Bernadette Luna

Physiologic and functional responses of MS patients to body cooling.

ObjectiveThe objective of this study was to compare the responses of multiple sclerosis (MS) patients to short-term cooling therapy using three different vest configurations. DesignEach garment was used to cool 13 male and 13 female MS subjects (31–67 yr). Oral and right and left ear temperatures were logged manually every 5 min. Arm, leg, chest, and rectal temperatures, heart rate, and respiration were recorded continuously on a Biolog ambulatory monitor. Each subject was given a series of subjective and objective evaluation tests before and after cooling. ResultsThe Life Enhancement Technologies and Steele vests test groups had similar, significant (P < 0.01) cooling effects on oral and ear canal temperatures, which decreased approximately 0.4°C and 0.3°C, respectively. The Life Enhancement Technologies active liquid cooling vest produced the coldest (P < 0.01) skin temperature and provided the most improvement on subjective and objective performance measures. ConclusionsThese results show that the various garment configurations tested do not produce similar thermal responses in all MS patients. The circulating liquid cooling vest was found to be more effective than either of the two passive cooling garments tested.

High pressure excess isotherms for adsorption of oxygen and nitrogen in zeolites.

High-pressure oxygen is an integral part of fuel cell systems, many NASA in situ resource utilization concepts, and life support systems for extravehicular activity. Due to the limited information available for system designs over wide ranges of temperature and pressure, volumetric methods are applied to measure adsorption isotherms of O(2) and N(2) on NaX and NaY zeolites covering temperatures from 105 to 448 K and pressures up to 150 bar. Experimental data measured using two apparatuses with distinctly different designs show good agreement for overlapping temperatures. Excess adsorption isotherms are modeled using a traditional isotherm model for absolute adsorption with a correction for the gas capacity of the adsorption space. Comparing two models with temperature-dependent coefficients, a virial isotherm model provides a better description than a Toth isotherm model, even with the same number of parameters. With more virial coefficients, such as a cubic form in loading and quadratic form in reciprocal temperature, the virial model can describe all data accurately over wide ranges of temperature and pressure.

Evaluation of Commercial Off-the-Shelf Sorbents and Catalysts for Control of Ammonia and Carbon Monoxide

Designers of future space vehicles envision simplifying the Atmosphere Revitalization (AR) system by combining the functions of trace contaminant (TC) control and carbon dioxide removal into one swing-bed system. Flow rates and bed sizes of the TC and CO2 systems have historically been very different. There is uncertainty about the ability of trace contaminant sorbents to adsorb adequately in high-flow or short bed length configurations, and to desorb adequately during short vacuum exposures. There is also concern about ambient ammonia levels in the absence of a condensing heat exchanger. In addition, new materials and formulations have become commercially available, formulations never evaluated by NASA for purposes of trace contaminant control. The optimal air revitalization system for future missions may incorporate a swing-bed system for carbon dioxide (CO2) and partial trace contaminant control, with a reduced-size, low-power, targeted trace contaminant system supplying the remaining contaminant removal capability. This paper describes the results of a comparative experimental investigation into materials for trace contaminant control that might be part of such a system. Ammonia sorbents and low temperature carbon monoxide (CO) oxidation catalysts are the foci. The data will be useful to designers of AR systems for future flexible path missions. This is a continuation of work presented in a prior year, with extended test results.

Development Status of a Low-Power CO2 Removal and Compression System for Closed-Loop Air Revitalization

The ‘low-power CO2 removal (LPCOR) system’ is an advanced air revitalization system that is under development at NASA Ames Research Center. The LPCOR utilizes the fundamental design features of the ‘four bed molecular sieve’ (4BMS) CO2 removal technology of the International Space Station (ISS). It will reduce the cabin air CO2 concentration by 60% with a 50% power savings compared to the current ISS standard. In addition, it will recover pure, compressed CO2 for oxygen recovery. LPCOR improves the power efficiency by replacing the desiccant beds of the 4BMS with a membrane dryer and a state-of the art structured adsorbent device that require 25% of the thermal energy required by the 4BMS desiccant beds. The CO2 removal and recovery functions are performed in a two-stage adsorption compressor. CO2 is removed from the cabin air and partially compressed in the first stage. The second stage performs further compression and delivers the compressed CO2 to a reduction unit such as a Sabatier reactor for oxygen recovery. This paper describes the development status of the LPCOR system, including the breadboard experiments to determine the performance parameters of the full-scale LPCOR components for an optimized process, characterization tests and long-term performance testing of individual components. Also discussed in this paper are the flow distribution challenges encountered in a low pressure-drop system such as the residual water adsorber, configured as an engineered structured sorbent, and the efforts to mitigate the flow-related issues.

The Low-Power CO2 Removal and Compression System: Design Advances and Development Status

Active resource recovery from metabolic CO2 facilitates long-duration missions by decreasing cost and increasing self-sustainability. To provide this capability, theLow-Power CO2 Removal � (LPCOR) closed- loop air revitalization system is under development at NASA Ames Research Center. The LPCOR system is designed to perform the same CO2 removal function as the four-bed molecular sieve (4BMS) system currently employed on the International Space Station (ISS), with the additional integrated ability to purify and thermally compress CO2 to supply downstream CO2 recovery units. The LPCOR design goals include decreasing cabin air CO2 concentration up to 60% while yielding a 50% power savings when compared to current ISS levels. The LPCOR system increases power efficiency by replacing the desiccant (packed) beds of the 4BMS with a passive, Nafion ® hollow-fiber membrane bulk dryer and a state-of-the-art engineered structured sorbent device that requires only 25% of the thermal energy required by the 4BMS desiccant beds. CO2 removal, purification, and compression functions are performed in an integrated 2-Stage adsorption canister. CO2 is removed from the cabin air and partially compressed in Stage 1. The CO2 is concentrated in a smaller Stage 2, where thermal desorption is then used to further compress the CO2 for delivery to a reduction unit (e.g., a Sabatier reactor) for oxygen recovery. This paper presents the ongoing design considerations and development status of the LPCOR system, including overall design principles, characterization tests, airflow distribution modeling, and potential design strategies for current and future components.

Development and Testing of a Microwave Powered Regenerable Air Purification Technology Demonstrator

Dielectric heating via microwave irradiation of contaminant laden sorbents offers distinct advantages in comparison to conventional thermal regeneration techniques. High temperatures may be achieved very rapidly because electromagnetic energy is absorbed directly by the sorbent material. A Technology Demonstrator, incorporating efficient rectangular waveguide based sorbent cartridge designs and effective microwave transmission systems was designed, fabricated and tested. Importantly, the performance of the Molecular Sieve 13X Waveguide Cartridge for the removal of water vapor, the Molecular Sieve 5A Waveguide Cartridge for the removal of CO2, and the Activated Carbon Waveguide Cartridge for removal of volatile organics from air, were each validated by successive sorption/ microwave desorption cycles.

The Concept and Experimental Investigation of CO2 and Steam Co-electrolysis for Resource Utilization in Space Exploration

CO 2 acquisition and utilization technologies will have a vital role in designing sustainable and affordable life support and in situ fuel production architectures for human and robotic exploration of the Moon and Mars. For long-term human exploration to be practical, reliable technologies have to be implemented to capture the metabolic CO 2 from the cabin air and chemically reduce it to recover oxygen. Technologies that enable the in situ capture and conversion of atmospheric CO 2 to fuel are essential for a viable human mission to Mars. This paper describes the concept and mathematical analysis of a closed-loop life support system based on combined electrolysis of CO 2 and steam (co-electrolysis). Products of the coelectrolysis process include oxygen and syngas (CO and H 2 ) that are suitable for life support and synthetic fuel production, respectively. The model was developed based on the performance of a co-electrolysis system developed at Idaho National Laboratory (INL). Individual and combined process models of the co-electrolysis and Sabatier, Bosch, Boudouard, and hydrogenation reactions are discussed and their performance analyses in terms of oxygen production and CO 2 utilization are presented.

Dynamic Model of the BIO-Plex Air Revitalization System

The BIO-Plex facility will need to support a variety of life support system designs and operation strategies. These systems will be tested and evaluated in the BIO-Plex facility. An important goal of the life support program is to identify designs that best meet all size and performance constraints for a variety of possible future missions. Integrated human testing is a necessary step in reaching this goal. System modeling and analysis will also play an important role in this endeavor. Currently, simulation studies are being used to estimate air revitalization buffer and storage requirements in order to develop the infrastructure requirements of the BIO-Plex facility. Simulation studies are also being used to verify that the envisioned operation strategy will be able to meet all performance criteria. In this paper, a simulation study is presented for a nominal BIO-Plex scenario with a high-level of crop growth. A general description of the dynamic mass flow model is provided, along with some simulation results. The paper also discusses sizing and operations issues and describes plans for future simulation studies.

Removal of Carbon Dioxide from Light Gas Mixtures using a Porous Strontium(II) Silicoaluminophosphate Fixed Bed: Closed Volume and Portable Applications

A Sr2+ -SAPO-34 bed was assembled to study CO2 dynamic adsorption under conditions that emulate those found in closed volume and portable applications. Although the surface area was reduced by 7% during pelletization, adsorption capacities estimated from breakthrough curves compared well with static volumetric adsorption data. Modeling of the breakthrough adsorption was achieved using a Linear Driving Force mass transfer rate model, showing good agreement with the experimental data and confirming fast kinetics and efficient use of the bed. Fast kinetics were also evidenced by the length of the unused section of the bed as calculated from a Mass Transfer Zone model. Adsorption capacity degradation was not observed after multiple regeneration cycles. Apparent and equilibrium adsorption isotherm data estimated from the bed and static volumetric experiments at 25° C were compared to that of 5A Zeolite. These showed that Sr2+ -SAPO-34 is a superior adsorbent for CO2 removal in the low partial pressure range (<1500 ppm). CO2 and H2 O multicomponent adsorption breakthrough curves were also gathered for a CO2 inlet concentration of 1000 ppm and dew points of −5 and 8° C. The addition of moisture resulted in a decrease in total processed gas volume by 31 and 47%, respectively.

The Mathematical Analysis of a Novel Approach to Maximize Waste Recovery in a Life Support System

NASA has been evaluating closed-loop atmosphere revitalization architectures that include carbon dioxide (CO2 ) reduction technologies. The CO2 and steam (H2 O) co-electrolysis process is one of the reduction options that NASA has investigated. Utilizing recent advances in the fuel cell technology sector, the Idaho National Laboratory, INL, has developed a CO2 and H2 O co-electrolysis process to produce oxygen and syngas (carbon monoxide (CO) and hydrogen (H2 ) mixture) for terrestrial (energy production) application. The technology is a combined process that involves steam electrolysis, CO2 electrolysis, and the reverse water gas shift (RWGS) reaction. Two process models were developed to evaluate novel approaches for energy storage and resource recovery in a life support system. In the first model, products from the INL co-electrolysis process are combined to produce methanol fuel. In the second co-electrolysis, products are separated with a pressure swing adsorption (PSA) process. In both models the fuels are burned with added oxygen to produce H2 O and CO2 , the original reactants. For both processes, the overall power increases as the syngas ratio, H2 /CO, increases because more water is needed to produce more hydrogen at a set CO2 incoming flow rate. The power for the methanol cases is less than pressure swing adsorption, PSA, because heat is available from the methanol reactor to preheat the water and carbon dioxide entering the co-electrolysis process.Copyright