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A system performance study on a portable life support system being developed for use in the Weightless Environment Training Facility (WETF) and the Neutral Buoyancy Laboratory (NBL) has been completed. The Neutral Buoyancy Portable Life Support System (NBPLSS) will provide life support to suited astronauts training for extravehicular activity (EVA) under water without the use of umbilicals. The basic configuration is characterized by the use of medium pressure (200 - 300 psi) cryogen (liquid nitrogen/oxygen mixture) which provides cooling within the Extravehicular Mobility Unit (EMU), the momentum which enables flow in the vent loop, and oxygen for breathing. NBPLSS performance was analyzed by using a modified Metabolic Man program to compare competing configurations. Maximum sustainable steady state metabolic rates and transient performance based on a typical WETF metabolic rate profile were determined and compared.

A computer modeling tool is being developed for the detailed transient modeling of an Extravehicular Activity Atmospheric Control Subsystem (EVA ACS). An EVA ACS includes the astronaut, CO2 removal, moisture control, temperature control, and oxygen make-up components. This modeling tool will be used in trade studies evaluating competing components and subsystems to guide the selection and development of hardware for lunar and Martian missions. Several computerized modeling packages already exist, but no single program has all the capabilities needed. These capabilities include models of all EVA components on both steady-state and transient bases and sophisticated, general-purpose chemical process modeling capabilities.

ASDA was developed to evaluate the heat and mass transfer characteristics of advanced pressurized suit design concepts for use in low pressure or vacuum planetary environments. The model incorporates a generalized 3-layer suit, constructed with the Systems Integrated Numerical Differencing Analyzer '85 (SINDA '85), with a 41- node FORTRAN routine that simulates the transient heat transfer and respiratory processes of a human body in a suited environment. User options for the suit include a liquid cooled garment, a removable jacket, a CO2/H2O permeable layer and a phase change layer. The model also has an option to isolate flowing oxygen in the helmet from stagnant or flowing gas in the torso and limbs. Options for the environment include free and forced convection with a user input atmosphere, incident solar/infrared fluxes, radiation to a background sink and radiation and conduction to a surface. Results from a study of Mars suit concepts will also be presented.

With new direction to return to the Moon, NASA is developing highly efficient and lightweight extravehicular activity (EVA) equipment for working on the rugged lunar terrain. This paper presents results and evaluations of lunar thermal environments and design challenges for the EVA system. The evaluations include a review of basic lunar environment data, a review of metabolic rate predictions, analyses and reviews of spacesuit heat leak effects in past designs, and methods to improve the performance of spacesuit-mounted radiators in a hot lunar environment. In addition to reviewing existing lunar thermal environment data, a simplified thermal model is presented that can simulate the lunar surface temperature variation as a function of latitude and time on the lunar surface. The assumed physical and optical properties of the lunar soil as well as the solar heating on the Earth's Moon are also presented.

A preliminary evaluation of several portable life support system (PLSS) concepts which could be used during the First Lunar Outpost (FLO) mission extravehicular activities (EVA's) has been performed. The weight, volume and consumables characteristics for the various PLSS concepts were estimated. Thermal effects of day and night EVA's on PLSS consumables usage and hardware requirements were evaluated. The benefit of adding a radiator and the total PLSS weight to be carried by the astronaut were also evaluated for each of the concepts. The results of the evaluation were used to provide baseline weight, volume and consumables characteristics of the PLSS to be used on the 45 day FLO mission. The benefit of radiators was shown to be substantial. Considerable consumables savings were predicted for EVA schedules with a high concentration of nighttime EVA's versus daytime EVA's.

A series of hot and cold thermal vacuum tests compared the radiation and contact conduction thermal performance of two Space Shuttle extravehicular pressure suit glove designs. An ambient test established the relationship between heat transfer and contact pressure. Contact with hot and cold objects was tolerated longer with an enhanced fingertip insulation design. The data obtained was used to correlate a glove model for predicting skin temperatures of advanced gloves in extreme extravehicular thermal environments.

A thermoelectric liquid cooling system recently developed at the Johnson Space Center was evaluated in manned and unmanned ground tests as an alternative to the Space Shuttle launch and entry suit personal fan. The liquid cooling system provided superior cooling in environments simulating flight deck conditions during launch and postlanding.

An Extravehicular Mobility Unit (EMU) Portable Life Support Subsystem (PLSS) has among its primary functions requirements to remove metabolically generated heat and respiratory byproducts to maintain an atmosphere which is both physiologically safe and comfortable for the Extravehicular Activity (EVA) crew person. The EMU thermal control system interacts with the crew member through the Liquid Cooling and Ventilation Garment (LCVG), which circulates the ventilation gas to remove carbon dioxide, humidity, and trace contaminants, and the cooling water to remove metabolically produced heat. To maintain thermal comfort, the crew member may vary the LCVG inlet water temperature. The thermal interaction between the EMU and the crew member is very complex and highly dependent upon the individual crew member's cooling preferences and the exterior environment.

The Thermal Micrometeoroid Garment (TMG) is the outer portion of the Extravehicular Mobility Unit (EMU). The TMG minimizes the amount of heat transfer between an astronaut and the space environment, and provides protection from micrometeoroids. Multilayer insulation separates the outer surface of the TMG from the inner surface and crewperson. The performance of the present TMG insulation may be a contributing factor to the cold discomfort experienced by the astronauts. The TMG Thermal Performance Study tested combinations of insulation materials based on thermal conditions, total heat transfer, and insulation properties. The results from this study will be used to support design refinements for future developments of an extravehicular mobility unit.