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Carbon dioxide (CO2), a natural product of human metabolism, accumulates quickly in sealed environments when humans are present, and can induce headaches, among other symptoms. Major resources are expended to control CO2 levels to concentrations that are tolerable to the crews of spacecraft and submersible craft. It is not practical to control CO2 levels to those found in the ambient environment on earth. As NASA looks ahead to long-duration missions conducted far from earth, difficult issues arise related to the management and effects of human exposure to CO2. One is the problem of “pockets” of CO2 in the habitat caused by excess generation of the gas in one location without a mechanism to purge the area with fresh air. This results in the crew rebreathing CO2 from their exhaled breath, exposing them to a much higher concentration of CO2 than whole-module measurements would suggest. Another issue is the potential increased sensitivity to CO2 in microgravity.

The Lunar Mars Life Support Test Project (LMLSTP) Phase III test was the final test in a series of tests conducted to evaluate regenerative life support systems performance over increasingly longer durations. The Phase III test broke new ground for the U.S. Space Program by being the first test to look at integration of biological and physical-chemical systems for air, water and solid waste recovery for a crew of four for 91 days. Microbial bioreactors were used as the first step in the water recovery system (WRS). This biologically based WRS continuously recovered 100% of the water used by the crew consistent with NASA's strict potable standards. The air revitalization system was a combination of physical-chemical hardware and wheat plants which worked together to remove and reduce the crew's metabolically produced carbon dioxide and provide oxygen.

The Lunar-Mars Life Support Systems Test Project's Phase iii Test utilized the Variable Pressure Growth Chamber to contribute to the air revitalization and food requirements of a crew of four for a period of 91 days. USU-Apogee wheat was planted and harvested using a staged approach to provide more uniform levels of air revitalization and a staggered production of grain. The wheat crop provided an average of 1 .1 person-equivalents per day of carbon dioxide removal for air revitalization over the 91 -day human test. Over 34 kg of grain was harvested. it was found that staged cropping required more intensive management of the nutrient solution than single batch cropping. it was also found that salts which were biologically recovered from the plant biomass were as effective as conventional reagent-grade salts for use in the hydroponic nutrient solution.

NASA has unique requirements for the development and application of air quality standards for human space flight. Such standards must take into account the continuous nature of exposures, the possibility of increased susceptibility of crewmembers to the adverse effects of air pollutants because of the stresses of space flight, and the recognition that rescue options may be severely limited in remote habitats. NASA has worked with the National Research Council Committee on Toxicology (NRCCOT) since the early 1990s to set and document appropriate standards. The process has evolved through 2 rounds. The first was to set standards for the space station era, and the second was to set standards for longer stays in space and update the original space station standards. The update was to be driven by new toxicological data and by new methods of risk assessment for predicting safe levels from available data. The last phase of this effort has been completed.

The Toxicology Laboratory at Johnson Space Center (JSC) had provided the combustion products analyzer (CPA) since the early 1990s to monitor the spacecraft atmosphere in real time if a thermodegradation event occurred aboard the Shuttle. However, as the operation of the International Space Station (ISS) grew near, an improved CPA was sought that would include a carbon monoxide sensor that did not have a cross-sensitivity to hydrogen. The Compound Specific Analyzer-Combustion Products (CSA-CP) was developed for use on the International Space Station (ISS). The CSA-CP measures three hazardous gases, carbon monoxide, hydrogen cyanide, and hydrogen chloride, as well as oxygen. The levels of these compounds in the atmosphere following a thermodegradation event serve as markers to determine air quality. The first permanent ISS crew performed the CSA-CP checkout operations and collected baseline data shortly after arrival aboard the ISS in December 2000.

Current dosimetric practices do not provide comprehensive classification of high-energy charged particle radiation, so that the ability to adequately project health risk to astronaut crews is limited. To address this shortcoming in dosimetry for Space Station missions, a new generation of active radiation monitors is being developed to supplement traditional dosimetry. One active monitor is a Tissue Equivalent Proportional Counter (TEPC) to measure the linear energy transfer (LET) spectrum of space radiation. Two versions of a second type of active monitor, the Charged Particle Directional Spectrometer (CPDS), will be deployed, one internal and one external to the Station. The CPDS consists of a stack of lithium-drifted silicon detectors used to classify the radiation by particle charge and energy. The comprehensive data set obtained by using the TEPC and the CPDS permits significant improvement in assessing crew radiation exposures.

The crew of flight 2A.1 that manned the International Space Station (ISS) assembly mission (STS-96) in May 1999 experienced symptoms that they attributed to poor air quality while working in the ISS modules. Some of these symptoms suggested that an accumulation of carbon dioxide (CO2) in the work area could have contributed to temporary health impacts on the crew. Currently, a fixed-position CO2 monitor in the FGB is the only means of measuring this air contaminant aboard ISS. As a result of this incident, NASA directed the Toxicology Laboratory at Johnson Space Center (JSC) to deliver a portable CO2 monitor for the next ISS assembly mission (STS-101). The Toxicology Laboratory developed performance requirements for a CO2 monitor and surveyed available CO2 monitoring technologies. The selected portable CO2 monitor uses nondispersive infrared spectroscopy for detection. This paper describes this instrument, its operation, and presents the results from ground-based performance testing.

Two types of supersonic jets, long and short, were designed for an advanced technology spacesuit ejector. Previously, a sonic jet was used in the ejector to improve its performance by reducing oxygen flow through thejetin order to achieve the required suit circulation. The manufacturing of long and short supersonic jets was a challenge which was met successfully by the Miniature Manufacturing Laboratory at NASA/JSC. The jets were tested and their performance was compared with the sonic jet, and it was found that both jets showed improved performance by achieving higher ejector mass ratios.

As part of NASA’s TransHab inflatable habitat program, a Radiation Shield Water Tank (RSWT) is being developed to provide a safe haven from peak solar particle events. The RSWT will provide an 11 ft. (3.35 m) diameter by 7 ft. (2.13 m) tall “safe haven” with a 2.26 in. (0.0574 m) thick wall of water for astronaut residence during peak solar events. The RSWT also functions as a water processing storage tank and must be capable of being filled and drained at will. Because of the unique shape of the RSWT, standard bellows and bladder designs cannot be used for inventory control. Therefore NASA has developed a bladderless tank where capillary forces govern the positioning of the liquid inventory. A combination of hydrophobic and hydrophilic membranes and wetting surfaces allows the tank to be filled and emptied as desired. In the present work, background on space-borne radiation is presented, the bladderless RSWT concept is described, and its theory of operation is discussed.

The ability to use local resources to “live off the land”, commonly referred to as In-Situ Resource Utilization (ISRU), is essential in establishing a long-term human presence and enabling the commercial development of space. The chief benefits of ISRU are that it can reduce the mass, cost, and risk of robotic and human exploration while providing capabilities that enable the commercial development of space. A key subset of ISRU which has significant cost and risk reduction benefits, and which requires a minimum of infrastructure, is In-Situ Consumable Production (ISCP). ISCP involves acquiring, manufacturing, and storing propellants, fuel cell reagents, and consumables for life support, scientific, and pneumatic equipment using resources available at the site of exploration. The NASA Johnson Space Center (JSC) is currently coordinating and focusing the Agency’s development of ISCP technologies and systems for robotic and human exploration.