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NASA NTRS2014

International Space Station (ISS) Orbital Replaceable Unit (ORU) Wet Storage Risk Assessment

The International Space Station (ISS) Program requested the NASA Engineering and Safety Center (NESC) to evaluate the risks posed by the practice of long-term wet storage of ISS Environmental Control and Life Support (ECLS) regeneration system orbital replacement units (ORUs). The ISS ECLS regeneration system removes water from urine and humidity condensate and converts it into potable water and oxygen. A total of 29 ORUs are in the ECLS system, each designed to be replaced by the ISS crew when necessary. The NESC assembled a team to review the ISS ECLS regeneration system and evaluate the potential for biofouling and corrosion. This document contains the outcome of the evaluation.

Squire, Michael D.↗

NASA NTRS2017

Comparing Trash Disposal and Reuse Options for Deep Space Gateway and Mars Missions

Taking out the trash at NASA's newly proposed Deep Space Gateway (DSG) will not be a trivial task. While not the most important aspect of planning this cislunar outpost, there are several options that should be carefully considered since they may affect the crew as well as mission mass and volume. This study extends an earlier one, which focused on waste disposal options for a Mars Transit Vehicle. In that study, gasifying and venting trash along the way was found to noticeably reduce propellant needs and launch mass, whereas keeping processed trash on board in the form of radiation shielding tiles would significantly lower the crew's radiation dose during a solar particle event. Another favorable strategy was packing trash in a used logistics module for disposal. Since the DSG does not need much propulsion to maintain its orbit and Orion will be present with its own radiation storm shelter at the Gateway, the driving factors of the waste disposal trade study are different than for the Mars mission. Besides reviewing the propulsion and radiation shielding factors, potential drivers such as mass, power, volume, crew time, and human factors (e.g. smell) were studied. Disposal options for DSG include jettison of a used logistics module containing waste after every human stay, jettison of the same logistics module after several missions once it is full, regular disposal of trash via an airlock, or gasifying waste products for easier disposal or reuse. Conversely, a heat melt compactor device could be used to remove water and stabilize trash into tiles which could be more compactly stored on board and used as radiation shielding. Equivalent system mass analysis is used to tally the benefits and costs (mass, volume, power, crew time) of each case on an equivalent mass basis. Other more subjective factors are also discussed. Recommendations are made for DSG and Mars mission waste disposal.

Ewert, Michael↗

NASA NTRS2017

Non-Flow Through Fuel Cell Power Module Demonstration on the SCARAB Rover

NASA demonstrated the Advanced Product Water Removal (APWR) Non-Flow-Through (NFT) PEM fuel cell technology by powering the Scarab rover over three-(3) days of field operations. The latest generation APWR NFT fuel cell stackwas packaged by the Advanced Exploration Systems (AES) Modular Power Systems (AMPS) team into a nominallyrated 1-kW fuel cell power module. This power module was functionally verified in a laboratory prior to field operations on the Scarab rover, which concluded on 2 September 2015. During this demonstration, the power module satisfied all required success criteria by supporting all electrical loads as the Scarab navigated the NASA Glenn Research Center.

Fuel Cell↗

NASA NTRS2014

Continued Development of the Brine Evaporation Bag

The Brine Evaporation Bag (BEB) is a membrane-based bag system for the dewatering of brine. Previous studies showed the ability of the BEB to dewater brine at low temperatures with a 96 percent mass reduction. Additionally, a microgravity flight showed the BEB is microgravity compatible. Current work focuses on the effects of temperature, vacuum, purge gas flow rate, membrane area, and membrane permeability on the rate of dewatering within a vacuum oven configured to mimic the Heat Melt Compactor. Within this study, it was found that changing the temperature or level of vacuum would change the rate of dewatering. The purge gas, membrane area, and membrane permeability did not affect the dewater rate. The reason for this behavior may be that the dewatering is heat transfer limited, and out of all the parameters studied, only the temperature and vacuum have an effect on the heat transfer rate. The ISS (International Space Station) produces brine at a rate of 1.2 liters per day. This initial study showed that it is possible to remove water from a BEB at a rate of 1.6 liters per day in this breadboard configuration; even at moderate temperatures. Development of a dedicated BEB Evaporator will be discussed. In addition, it is further postulated that a specifically designed BEB Evaporator would result in an increased dewatering rate allowing for even lower operating temperatures or faster dewatering rates.

Recycling↗

NASA NTRS2021

Effect of Reactant Pressure on Proton Exchange Membrane Fuel Cell Performance

It is an objective of the National Aeronautics and Space Administration (NASA) to return to the moon and to create sustained lunar operations. Since many applicable lander and upper stage vehicles utilize cryogenic hydrogen and oxygen propellants, it is appealing to incorporate fuel cells into potential mission concepts. A fuel cell could generate electricity, heat, and water from the residual hydrogen and oxygen propellants. Such a concept depends on the capability of the fuel cell to utilize dry, propellant-grade reactants at reduced pressures compared to typical fuel cell operating conditions. This report describes a NASA evaluation of two passive water removal, non-flow-through proton exchange membrane (PEM) fuel cells: a twelve-cell 50 sq. cm active area stack and a seven-cell 150 sq. cm active area stack. Both stacks operated on research grade hydrogen and oxygen reactants supplied at pressures ranging from 20 psia up to the 45-48 psia design operating point, reliably supporting current densities of at least 450 mA/sq. cm at reduced pressures. Polarization curves, fitted with a semi-empirical equation for overpotential, show an increase in effective ohmic resistance and decrease in reversible cell potential, hydrogen crossover current, and Tafel slope when operating at lower pressures, resulting in a reduction in cell voltage at all current densities. Fitted parameters are compared to published values and rationalized with first principles explanations.

fuel cells↗

NASA NTRS2021

Effect of Reactant Purity on Proton Exchange Membrane Fuel Cell Performance

NASA has set a goal to return to the Moon and to establish a sustained lunar presence. Many applicable lander and upperstage vehicle concepts utilize cryogenic H2 and O2 propellants. This propellant selection enables appealing potential mission concepts wherein electricity is generated by operating a fuel cell on residual H2 and O2 propellants. This concept depends on the capability of the fuel cell to utilize dry, propellant-grade reactants with concentrations of up to 30 percent He present. This study consists of the evaluation of a 12-cell non-flow-through proton exchange membrane fuel cell stack of 50 sq. cm active area with passive water removal. This stack was supplied with three levels of reactant purity: >99.999, 99.1, and 70 mol%, with the remainder made up of He. The reactant humidity and flow-through rate were also assessed as performance factors, and the fuel stack repeatedly supported a load profile with current densities up to 500 mA/sq. cm (25 A). The fuel cell performed consistently over the course of testing, with cell voltages decreasing approximately 50 mV at the maximum current density when supplied with reactants with 30 percent He present.

electrochemistry↗

NASA NTRSDate not supplied

Lessons Learned in Space Life Support System Testing

The earlier problems can be found and corrected, the easier and cheaper it is to fix them. Doing less testing saves cost and time but doing too little testing increases the risk of operational failures causing large costs and delays. Integrated test is necessary to determine if the subsystems work together and the overall architecture performs as intended. This report reviews the testing lessons learned from the NASA Systems Engineering Handbook, a National Research Council report, and five reviews of International Space Station (ISS) lessons learned. The five reviews all mention two important points. First, that testing should be performed on the final integrated system, one as close as possible to the intended flight system. Second, “test as you fly,” while operating as planned in an environment as close as possible to the expected flight environment. Other lessons are the need for extensive preflight ground testing, the need to establish and defend an adequate budget, the problems using protoflight hardware on ISS, and the benefit of having ISS as a zero gravity test bed. The major ISS life support systems, carbon dioxide removal, water recycling, and oxygen recovery, were protoflight systems with little testing before launch to ISS. The failure rates of these systems have been much greater than predicted and this has caused dissatisfaction with the protoflight approach. The more costly traditional approach builds qualification and test units in addition to flight units. The test units are used to find, analyze, and fix failure modes. Other work shows that there is an optimum cost-effective amount of testing when redundant systems must have a specified reliability and confidence.

Harry W. Jones↗

NASA NTRSDate not supplied

Reduction of Equivalent System Mass of a Trash Compaction Processing System with an Emphasis on Improved Thermal Efficiency

A device known as the Trash Compaction Processing System or TCPS has been under development at NASA as part of the Advanced Life Support and Logistics Reduction Program Waste Management element. The TCPS processes trash that includes a variety of components such as plastic pouches that contain wet food and drinks, used cloth towels and t-shirts, adhesive tapes, deodorant, and many other items. The TCPS uses heat and pressure to compact the waste composite into a sturdy and well-defined shape designed to fit in a storage area on a spacecraft. The TCPS removes water from the trash and renders it safe against microbial activity. The focus of this paper is on methods for reducing the Equivalent System Mass of a TCPS with an emphasis on increasing the thermal efficiency of the system.

Trash Compaction Processing System↗

NASA NTRS1994

Apparatus Removes Organic Contaminants From Water

Catalytic-oxidation apparatus removes low-molecular-weight, polar, nonionizable organic contaminants from wastewater. Wastewater stream, previously treated by multifiltration process, pumped through apparatus for removal of trace organic contaminants. After injection of oxygen, flow preheated and enters catalytic reactor, where organic contaminants broken down into carbon dioxide and water. Carbon dioxide and unused oxygen removed in degasser.

Akse, James R.↗

NASA NTRS1992

Operation of a breadboard liquid-sorbent/membrane-contactor system for removing carbon dioxide and water vapor from air

Processes to remove and recover carbon dioxide (CO2) and water vapor from air are essential for successful long-duration space missions. This paper presents results of a developmental program focused on the use of a liquid-sorbent/membrane-contactor (LSMC) system for removal of CO2 and water vapor from air. In this system, air from the spacecraft cabin atmosphere is circulated through one side of a hollow-fiber membrane contactor. On the other side of the membrane contactor is flowed a liquid sorbent, which absorbs the CO2 and water vapor from the feed air. The liquid sorbent is then heated to desorb the CO2 and water vapor. The CO2 is subsequently removed from the system as a concentrated gas stream, whereas the water vapor is condensed, producing a water stream. A breadboard system based on this technology was designed and constructed. Tests showed that the LSMC breadboard system can produce a CO2 stream and a liquid-water stream. Details are presented on the operation of the system, as well as the effects on performance of variations in feed conditions.

Mccray, Scott B.↗

NASA NTRS2026

Hot Water, Cold Reality: Feasibility Assessment of Iodine Removal in Heated Spacecraft Potable Water Systems

The current eXploration Potable Water Dispenser (xPWD) design removes iodine upstream of the heated leg due to concerns with the Activated Carbon and Ion Exchange (ACTEX) functionality in hot water, leaving the downstream volume without residual biocide. The NESC determined that this non-iodinated volume is a concern for microbial growth during exploration missions and proposed 33 biocide architecture options for future missions that could address this concern. The top-ranked architecture out of the report was Option 1: moving the iodine removal media as close to the dispensing needle as possible to minimize the wetted components without biocide in the xPWD. Three main challenges were identified with this proposed configuration. First, the hot water at 175 ± 25 °F is a concern for the potential physical degradation of the ion exchange resin and lowered adsorption capacity in activated carbon. Second, moving the ACTEX or alternative sorption media closer to the dispense needle increases the unheated volume downstream of the heater, challenging the ability for dispensed water to meet temperature requirements. Finally, bubbles evolved from dissolved gas coming out of solution in the heater could clog or reduce the efficiency of the sorption media. To address the first challenge, more thermally robust ion exchange resins were identified and adsorption capacity tests were planned and will be discussed in a companion ICES paper (ICES-2026-5). To address the dispense temperature concerns, allowable bed size and architectural configuration changes are proposed. The value of adding phase separators to remove bubbles and potential implementation schemes are discussed. These findings support the development of potable water systems resilient to microbial risks during long-duration space missions.

Biocide↗

NASA NTRS2026

Hot Water, Cold Reality: Feasibility Assessment of Iodine Removal in Heated Spacecraft Potable Water Systems

PWD↗

NASA NTRS2012

Space Suit Portable Life Support System Test Bed (PLSS 1.0) Development and Testing

A multi-year effort has been carried out at NASA-JSC to develop an advanced extra-vehicular activity Portable Life Support System (PLSS) design intended to further the current state of the art by increasing operational flexibility, reducing consumables, and increasing robustness. Previous efforts have focused on modeling and analyzing the advanced PLSS architecture, as well as developing key enabling technologies. Like the current International Space Station Extra-vehicular Mobility Unit PLSS, the advanced PLSS comprises three subsystems required to sustain the crew during extra-vehicular activity including the Thermal, Ventilation, and Oxygen Subsystems. This multi-year effort has culminated in the construction and operation of PLSS 1.0, a test bed that simulates full functionality of the advanced PLSS design. PLSS 1.0 integrates commercial off the shelf hardware with prototype technology development components, including the primary and secondary oxygen regulators, Ventilation Subsystem fan, Rapid Cycle Amine swingbed carbon dioxide and water vapor removal device, and Spacesuit Water Membrane Evaporator heat rejection device. The overall PLSS 1.0 test objective was to demonstrate the capability of the Advanced PLSS to provide key life support functions including suit pressure regulation, carbon dioxide and water vapor removal, thermal control and contingency purge operations. Supplying oxygen was not one of the specific life support functions because the PLSS 1.0 test was not oxygen rated. Nitrogen was used for the working gas. Additional test objectives were to confirm PLSS technology development components performance within an integrated test bed, identify unexpected system level interactions, and map the PLSS 1.0 performance with respect to key variables such as crewmember metabolic rate and suit pressure. Successful PLSS 1.0 testing completed 168 test points over 44 days of testing and produced a large database of test results that characterize system level and component performance. With the exception of several minor anomalies, the PLSS 1.0 test rig performed as expected; furthermore, many system responses trended in accordance with pre-test predictions.

Watts, Carly↗

NASA NTRS1990

Selective removal of organics for water reclamation

Electrooxidation is a means of removing organic solutes directly from waste waters without the use of chemical expendables. The feasibility of the concept for oxidation of organic impurities common to urine, shower waters and space habitat humidity condensates was demonstrated. Electrooxidation of urine and waste water ersatz was experimentally demonstrated. The electrooxidation principle, reaction kinetics, efficiency, power, size, experimental test results and water reclamation applications are described. Process operating potentials and the use of anodic oxidation potentials that are sufficiently low to avoid oxygen formation and chloride oxidation are also described. The design of a novel electrochemical system that incorporates a proton exchange membrane (PEM) electrolyte is presented based on parametric test data and current fuel cell technology.

Murphy, Oliver J.↗

NASA NTRS2006

Development and Verification of a Finite-Difference Model of the Sorbent-Based Atmosphere Revitalization System for the Crew Exploration

A vacuum-swing adsorption (VSA) process to remove metabolic water, metabolic carbon dioxide, and metabolic and equipment generated trace contaminant gases from the Crew Exploration Vehicle (CEV) atmosphere is being designed. For the CEV, the approach is taken that all metabolic water must be removed by the Sorbent-Based Atmosphere Revitalization System (SBAR), a technology approach that has not been used in previous spacecraft life support systems. To support the design of the SBAR, a Finite Difference computer model has been developed. In addition, examination of the competitive adsorption aspects of water and carbon dioxide on various sorbents is being investigated in order to both refine the computer simulation and gain understanding of the VSA process

Ritter, James↗

NASA NTRS1994

A new material for removing heavy metals from water

The NASA Lewis Research Center developed and is patenting a new high capacity ion exchange material (IEM) that removes toxic metals from contaminated water in laboratory tests. The IEM can be made into many forms, such as thin films, coatings, pellets, and fibers. As a result, it can be adapted to many applications to purify contaminated water wherever it is found, be it in waste water treatment systems, lakes, ponds, industrial plants, or in homes. Laboratory tests have been conducted on aqueous solutions containing only one of the following metal cations: lead, copper, mercury, cadmium, silver, chromium (III), nickel, zinc, and yttrium. Tests were also conducted with: (1) calcium present to determine its effects on the uptake of cadmium and copper, and (2) uranium and lanthanides which are stand-ins for other radioactive elements, (3) drinking water for the removal of copper and lead, and (3) others compositions. The results revealed that the IEM removes all these cations, even in the presence of the calcium. Of particular interest are the results of the tests with the drinking water: the lead concentration was reduced from 142 ppb down to 2.8 ppb (well below the accepted EPA standard).

Philipp, Warren H., Jr.↗

NASA NTRS1995

Performance and optimization of a combustion interface for isotope ratio monitoring gas chromatography/mass spectrometry

Conditions and systems for on-line combustion of effluents from capillary gas chromatographic columns and for removal of water vapor from product streams were tested. Organic carbon in gas chromatographic peaks 15 s wide and containing up to 30 nanomoles of carbon was quantitatively converted to CO2 by tubular combustion reactors, 200 x 0.5 mm, packed with CuO or NiO. No auxiliary source of O2 was required because oxygen was supplied by metal oxides. Spontaneous degradation of CuO limited the life of CuO reactors at T > 850 degrees C. Since NiO does not spontaneously degrade, its use might be favored, but Ni-bound carbon phases form and lead to inaccurate isotopic results at T < 1050 degrees C if gas-phase O2 is not added. For all compounds tested except CH4, equivalent isotopic results are provided by CuO at 850 degrees C, NiO + O2 (gas-phase mole fraction, 10(-3)) at 1050 degrees C and NiO at 1150 degrees C. The combustion interface did not contribute additional analytical uncertainty, thus observed standard deviations of 13C/12C ratios were within a factor of 2 of shot-noise limits. For combustion and isotopic analyses of CH4, in which quantitative combustion required T approximately 950 degrees C, NiO-based systems are preferred, and precision is approximately 2 times lower than that observed for other analytes. Water must be removed from the gas stream transmitted to the mass spectrometer or else protonation of CO2 will lead to inaccuracy in isotopic analyses. Although thresholds for this effect vary between mass spectrometers, differential permeation of H2O through Nafion tubing was effective in both cases tested, but the required length of the Nafion membrane was 4 times greater for the more sensitive mass spectrometer.

NASA Discipline Exobiology↗

NASA NTRS2006

Development and Testing of a Sorbent-Based Atmosphere Revitalization System for the Crew Exploration Vehicle

The design of a vacuum-swing adsorption process to remove metabolic water, metabolic carbon dioxide, and metabolic and equipment generated trace contaminant gases from the Crew Exploration Vehicle (CEV) atmosphere is presented. For the CEV, the approach is taken that all metabolic water must be removed by the Sorbent-Based Atmosphere Revitalization System (SBAR), a technology approach that has not been used in previous spacecraft life support systems. Design and development of a prototype SBAR, a facility test stand, and subsequent testing of the SBAR is discussed.

Knox, James C.↗