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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

Potential of a New Lunar Surface Radiator Concept for Hot Lunar Thermal Environments

The optimum radiator configuration in hot lunar thermal environments is one in which the radiator is parallel to the ground and has no view to the hot lunar surface. However, typical spacecraft configurations have limited real estate available for top-mounted radiators, resulting in a desire to use the spacecraft's vertically oriented sides. Vertically oriented, flat panel radiators will have a large view factor to the lunar surface, and thus will be subjected to significant incident lunar infrared heat. Consequently, radiator fluid temperatures will need to exceed ~325 K (assuming standard spacecraft radiator optical properties) in order to provide positive heat rejection at lunar noon. Such temperatures are too high for crewed spacecraft applications in which a heat pump is to be avoided.
Technical Paper

PLSS Thermal Model Requirements for Control

This paper discusses several issues related to the PLSS thermal model requirements for a planned generalized EVA Simulation Test Bed. The existing models of the extravehicular mobility unit (EMU) are briefly discussed and then the paper focuses specifically on the NASA JSC Shuttle EMU model (referred to as SINDA EMU). After the SINDA EMU model review, the PLSS thermal model requirements for the EVA Simulation Test Bed are discussed in detail.
Technical Paper

LSOPP II-A Program for Advanced EVA System Modeling and Trade Studies

A computer analysis program designed to predict and evaluate the steady state performance and size of integrated extravehicular mobility unit (EMU) life support systems has been developed for advanced missions. Trade study evaluations for various extravehicular activity (EVA) technologies can be accomplished using the Life Support Options Performance Program, version 2.0 (LSOPP II). LSOPP II is an interactive menu-driven program based upon a dual loop structure (vent loop - water loop). It solves for the outlet flow conditions of each component in a loop, given the associated heat loads and inlet flow conditions. System and component results of LSOPP II include heat load, flow rate, pressure, temperature, power, weight, and volume.
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

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

Extravehicular Activity (EVA) Thermal Micrometeoroid Garment (TMG) Thermal Performance Study

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.
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.
Technical Paper

EMU Thermal Performance Characteristics

The NASA JSC Shuttle EMU computer model (SINDA EMU) is presently used to analyze the thermal behavior of the Space Shuttle EMU. This paper uses the SINDA EMU model along with EMU experimental and flight data to investigate and define several performance characteristics of the Space Shuttle EMU related to thermal comfort control.