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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS2014

Advanced Supported Liquid Membranes for CO2 Control in Extravehicular Activity Applications

Developing a new, robust, portable life support system (PLSS) is currently a high priority for NASA in order to support longer and safer extravehicular activity (EVA) missions. One of the critical PLSS functions is maintaining the carbon dioxide (CO2) concentration in the suit at acceptable levels. Although the Metal Oxide (MetOx) canister has worked well, it has a finite CO2 adsorption capacity. Consequently, the unit would have to be larger and heavier to extend EVA times. Therefore, new CO2 control technologies must be developed to meet mission objectives without increasing the size of the PLSS. Although recent work has centered on sorbents that can be regenerated during the EVA, this strategy increases the system complexity and power consumption. A simpler approach is to use a membrane that selectively vents CO2 to space. A membrane has many advantages over current technology: it is a continuous system with no theoretical capacity limit, it requires no consumables, and it requires no hardware for switching beds between absorption and regeneration. Unfortunately, conventional gas separation membranes do not have adequate selectivity for use in the PLSS. However, the required performance could be obtained with a supported liquid membrane (SLM), which consists of a micro porous material filled with a liquid that selectively reacts with CO2 over oxygen (O2). In a current Phase II SBIR project, Reaction Systems has developed a new reactive liquid, which has effectively zero vapor pressure making it an ideal candidate for use in an SLM. The SLM function has been demonstrated with representative pressures of CO2, O2, and water (H2O). In addition to being effective for CO2 control, the SLM also vents moisture to space. Therefore, this project has demonstrated the feasibility of using an SLM to control CO2 in an EVA application.

Wickham, David T.↗
NASA NTRS2014

Spacesuit Water Membrane Evaporator; An Enhanced Evaporative Cooling System for the Advanced Extravehicular Mobility Unit Portable Life Support System

Development of the Advanced Extravehicular Mobility Unit (AEMU) portable life support subsystem (PLSS) is currently under way at NASA Johnson Space Center. The AEMU PLSS features a new evaporative cooling system, the Generation 4 Spacesuit Water Membrane Evaporator (Gen4 SWME). The SWME offers several advantages when compared with prior crewmember cooling technologies, including the ability to reject heat at increased atmospheric pressures, reduced loop infrastructure, and higher tolerance to fouling. Like its predecessors, Gen4 SWME provides nominal crew member and electronics cooling by flowing water through porous hollow fibers. Water vapor escapes through the hollow fiber pores, thereby cooling the liquid water that remains inside of the fibers. This cooled water is then recirculated to remove heat from the crew member and PLSS electronics. Test results from the backup cooling system which is based on a similar design and the subject of a companion paper, suggested that further volume reductions could be achieved through fiber density optimization. Testing was performed with four fiber bundle configurations ranging from 35,850 fibers to 41,180 fibers. The optimal configuration reduced the Gen4 SWME envelope volume by 15% from that of Gen3 while dramatically increasing the performance margin of the system. A rectangular block design was chosen over the Gen3 cylindrical design, for packaging configurations within the AEMU PLSS envelope. Several important innovations were made in the redesign of the backpressure valve which is used to control evaporation. A twin-port pivot concept was selected from among three low profile valve designs for superior robustness, control and packaging. The backpressure valve motor, the thermal control valve, delta pressure sensors and temperature sensors were incorporated into the manifold endcaps, also for packaging considerations. Flight-like materials including a titanium housing were used for all components. Performance testing of the Gen4 SWME is underway.

Bue, Grant C.↗
NASA NTRS2015

Continued Advancement of Supported Liquid Membranes for Carbon Dioxide Control in Extravehicular Activity Applications

The development of a new, robust, portable life support system (PLSS) is a high priority for NASA in order to support longer and safer extravehicular activity (EVA) missions. One of the critical PLSS functions is maintaining the carbon dioxide (CO2) concentration in the suit at acceptable levels. Although the Metal Oxide (MetOx) canister has historically performed very well, it has a finite CO2 adsorption capacity. Therefore, the size and weight of the unit would have to be increased to extend EVA times. Consequently, new CO2 control technologies must be developed in order to meet mission objectives without increasing the size of the PLSS. Recent work has centered on sorbents that can be regenerated during the EVA; however, this strategy increases the system complexity and power consumption. A much simpler approach is to employ a membrane that vents CO2 to space and retains oxygen (O2). A membrane has many advantages over current technology: it is a continuous system with no limit on capacity, it requires no consumables, and it does not need any hardware to switch beds between absorption and regeneration. Unfortunately, conventional gas separation membranes do not have the needed selectivity for use in the PLSS. However, the required performance could be obtained with a supported liquid membrane (SLM), which consists of a microporous material filled with a liquid that selectively reacts with CO2 over O2. In a recently completed Phase II SBIR project, Reaction Systems, Inc. achieved the required CO2 permeance and selectivity with an SLM in a flat sheet configuration. This paper describes work to convert the SLM into a more compact form and to scale it up to handle more representative process flow rates.

Wickham, David T.↗
NASA NTRS2015

Experimentally Determined Heat Transfer Coefficients for Spacesuit Liquid Cooled Garments

A Human-In-The-Loop (HITL) Portable Life Support System 2.0 (PLSS 2.0) test has been conducted at NASA Johnson Space Center in the PLSS Development Laboratory from October 27, 2014 to December 19, 2014. These closed-loop tests of the PLSS 2.0 system integrated with human subjects in the Mark III Suit at 3.7 psi to 4.3 psi above ambient pressure performing treadmill exercise at various metabolic rates from standing rest to 3000 BTU/hr (880 W). The bulk of the PLSS 2.0 was at ambient pressure but effluent water vapor from the Spacesuit Water Membrane Evaporator (SWME) and the Auxiliary Membrane Evaporator (Mini-ME), and effluent carbon dioxide from the Rapid Cycle Amine (RCA) were ported to vacuum to test performance of these components in flight-like conditions. One of the objectives of this test was to determine the heat transfer coefficient (UA) of the Liquid Cooling Garment (LCG). The UA, an important factor for modeling the heat rejection of an LCG, was determined in a variety of conditions by varying inlet water temperature, flowrate, and metabolic rate. Three LCG configurations were tested: the Extravehicular Mobility Unit (EMU) LCG, the Oceaneering Space Systems (OSS) LCG, and the OSS auxiliary LCG. Other factors influencing accurate UA determination, such as overall heat balance, LCG fit, and the skin temperature measurement, will also be discussed.

Bue, Grant↗
NASA NTRS2015

Continued Advancement of Supported Liquid Membranes for Carbon Dioxide Control in Extravehicular Activity Applications

The Development of a new, robust, portable life support system (PLSS) is currently a high NASA priority in order to support longer and safer extravehicular activity (EVA) missions that will be necessary as space travel extends to near-Earth asteroids and eventually Mars. One of the critical PLSS functions is maintaining the carbon dioxide (CO2) concentration in the suit at acceptable levels. The Metal Oxide (MetOx) canister has a finite CO2 adsorption capacity and therefore in order to extend mission times, the unit would have to be larger and heavier, which is undesirable; therefore new CO2 control technologies must be developed. While recent work has centered on the use of alternating sorbent beds that can be regenerated during the EVA, this strategy increases the system complexity and power consumption. A simpler approach is to use a membrane that vents CO2 to space but retains oxygen(O2). A membrane has many advantages over current technology: it is a continuous system with no theoretical capacity limit, it requires no consumables, and it requires no hardware for switching beds between absorption and regeneration. Conventional gas separation membranes do not have adequate selectivity for use in the PLSS, but the required performance could be obtained with a supported liquid membrane (SLM), which consists of a microporous film filled with a liquid that selectively reacts with CO2 over oxygen (O2). In a recently completed Phase II Small Business Innovative Research project, Reaction Systems developed a new reactive liquid that has effectively zero vapor pressure, making it an ideal candidate for use in an SLM. Results obtained with the SLM in a flat sheet configuration with representative pressures of CO2, O2, and water (H2O) have shown that the CO2 permeation rate and CO2/O2 selectivity requirements have been met. In addition, the SLM vents moisture to space very effectively. The SLM has also been prepared and tested in a hollow fiber form, which will be necessary to meet size requirements in the PLSS. In initial tests, the required CO2 permeance values have been obtained, while the current CO2/O2 selectivity values are somewhat lower than needed. However, the performance of the SLM is a strong function of the method used to impregnate the sorbent in the hollow fiber walls and rapid progress is being made in that area.

Wickham, David T.↗
NASA NTRS2015

Experimentally Determined Overall Heat Transfer Coefficients for Spacesuit Liquid Cooled Garments

A Human-In-The-Loop (HITL) Portable Life Support System 2.0 (PLSS 2.0) test has been conducted at NASA Johnson Space Center in the PLSS Development Laboratory from October 27, 2014 to December 19, 2014. These closed-loop tests of the PLSS 2.0 system integrated with human subjects in the Mark III Suit at 3.7 psi to 4.3 psi above ambient pressure performing treadmill exercise at various metabolic rates from standing rest to 3000 BTU/hr (880 W). The bulk of the PLSS 2.0 was at ambient pressure but effluent water vapor from the Spacesuit Water Membrane Evaporator (SWME) and the Auxiliary Membrane Evaporator (Mini-ME), and effluent carbon dioxide from the Rapid Cycle Amine (RCA) were ported to vacuum to test performance of these components in flight-like conditions. One of the objectives of this test was to determine the overall heat transfer coefficient (UA) of the Liquid Cooling Garment (LCG). The UA, an important factor for modeling the heat rejection of an LCG, was determined in a variety of conditions by varying inlet water temperature, flow rate, and metabolic rate. Three LCG configurations were tested: the Extravehicular Mobility Unit (EMU) LCG, the Oceaneering Space Systems (OSS) LCG, and the OSS auxiliary LCG. Other factors influencing accurate UA determination, such as overall heat balance, LCG fit, and the skin temperature measurement, will also be discussed.

Bue, Grant↗
NASA NTRS2015

Utilizing a Suited Manikin Test Apparatus and Space Suit Ventilation Loop to Evaluate Carbon Dioxide Washout

NASA is pursuing technology development of an Advanced Extravehicular Mobility Unit (AEMU) which is an integrated assembly made up of primarily a pressure garment system and a portable life support subsystem (PLSS). The PLSS is further composed of an oxygen subsystem, a ventilation subsystem, and a thermal subsystem. One of the key functions of the ventilation system is to remove and control the carbon dioxide (CO2) delivered to the crewmember. Carbon dioxide washout is the mechanism by which CO2 levels are controlled within the space suit helmet to limit the concentration of CO2 inhaled by the crew member. CO2 washout performance is a critical parameter needed to ensure proper and robust designs that are insensitive to human variabilities in a space suit. A suited manikin test apparatus (SMTA) was developed to augment testing of the PLSS ventilation loop in order to provide a lower cost and more controlled alternative to human testing. The CO2 removal function is performed by the regenerative Rapid Cycle Amine (RCA) within the PLSS ventilation loop and its performance is evaluated within the integrated SMTA and Ventilation Loop test system. This paper will provide a detailed description of the schematics, test configurations, and hardware components of this integrated system. Results and analysis of testing performed with this integrated system will be presented within this paper.

Chullen, Cinda↗
NASA NTRSDate not supplied

Space Suit Portable Life Support System Thermal Control Valve Ball Design

A Thermal Control Valve (TCV) has been in development for the Exploration Extravehicular Mobility Unit Portable Life Support System (xEMU PLSS). The xEMU PLSS TCV controls flow going to the liquid cooling and ventilation garment that the crew member wears during extra-vehicular activity to expel waste heat. A pervious TCV version with a linear actuator and diverter valve has been tested extensively to attempt to control the flow accurately. The previous TCV diverter valve has a non-linear flow response relative to valve position and has struggled to accurately meet the setpoints desired for precision thermal control. While many diverter valve design variations have been attempted, previous designs have all had difficulty in meeting set points. Additionally, high precision machining is required for these diverter valves to create a metal-on-metal seal which has its own drawbacks and doesn’t always meet requirements for internal leakage. This metal compression seal also requires stalling the linear actuator to load the seal in compression or tension which has demonstrated valve sticking failures when stalled. The xEMU PLSS TCV implements a new approach and design for a TCV which uses a rotational ball to control flow and has demonstrated a much more precise and linear flow control. The design functions like a two-way ball valve with two Teflon seats that cradle and compress the ball for sealing. A new geometric design modification to the ball outlet can create a set-able orifice like hole which is more predictable at controlling flow than using an annulus with the previous diverter valve. Additionally, the Teflon seat performs much better for preventing internal leakage than the metal seal and prevents sticking by having a large range in which it is sealed without having to stall the actuator. This paper will review a new proposed xEMU PLSS TCV ball design and compare it with previous iterations of the design.

Ryan Ogilvie↗
NASA NTRSDate not supplied

Rapid Cycle Amine 4.0 System Development

Carbon dioxide (CO2) and humidity control is a key function of the spacesuit Portable Life Support Subsystem (PLSS). The latest spacesuit design utilizes a pressure swing bed containing a solid amine sorbent to scrub CO2 and humidity produced by the crewmember from the ventilation loop. The solid amine sorbent removes CO2 and humidity from the ventilation loop through a chemisorption mechanism. Simultaneously, CO2 and humidity are desorbed to vacuum via the two-bed pressure swing system during operation. This continuous regeneration allows for longer Extravehicular Activity (EVA) times while minimizing maintenance, consumables, and power usage. This concept has been in development for over 20 years, during which many prototypes and design iterations have been fabricated and evaluated. This paper discusses the recent Rapid Cycle Amine (RCA) design, development, and testing that has been done to advance the technology. The most recent fabrication is the RCA 3.0. It was delivered to NASA Johnson Space Center in 2015 and has since been tested at the component level and at the integrated PLSS level. The purpose of the component level testing was to understand CO2 removal capacity, end-of-life performance, and establish a baseline performance prior to integrated testing. The RCA 3.0 was integrated into the Exploration Extravehicular Mobility Unit (xEMU) PLSS for a comprehensive Design Verification Test (DVT) series. The integrated testing provided the benefit of characterizing the impact performance degradation has on the system. Many of the RCA requirements were developed through analysis, based on the limitations of the PLSS and, in some cases, assumptions about the system and flow behavior. Integrated testing was an opportunity to validate those requirements and assumptions. While the RCA 3.0 was being tested, the next design iteration, RCA 4.0, was under development. The RCA 4.0 preliminary design phase began in late-2019 and shortly after the Preliminary Design Review, the critical design phase began in 2021. The design work has concluded with the completion of a Pre-Manufacturing Review in 2022. This paper provides an overview of the RCA 4.0 system design, summarizes the results of integrated RCA 3.0 testing, and discusses the pertinence of driving requirements such as mass, volume, and power consumption.

Kelsey Bloom↗
NASA NTRS1987

Electrochemically regenerable carbon dioxide/moisture control technology for an Advanced Extravehicular Mobility Unit

Regenerable CO2/moisture removal techniques that reduce the expendables and logistics requirements are needed to sustain people undertaking EVAs for the Space Station. Here, the development of electrochemically regenerable CO2 absorption (ERCA) technology to replace the nonregenerable LiOH absorber for the advanced Portable Life Support System (PLSS) is reported. During EVA the ERCA uses a mechanism involving gas absorption into a liquid absorbent for the removal and storage of the metabolically produced CO2 and moisture. Following the EVA, the expended absorbent is regenerated onboard the Space Station by an electrochemical CO2 concentrator. The ERCA concept has the ability to effectively satisfy the high metabolic CO2 and moisture removal requirements of PLSS applications. This paper defines the ERCA concept and its advantages for the PLSS application, reviews breadboard test data, and presents physical characteristics of the breadboard and projected flight hardware.

Lee, M. C.↗
NASA NTRS1988

Electrochemically regenerable metabolic CO2 and moisture control system for an advanced EMU application

Regenerable CO2 and moisture removal techniques that reduce expendables and logistics requirements are needed to sustain people undertaking extravehicular activities for the Space Station. NASA has been investigating ways to advance the Electrochemically Regenerable CO2 and Moisture Absorption (ERCA) technology to replace the nonregenerable solid lithium hydroxide absorber for the advanced Portable Life Support System (PLSS). The ERCA technology, due to its use of liquid absorbent, has the ability to effectively satisfy the high metabolic CO2 and moisture removal requirements of PLSS applications. This paper defines the ERCA technology concept and its advantages for the PLSS application, reviews breadboard and subscale testdata and presents the results of design concepts for a prototype Absorber Module of improved performance and the physical characteristics of the projected flight hardware.

Lee, M. C.↗
NASA NTRS1998

Advanced Spacesuit Portable Life Support System Packaging Concept Mock-Up Design & Development

A concentrated development effort was begun at NASA Johnson Space Center to create an advanced Portable Life Support System (PLSS) packaging concept. Ease of maintenance, technological flexibility, low weight, and minimal volume are targeted in the design of future micro-gravity and planetary PLSS configurations. Three main design concepts emerged from conceptual design techniques and were carried forth into detailed design, then full scale mock-up creation. "Foam", "Motherboard", and "LEGOtm" packaging design concepts are described in detail. Results of the evaluation process targeted maintenance, robustness, mass properties, and flexibility as key aspects to a new PLSS packaging configuration. The various design tools used to evolve concepts into high fidelity mock ups revealed that no single tool was all encompassing, several combinations were complimentary, the devil is in the details, and, despite efforts, many lessons were learned only after working with hardware.

O''Connell, Mary K.↗
NASA NTRS2007

Development of a Rapid Cycling CO(sub 2) and H(sub 2)O Removal Sorbent

The National Aeronautics and Space Administration (NASA) planned future missions set stringent demands on the design of the Portable Life Support System (PLSS), requiring dramatic reductions in weight, decreased reliance on supplies and greater flexibility on the types of missions. Use of regenerable systems that reduce weight and volume of the Extravehicular Mobility Unit (EMU) is of critical importance to NASA, both for low orbit operations and for long duration manned missions. The carbon dioxide and humidity control unit in the existing PLSS design is relatively large, since it has to remove and store 8 hours worth of CO2. If the sorbent regeneration can be carried out during the extravehicular activity (EVA) with a relatively high regeneration frequency, the size of the sorbent canister and weight can be significantly reduced. The progress of regenerable CO2 and humidity control is leading us towards the use of a rapid cycling amine system. TDA Research, Inc. is developing compact, regenerable sorbent materials to control CO2 and humidity in the space suit ventilation loop. The sorbent can be regenerated using space vacuum during the EVA, eliminating all carbon dioxide and humidity duration-limiting elements in the life support system. The material also has applications in other areas of space exploration such as the Orion spacecraft and other longer duration exploration missions requiring regenerable technologies. This paper summarizes the results of the sorbent development, testing, and evaluation efforts to date. The results of a preliminary system analysis are also included, showing the size and volume reductions for PLSS provided by the new system.

Paul, Heather↗
NASA NTRS2008

Ventilation Transport Trade Study for Future Space Suit Life Support Systems

A new and advanced portable life support system (PLSS) for space suit surface exploration will require a durable, compact, and energy efficient system to transport the ventilation stream through the space suit. Current space suits used by NASA circulate the ventilation stream via a ball-bearing supported centrifugal fan. As NASA enters the design phase for the next generation PLSS, it is necessary to evaluate available technologies to determine what improvements can be made in mass, volume, power, and reliability for a ventilation transport system. Several air movement devices already designed for commercial, military, and space applications are optimized in these areas and could be adapted for EVA use. This paper summarizes the efforts to identify and compare the latest fan and bearing technologies to determine candidates for the next generation PLSS.

Kempf, Robert↗
NASA NTRS2008

Investigation of Condensing Ice Heat Exchangers for MTSA Technology Development

Metabolic heat regenerated Temperature Swing Adsorption (MTSA) technology is being developed for thermal, carbon dioxide (CO2) and humidity control for a Portable Life Support Subsystem (PLSS). Metabolically-produced CO2 present in the ventilation gas of a PLSS is collected using a CO2selective adsorbent via temperature swing adsorption. The temperature swing is initiated through cooling to well below metabolic temperatures. Cooling is achieved with a sublimation heat exchanger using water or liquid carbon dioxide (LCO2) expanded below sublimation temperature when exposed to low pressure or vacuum. Subsequent super heated vapor, as well as additional coolant, is used to further cool the astronaut. The temperature swing on the adsorbent is then completed by warming the adsorbent with a separate condensing ice heat exchanger (CIHX) using metabolic heat from moist ventilation gas. The condensed humidity in the ventilation gas is recycled at the habitat. The water condensation from the ventilation gas is a significant heat transfer mechanism for the warming of the adsorbent bed because it represents as much as half of the energy potential in the moist ventilation gas. Designing a heat exchanger to efficiently transfer this energy to the adsorbent bed and allow the collection of the water is a challenge since the CIHX will operate in a temperature range from 210K to 280K. The ventilation gas moisture will first freeze and then thaw, sometimes existing in three phases simultaneously. A NASA Small Business Innovative Research (SBIR) Phase 1 contract was performed to investigate condensing and icing as applied to MTSA to enable higher fidelity modeling and assess the impact of geometry variables on CIHX performance for future CIHX design optimization. Specifically, a design tool was created using analytical relations to explore the complex, interdependent design space of a condensing ice heat exchanger. Numerous variables were identified as having nontrivial contributions to performance such as hydraulic diameter, heat exchanger effectiveness, ventilation gas mass flow rate and surface roughness. Using this tool, four test articles were designed and manufactured to map to a full MTSA subassembly (the adsorbent bed, the sublimation heat exchanger for cooling and the condensing ice heat exchanger for warming). The design mapping considered impacts due to CIHX geometry as well as subassembly impacts such as thermal mass and thermal resistance through the adsorbent bed. The test articles were tested at simulated PLSS ventilation loop temperature, moisture content and subambient pressure. Ice accumulation and melting were observed. Data and test observations were analyzed to identify drivers of the condensing ice heat exchanger performance. This paper will discuss the analytical models, the test article designs, and testing procedures. Testing issues will be discussed to better describe data and share lessons learned. Data analysis and subsequent conclusions will be presented.

Padilla, Sebastian↗
NASA NTRS2010

Space Suit Portable Life Support System Rapid Cycle Amine Repackaging and Sub-Scale Test Results

NASA is developing technologies to meet requirements for an extravehicular activity (EVA) Portable Life Support System (PLSS) for exploration. The PLSS Ventilation Subsystem transports clean, conditioned oxygen to the pressure garment for space suit pressurization and human consumption, and recycles the ventilation gas, removing carbon dioxide, humidity, and trace contaminants. This paper provides an overview of the development efforts conducted at the NASA Johnson Space Center to redesign the Rapid Cycle Amine (RCA) canister and valve assembly into a radial flow, cylindrical package for carbon dioxide and humidity control of the PLSS ventilation loop. Future work is also discussed.

Paul, Heather L.↗
NASA NTRS2010

Humidifier Development and Applicability to the Next Generation Portable Life Support System

A development effort at the NASA Johnson Space Center investigated technologies to determine whether a humidifier would be required in the Portable Life Support System (PLSS) envisioned for future exploration missions. The humidifier has been included in the baseline PLSS schematic since performance testing of the Rapid Cycle Amine (RCA) indicates that the RCA over-dries the ventilation gas stream. Performance tests of a developmental humidifier unit and commercial off-the-shelf (COTS) units were conducted in December 2009. Following these tests, NASA revisited the need for a humidifier via system analysis. Results of this investigation indicate that it is feasible to meet humidity requirements without the humidifier if other changes are made to the PLSS ventilation loop and the Liquid Cooling and Ventilation Garment (LCVG).

Conger, Bruce↗
NASA NTRS2011

Humidifier Development and Applicability to the Next Generation Portable Life Support System

A development effort at the NASA Johnson Space Center investigated technologies to determine whether a humidifier would be required in the Portable Life Support System (PLSS) envisioned for future exploration missions. The humidifier has been included in the baseline PLSS schematic since performance testing of the Rapid Cycle Amine (RCA) indicates that the RCA over-dries the ventilation gas stream. Performance tests of a developmental humidifier unit and commercial off-the-shelf (COTS) units were conducted in December 2009. Following these tests, NASA revisited the need for a humidifier via system analysis. Results of this investigation indicate that it is feasible to meet humidity requirements without the humidifier if other changes are made to the PLSS ventilation loop and the Liquid Cooling and Ventilation Garment (LCVG).

Conger, Bruce C.↗