Environmental Life Support System 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.

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.

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.

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.

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.

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).

Experimental Investigation of Dropwise Condensation Shedding by Shearing Airflow in Microgravity Using Different Surface Coatings.

The shedding kinematics of water droplets in a condensation environment when exposed to aerodynamic forces in microgravity was studied. Understanding the shedding of droplets from a surface is a critical part of the dropwise condensation process for improving heat transfer. Because gravity as a droplet removal technique is not available in space, the use of airflow to shed droplets is considered for condensing heat exchangers in environmental control and life support systems. Surface coatings affect drop adhesion, and here, four different surfaces (PMMA, PS, PTFE, and SHS) and various droplet sizes (80, 60, and 40 μL) were used to understand the above phenomenon. It was found that the critical velocity to shed a droplet in microgravity was up to 8% lower than that in normal gravity. Also, the effect of the droplet size was investigated for both microgravity and normal gravity; the shedding velocity was lower for microgravity, and it decreased as droplet size increased. Increasing the hydrophobicity of the coating decreased the critical velocity for shedding. Finally, the droplet was found to detach from superhydrophobic surfaces in microgravity. The detachment of droplets from the substrate will hamper the condensation process that can produce a larger fresh area; also, detachment of droplets and entrainment in airflow counter the concept of removing moisture from the air in a dehumidification process.

THE ROLE OF TOURISM INDUSTRY GROWTH IN ATTAINING SUSTAINABLE DEVELOPMENT GOALS IN A MODERN GLOBALIZED WORLD

This article seeks to explore the effects of socioeconomic growth in the tourism industry to attain sustainable development goals in the contemporary globalized environment. A study on tourism as one of the fastest growing industries has revealed that modern tourism, an important area in foreign economic activity of many countries and a highly profitable sector, is a complex intersectoral phenomenon that contributes to tackling a number of critical economic and social issues. It is argued that tourism development promotes further integration and spurs international specialization. However, it is noted that rapid tourism growth might generate negative effects for the environment: soil and ocean pollution, climate change, inefficient use of energy sources, destruction of natural monuments, biodiversity loss, etc. In the context of this study, tourism is viewed as a promising management tool able to consolidate resources to meet economic, social and aesthetic needs along with preserving cultural identity, basic environmental processes, biodiversity and life support systems. Thus, the findings provide a rationale to assert that tourism boosting strategies should rely on sustainable development. It is emphasized that sustainable tourism development concept, in full compliance with the principles of harmonious development, is difficult to implement, however it is an ideal, a landmark that should be pursued. Despite the fact that over 4.2 million tourists visited Ukraine in 2021, the current tourism potential is yet to be further unlocked (the share of tourism industry in Ukraine's GDP makes only 1.5–2.5%). Among the key barriers to enhancing the tourism sector growth in Ukraine are the global COVID-19 pandemic as well as a range of managerial, economic, social, environmental and cultural factors. The study presents an overview on the recommendations of the Global Tourism Crisis Committee plan to restore the global tourism industry with a particular focus to attain sustainable development goals and the use of opportunities for transition to a circular economy.

Terraform Sustainability Assessment Framework for Bioregenerative Life Support Systems

In this perspective paper, we raise attention to the lack of methods or data to measure claims of sustainability for bioregenerative life support system designs and propose a method for quantifying sustainability. Even though sustainability is used as a critical mission criterion for deep space exploration, there result is a lack of coherence in the literature with the use of the word sustainability and the application of the criterion. We review a Generalized Resilient Design Framework for quantifying the engineered resilience of any environmental control and life support system and explain how it carries assumptions that do not fit the assumptions of sustainability that come out of environmental science. We explain bioregenerative life support system sustainability in the context of seven theoretical frameworks: a planet with soil, biogeochemical cycles, and ecosystem services provided to humans; human consumption of natural resources as loads and disturbances; supply chains as extensions of natural resources engineering application of; forced and natural cycles; bioregenerative systems as fragmented ecosystems; ecosystems as a network of consumer-resource interactions with critical factors occurring at ecosystem control points; and stability of human consumer resources. We then explain the properties of environmental stability and propose a method of quantifying resistance and resilience that are impacted by disturbances, extend this method to quantifying consistence and persistence that are impacted by feedback from loads. Finally, we propose a Terraform Sustainability Assessment Framework for normalizing the quantified sustainability properties of a bioregenerative life support system using the Earth model to control for variance.

Metabolic response of Chlorella vulgaris to a transient thermal environment for supporting simultaneous air revitalization and thermal control in a crewed habitat

Implementing multifunctional bioregenerative technologies may provide mission carbon loop closure while simultaneously addressing multiple environmental control and life support system requirements. This paper proposes using water-based algal medium for thermal control of the spacecraft cabin, while taking advantage of the algae's photosynthetic activity for air revitalization. Consequently, this could expose the algal culture to transient thermal environments fluctuating between +4 °C and +30 °C, in the span of minutes, reflecting the operation of the International Space Station (ISS) internal thermal control and cabin system. This paper presents an initial investigation of the metabolic response of Chlorella vulgaris to transient environmental temperatures, reflecting temperature ranges and cycling frequency of the ISS cooling loop (+9 °C to +27 °C, 30 min). The constant 19 °C control represented the time-averaged temperature of the cycled condition. Growth and acclimation were observed in both tested conditions through pH, dissolved oxygen, optical density, and photosynthetic quantum yield measurements. However, there was significant reduction in the oxygen production rate, measured pH, and optical density for the cycled temperature condition when compared to the control (cycled temperature = 0.95 gO2 L−1 d−1, pH = 6.75, OD = 0.05; control = 1.17 gO2 L−1 d−1, pH = 8.20, OD = 0.08). No significant reduction in growth rate or photosynthetic quantum yield were recorded between the two tested conditions. Growth rate of the cycled temperature condition reflected those of psychrotolerant algae, suggesting some amount of culture acclimation to the rapidly dynamic environment. Results suggest that while C. vulgaris was viable within the tested temperature environment reflecting the ISS thermal control loop and cabin, there was a measurable reduction in the oxygen production rate.

Education in Ecological Engineering\u2014a Need Whose Time Has Come

Overcoming Limitations of Ecology and Engineering in Addressing Society’s ChallengesBy providing an integrated, systems-approach to problem-solving that incorporates ecological principles in engineering design, ecological engineering addresses, many of the limitations of Ecology and Engineering needed to work out how people and nature can beneficially coexist on planet Earth. Despite its origins in the 1950s, ecological engineering remains a niche discipline, while at the same time, there has never been a greater need to combine the rigour of engineering and science with the systems-approach of ecology for pro-active management of Earth’s biodiversity and environmental life-support systems. Broad consensus on the scope and defining elements of ecological engineering and development of a globally consistent ecological engineering curriculum are key pillars to mainstream recognition of the discipline and practice of ecological engineering.The Importance of Ecological Engineering in SocietyIn this paper, the importance of ecological engineering education is discussed in relation to the perceived need of our society to address global challenges of sustainable development. The perceived needs of industry, practitioners, educators and students for skills in ecological engineering are also discussed.The Importance and Need for Ecological Engineering EducationThe need for integrative, interdisciplinary education is discussed in relation to the scope of ecology, engineering and the unique role of ecological engineering.Scope for a Universally Recognised Curriculum in Ecological EngineeringThe scope for a universally recognised curriculum in ecological engineering is presented. The curriculum recognises a set of overarching principles and concepts that unite multiple application areas of ecological engineering practice. The integrative, systems-based approach of ecological engineering distinguishes it from the trend toward narrow specialisation in education. It is argued that the systems approach to conceptualising problems of design incorporating ecological principles is a central tenant of ecological engineering practice.Challenges to Wider Adoption of Ecological Engineering and Opportunities to Increase AdoptionChallenges and structural barriers to wider adoption of ecological engineering principles, embedded in our society’s reliance on technological solutions to environmental problems, are discussed along with opportunities to increase adoption of ecological engineering practice. It is suggested that unifying the numerous specialist activity areas and applications of ecological engineering under an umbrella encompassing a set of core principles, approaches, tools and way of thinking is required to distinguish ecological engineering from other engineering disciplines and scale up implementation of the discipline. It is concluded that these challenges can only be realised if ecological engineering moves beyond application by a relatively small band of enthusiastic practitioners, learning by doing, to the education of future cohorts of students who will become tomorrow’s engineers, project managers, procurement officers and decision makers, applying principles informed by a growing body of theory and knowledge generated by an active research community, a need whose time has come, if we are to deploy all tools at our disposal toward addressing the grand challenge of creating a sustainable future.

Electro-oxidation of urine and constituent analysis of resulting wastewater and generated gases for water recovery in space

Electro-oxidation is a promising technology to recover water from urine for space applications. The process generates oxidants such as reactive oxygen species and chlorine containing species that prevent microbial growth in the plumbing and decrease total organic carbon (TOC), chloride, and ammonia while waste heat generated from the electrochemical process facilitates evaporation of water to be recovered elsewhere. Resulting wastewater and generated gas constituents could be useful for recycling, further closing the environmental loop, and reducing trash/waste volume. In order to investigate the wastewater and generated gas constituents comprehensively, a full-scale urine processor for four crewmembers was built. Raw human urine (8.4 L) was circulated and processed by a flow-through oxidation cell (anode: boron-doped diamond on Niobium, cathode: Tungsten). The average water evaporation rate was 2.0 g/min. The 30-A current decreased TOC, chloride, and ammonia essentially to zero in the urine wastewater within 532, 622, and 373 A h, respectively. Total nitrogen (TN) was decreased from 5695 mg/L to 725 mg/L within 400 A h. Most of the remaining nitrogen was nitrate. Approximately 2.6 g of chlorine/chlorine dioxide, 0.85 g of ozone, 46.5 g of carbon dioxide, 15 g of hydrogen, and 0.1 g of ammonia gases were generated from 8.4 L of urine. The test demonstrated water evaporation for water recovery and identified useful gases to be recycled in an environmental control and life support system for space applications.

Material Characterization of Additively Manufactured Ti-6Al-4V Parts for an Environmental Control and Life Support System in Space Flight Hardware

Abstract Additive manufacturing has been added to the repertoire of production processes for components in the environmental control and life support system of space-faring habitable modules. In addition to cost savings over conventional machining, additive manufacturing expands the design space to enable more compact hardware configurations, resulting in reduced hardware volume and weight. Volume and weight reductions are coveted attributes of any spaceflight hardware in orbit or transit. The reliability of environmental control and life support systems is of paramount importance. Failure of these systems can result in catastrophic consequences. As part of an effort to implement additively manufactured parts in mission critical hardware, development hardware will be operated on the International Space Station in parallel with the existing qualified hardware. In order to support strength and durability assessment of the development hardware, a limited material characterization plan was developed. The derived data, describing some of the mechanical and metallurgical characteristics of a Ti-6Al-4V component built with a selective laser-melting additive manufacturing process, are presented. The number of test samples in the characterization are limited to one or two samples of each test type, precluding a statistical assessment of the properties, but a wide range of properties (including cross sectional metallography, Poisson’s ratio, tensile strength, fracture toughness, crack growth rate, and high cycle fatigue) are discussed.

SUSTAINABLE DEVELOPMENT OF THE TOURISM INDUSTRY: ENVIRONMENTAL AND STATISTICAL DIMENSION

Introduction. Tourism is an important area of socio-economic activity and makes a significant contribution to the state budget revenues of many countries. The growing importance of tourism and the exacerbation of problems associated with its development, make us talk about the need for change and the search for new vectors of development. This has led to numerous attempts to adapt the main provisions and principles of the concept of sustainable development in the context of the functioning of tourism. It should be noted that the first attempt to define sustainable tourism was made in 1988 by the World Tourism Organization. Sustainable tourism was seen as a direction that leads to the management of all resources in such a way that economic, social and aesthetic needs can be met while preserving cultural identity, basic environmental processes, biodiversity and life support systems. Goal. The purpose of the study is to introduce aspects of sustainable development of tourism as a purposeful influence on the processes of formation and maintenance of the tourist and recreational environment in the interests of society. Method (methodology). The methodological basis of the study were interdisciplinary and systematic approaches to the study of the functioning of the tourism industry. Results. This article reveals the features of the tourism industry from the standpoint of sustainable development.

Simulation and Experimental Research on a Gas Liquid Separator with Rotary Impeller

Gas-liquid separation technology under microgravity is the basis for various gas and liquid treatments on a manned spacecraft, which has a wide range of applications in Environmental Control and Life Support System. Dynamic gas-liquid separator is commonly used for the separation of gas-liquid two-phase flow, which has two essential performance parameters called liquid outlet pressure and separating efficiency. Predicting these two parameters accurately under a specific structure has guiding significance for design and application of the dynamic gas-liquid separator. In this study, CFD simulations were conducted using the Volume of Fluid (VOF) model at steady state conditions. In addition, experiments were designed to verify the accuracy of numerical results. Finally, the performance of the separator under microgravity was predicted. It is showed that the simulation method can be utilized to determine the transport performance of dynamic gas-liquid separator, which has significant value in design and optimization.