Spacecraft Life Support Systems Research Articles

Recent Progress in Electrocatalytic Reduction of CO2

A stable life support system in the spacecraft can greatly promote long-duration, far-distance, and multicrew manned space flight. Therefore, controlling the concentration of CO2 in the spacecraft is the main task in the regeneration system. The electrocatalytic CO2 reduction can effectively treat the CO2 generated by human metabolism. This technology has potential application value and good development prospect in the utilization of CO2 in the space station. In this paper, recent research progress for the electrocatalytic reduction of CO2 was reviewed. Although numerous promising accomplishments have been achieved in this field, substantial advances in electrocatalyst, electrolyte, and reactor design are yet needed for CO2 utilization via an electrochemical conversion route. Here, we summarize the related works in the fields to address the challenge technology that can help to promote the electrocatalytic CO2 reduction. Finally, we present the prospective opinions in the areas of the electrocatalytic CO2 reduction, especially for the space station and spacecraft life support system.

Meeting the Challenge of Transmission Delay: Communication Protocols for Space Operations.

Several studies were conducted to assess media-specific communication protocols as a countermeasure to challenges of asynchronous space-ground communication. Previous research demonstrated that transmission delay can negatively impact space-ground communication, collaboration, and task performance. We created media-specific protocols designed to mitigate identified problems associated with asynchronous communication and examined their effects on team communication and task performance. The lab study included 24 teams of three who collaborated remotely via voice or text on computer-based tasks simulating failures in a spacecraft's life support system. Training and availability of communication protocols was the between-groups variable. Perceived usability, criticality, and effectiveness of the communication protocols were also assessed in space-analog simulations. Lab study data revealed that communication protocols facilitated some aspects of team communication; specifically, they reduced threats to common ground and information splitting but not instances of miscommunication. Analog data indicated that protocol compliance was high, participants evaluated most elements as highly important, and protocols maintained perceived communication effectiveness between space crews and mission control during time delay comparably to no-time-delay conditions. Converging data attest to the feasibility, usability, and effectiveness of empirically derived communication protocols as a countermeasure to the negative impacts of transmission delay and also point to technological solutions. The communication protocols have been adopted for training in NASA analog simulations involving time-delayed communication. They could also support communication among remote team members in medical operations, command-and-control teams, or disaster response under asynchronous conditions or when time is limited and precise communication is critical.

Microbiome and Metagenome Analyses of a Closed Habitat during Human Occupation.

Microbial contamination during long-term confinements of space exploration presents potential risks for both crew members and spacecraft life support systems. A novel swab kit was used to sample various surfaces from a submerged, closed, analog habitat to characterize the microbial populations. Samples were collected from various locations across the habitat which were constructed from various surface materials (linoleum, dry wall, particle board, glass, and metal), and microbial populations were examined by culture, quantitative PCR (qPCR), microbiome 16S rRNA gene sequencing, and shotgun metagenomics. Propidium monoazide (PMA)-treated samples identified the viable/intact microbial population of the habitat. The cultivable microbial population ranged from below the detection limit to 106 CFU/sample, and their identity was characterized using Sanger sequencing. Both 16S rRNA amplicon and shotgun sequencing were used to characterize the microbial dynamics, community profiles, and functional attributes (metabolism, virulence, and antimicrobial resistance). The 16S rRNA amplicon sequencing revealed abundance of viable (after PMA treatment) Actinobacteria (Brevibacterium, Nesternkonia, Mycobacterium, Pseudonocardia, and Corynebacterium), Firmicutes (Virgibacillus, Staphylococcus, and Oceanobacillus), and Proteobacteria (especially Acinetobacter) on linoleum, dry wall, and particle board (LDP) surfaces, while members of Firmicutes (Leuconostocaceae) and Proteobacteria (Enterobacteriaceae) were high on the glass/metal surfaces. Nonmetric multidimensional scaling determined from both 16S rRNA and metagenomic analyses revealed differential microbial species on LDP surfaces and glass/metal surfaces. The shotgun metagenomic sequencing of samples after PMA treatment showed bacterial predominance of viable Brevibacterium (53.6%), Brachybacterium (7.8%), Pseudonocardia (9.9%), Mycobacterium (3.7%), and Staphylococcus (2.1%), while fungal analyses revealed Aspergillus and Penicillium dominance.IMPORTANCE This study provides the first assessment of monitoring cultivable and viable microorganisms on surfaces within a submerged, closed, analog habitat. The results of the analyses presented herein suggest that the surface material plays a role in microbial community structure, as the microbial populations differed between LDP and metal/glass surfaces. The metal/glass surfaces had less-complex community, lower bioburden, and more closely resembled the controls. These results indicated that material choice is crucial when building closed habitats, even if they are simply analogs. Finally, while a few species were associated with previously cultivated isolates from the International Space Station and MIR spacecraft, the majority of the microbial ecology of the submerged analog habitat differs greatly from that of previously studied analog habitats.

Effect of altered nitrogen partial pressure on Chlorellaceae for spaceflight applications

Algal-based photobioreactors offer a promising bioregenerative technology that can perform the functions of air revitalization, water recycling, and food production in a human spacecraft life support system. In order to assess their performance in this context, this study exposed a non-axenic green algal culture (Chlorellacea) to an atmospheric pressure of 8.2psia [56.5 kPa] with an oxygen concentration of 34%, which are currently proposed cabin atmosphere conditions for future space exploration missions. Growth and metabolism of green algae were compared to a control experiment kept at 14.7psia [101.3 kPa] with oxygen and carbon dioxide partial pressure maintained at constant levels of 3.1 and 0.147psia [21.3 and 1.0 kPa], respectively, which represent concentrations of 21 and 1% at standard sea level pressure. To conduct the evaluation, a flow-through photobioreactor was developed that can precisely control atmospheric compositions such as partial pressures of oxygen and carbon dioxide and set the total pressure solely by altering the nitrogen partial pressure. Algal performance was measured by daily cell counts and optical density measurements. Additionally, continuous measurements of dissolved oxygen and pH in the liquid phase, as well as evolved oxygen and absorbed carbon dioxide in the gaseous phase, were collected. A metagenomic analysis was conducted on the algal culture to assure the composition of the algal culture remained consistent during the experimental phase, as well as to characterize the nature of coexisting contaminants in the non-axenic culture. The performance of the algal culture was compared to related, previously published literature values. The hypothesized increase in performance of the algal culture under reduced pressures was not verified, rather it was shown that the nitrogen partial pressure neither benefits nor inhibits algal growth under the tested conditions.

Optimal Design of Porous Structures for the Fastest Liquid Absorption

Porous materials engineered for rapid liquid absorption are useful in many applications, including oil recovery, spacecraft life-support systems, moisture management fabrics, medical wound dressings, and microfluidic devices. Dynamic absorption in capillary tubes and porous media is driven by the capillary pressure, which is inversely proportional to the pore size. On the other hand, the permeability of porous materials scales with the square of the pore size. The dynamic competition between these two superimposed mechanisms for liquid absorption through a heterogeneous porous structure may lead to an overall minimum absorption time. In this work, we explore liquid absorption in two different heterogeneous porous structures [three-dimensional (3D) circular tubes and porous layers], which are composed of two sections with variations in radius/porosity and height. The absorption time to fill the voids of porous constructs is expressed as a function of radius/porosity and height of local sections, and the absorption process does not follow the classic Washburn's law. Under given height and void volume, these two-section structures with a negative gradient of radius/porosity against the absorption direction are shown to have faster absorption rates than control samples with uniform radius/porosity. In particular, optimal structural parameters, including radius/porosity and height, are found that account for the minimum absorption time. The liquid absorption in the optimized porous structure is up to 38% faster than in a control sample. The results obtained can be used a priori for the design of porous structures with excellent liquid management property in various fields.

Experimental Research on Sealing Structure Leak-Rate of Pressurized Tube

In aerospace engineering, seal is an important component of manned spacecraft life-support system. The pressurized tube sealing equipment is designed, and the experimental system of principle leak-rate of pressurized tube is built, and the experimental theory of the principle leak-rate of pressurized tube is carried out. The experimental results show that leak-rate of pressurized tube is related with the internal pressure of pressurized tube, and sealing ability can be adjusted by controlling the pressure in tube. And leak-rate of pressurized tube is involved with sealed pressure differential, and the bigger pressure differential is, the larger leak-rate becomes. And pressurized tube can fit for big structure transfiguration, which provides condition for lessening structural weight. And the pressurized tube can meet the demands of sealing of space station.

Cognitive diversity and team performance in a complex multiple task environment

This article examines the multiple effects of cognitive diversity in teams operating complex human-machine-systems. The study employed a PC-based multiple-task environment, called the Cabin Air Management System, which models a process control task in the operational context of a spacecraft's life support system. Two types of cognitive diversity were examined: system understanding and team specialization. System understanding referred to the depth of understanding team members were given during training (low-level procedure-oriented vs. high level knowledge-oriented training). Team specialization referred to the degree to which knowledge about system fault scenarios was distributed between team members (specialized vs. non-specialized). A total of 72 participants took part in the study. After having received 4.5 h of training on an individual basis, participants completed a 1-h experimental session, in which they worked in two-person teams on a series of fault scenarios of varying difficulty. Measures were taken of primary and secondary task performance, system intervention and information sampling strategies, system knowledge, subjective operator state, communication patterns and conflict. The results provided evidence for the benefits of cognitive diversity with regard to system understanding. This manifested itself in better primary task performance and more efficient manual system control. No advantages were found for cognitive diversity with regard to specialization. There was no effect of cognitive diversity on intra-team conflict, with conflict levels generally being very low. The article concludes with a discussion of the implications of the findings for the engineering of cognitive diversity in teams operating complex human-machine-systems.

Analysis of a spacecraft life support system for a Mars mission

This report summarizes a trade study conducted as part of the Fall 2002 semester Spacecraft Life Support System Design course (ASEN 5116) in the Aerospace Engineering Sciences Department at the University of Colorado. It presents an analysis of current life support system technologies and a preliminary design of an integrated system for supporting humans during transit to and on the surface of the planet Mars. This effort was based on the NASA Design Reference Mission (DRM) for the human exploration of Mars [NASA Design Reference Mission (DRM) for Mars, Addendum 3.0, from the world wide web: http://exploration.jsc.nasa.gov/marsref/contents.html.]. The integrated design was broken into four subsystems: Water Management, Atmosphere Management, Waste Processing, and Food Supply. The process started with the derivation of top-level requirements from the DRM. Additional system and subsystem level assumptions were added where clarification was needed. Candidate technologies were identified and characterized based on performance factors. Trade studies were then conducted for each subsystem. The resulting technologies were integrated into an overall design solution using mass flow relationships. The system level trade study yielded two different configurations—one for the transit to Mars and another for the surface habitat, which included in situ resource utilization. Equivalent System Mass analyses were used to compare each design against an open-loop (non-regenerable) baseline system.

CAMS as a tool for human factors research in spaceflight

The paper reviews a number of research studies that were carried out with a PC-based task environment called Cabin Air Management System (CAMS) simulating the operation of a spacecraft's life support system. As CAMS was a multiple task environment, it allowed the measurement of performance at different levels. Four task components of different priority were embedded in the task environment: diagnosis and repair of system faults, maintaining atmospheric parameters in a safe state, acknowledgement of system alarms (reaction time), and keeping a record of critical system resources (prospective memory). Furthermore, the task environment permitted the examination of different task management strategies and changes in crew member state (fatigue, anxiety, mental effort). A major goal of the research programme was to examine how crew members adapted to various forms of sub-optimal working conditions, such as isolation and confinement, sleep deprivation and noise. None of the studies provided evidence for decrements in primary task performance. However, the results showed a number of adaptive responses of crew members to adjust to the different sub-optimal working conditions. There was evidence for adjustments in information sampling strategies (usually reductions in sampling frequency) as a result of unfavourable working conditions. The results also showed selected decrements in secondary task performance. Prospective memory seemed to be somewhat more vulnerable to sub-optimal working conditions than performance on the reaction time task. Finally, suggestions are made for future research with the CAMS environment.

Effects of training on short- and long-term skill retention in a complex multiple-task environment

The paper reports the results of an experiment on the performance and retention of a complex task. This was a computer-based simulation of the essential elements of a spacecraft's life support system. It allowed the authors to take a range of measures, including primary and secondary task performance, system intervention and information sampling strategies, mental model structure, and subjective operator state. The study compared the effectiveness of two methods of training, based on low level (procedure-based) and high level (system-based) understanding. Twenty-five participants were trained extensively on the task, then given a 1-h testing session. A second testing session was carried out 8 months after the first (with no intervening practice) with 17 of the original participants. While training had little effect on control performance, there were considerable effects on system management strategies, as well as in structure of operator's mental model. In the second testing session, the anticipated general performance decrement did not occur, though for complex faults there was an increase in selectivity towards the primary control task. The relevance of the findings for training and skill retention in real work environments is discussed in the context of a model of compensatory control.

On Measuring the Oxygen Stocks in Spacecraft Life-Support Systems

For measuring the on-board oxygen stocks this paper suggests that a high frequency resonance technique for measuring non-electric quantities be used. The problem is solved by using a pick-up made of a section of a non-uniform long line with an oxygen tank as one of its conductors and a metal line evenly distributed over the tank volume as the other. Analysis shows that the resonant frequency of such pick-up’s oscillations is invariant with the geometry of its distribution inside the tank volume and characterises only its stock (mass).

Task Committee on Civil Engineering in Space of the Committee on Space Facilities of the Aero-Space Transport Division

Engineers with degrees in civil engineering have made and will continue to make important contributions to the national aerospace program. It is well known that many civil engineers have for years contributed to aircraft and spacecraft design by virtue of their education in stress analysis and structural design. Civil engineers have also contributed to the development of spacecraft life support systems. Their activities in construction of ground support facilities are well known. The Civil Engineer in Space Task Committee was chartered to study and define the present and future role of the civil engineer in aerospace programs. The Committee therefore decided to survey selected segments of the industrial, governmental, and university communities to ascertain the extent of present involvement of civil engineers in aerospace work.