Environmental Control And Life Support System Research Articles

Importance and challenges of integrating BLSS into ECLSS

Bioregenerative Life Support Systems (BLSS) are a key facet of plans for long term habitats on other celestial bodies. With the Artemis program headed to the moon and SpaceX pushing towards Mars the roadmap is about 10–20 years. Therefore it is vital to consider how BLSS will work with the traditional physicochemical Environmental Control and Life Support Systems (ECLSS). Biological systems are complicated. Their inputs and outputs cannot be turned on and off the way physicochemical systems can. Therefore the accurate monitoring and prediction of these systems is fundamental to integrating the BLSS into the life support system as a whole. This paper will summarize the history of BLSS research, the system requirements for integrating a BLSS into the ECLSS, and the research needed to meet these requirements. As the world looks towards the future of humans living on other celestial bodies, there is a lot of work to do to support keeping them safe and healthy. Bioregenerative Life Support Systems have potential to provide massive support, if they are effectively integrated with the physicochemical systems.

Improvement and optimization of spacecraft environmental control and life support systems

Environmental control and life support systems (ECLSS) are essential for the triumph of human spaceflight missions, furnishing astronauts with crucial resources like breathable air, purified water, nourishment, and protection from radiation. The unique and challenging space environment, coupled with the critical nature of ECLSS components, necessitates a high degree of reliability to prevent catastrophic failures. This paper conducts a comprehensive examination of various ECLSS subsystems, including air revitalization, water processing, food storage, waste management, and radiation shielding. Gaining perspectives from historical missions like Apollo, Skylab, and the International Space Station (ISS), the research outlines strategic approaches to improve the fault tolerance of ECLSS. The implementation of advanced simulation modeling, strategic component redundancy, and improved subsystem interconnectivity are posited as pivotal measures to bolster the reliability of ECLSS. These improvements are vital to guarantee the safety and viability of prolonged space missions to the Moon, Mars, and beyond, thereby facilitating humanitys ongoing exploration of the universe.

Energy system and resource utilization in space: A state-of-the-art review

<p>Deep space exploration expands our understanding about the evolution history of solar system, while the future development heavily relies on the construction of energy systems and utilization of resources on the planet. This paper systematically reviewed the progress in the environmental control and construction technologies of space bases, extraterrestrial in situ resource utilization technology, energy systems, key technologies for planetary transportation platforms, and geological explorations. The current status, pros and cons of these technologies and systems are introduced and discussed. As an important artificial microenvironment in the space base, the environmental control and life support system (ECLSS) provides necessary resources for human. Sintering and additive manufacturing technologies demonstrate the potential to construct a space base with lunar regolith or simulants. The extraction and in situ utilization of resources on the Moon, including water ice, oxygen, and helium-3, are crucial to maintain life support for lunar exploration. Typical energy systems that can be used on the Moon include photovoltaic cell, Stirling power generation technology, closed Brayton cycle (CBC) system, Rankine cycle system, heat storage system, and integrated energy system. The CBC system has the highest thermal efficiency (39%) among them, making it suitable for late-period energy supply. The performance of various planetary rovers, the most important transportation platforms, are summarized. Through geological explorations, the resource distribution, content, and occurrence can be obtained. Perspectives on the future, promotions of environment adaptation, resource recovery, energy efficiency, and intelligence of the existing technologies are still needed to move forward on space explorations.</p>

Updating subsystem-level fault-symptom relationships for Temperature and Humidity Control Systems with redundant functions

As we aim for deep space exploration, supporting vital systems, such as the Temperature and Humidity Control System (THCS) in the Environmental Control and Life Support System (ECLSS), through timely onboard fault detection and diagnosis becomes paramount for mission success. Many existing fault diagnosis approaches assume that the function that models the relationship between faults and associated symptoms (fault-symptom relationships) will remain constant throughout the THCS’ lifetime. Therefore, many of these diagnosis methods are not robust enough to automatically account for changes in fault-symptom relationships as a result of changes in the habitat (e.g., system reconfiguration). The work highlighted here is on (i) surveying existing work on adaptable fault diagnosis methods and (ii) showcasing a real-life case study, in which we identified the need for an automatically adaptable fault diagnosis method. The case study focuses on a reconfigured terrestrial THCS analog, the Heating, Ventilation, and Air Conditioning (HVAC) system, where the original fault-symptom relationship is revealed to be no longer accurate. We then apply current adaptable fault-symptom relationship generation methods, such as Model-Based Dependability Analysis (MBDA) methods and data-driven causal discovery methods. Through this analysis, we detail our procedure in (i) identifying relevant fault-free system information, such as redundancy, to revise fault-symptom relationships used in fault diagnosis and (ii) evaluating the fault diagnosis performance in a THCS with the original and revised fault-symptom relationship. Our contribution lies in identifying the shortcomings of current methods and pinpointing future steps in creating an adaptable fault diagnosis framework. We found that although the MBDA methods can automatically generate fault-symptom relationships given system flow information and fault mode of components, they also required manual revision of the aforementioned information to create fault-symptom relationships that reflect redundancies. On the other hand, we concluded that the causal discovery methods can detect fault-free system information, such as redundancies, that may help us revise fault-symptom relationships, but suspect variables that contribute to redundancies may have to be hand-picked.

Space aquatic chemistry: A roadmap for drinking water treatment in microgravity

Rapid advancement in aerospace technology has successfully enabled long-term life and economic activities in space, particularly in Low Earth Orbit (LEO), extending up to 2000 km from the mean sea level. However, the sustainance of the LEO Economy and its Environmental Control and Life Support System (ECLSS) still relies on a regular cargo supply of essential commodities (e.g., water, food) from Earth, for which there still is a lack of adequate and sustainable technologies. One key challenge in this context is developing water treatment technologies and standards that can perform effectively under microgravity conditions. Solving this technical challenge will be a milestone in providing a scientific basis and the necessary support mechanisms for establishing permanent bases in outer space and beyond. To identify clues towards solving this challenge, we looked back at relevant scientific research exploring novel technologies and standards for deep space exploration, also considering feedback for enhancing these technologies on land. Synthesizing our findings, we share our outlook for the future of drinking water treatment in microgravity. We also bring up a new concept for space aquatic chemistry, considering the closed environment of engineered systems operating in microgravity.

Experimental and kinetic study on the cyclic removal of low concentration CO2 by amine adsorbents in confined spaces

Amine-based adsorbents show great promise for removing low-concentration CO2 from environmental control and life support systems (ECLSSs) to ensure crew safety and task execution. In this work, granular silica gel (SG) support was prepared by the extrusion–spheronization (ES) method, and amine-based adsorbent pellets were synthesized by impregnating the SG support with tetraethylenepentamine (TEPA). Dynamic CO2 circulation removal tests were carried out under simulated confined space conditions in a 100 L chamber to evaluate the low concentration CO2 removal performance of the adsorbent pellets. The effect of operating parameters on CO2 removal performance was investigated by orthogonal experiments. CO2 adsorption capacity and removal efficiency were significantly affected by CO2 concentration and reaction temperature, while reaction rate was intimately depended on CO2 concentration and gas flow rate. The maximum CO2 adsorption capacity (0.55 mmol CO2/g), removal efficiency (83.25%) and reaction rate (0.93 mmol CO2/min) were achieved under the optimized conditions of 20 °C, 1.25%CO2 and 2 L/min. A kinetic equation well representing the correlation between reaction rate and CO2 concentration and gas flow rate was established. The TEPA-SG-ES adsorbent pellets exhibited satisfactory working stability, with CO2 removal efficiency and adsorption capacity slightly decreased from 83.25% and 0.55 mmol CO2/g to 75.45% and 0.53 mmol CO2/g in 10 cycles, respectively. The slight decay in CO2 adsorption performance was associated with the oxidative degradation of amine species in oxygenated atmosphere to form amide, nitrite and imine phases, and the change of amine distribution over the pellets in multiple cycles. Overall, the desired TEPA-SG-ES adsorbent pellets could be nice scavenger candidates for circulating purification of CO2 in confined spaces.

Design and Verification of Urine Collection Hose Assembly Used for Environment Control and Life Support System

The urine collection hose assembly is u sed in the urine collection subsystem of the environmental control and life support system (ECLSS) of the space station to connect the products or components in the urine collection subsystem and transmit the working medium. This paper introduces the design scheme and verification test of urine collection hose assembly. The urine collection hose adopts the design scheme of stainless steel wire armored polytetrafluoroethylene hose. Through the verification test, the results show that the scheme can meet the performance requirements of the space station toilet collection subsystem hose assembly.

The potential of catalysis for closing the loop in human space exploration

This mini-review provides a perspective on how catalysis can contribute to the challenge of human space exploration, i.e. to the establishment of a space habitat on the Moon in the near future and the realization of a journey to Mars in the far future. The role of catalysis for space exploration is reviewed along elemental resource provisions for human life that are based on catalytic chemical processes. As a secondary effect, learning about catalysis under the high constraints of the sustainability requirements inherent to long-term space missions can be beneficial for the advancement of currently developed catalytic processes for a green, circular economy on Earth. In-depth research into catalysis for space applications could therefore also provide answers to urgent industrial, environmental and social sustainability challenges on our planet e.g., as expressed by the United Nations Sustainability Development Goals. Even for today’s short-term space missions, catalysis already plays a key role in the Environmental Control and Life Support System (ECLSS) on the International Space Station (ISS) and moreover, in fuel and propellant synthesis as well as the recycling of combustion products such as CO2.

Facile fabrication of silica aerogel supported amine adsorbent pellets for Low-concentration CO2 removal from confined spaces

Amine-based adsorbents show promise for removing low-concentration CO2 from environmental control and life support systems (ECLSSs), while the powder adsorbents are facing the challenges of reaction non-uniformity, pressure drop and material elutriation. To solve the problems, amine-based adsorbent pellets are fabricated by the extrusion–spheronization (ES), agar-assisted moulding (AM) and graphite-casting (GC) methods. The adsorbent pellets are further modified with pore-forming template for improved CO2 adsorption performance. The influences of granulation and pore-forming template modification on the structure-performance relationships of the adsorbent pellets are investigated. Granulation exerts adverse effect on the pore structure of tetraethylenepentamine supported on silica gel (TEPA-SG) adsorbent, which is not conducive to the bulk diffusion of CO2, and the CO2 adsorption capacity and kinetics thus have been impaired. The TEPA-SG-ES adsorbent pellets prepared by the extrusion–spheronization method show a relatively higher CO2 capture capacity of 1.01 mmol CO2/g due to better textural parameters and uniform dispersion of amine species. Thanks to the extrusion process, the adsorbent pellets also exhibit good mechanical properties with a high compressive strength of 10.90 MPa and low abrasion index of 0.36%. Both the textural properties and CO2 uptakes of the pellets can be restored upon template modification, and the promoting effect depends on the different templates employed due to their distinct pyrolysis rates and pathways. Mechanical properties will be adversely affected by the doped pore-forming template. The TEPA-SG-ES-UA pellets prepared with urea modification exhibit a great CO2 capture capacity of 1.48 mmol CO2/g and good mechanical properties with a high compressive strength of 4.90 MPa and a low abrasion index of 0.87%, and it could be a nice adsorbent candidate for removing low-concentration CO2 from ECLSSs.

Lessons learned on the implementation of probabilistic graphical model-based digital twins: A space habitat study

Habitats for future human spaceflights will require more resilient environmental control and life support systems (ECLSS). To that end, it is important to facilitate decision making in case of unexpected failure by quantifying the uncertain and dynamic nature of the physical phenomena involved. Combining probabilistic and deterministic models is a particularly promising approach to address this issue. In particular, Probabilistic Graphical Model (PGM) based digital twins are relevant as they embed random variables evolving overtime. Previous research used this modeling method for several applications such as monitoring structural health or manufacturing processes. We envision that the space exploration sector can also benefit from this approach by using the insight gained on specific sub-systems. In this study, we propose lessons learned on the implementation process of PGM-based Digital Twin to quantify uncertainties for temperature prognosis in ECLSS. These findings are introduced as a step-by-step guideline which result in developing a probabilistic model applicable to space habitats. We focused on directed acyclic graphs as this type of PGM can integrate expert's knowledge with data which has been proven to enhance accuracy. A literature review was conducted to identify the state-of-the-art practices and the proposed lessons learned were derived from the study of a physical infrastructure meant to predict the behavior of a space habitat. A temperature control failure scenario was considered, and the Digital Twin estimated the time available before the temperature would become critical. Experiments were conducted on three office rooms to simulate the behavior of an ECLSS. The model was trained offline using historical sensor data and performed inference online by computing the conditional probability of a multivariate normal density. We found that a successful implementation process requires to iteratively go through four stages: outline, design, calibrate and evaluate. It involves selecting ECLSS relevant functionalities and an associated decision-making problem that relies on habitability criteria. Observable variables must be chosen according to a sensors architecture that is compatible with a typical habitat infrastructure. As real space systems are not easily available for model validation, we suggest evaluating early designs on high fidelity analogs. In future work, we envisage to further assess the impact of the design stage on the model's performance by considering computational cost and inference capability.

Development of a NASA roadmap for planetary protection to prepare for the first human missions to Mars

As part of planning for future space exploration, COSPAR (The Committee on Space Research) together with participating space agencies, organized and held interdisciplinary meetings to consider next steps in addressing knowledge gaps for planetary protection for future human missions to Mars. Beginning with the results of these meetings and earlier work by NASA, ESA, and COSPAR (e.g., Criswell et al., 2005; Hogan et al., 2006; Rummel et al., 2008) as a base the authors of this paper carried out a follow-on NASA planning activity to identify the necessary steps to be accomplished to close knowledge gaps. We identified significant overlap between the planetary protection needs and other sets of Mars preparation roadmaps (1) microbial monitoring requirements for crew health and medical systems, (2) studies of the microbiome of the built environment, (3) environmental control and life support systems (ECLSS), (4) waste management, and (5) planetary surface operations. In many cases, efforts to mature exploration class systems for Mars that are occurring in other domains can be leveraged with minor changes to address planetary protection gaps as well. In other cases, work planned for testing on the International Space Station (ISS) as an analog for crew Mars transit, or on the lunar surface as an analog for Mars surface operations can be used to close planetary protection technology and knowledge gaps. An overall strategic framework that combines these domains has the advantage of being more comprehensive, efficient, and timely for closing gaps.This approach has led to the development of a NASA roadmap for addressing planetary protection integrated with other related roadmaps. NASA's development and execution of the planetary protection is now viewed in an integrated way with related technology development and testing. Key features of the integrated capabilities roadmap include:•A focus on microbial monitoring needs for crewed systems overall, and the additional work needed to develop and demonstrate baseline vs. abnormal changes in microbial communities over time.•Integrated consideration of planetary protection and crew health requirements relevant to crew quarantine and science sample transportation.•Specific and targeted studies of microbial growth and biofilms in microgravity and lunar surface ECLSS systems.•Development of sterilization, cleaning, and waste handling technologies that meet habitation needs as well as planetary protection needs.

Preparation for and performance of a Pseudomonas aeruginosa biofilm experiment on board the International Space Station

Biofilms are problematic on Earth due to their ability to both degrade the materials upon which they grow and promote infections. Remarkably, 65% of infections and 80% of chronic diseases on Earth are associated with biofilms. The impact of biofilms is even greater in space, as the crew's lives and mission success depend on nominal operation of mechanical systems which can be interrupted by material damage associated with biofilm growth. Furthermore, the isolated confined environment nature of spaceflight may increase the rates of disease transmission. In the case of the International Space Station (ISS), biofilms are an identified problem on the Environmental Control and Life Support System (ECLSS), namely on the water processor assembly (WPA). In late 2019, the bacterial component of the Space Biofilms experiment launched to ISS to (i) characterize the mass, thickness, morphology, and gene expression of biofilms formed in space compared to matched Earth controls, (ii) interrogate the expression of antimicrobial resistance genes, and (iii) test novel materials as potential biofilm control strategies for future ECLSS components. For this, 288 bacterial samples were prepared prior to the launch of the Northrop Grumman CRS-12 mission from NASA's Wallops Flight Facility. The samples were integrated into the spaceflight hardware, BioServe's Fluid Processing Apparatus (FPA), packed in sets of eight in Group Activation Packs (GAP). Half of these samples were activated and terminated on orbit by NASA astronauts Jessica Meir and Christina Koch, while the remaining half were processed equivalently on Earth. The spaceflight bacterial samples of Space Biofilms returned on board the SpaceX CRS-19 Dragon spacecraft in early 2020. We here describe the test campaign implemented to verify the experiment design and confirm it would enable us to achieve the project's scientific goals. This campaign ended with the Experiment Verification Test (EVT), from which we present example morphology and transcriptomic results. We describe in detail the sample preparation prior to flight, including cleaning and sterilization of the coupons of six materials (SS316, passivated-SS316, lubricant impregnated surface, catheter-grade silicone with and without a microtopography, and cellulose membrane), loading and integration of growth media, bacterial inoculum, and the fixative and preservative to enable experiment termination on orbit. Additionally, we describe the performance of the experiment on board the ISS, including crew activities, use of assets, temperature profile, and experiment timeline; all leading to a successful spaceflight experiment. Hence, this manuscript focuses on the steps implemented to ensure the experiment would be ready for spaceflight, as well as ISS and ground operations, with results presented elsewhere. The processes discussed here may serve as a guideline to teams planning their own gravitational microbiology experiments. This material is based upon work supported by the National Aeronautics and Space Administration under Grant No. 80NSSC17K0036.

LIFE SUPPORT SYSTEMS BEYOND LOW EARTH ORBIT ADVOCATES FOR AN IMPROVED RESOURCES MANAGEMENT APPROACH

Nowadays, there are still many challenges to overcome in order to enable long-termed human space exploration beyond low Earth orbit (LEO) and metabolic resources management (reliable air, water and food supply for the crew) is of utmost importance. Currently, Environmental Control and Life Support Systems (ECLSS) aim to overcome the challenge of constant re-supply from Earth requirement by revitalization of air and water. Here, we provide an overview of the existing and operating ECLSS on-board the International Space Station (ISS) as well as identify potential areas of technology development for biological ECLSS for long-term human space missions focusing on the inclusion of waste treatment and food production.

Experimental and kinetics investigations of low-concentration CO2 adsorption on several amine-functionalized adsorbents

The rapid cleanup of endogenous CO2 has become a necessity in environmental control and life support systems (ECLSSs), to ensure crew safety and long-term task execution. The extensively used non-regenerable LiOH and soda lime adsorbents, although exhibit high CO2 storage capacities and fast kinetics, can hardly fulfill the demands of reduced launch weight and storage volume in the space- and load-limited ECLSSs. New CO2 adsorbents with desirable attributes including high CO2 uptakes, good selectivity, facile regeneration, fast adsorption and desorption kinetics, and good multicycle stability are urgently needed. We developed amine-functionalized adsorbents by loading tetraethylenepentamine (TEPA) on mesoporous supports of activated carbon (AC), aluminum oxide (AO) and silica gel (SG). The adsorbents were characterized by N2 adsorption-desorption, thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscope (SEM) to study their microstructural properties. CO2 adsorption capacities and kinetic performance of the adsorbents with different supports and various amine loadings (10–50 wt%) were evaluated in 2%CO2 at 20 °C. The effects of support and amine loading on the structure-performance relationships of the adsorbents were demonstrated. The TEPA-SG-20 adsorbent (20 wt% TEPA loaded on silica gel support) exhibits the highest CO2 adsorption capacity of 1.90 mmol CO2/g and the maximum amine efficiency of 0.48 mmol CO2/mmol N. TEPA-SG-20 also exhibits fast CO2 adsorption kinetics, and the Avrami fractional order kinetic model provides a satisfactory correlation of the experimental CO2 uptakes. Furthermore, the TEPA-SG-20 adsorbent can be efficiently regenerated at 110 °C with a great regeneration efficacy of 97%. The desired adsorbent also exhibits good working stability with a low loss-in-capacity of 4.32% in 10 consecutive cycles. The good CO2 adsorption performance of TEPA-SG-20 is associated with the excellent microstructural properties such as high surface area, great pore volume and uniform dispersion of amine species. Overall, the desired TEPA-SG-20 adsorbent shows promise for low-concentration CO2 removal in ECLSSs.

Development of Peristaltic Transfer System to Transport Feces in Space: Proposal of Driving Method Using Pressure Difference in Peristaltic Pump

We propose a transport system combining peristaltic motion and a negative pressure as a new method of transporting and collecting feces for space toilets. In recent years, for the development of space exploration, the need for a regenerative Environmental Control and Life Support System (ECLSS) to perform manned space exploration for long periods without resource supply has emerged. Currently, human feces is disposed of, but if it can be reused like urine, the performance of the ECLSS can be significantly improved. Existing space toilets do not reuse of feces, and the transfer of feces presents a technical problem. There is no technology that can reliably transport highly viscous solid–liquid mixtures on an intermittent basis. If such technologies are developed, they will be useful for transporting not only feces in space but also chemicals on the ground. Therefore, the authors propose a peristaltic system based on the intestinal tracts of living organisms for the transport of feces in space. Each unit of the system can be actively closed and opened by air pressure. The units are operated in turn to transport feces. The proposed driving method utilizes the pressure difference between the units of a peristaltic pump to increase the transfer rate. A prototype system consisting of three units was developed, and a simulated feces transfer experiment was conducted to validate the proposed method. In the experiment, we compared the conventional peristaltic driving method and the proposed peristaltic driving method, and the results indicated that the proposed method can carry more than twice the amount of simulated feces. Thus, the proposed method is suitable for the transfer of feces in space and can be used to transfer highly viscous solid–liquid mixed fluids under intermittent supply and with little water consumption.

Exergy Analysis of Electrochemical Systems for Space Exploration

Human exploration of space, facilitated by electrochemical systems, will require integration of many seemingly disparate systems including but not limited to power systems, in situ resource utilization (ISRU), and environmental control and life support (ECLS). Through combining expressions of the First and Second Laws of Thermodynamics exergy quantifies the useful work that can be obtained from a system, subject to environmental limitations. This approach provides a means of integrating diverse systems and components based on one consistent and physically meaningful property: exergy. Using this property as a basis, diverse systems can be analyzed and integrated effectively based on the exergy destruction and exergy efficiency. Here, the applicability of exergy analysis to systems design and integration is demonstrated through two examples involving electrochemical systems that support human space exploration.First, analysis of the ECLS system aboard the International Space Station (ISS) is conducted to assess its overall performance in terms of exergy destruction rates and exergy efficiency. The ECLS system is divided into constituent subsystems which are further divided into key components. Based on this system decomposition, exergy balances are derived for each component and subsystem. Special focus is given to the Oxygen Generation Assembly (OGA) within the ECLS Atmospheric Revitalization Subsystem. The results of parametric studies of the OGA proton exchange membrane electrolyzer performance are presented with an emphasis on the impacts of operational conditions on exergy efficiency. This electrolyzer is a significant contributor to system exergy destruction and exhibits a low exergetic efficiency. It therefore presents an opportunity for improving overall ECLS system performance.Following the example of ECLS exergy analysis, the application of exergy analysis to the integration of power and ISRU systems for lunar exploration is presented through system level models. Exergy destruction and efficiency are quantified over the lunar diurnal cycle for power and ISRU systems. The power systems analysis focuses on photovoltaic arrays paired with battery and regenerative fuel cell systems. The ISRU system analysis focuses on production of oxygen from lunar regolith through the reduction of ilmenite combined with water electrolysis. Here the application of exergy analysis identifies key opportunities for the use of byproduct heat and the optimal sizing of system components.The studies presented demonstrate the capability of exergy analysis to support the design and integration of electrochemical systems within larger power, ISRU, and ECLS systems supporting space exploration. This approach can enable the full and efficient use of a system’s available work potential based on a consistent, physically meaningful property. Therefore, exergy analysis is shown to be a key tool for the future design and integration of electrochemical systems for space exploration.

Next Generation Water Recovery for a Sustainable Closed Loop Living

In order to facilitate extended human space travel, solutions and innovations are required to enable habitation in microgravity spacecraft habitats such as International space station (ISS), with limited supply availability. At present, the Environmental Control and Life Support System (ECLSS) within the ISS recovers and recycles 90% of the water from human waste. However, their efficiency decreases during their lifetime owing to unmanageable process contaminants, requiring ground support to supply complex hazardous chemicals to treat these system components such that they maintain their targeted performance[i] ,[ii],[iii]. As human missions travel further into the solar system, the availability of ground support will be diminished. Therefore, next-generation systems to recycle water are required to reduce waste and improve system efficiency. Within this context, Faraday Technology Inc. and the University of Puerto Rico (UPR) are developing a bio-electrochemical waste water treatment system. Within this system, a bioreactor will convert urea from the waste water to ammonia by hydrolysis:NH2(CO)NH2 + H2O → 2NH3 + CO2 (1)Next the effluent of the bioreactor will flow through the ammonia oxidation reactor:2NH3 → N2 + 3H2 (2)Thus, generating urea free waste water effluent for further filtration and enhancement. The developed technology has the potential to be compatible with existing ECLSS systems and be an integral part of the closed loop living systems required for long term life support on NASA’s manned space missions.Ongoing activity between Faraday Technology and UPR has demonstrated an 85% conversion of urea to ammonia in a bioreactor and a near complete conversion of ammonia in an electrochemical reactor in a laboratory set-up utilizing a synthetic urine electrolyte[iv] ,[v]. Based on the studies, Faraday has designed and built an alpha scale reactor to process 6 L volume of urine per day as per NASA specifications. The next step in reactor demonstration activities is to understand the effects of zero-gravity on the ammonia reactor. The electrochemical reactor and components are assembled in an electrochemical microgravity laboratory setup (Figure 1). Optimized conditions from ground-based performance data will be implemented during the zero-gravity flight test to evaluate the feasibility of ammonia oxidation in zero-gravity environment. The flight test is scheduled for May 2021.In this talk we will be discussing the ongoing developments at Faraday, where we have (1) leveraged existing knowledge to design and test the bio-electrochemical reactor under zero gravity conditions; (2) evaluated electrocatalyst for ammonia oxidation reactor; (3) optimized the electrocatalytic efficiency and waste water treatment rate with urine simulants; (4) designed and built a demonstration-scale bio-electrochemical reactor unit capable of meeting NASA required specifications; and (5) will be validating operation under zero gravity conditions during the May 2021 zero gravity test flight. Acknowledgements: The financial support of NASA Contract No. NNX17CA30P and 80NSSC18C0222 is acknowledged.

Development of Nitrogen Recycling Strategies for Bioregenerative Life Support Systems in Space.

To enable long-distance space travel, the development of a highly efficient and robust system to recover nutrients from waste streams is imperative. The inability of the current physicochemical-based environmental control and life support system (ECLSS) on the ISS to produce food in situ and to recover water and oxygen at high enough efficiencies results in the need for frequent resupply missions from Earth. Therefore, alternative strategies like biologically-based technologies called bioregenerative life support systems (BLSSs) are in development. These systems aim to combine biological and physicochemical processes, which enable in situ water, oxygen, and food production (through the highly efficient recovery of minerals from waste streams). Hence, minimalizing the need for external consumables. One of the BLSS initiatives is the European Space Agency’s (ESA) Micro-Ecological Life Support System Alternative (MELiSSA). It has been designed as a five-compartment bioengineered system able to produce fresh food and oxygen and to recycle water. As such, it could sustain the needs of a human crew for long-term space exploration missions. A prerequisite for the self-sufficient nature of MELiSSA is the highly efficient recovery of valuable minerals from waste streams. The produced nutrients can be used as a fertilizer for food production. In this review, we discuss the need to shift from the ECLSS to a BLSS, provide a summary of past and current BLSS programs and their unique approaches to nitrogen recovery and processing of urine waste streams. In addition, compartment III of the MELiSSA loop, which is responsible for nitrogen recovery, is reviewed in-depth. Finally, past, current, and future related ground and space demonstration and the space-related challenges for this technology are considered.

Complexity Evaluation of an Environmental Control and Life-Support System Based on Directed and Undirected Structural Entropy Methods.

During manned space missions, an environmental control and life-support system (ECLSS) is employed to meet the life-supporting requirements of astronauts. The ECLSS is a type of hierarchical system, with subsystem—component—single machines, forming a complex structure. Therefore, system-level conceptual designing and performance evaluation of the ECLSS must be conducted. This study reports the top-level scheme of ECLSS, including the subsystems of atmosphere revitalization, water management, and waste management. We propose two schemes based on the design criteria of improving closure and reducing power consumption. In this study, we use the structural entropy method (SEM) to calculate the system order degree to quantitatively evaluate the ECLSS complexity at the top level. The complexity of the system evaluated by directed SEM and undirected SEM presents different rules. The results show that the change in the system structure caused by the replacement of some single technologies will not have great impact on the overall system complexity. The top-level scheme design and complexity evaluation presented in this study may provide technical support for the development of ECLSS in future manned spaceflights.

Development of acoustic mufflers for cabin noise reduction in Orion spacecraft

Controlling cabin acoustic noise levels in the Crew Module (CM) of the Orion spacecraft is critical for adequate speech intelligibility, avoid fatigue, and prevent any possibility of temporary and permanent hearing loss to the crew. The primary source of cabin noise for the on-orbit phase of the mission is from the Environmental Control and Life Support System (ECLSS) which recycles and conditions breathing air and maintains cabin pressurization through its ducting network and components. Unfortunately, as a side effect, noise from the ECLSS fans propagates through theses ducts and emanate into the cabin habitable volume via the ECLSS inlet and outlets. To mitigate excessive duct-borne noise, two ECLSS mufflers have been designed to provide significant acoustic transmission loss (TL) so that the cabin noise requirements can be met. Each muffler is meant to be installed in the ducting of the ECLSS air inlet and outlet sides, respectively. Packaging constraints and tight volume requirements necessitated the mufflers to be of complex geometry and compatible with the bends of the ECLSS duct layout. To design and characterize the acoustic performance of the inlet and outlet mufflers, computational acoustic models were developed using the Finite Element Method (FEM) with software. Characterization of the acoustic material and perforations in the mufflers were addressed with poro-elastic theory. Once the mufflers were designed on paper and its TL predicted, prototypes of these mufflers were created using additive manufacturing. The muffler prototypes were subsequently tested for acoustic TL in the laboratory with various configurations of acoustic materials. Comparing the analytical predictions to the test performance yielded excellent correlation for acoustic TL and demonstrated significant broadband noise attenuation. The ECLSS mufflers are currently scheduled to be installed on the Artemis II CM of the Orion spacecraft and will provide significant cabin comfort to crew during the mission.