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The International Space Station (ISS) requires advanced life support to continue its mission as a permanently-manned space laboratory and to reduce logistic resupply requirements as the Space Shuttle retires from service. Additionally, as humans reach to explore the moon and Mars, advanced vehicles and extraterrestrial bases will rely on life support systems that feature in-situ resource utilization to minimize launch weight and enhance mission capability. An obvious goal is the development of advanced systems that meet the requirements of both mission scenarios to reduce development costs by deploying common modules. A high pressure oxygen generating assembly (HPOGA) utilizing a high differential pressure (HDP) water electrolysis cell stack can provide a recharge capability for the high pressure oxygen storage tanks on-board the ISS independently of the Space Shuttle as well as offer a pathway for advanced life support equipment for future manned space exploration missions.

Human rated space vehicles must provide safe breathing air to the crew, in the event of fire or other upset that affects air quality. In very short missions, like those in Mercury, the crew could remain in their flight suit. As mission duration increased, some sort of emergency breathing apparatus was used to provide safe breathing air in emergency situations. The Orion vehicle has a unique set of emergency breathing apparatus design challenges: the vehicle is small compared to shuttle and station, the vehicle does not have a pressurized supply of breathing air, the vehicle has a 30% oxygen design limit, no airlocks or alternate habitable volumes, and during lunar missions the crew members need to remain in the vehicle for many hours after an emergency. A filtering respirator shows special promise to address the needs of Orion, but a filtering respirator for combustion products has never been built and qualified for space.

Recent efforts have been pursued to establish the usefulness of Space Shuttle Orbiter lithium hydroxide (LiOH) canisters beyond their certified two-year shelf life, at which time they are currently considered “expired.” A stockpile of Orbiter LiOH canisters are stowed on the International Space Station (ISS) as a backup system for maintaining ISS carbon dioxide Canisters with older (CO2) control. Canister with older pack dates must routinely be replaced with newly packed canisters off-loaded from the Orbiter Middeck. Since conservation of upmass is critical for every mission, the minimization of canister swap-out rate is paramount. LiOH samples from canisters with expired dates that had been returned from the ISS were tested for CO2 removal performance at the NASA Johnson Space Center (JSC) Crew and Thermal Systems Division (CTSD). Through this test series and subsequent analysis, performance degradation was established.

The use of a unique laser based compact gas sensor based on continuous wave (cw) difference frequency generation using non-linear optical conversion is reported for on-line, real-time measurements of H2CO, CH4 and H2O. Specifically, this portable sensor was used to monitor H2CO levels with a sensitivity of ~30 ppb during the 90 day Lunar-Mars Life Support Test Program conducted at NASA-JSC in 1997.

Future long-term space missions, such as a manned mission to Mars, will require regenerative life support systems which will enable crews more self-sufficiency and less dependence on resupply. Toward this effort, a series of tests called the Lunar-Mars Life Support Test Project have been conducted as part of the National Aeronautical and Space Administration (NASA's) advanced life support technology development program. The last test in this series was the Phase III test which was conducted September 19 - December 19, 1997 in the Life Support Systems Integration Facility at the Johnson Space Center. The overall objective of the Phase III test was to conduct a 90-day regenerative life support system test with four human test subjects demonstrating an integrated biological and physicochemical life support system to produce potable water, maintain a breathable atmosphere, and maintain a shirt sleeve environment.

The current regenerative CO, Removal System (RCRS) is a two sorbent bed, vacuum pressure swing, CO, adsorption/desorption system. While one bed is removing CO, and moisture from cabin air, the other bed is vented to space vacuum so that the CO, and water can be desorbed off the bed. To guard against the possibility that cabin air can be vented directly to space, 11 valves and a series of mechanical linkages control the flow paths. The RCRS has one set of adsorption beds, one fan, one compressor, and two redundant controllers. A single failure could cause a loss of function; so a contingency CO, removal system must, and is flown. A new sorbent material has been developed that greatly decreases the required size of the sorbent bed. A new valve design is proposed that replaces the complex series of valves and linkages with one moving part. Using the new bed material and new valve design, system size and weight can be cut approximately in half.

A novel photocatalytic oxidation technology is described for destruction of trace contaminants such as ethylene encountered in spacecraft. Results are presented of both laboratory and prototype ethylene scrubbers capable of treating 2 to 6 SCFM of contaminated humid air. The scrubbers provided high destruction capacity per unit of photocatalyst, requiring minimal power usage for UV light illumination. Extremely active and humidity resistant photocatalysts were developed and destruction of ethylene was accomplished with residence times of less than 0.1 s with no byproduct formation.

Advanced life support research at NASA Johnson Space Center is focused on developing regenerative life support systems to support longer duration missions. One component of human life support, trace contaminant control, presently relies on non regenerative charcoal adsorption. Photocatalytic oxidation holds great promise as a regenerative alternative to charcoal adsorption. It operates at ambient temperature, oxidizes a wide variety of organics, and has rapid destruction kinetics at low concentrations. While the scientific concept of photocatalysis has been demonstrated, many of the engineering issues associated with photocatalytic oxidation have not yet been adequately addressed. The effects of dewpoint, catalyst poisoning and rejuvenation, complex contaminant streams, and reactor design are some of the issues that must be better understood before this technology can be turned into flight hardware.

There is a possibility that trace contaminants in the Shuttle Orbiter cabin atmosphere may chemically react with amine beads found in the Regenerative Carbon Dioxide Removal System and degrade system performance. Two contaminant compounds were exposed to the amine beads, and performance changes were measured. Acetone was tested because it is sometimes found in small but appreciable quantities in the cabin, and it has chemical properties that make it a potential poison. Halon 1301 was tested because it is the fire extinguishant, and a discharge of a Halon canister would trigger high concentrations in the cabin. Acetone was shown to be weakly and reversibly adsorbed. It does not poison the bed, and the RCRS was shown to remove small quantities of acetone. Halon was shown to be inert to the amine. It does not poison the RCRS, and is not removed by the RCRS.