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As the United States makes plans to return astronauts to the moon and eventually send them on to Mars, designing the most effective, efficient, and robust spacesuit life support system that will operate successfully in dusty environments is vital. Some knowledge has been acquired regarding the contaminants and level of infiltration that can be expected from lunar and Mars dust, however, risk mitigation strategies and filtration designs that will prevent contamination within a spacesuit life support system are yet undefined. A trade study was therefore initiated to identify and address these concerns, and to develop new requirements for the Constellation spacesuit element Portable Life Support System. This trade study investigated historical methods of controlling particulate contamination in spacesuits and space vehicles, and evaluated the possibility of using commercial technologies for this application. The trade study also examined potential filtration designs.

In support of the Constellation Program, NASA conducted an analysis of crew clothing and laundry options. Disposable clothing is currently used in human space missions. However, the new mission duration, goals, launch penalties and habitat environments may lead to a different conclusion. Mass and volume for disposable clothing are major penalties in long-duration human missions. Equivalent System Mass (ESM) of crew clothing and hygiene towels was estimated at about 11% of total life support system ESM for a 4-crew, 10-year Lunar Outpost mission. Ways to lessen this penalty include: reduce clothing supply mass through using clothes made of advanced fabrics, reduce daily usage rate by extending wear duration and employing a laundry with reusable clothing. Lunar habitat atmosphere pressure and therefore oxygen volume percentage will be different from Space Station or Shuttle. Thus flammability of clothing must be revisited.

Future manned habitats for a Lunar outpost or Martian base will require increased levels of self-sufficiency over Space Station Freedom to reduce the high costs and complexities of resupplying expendables, such as food for the crew. By growing food at these remote sites, not only will self-sufficiency be greatly increased, but significant benefits for crew life support will also be realized. Higher plants, such as those grown typically for food, are capable of consuming carbon dioxide (CO2), producing oxygen (O2), and reclaiming water (H2O) via transpiration. At NASA's Johnson Space Center (JSC) in Houston, Texas, the Regenerative Life Support Systems (RLSS) Test Bed project will use higher plants grown in a closed, controlled environment in conjunction with physicochemically-based life support systems to create an integrated biological/physicochemical RLSS.

In preparation for the contract award of the Crew Exploration Vehicle (CEV), the National Aeronautics and Space Administration (NASA) produced two design reference missions for the vehicle. The design references used teams of engineers across the agency to come up with two configurations. This process helped NASA understand the conflicts and limitations in the CEV design, and investigate options to solve them.

An energy balance was performed on the life support equipment used during the Phase III, 90-day, human Lunar-Mars Life Support Test Project at the Johnson Space Center. The purpose of the analysis was to account for all the energy sources, uses, and losses in the test-bed. Knowledge from this task may allow more energy efficient designs to be developed. Control volumes were defined and energy balance equations were generated for major systems. The analyses succeeded in balancing the energy fairly well for several systems. Further, the data showed that inefficiencies existed, and means of design optimization were subsequently suggested.

Exploration Life Support (ELS) is a technology development project under the National Aeronautics and Space Administration's (NASA) Exploration Technology Development Program. The ELS Project's goal is to develop and mature a suite of Environmental Control and Life Support System (ECLSS) technologies for potential use on human spacecraft under development in support of U.S. Space Exploration Policy. Technology development is directed at three major vehicle projects within NASA's Constellation Program: the Orion Crew Exploration Vehicle (CEV), the Altair Lunar Lander and Lunar Surface Systems, including habitats and pressurized rovers. The ELS Project includes four technical elements: Atmosphere Revitalization Systems, Water Recovery Systems, Waste Management Systems and Habitation Engineering, and two cross cutting elements, Systems Integration, Modeling and Analysis, and Validation and Testing.

As part of NASA's initiative to develop an advanced portable life support system (PLSS), a baseline schematic has been chosen that includes gaseous oxygen in a closed circuit ventilation configuration. Supply oxygen enters the suit at the back of the helmet, passes over the astronaut's body, and is extracted at the astronaut's wrists and ankles through the liquid cooling and ventilation garment (LCVG). The extracted gases are then treated using a rapid cycling amine (RCA) system for carbon dioxide and water removal and activated carbon for trace gas removal before being mixed with makeup oxygen and reintroduced into the helmet. Thermal control is provided by a suit water membrane evaporator (SWME). As an extension of the original schematic development, NASA evaluated several Helmet Exhalation Capture System (HECS) configurations as alternatives to the baseline.

Metabolic heat regenerated temperature swing adsorption (MTSA) technology is being developed for removal and rejection of carbon dioxide (CO2) and heat from a portable life support system (PLSS) to the Martian environment. Previously, hardware was built and tested to demonstrate using heat from simulated, dry ventilation loop gas to affect the temperature swing required to regenerate an adsorbent used for CO2 removal. New testing has been performed using a moist, simulated ventilation loop gas to demonstrate the effects of water condensing and freezing in the heat exchanger during adsorbent regeneration. Also, the impact of MTSA on PLSS design was evaluated by performing thermal balances assuming a specific PLSS architecture. Results using NASA's Extravehicular Activity System Sizing Analysis Tool (EVAS_SAT), a PLSS system evaluation tool, are presented.

Performing extravehicular activity at various locations on the lunar surface presents thermal challenges that exceed those that have been experienced in space flight to date. The lunar Portable Life Support System (PLSS) cooling unit must maintain thermal conditions within the spacesuit (SS) and reject heat loads that are generated by both the crew member and the PLSS equipment. The amount of cooling that will be required varies based on lunar location and terrain due to the heat that is transferred between the suit and its surroundings, A study, which assumes three different thermal technology categories, has been completed that studied the resources that are required to provide cooling under various lunar conditions as follows: 1. SS water membrane evaporator 2. Sub-cooled phase change material (SPCM) 3.

With the Preliminary Design Review (PDR) for the Orion Crew Exploration Vehicle planned to be completed in 2009, Exploration Life Support (ELS), a technology development project under the National Aeronautics and Space Administration's (NASA) Exploration Technology Development Program, is focusing its efforts on needs for human lunar missions. The ELS Project's goal is to develop and mature a suite of Environmental Control and Life Support System (ECLSS) technologies for potential use on human spacecraft under development in support of U.S. Space Exploration Policy. ELS technology development is directed at three major vehicle projects within NASA's Constellation Program (CxP): the Orion Crew Exploration Vehicle (CEV), the Altair Lunar Lander and Lunar Surface Systems, including habitats and pressurized rovers.

As development of the Constellation spacesuit element progresses, designing the most effective and efficient life support systems is critical. The baseline schematic analysis for the Portable Life Support System indicates that the ventilation loop will need some method of heat exchange and humidification prior to entering the helmet. A trade study was initiated to identify the challenges that are associated with conditioning the spacesuit breathing gas stream for temperature and water vapor control; to survey technological literature and resources on heat exchanger and humidifiers to provide solutions to the problems of conditioning the spacesuit breathing gas stream; and to propose potential candidate technologies to perform the heat exchanger and humidifier functions. This paper summarizes the results of this trade study, and also describes the conceptual designs that NASA developed to address these issues.

The amount of oxygen consumption for crew extravehicular activity (EVA) in future lunar exploration missions will be significant. Eight technologies to provide high pressure EVA O2 were investigated. They are: high pressure O2 storage, liquid oxygen (LOX) storage followed by vaporization, scavenging LOX from Lander followed by vaporization, LOX delivery followed by sorption compression, water electrolysis followed by compression, stand-alone high pressure water electrolyzer, Environmental Control and Life Support System (ECLSS) and Power Elements sharing a high pressure water electrolyzer, and ECLSS and In-Situ Resource Utilization (ISRU) Elements sharing a high pressure electrolyzer. A trade analysis was conducted comparing launch mass and equivalent system mass (ESM) of the eight technologies in open and closed ECLSS architectures. Technologies considered appropriate for the two architectures were selected and suggested for development.

Engineers at the Johnson Space Center (JSC) are using innovative strategies to design the TCS for the Bio-regenerative Planetary Life Support Systems Test Complex (BIO-Plex), a regenerative advanced life support system ground test bed. This paper provides a current description of the BIO-Plex TCS design, testing objectives, analyses, descriptions of the TCS test articles expected to be tested in the BIO-Plex, and forward work regarding TCS. The TCS has been divided into some subsystems identified as permanent “infrastructure” for the BIO-Plex and others that are “test articles” that may change from one test to the next. The infrastructure subsystems are the Heating, Ventilation and Air-Conditioning (HVAC), the Crew Chambers Internal Thermal Control Subsystem (CC ITCS), the Biomass Production Chamber Internal Thermal Control Subsystem (BPC ITCS), the Waste Heat Distribution Subsystem (WHDS) and the External Thermal Control Subsystem (ETCS).

The development of an optimum regenerative Advanced Life Support (ALS) system for future Mars missions has been a crucial issue in the space industry. Considering the numerous potential technologies for subsystems with the complexity of the Air Revitalization System (ARS), Water Reclamation System (WRS), and Waste Management System of the Environmental Control and Life Support System (ECLSS), it will be time-consuming and costly to determine the best combination of these technologies without a powerful sizing analysis tool. Johnson Space Center (JSC), therefore, initiated the development of ALSSAT using Microsoft® Excel for this purpose. ALSSAT has been developed based upon the ALS Requirement and Design Definition Document (Ref. 18). In 1999, a paper describing the development of ALSSAT with its built-in ARS mass balance model (Ref. 21) was published in ICES.

The Systems Integration, Modeling and Analysis (SIMA) element1 of the National Aeronautics and Space Administration (NASA) Advanced Life Support (ALS) Project conducts on-going studies to determine the most efficient means of achieving a human mission to Mars. Life support for the astronauts constitutes an extremely important part of the mission and will undoubtedly add significant mass, power, volume, cooling and crew time requirements to the mission. Equivalent system mass (ESM) is the sum of these five parameters on an equivalent mass basis and can be used to identify potential ways to reduce the overall cost of the mission. SIMA has documented several reference missions in enough detail to allow quantitative studies to identify optimum ALS architectures. The Mars Dual Lander Mission, under consideration by the Johnson Space Center (JSC) Exploration Office, is one of those missions.

To effectively develop advanced life support technologies to support humans on future missions into space, the requirements for these missions must first be defined. How many people will go? Where will they go? What risks must be protected against? Since NASA does not officially establish new exploration programs until authorized by Congress, there are no program requirements documents or list of “planned missions” to refer to. Therefore, technology developers must look elsewhere for information on how and where their development efforts and concepts may be used. This paper summarizes the development of several sources designed to help Advanced Life Support researchers working to extend a human presence in space.

The Portable Life Support System (PLSS) emergency oxygen system is being reexamined for the next generation of suits. These suits will be used for transit to Low Earth Orbit, the Moon and to Mars as well as on the surface of the Moon and Mars. Currently, the plan is that there will be two different sets of suits, but there is a strong desire for commonality between them for construction purposes. The main purpose of this paper is to evaluate what the emergency PLSS requirements are and how they might best be implemented. Options under consideration are enlarging the tanks on the PLSS, finding an alternate method of storage/delivery, or providing additional O2 from an external source. The system that shows the most promise is the cryogenic oxygen system with a composite dewar which uses a buddy system to split the necessary oxygen between two astronauts.

When permanent bases are established on the moon, various methods may be employed to reject the heat generated by the base. One proposed concept is the use of a heat pump operating with a vertical, flow-through thermal radiator which is mounted on a Space Station type habitation module. Since the temperature of the lunar surface varies over the lunar day, the sink temperature for heat pump heat rejection will vary. As a result, the heat pump power demand will also vary over the lunar day. This variable power requirement could be provided by a fixed horizontal solar photovoltaic (PV) array placed on the lunar surface, since its power production will vary sinusoidally with the time of day. Using a dedicated PV array to power the heat pump may represent a favorable mass trade-off compared to enlarging the size of the base's central power grid due to power system simplification and improvements in efficiency.

In an era of tight fiscal constraints, research and development funds are not sufficient to study all possible avenues for technology development. Hence, development priorities must be set and funding decisions made based on the projected benefits which will arise from fully developing different technologies. In order to identify promising development initiatives for advanced thermal control systems, a study was conducted which quantified the potential mass savings of various technologies. Assessments were made for five reference missions considered to be likely candidates for major human space flight initiatives beyond the International Space Station. The reference missions considered were Space Station Evolution, Space Shuttle Replacement, First Lunar Outpost Lander, Permanent Lunar Base, and Mars Lander. For each mission a baseline active thermal control system was defined and mass estimates were established.

Technology developers understand the need to optimize technologies for human missions beyond Earth. Greater benefits are achievable when systems that share common interfaces are optimized as an integrated unit, including taking advantage of possible synergies or removing counterproductive efforts at the mission level. Life support, extravehicular activity (EVA), and habitability are three systems that have significant interfaces with the crew, and thus share many common interfaces with each other. Technologies and architectures developed for these systems need to account for the effect that design decisions will have on each of the other systems. Many of these impacts stem from the use of water by the crew and the way that the life support system provides and processes that water. Other resources, especially air-related, can have significant impacts as well.