Environmental Life Support Research Articles

Framework for Seismic Vulnerability Assessment of Nonstructural Elements Inside an Inflatable Lunar Habitat

The pursuit of knowledge and curiosity are once again driving humanity to seek a human presence on extraterrestrial bodies. While numerous challenges must be overcome on the moon to achieve this goal, the moonquake hazard has often been overlooked. Using NASA’s Moon to Mars Architecture requirements for surface habitation and accounting for the midterm/long-term mission duration, a framework for vulnerability assessment is developed for essential nonstructural elements (NSEs) inside an inflatable habitat subjected to moonquakes. The aim of this study is to develop an approach to assess the vulnerability of typical NSEs that support essential equipment, such as the environmental control and life support system, under a paucity of information related to the seismic hazard. We also emphasize that the launch dynamic environment and lunar seismic environment exhibit notable differences in their characteristics, which can lead to higher lateral acceleration levels than initially expected. This acceleration may be linked to high-occurrence seismic events. However, due to the lack of information regarding the frequency of these events, the risk of NSEs being subjected to unforeseen loads increases. It is imperative to equip future lunar habitats with seismic mitigation measures until additional seismometers are deployed near upcoming surface human outposts.

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.

Digital Twin Technologies for Autonomous Environmental Control and Life Support Systems

Environmental control and life support systems will require enhanced self-awareness and self-sufficiency as human spaceflights are designed to reach further destinations. These requirements have led to the development of autonomous technologies and systems to enable more Earth independence, while at the same time relying more heavily on the knowledge contained in their computational models (as opposed to the knowledge of ground control experts). For environmental control and life support systems, these consist of disparate models often tailored to specific subsystems and use cases, such as temperature control and CO2 removal. Therefore, there is a need for technologies supporting the integration of existing models. We propose to extend existing digital twin frameworks to integrate models and serve as a tool for answering onboard queries during operation. Toward this vision, we identify research directions for three types of technologies: i) streamlining the process of merging information models without redundancies by leveraging model-based systems engineering languages; ii) the calibration of simulation models that requires a better understanding of how to encode domain knowledge into a probabilistic representation of subsystem states and model parameters; and iii) automating the query understanding process and constructing a mapping between information and simulation models.

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>

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.

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.

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.

Investigation of Droplet Dynamics Under Shear Flow

The dynamics of droplet under shear flow was investigated in normal gravity and microgravity. Drop under shear flow has many applications in aerospace such as aircraft de-icing and environmental control and life support system in space station. Shape analysis of the droplet showed that drop in microgravity have a greater contact angle and height, but a smaller contact radius, than that in normal gravity. The difference between advancing and receding contact angle θa-θr is greater in microgravity than that in normal gravity under the same wind speed. The effect of airflow on the droplet is mainly dependent on the We number and the dimensionless number k′, which characterizes the ratio of wind force and adhesion force. the k’ in microgravity is larger than that in normal gravity. The droplet exposed to airflow from static to motion state can be divided into three regimes.

(Invited) Leveraging Magnetohydrodynamic Mechanisms for Stable and Efficient Microgravity Electrolysis

Water electrolysis is the fundamental chemical process for oxygen and hydrogen production in space. It is widely employed in modern environmental control and life support systems, propulsion technologies, and high-density energy storage devices. Furthermore, future interplanetary missions are likely to employ water as a commodity acquired and processed by In Situ Resource Utilization (ISRU) methodologies to produce propellants, thereby reducing vehicle launch mass.The absence of buoyancy results in major technical challenges for the operation of electrolytic cells in low gravity. The need to detach and collect oxygen and hydrogen bubbles has been traditionally addressed by means of forced water recirculation loops. However, this leads to complex, inefficient, and unreliable liquid management devices composed of multiple elements and moving parts. Two distinct magnetohydrodynamic (MHD) mechanisms may instead be employed to induce phase separation: diamagnetic, and Lorentz forces. The former arises in the presence of strong, inhomogeneous magnetic fields and results in a magnetic buoyancy effect. The latter is a consequence of the imposition of a magnetic field to the current generated between two electrodes. Both approaches can potentially lead to a new generation of electrolytic cells with minimum or no moving parts, hence enabling the human deep space operations with minimum mass and power penalties.Dedicated microgravity experiments are required to study these novel magnetically enhanced electrolysis concepts. This presentation introduces the fundamentals of both methods and discusses the experimental design and results from several experimental campaigns at ZARM’s drop tower and Blue Origin’s New Shepard. The performance of representative electrolytic cells subject to different MHD regimes is addressed from an electrochemical and fluid dynamic perspectives. It is demonstrated that the MHD force effectively detaches and collects gas bubbles in microgravity while increasing the current density and improving the stability of the electrolytic cell. Ultimately, this opens the door for the development of highly-efficient space electrolytic cells with applications to human and robotic space exploration.

Analytical Model for Sparing Policy Analysis and Optimization for Space Habitat Operations

The inclusion of operational sparing policies in early system definition can ensure that spares’ allocations can optimally meet desired system reliabilities consistent with the planned maintenance of a crewed vehicle. This approach is critical for long-duration crewed missions where mass allocations are constrained and lack of safe abort contingencies limit options in the event of significant system degradation, especially in the environmental control and life support systems. This paper presents an analytical model for analyzing and optimizing sparing policies as part of an overall evaluation of the probability of sufficiency for a system configuration. The repair transition parameters are varied to change the state visitation probabilities that drive a change in the probability of sufficiency observed for a given mass allocation. These parameters are optimized using a particle swarm optimizer to identify the preferred strategy for a desired allocation mass.

Genome Sequences of Bacteria Isolated from the International Space Station Water Systems.

We report draft genomes of five bacteria recovered from the U.S. and Russian water systems onboard the International Space Station. The five genera include Ralstonia, Burkholderia, Cupriavidus, Methylobacterium, and Pseudomonas. These sequences will help further the understanding of water reclamation and environmental control and life support systems in space.

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.

Quiet Spacecraft Cabin Ventilation Fan Development: Motivation and Context

It is important to control acoustical noise aboard crewed space vehicles and space habitats to provide a satisfactory environment for voice communications, alarm audibility, and restful sleep, and to minimize the risk for hearing loss and annoyance. As with most noise control efforts, it is best to control the noise at the source, and for spaceflight vehicles these are typically the fans associated with the Environmental Control and Life Support system. These include cabin ventilation fans and intermodule ventilation fans, among others. Throughout the history of crewed spaceflight, there have been issues with noise from ventilation fans, going back to Apollo. And, with the spaceflight vehicles and habitats currently being developed, there are again concerns with noise from ventilation fans. To address this problem, NASA is working to leverage the technology developed in its Aeronautics Research Mission Directorate, specifically at the Glenn Research Center, to design highly efficient and quiet fans for reducing community noise levels from civilian aircraft. This paper will discuss the need for transfer of this technology to spaceflight use, and will discuss the potential benefits, which are significant and will be crucial for the successful development and operations of future spaceflight vehicles, space suits, and habitats.

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.

Reinforcement learned adversarial agent (ReLAA) for active fault detection and prediction in space habitats

With growing interest for human space tourism in the twenty-first century, much attention has been directed to the robust engineering of Environmental Control and Life Support Systems in space habitats. The stable, reliable operation of such a habitat is partly achieved with an ability to recognize and predict faults. For these two purposes, a reinforcement learning adversarial agent (ReLAA) is utilized in this work. A ReLAA is trained with experimental data to actively recognize and predict faults. These capabilities are achieved by proposing actions that activate known faults in a system. Instead of issuing these harmful actions to the actual hardware, a digital twin of the mock space habitat is simulated to discover vulnerabilities that would lead to faulted operation. The methods developed in this work will allow for the discovery of damaging latent behavior, and the reduction of false positive and negative fault identification.

Training of organizational and managerial personnel responsible for the environmental safety strategy

The article discusses the reasons for the inconsistency of the university training program for organizational and managerial personnel responsible for the environmental safety strategy in the areas of study implemented at the university, taking into account the international requirements of the ESG strategy, which comprehensively evaluates all factors: social, environmental and managerial, both on the production system and on environment and is being widely implemented in various global business firms. The main ways of improving the quality of training of organizational and managerial personnel responsible for the creation of new enterprises and the improvement of existing ones in order to ensure high efficiency of environmental safety and life support are determined. A program of disciplines and methods have been developed to ensure the process of its implementation.

Causal Signal Temporal Logic for the Environmental Control and Life Support System’s Fault Analysis and Explanation

Modern cyber-physical systems would often fall victim to unanticipated anomalies. Humans are still required in many operations to troubleshoot and respond to such anomalies, such those in future deep space habitats. To maximize the effectiveness and efficiency of the anomaly response process, the information provided by anomaly response technologies to their human operators must be epistemically accessible or explainable. This paper offers a first step towards developing explainable anomaly response systems. It proposes a logic, Causal Signal Temporal Logic (CaSTL), which can formally describe cause-effect relationships pertaining to fault explanation. Moreover, it develops an algorithm to infer a CaSTL formula that explains why a fault has happened in a system, given the model of the system and an observation about the fault. The effectiveness of the proposed algorithm is demonstrated with a simulated Environmental Control and Life Support System (ECLSS).