionality for each crewed mission phase.7

V. An Evolvable Reference Architecture The evolvable architecture shown schematically by Fig. 2 provides for atmosphere revitalization, water recovery and management, environmental monitoring, and various habitation functions. The system design is guided by core requirements obtained from the NASA Human-System Standard (NASA-STD-3001, Vol. 2) supplement- ed by the Human Integration Design Handbook (NASA/SP-2010-3407) and tailored, as necessary, to the unique mission characteristics. Details on the functional architecture and guiding requirements are provided elsewhere.8, 9 The following briefly describes the core ECLSS subsystems depicted by Fig. 2.

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A. Atmosphere Revitalization The atmosphere revitalization (AR) subsystem maintains the cabin’s and composition within specified standards to ensure crew safety, health, and performance. The functions span cabin atmospheric pressure, temperature, humidity, and composition management as well as carbon dioxide removal, suspended particulate matter removal, and trace contaminant control. The AR subsystem depends on a robust cabin ventilation system to ensure uniform mixing. To minimize logistics requirements the AR subsystem enables oxygen (O2) and water resource recovery through carbon dioxide reduction processes.10-12 For exploration ECLSS development, the developmental efforts are focused on addressing the following:

 Improving CO2 removal process reliability.  Replacing commercially obsolete adsorbent and catalyst media.  Achieving >90% oxygen recovery from CO2.  Simplifying oxygen generation equipment operations to realize mass and maintainability improvements.  Implementing fit and form aspects to enable accessibility for in-flight maintenance and reduce spare part mass.

B. Water Recovery, Processing, and Management Water recovery, purification, and management is central to enabling long duration crewed exploration missions. The water recovery and management approach used aboard the ISS, while effective, has limitations that must be addressed to meet exploration mission needs. This requires a robust capability to handle the trace chemical contami- nant load that partitions into humidity condensate while minimizing water losses to concentrated waste streams. Recovering >85% of water from urine is a key capability of the future water recovery system. This capability is en- hanced by recovering water from brine produced by the urine processing unit. Increasing expendable element service life and reducing consumables consumption are necessary to realize future exploration functional objectives. The Ad- vanced Exploration Systems Life Support System (LSS) Project’s Water Recovery and Management (WRM) technical element is focused on technical advancements that meet objectives aligned with NASA’s technology roadmap toward increasing the fraction of water recovered from urine beyond 85%, increasing system reliability, and reducing mission logistics.13 The developmental efforts are focused on addressing the following:  Developing a urine stabilization method that achieves >85% water recovery from urine.  Developing and demonstrating a method to recover water from brine produced by urine distillation processes.  Developing a potable water antimicrobial additive that is both effective and long-lived.

C. Environmental Monitoring The environmental monitoring subsystem provides vital information about the state of the unique spacecraft cabin environment. Cabin pressure, composition, and temperature monitoring as well as potable water purity monitoring are primary functions. Microbial monitoring and contingency event monitoring, such as for fire and hazardous gas accu- mulation, are also provided.14 The cabin composition monitoring addresses the major atmospheric constituents of (N2), O2, CO2, and as well as trace chemical contaminants that arise from equipment offgassing and human metabolism. Major constituent monitoring works in conjunction with the cabin pressure control assembly to maintain the proper O2 partial pressure. Contingency event monitoring is closely related to cabin composition monitoring in that contami- nants arising from fires and chemical leaks impact overall cabin atmospheric quality in an acute manner. Target compounds for combustion product monitoring include carbon monoxide (CO), cyanide (HCN), hydrogen fluoride (HF), hydrogen chloride (HCl), and CO2 while targeted contaminants that may arise from leaks or EVA op- erations include ammonia (NH3), and hydrazine (N2H4). Such monitoring aids the crew for implementing remediation strategies and properly using personal protective equipment (PPE). Microbial monitoring addresses contamination in multiple environmental compartments—atmosphere, water, and surfaces. Ensuring that the cabin environment is healthy includes providing information to the crew to ensure that housekeeping practices and water supply contamination does not get out of control. The microbial monitoring capa- bility provides the crew with this vital information to assess bacterial and fungal contamination levels in the primary environmental compartments are within guidelines as well as aiding their approach to issues relating to infectious disease and microbial ecology of spaceflight which may become more challenging during long duration missions in deep space. Water quality monitoring ensures that the drinking water meets potable standards for total inorganic carbon, total organic carbon, volatile constituents, metals, and aesthetic properties such as taste, odor, turbidity, acidity, and dis- solved gases. The water quality monitor also ensures that antimicrobial additive levels are being maintained within prescribed limits. This monitoring not only ensures that the potable water supply is suitable for the crew’s consump- tion but also ensures that the water processing system is working properly. 6 International Conference on Environmental Systems

VI. Development and Test Campaign Extensive analyses of ECLSS operational lessons learned have provided a valuable set of design principles that will guide design and development of the ground engineering hardware and test campaigns. One of the fundamental lessons is to test hardware in a higher fidelity environment with higher fidelity test articles. The closer the test envi- ronment and hardware configuration are to the in-flight conditions and configuration, it is more likely that test cycles will help to identify equipment vulnerabilities that may occur. Several flight failures have occurred with ECLSS com- ponents and the test campaign will adopt test protocols that include flight like constituent processing, injecting identifiable potential contaminants into the equipment and system envelope testing to stress the components and iden- tify places where design robustness needs to be improved. Utilizing a continuous test program of improving components that fail during flight demonstrations or ground testing not only will assure a more robust fielded system, but will also help to characterize the needs for repair and refurbishment equipment needed for autonomous deep space operations. Additionally, it will provide valuable lessons regarding accessibility of the failed components for repair operations and help to devise strategies to minimize down time. By developing test confidence in the replacements for the failed components, a streamlined flight qualification process can be achieved by limiting the iterations caused by discovery of hidden latent design problems. Another benefit of having a robust high-fidelity ground test suite, is the flexibility to readily integrate new con- cepts and technologies that have potential for high pay-off but are not safety critical and more risky in terms of the technical approach into a flight like environment. By having clearly defined interfaces between the assemblies and designs for serviceability, components can be quickly changed in and out if they encounter unexpected problems dur- ing testing. If the test capabilities are robust and flight like, and the hardware is designed for repairability, NASA will have the potential to transition long run time proven hardware into the flight program with high confidence that it will meet the long duration autonomous needs that the deep space missions require.

VII. Conclusion NASA has invested significant resources to advance the state of the practice for crewed mission environmental monitoring, control, and life support. A strategy that includes demonstration aboard ISS demonstration, development of the NextSTEP universal ECLSS architecture, and a robust ground testing campaign will advance the capabilities toward an exploration-ready architecture that will provide NASA with the confidence to send crews on long dura- tion deep space missions with little or no resupply. The concerted and focused efforts to eliminate the loop closure performance gaps and increase the robustness of the ECLSS as a whole, including incorporating features that allow for in-flight maintenance and repair, will enable NASA confidently undertake the bold new crewed missions to ex- plore our local system and return the crew home safely.

Acknowledgments This work is funded by NASA’s Advanced Exploration Systems Program and the International Space Station Program.

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