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Future space exploration missions will require a lightweight spacesuit that expends no consumables. This paper describes the design and performance of a prototype heat rejection system that weighs less than current systems and vents zero water. The system uses regenerable LiCl/water absorption cooling. Absorption cooling boosts the heat absorbed from the crew member to a high temperature for rejection to space from a compact, non-venting radiator. The system is regenerated by heating to 100°C for two hours. The system provides refrigeration at 17°C and rejects heat at temperatures greater than 50°C. The overall cooling capacity is over 100 W-hr/kg.

In order to provide effective cooling for astronauts during extravehicular activities (EVAs), a liquid cooling and ventilation garment (LCVG) is used to remove heat by a series of tubes through which cooling water is circulated. To better predict the effectiveness of the LCVG and determine possible modifications to improve performance, computer simulations dealing with the interaction of the cooling garment with the human body have been run using the Wissler Human Thermal Model. Simulations have been conducted to predict the heat removal rate for various liquid cooled garment configurations. The current LCVG uses 48 cooling tubes woven into a fabric with cooling water flowing through the tubes. The purpose of the current project is to decrease the overall weight of the LCVG system. In order to achieve this weight reduction, advances in the garment heat removal rates need to be obtained.

An Advanced Automotive Manikin (ADAM), is used to evaluate liquid cooling garments (LCG) for advanced space suits for extravehicular applications and launch and entry suits. The manikin is controlled by a finite-element physiological model of the human thermoregulatory system. ADAM's thermal response to a baseline LCG was measured.The local effectiveness of the LCG was determined. These new thermal comfort tools permit detailed, repeatable measurements and evaluation of LCGs. Results can extend to other personal protective clothing including HAZMAT suits, nuclear/biological/ chemical protective suits, fire protection suits, etc.

Flexible fiber-reinforced aerogel composites were studied for use as insulation materials of a future space suit for Moon and Mars exploration. High flexibility and good thermal insulation properties of fiber-reinforced silica aerogel composites at both high and low vacuum conditions make it a promising insulation candidate for the space suit application. This paper first presents the results of a durability (mechanical cycling) study of these aerogels composites in the context of retaining their thermal performance. The study shows that some of these Aerogels materials retained most of their insulation performance after up to 250,000 cycles of mechanical flex cycling. This paper also examines the problem of integrating these flexible aerogel composites into the current space suit elements.

For planetary exploration, new thermal insulation materials are needed to deal with unique environmental conditions presented to extravehicular activity (EVA). The thermal insulation material and system used in the existing space suit were specifically designed for low orbit environment. They are not adequate for low vacuum condition commonly found in planetary environments with a gas atmosphere. This study attempts to identify the types of lofty nonwoven thermal insulation materials and the construction parameters that yield the best performance for such application. Lofty nonwovens with different construction parameters are evaluated for their thermal conductivity performance. Three different types of fiber material: solid round fiber, hollow fiber, and grooved fiber, with various denier, needling intensity, and web density were evaluated.

This paper presents the analysis findings of a study reducing the overall mass of the lightweight liquid cooling garment (LCG). The LCG is a garment worn by crew to actively cool the body, for spacesuits and launch/entry suits. A mass reduction of 66% was desired for advanced missions. A thermal math model of the LCG was developed to predict its performance when various mass-reducing changes were implemented. Changes included varying the thermal conductivity and thickness of the garment or of the coolant tubes servicing the garment. A second model was developed to predict behavior of the suit when the cooling tubes were to be removed, and replaced with a highly-conducting (waterless) material. Findings are presented that show significant reductions in weight are theoretically possible by improving conductivity in the garment material.

Meeting radiation protection requirements during EVA is predominantly an operational issue with some potential considerations for temporary shelter. The issue of spacesuit shielding is mainly guided by the potential of accidental exposure when operational and temporary shelter considerations fail to maintain exposures within operational limits. In this case, very high exposure levels are possible which could result in observable health effects and even be life threatening. Under these assumptions, potential spacesuit radiation exposures have been studied using known historical solar particle events to gain insight on the usefulness of modification of spacesuit design in which the control of skin exposure is a critical design issue and reduction of blood forming organ exposure is desirable.

Automatic thermal comfort control for the minimum consumables PLSS is undertaken using several control approaches. Accuracy and performance of the strategies using feedforward, feedback, and gain scheduling are evaluated through simulation, highlighting their advantages and limitations. Implementation issues, consumable usage, and the provision for the extension of these control strategies to the cryogenic PLSS are addressed.

The INTEGRITY Program will design and operate a test bed facility to help prepare for future beyond-LEO missions. The purpose of INTEGRITY is to enable future missions by developing, testing, and demonstrating advanced human space systems. INTEGRITY will also implement and validate advanced management techniques including risk analysis and mitigation. One important way INTEGRITY will help enable future missions is by reducing their risk. A risk analysis of human space missions is important in defining the steps that INTEGRITY should take to mitigate risk. This paper describes how a Probabilistic Risk Assessment (PRA) of human space missions will help support the planning and development of INTEGRITY to maximize its benefits to future missions. PRA is a systematic methodology to decompose the system into subsystems and components, to quantify the failure risk as a function of the design elements and their corresponding probability of failure.

Procedures for rapid microbiological analysis were performed during simulated surface extra-vehicular activity (EVA) at Meteor Crater, Arizona. The fully suited operator swabbed rock (‘unknown’ sample), spacesuit glove (contamination control) and air (negative control). Each swab sample was analyzed for lipopolysaccharide (LPS) and β-1, 3-glucan within 10 minutes by the handheld LOCAD PTS instrument, scheduled for flight to ISS on space shuttle STS-116. This simulated a rapid and preliminary ‘life detection’ test (with contamination control) that a human could perform on Mars. Eight techniques were also evaluated for their ability to clean and remove LPS and β-1, 3-glucan from five surface materials of the EVA Mobility Unit (EMU). While chemical/mechanical techniques were effective at cleaning smooth surfaces (e.g. RTV silicon), they were less so with porous fabrics (e.g. TMG gauntlet).

An ADvanced Automotive Manikin (ADAM) developed at the National Renewable Energy Laboratory (NREL) is used to evaluate NASA’s liquid cooling garments (LCGs) used in advanced spacesuits. The manikin has 120 separate heated/sweating zones and is controlled by a finite-element physiological model of the human thermo-regulatory system. Previous testing showed the thermal sensation and comfort followed expected trends as the LCG inlet fluid temperature was changed. The Phase II test data demonstrates the repeatability of ADAM by retesting the baseline LCG. Skin and core temperature predictions using ADAM in an LCG/arctic suit combination are compared to NASA physiological data to validate the manikin/model. An additional Orlan LCG configuration is assessed using the manikin and compared to the baseline LCG.

The challenges of missions to the Moon and Mars presents NASA with the need for more advanced life support systems, including better technologies for CO2 removal in spacecraft atmospheres and extravehicular mobility units (EMU). Amine-coated single wall carbon nanotubes (SWCNT) have been proposed as a potential solution because of their high surface area and thermal conductivity. Initial research demonstrated the need for functionalization of SWCNT to obtain optimal adherence of the amine to the SWCNT support phase [1]. Recent efforts focus on the development of new methods to chemically bond amines to SWCNT. Synthesis and characterization methods for these materials are discussed and some preliminary materials characterization data are presented. The CO2 adsorption capacity for several versions of SWCNT supported amine-based CO2 scrubber materials is also determined.

Fiber-reinforced Aerogel composite insulations provide superior thermal insulation protection in both the low-earth orbit (LEO) and near-earth neighborhood planetary environments. The flexible nature and thermal properties of these materials make them the best insulation candidates for advanced space suit application. This paper reviews the properties of various Aerogel composite materials developed for NASA by Aspen Systems, Inc. Previous studies showed that the Aerogel materials retained acceptable thermal performance after some amount of mechanical cycling. The goal of the current work is to reach a complete understanding of the mechanical properties of these materials in the domain of space suit application. Hence, a good knowledge of the durability of the aerogel composites is needed. This paper presents the extensive testing program needed to determine the life of these insulations for advanced space suit application.

Protecting astronauts from space radiation exposure is an important challenge for mission design and operations for future exploration-class and long-duration missions. Crew members are exposed to sporadic solar particle events (SPEs) as well as to the continuous galactic cosmic radiation (GCR). If sufficient protection is not provided the radiation risk to crew members from SPEs could be significant. To improve exposure risk estimates and radiation protection from SPEs, detailed evaluations of radiation shielding properties are required. A model using a modern CAD tool ProE™, which is the leading engineering design platform at NASA, has been developed for this purpose. For the calculation of radiation exposure at a specific site, the cosine distribution was implemented to replicate the omnidirectional characteristic of the 4π particle flux on a surface.

Similar to finding a home on Earth, location is important when selecting where to set up an exploration outpost. Essential considerations for comparing potential lunar outpost locations include: (1) areas nearby that would be useful for In-Situ Resource Utilization (ISRU) oxygen extraction from regolith for crew breathing oxygen as well as other potential uses; (2) proximity to a suitable landing site; (3) availability of sunlight; (4) capability for line-of-sight communications with Earth; (5) proximity to permanently-shadowed areas for potential in-situ water ice; and (6) scientific interest. The Mons Malapert1 (Malapert Mountain) area (85.5°S, 0°E) has been compared to these criteria, and appears to be a suitable location for a lunar outpost.

This paper describes the effort and accomplishments for developing flexible fabrics with high thermal conductivity (FFHTC) for spacesuits to improve thermal performance, lower weight and reduce complexity. Commercial and additional space exploration applications that require substantial performance enhancements in removal and transport of heat away from equipment as well as from the human body can benefit from this technology. Improvements in thermal conductivity were achieved through the use of modified polymers containing thermally conductive additives. The objective of the FFHTC effort is to significantly improve the thermal conductivity of the liquid cooled ventilation garment by improving the thermal conductivity of the subcomponents (i.e., fabric and plastic tubes).

The importance of being able to determine the usage rate of life support subsystem consumables was recognized well before the first Apollo Extravehicular Activity (EVA). Since that time, metabolic activity levels have been evaluated and recorded for each EVA crew member. Throughout the history of the United States space program, EVA metabolic rates have been shown to be variable depending upon the mission scenario and the equipment used. Knowing this historic information is invaluable for current EVA planning activities, as well as for the design of future Extravehicular Mobility Unit (EMU) systems. This paper presents an overview of historic metabolic expenditures for Apollo, Skylab, and Shuttle missions, along with a discussion of the types of EVA crew member activities which lead to various metabolic rate levels, and a discussion on how this data is being used to develop advanced EMU systems.

Sublimators have been used for heat rejection for a variety of space applications including the Apollo Lunar Module and the Extravehicular Mobility Unit (EMU). Sublimators are excellent candidates for heat rejection devices on future vehicles like the Crew Exploration Vehicle (CEV), the Lunar Surface Access Module (LSAM), and future spacesuits. One of the drawbacks of previous designs was sensitivity to contamination in the feedwater. Undissolved contaminants can be removed with filters, but dissolved contaminants would be left in the pores of the porous plates in which the feedwater freezes and sublimates. These contaminants build up and clog the relatively small pores (~3–6 μm), thereby blocking the flow of the feedwater, reducing the available area for freezing and sublimation, and degrading the performance of the sublimator. For the X-38 program, a new sublimator design was developed by NASA-JSC that is less sensitive to contaminants.

Metabolically produced carbon dioxide (CO2) removal in spacesuit applications has traditionally been accomplished utilizing non-regenerative Lithium Hydroxide (LiOH) canisters. In recent years, regenerative Metal Oxide (MetOx) has been developed to replace the Extravehicular Mobility Unity (EMU) LiOH canister for extravehicular activity (EVA) missions in micro-gravity, however, MetOx may carry a significant weight burden for potential use in future Lunar or planetary EVA exploration missions. Additionally, both of these methods of CO2 removal have a finite capacity sized for the particular mission profile. Metabolically produced water vapor removal in spacesuits has historically been accomplished by a condensing heat exchanger within the ventilation process loop of the suit life support system.

Sublimators have been used for heat rejection for a variety of space applications including the Apollo Lunar Module and the Extravehicular Mobility Unit (EMU). Some of the attractive features of sublimators are that they are compact, lightweight, and self-regulating. One of the drawbacks to previous designs has been sensitivity to non-volatile contamination in the feedwater, which can clog relatively small pores (∼3-µ6 μn) in the porous plates where ice forms and sublimates. The Contaminant Insensitive Sublimator (CIS) has been recently developed at NASA-JSC to be less sensitive to contaminants by using a larger pore size media (−350 um). Testing of a CIS Engineering Development Unit (EDU) has demonstrated good heat rejection performance. This paper describes testing that investigates different factors affecting efficient utilization of the feedwater.