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Technical Paper

Lunar EVA Thermal Environment Challenges

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.
Technical Paper

Extravehicular Activity System Sizing Analysis Tool (EVAS_SAT) for Advanced Spacesuit Systems

An effort was initiated by NASA/JSC in 2001 to develop an Extravehicular Activity System Sizing Analysis Tool (EVAS_SAT) for the sizing of Extravehicular Activity System (EVAS) architecture and studies. Its intent was to support space suit development efforts and to aid in conceptual designs for future human exploration missions. Its basis was the Life Support Options Performance Program (LSOPP), a spacesuit and portable life support system (PLSS) sizing program developed for NASA/JSC circa 1990. EVAS_SAT estimates the mass, power, and volume characteristics for user-defined EVAS architectures, including Suit Systems, Airlock Systems, Tools and Translation Aids, and Vehicle Support equipment. The tool has undergone annual changes and has been updated as new data have become available. Certain sizing algorithms have been developed based on industry standards, while others are based on the LSOPP sizing routines.
Technical Paper

Integrated Model of G189A and Aspen-Plus for the Transient Modeling of Extravehicular Activity Atmospheric Control Systems

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.
Technical Paper

Space Shuttle Launch Entry Suit Thermal Performance Evaluation

Comments of the Space Shuttle crew indicate that the Launch Entry Suit (LES) may provide inadequate cooling before launch and after reentry. During these periods some crewmembers experienced thermal discomfort induced by localized cabin heating, middeck experiments, and crewmembers' body heat and humidity. The NASA Johnson Space Center(JSC) Crew and Thermal System Division (CTSD) executed a two phase study, analysis and testing, to investigate this problem. The analysis phase used a computer model of the LES to study the transient heat dissipation and temperature response under the various Space Shuttle flight cabin environments. After the completion of the analysis, the testing phase was conducted to collect the engineering data in order to validate the analysis results. Due to the constraint of the test facility, the test was conducted on the air cooled techniques only. This paper presents the analytical model, its solution and an evaluation and summary of the test results.
Technical Paper

Space Station Surface Touch Temperature Study

In order to reduce the condensation in the Space Station Freedom module, the design of its surface and/or the meteoroid protection shield surface requires special coating to raise the surface temperature while on orbit. This raises a concern of whether the Extravehicular Mobility Unit (EMU) glove will be able to protect the crew member during the Extravehicular Activity (EVA) when the crew member touches the hot or cold surface. EMU gloves provide protection to crew members' hands from a hot or cold touch temperature during an EVA when grasping or touching an object. These gloves also provide protection to crew members in extreme thermal environments. A glove thermal model with the most up-to-date configuration information was developed and utilized to predict reliable touch temperature limits. The analyses performed evaluated several worst case scenarios of both hot and cold environments and object temperatures.
Technical Paper

First Lunar Outpost Extravehicular Life Support System Evaluation

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.
Technical Paper

Neutral Buoyancy Portable Life Support System Performance Study

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.
Technical Paper

ASDA - Advanced Suit Design Analyzer Computer Program

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.
Technical Paper

Crew Member/Extravehicular Mobility Unit Thermal Interactions Affecting Cooling Preferences and Metabolic Water Removal

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.
Technical Paper

Shuttle EMU 4000 Series and 4750 Series Glove Thermal Performance

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.
Technical Paper

Shuttle Launch Entry Suit Liquid Cooling System Thermal Performance

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.