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Over the last couple decades, there has been a growing interest in incorporating commercial off-the-shelf (COTS) technologies and open standards in the design of human-rated spacecraft. This approach is intended to reduce development and upgrade costs, lower the need for new design work, eliminate reliance on individual suppliers, and minimize schedule risk. However, it has not traditionally been possible for COTS solutions to meet the high reliability and fault tolerance requirements of systems implementing critical spacecraft functions. Byzantine faults are considered particularly dangerous to such systems because of their ability to escape traditional means of fault containment and disrupt consensus between system components. In this paper, we discuss the design of a voting protocol using Time-Triggered Ethernet capable of achieving data integrity in the presence of a single Byzantine fault.

The primary objectives of this study were to determine the factors that affect stability during locomotion in both lunar and martian gravity environments and to determine the criteria needed to enhance stability and traction. This study tested the effects of changing the speed of locomotion and the pattern of locomotion under three gravity conditions. The results showed that as the gravity level decreased, the amount of vertical and horizontal forces dropped significantly. The results also showed that there are some similarities across gravity levels with regard to changing the speed as well as the pattern of locomotion. In general, an increase in the speed resulted in an increase in the vertical and the horizontal forces. A change in the pattern of locomotion showed that even at reduced gravity, it will be more difficult to stop than compared to continue or start the motion.

The Spacesuit Water Membrane Evaporator (SWME) is the baseline heat rejection technology selected for development for the Constellation lunar suit. The first SWME prototype, designed, built, and tested at Johnson Space Center in 1999 used a Teflon hydrophobic porous membrane sheet shaped into an annulus to provide cooling to the coolant loop through water evaporation to the vacuum of space. This present study describes the test methodology and planning to compare the test performance of three commercially available hollow fiber materials as alternatives to the sheet membrane prototype for SWME, in particular, a porous hydrophobic polypropylene, and two variants that employ ion exchange through non-porous hydrophilic modified Nafion. Contamination tests will be performed to probe for sensitivities of the candidate SWME elements to ordinary constituents that are expected to be found in the potable water provided by the vehicle, the target feedwater source.

A generalized computer program for analysis of pressure and composition in multiple volume systems has been under development by the National Aeronautics and Space Administration (NASA) since 1976. This paper describes the most recent developments in the program. These improvements include the expansion of the program to nine volumes, improvements to the model of the International Space Station (ISS) carbon dioxide removal system, and addition of a detailed Sabatier carbon dioxide reduction mode. An evaluation of the feasibility of adding of trace contaminant tracking was also performed. This paper will also present the results of an analysis that compares model predictions with ISS flight data for carbon dioxide (CO2) maintenance.

Reduction of metabolic carbon dioxide is one of the essential steps in physiochemical air revitalization for long-duration manned space missions. Under contract with NASA Johnson Space Center, Hamilton Standard is developing an Advanced Carbon Reactor Subsystem (ACRS) to produce water and dense solid carbon from carbon dioxide and hydrogen. The ACRS essentially consists of a Sabatier Methanation Reactor (SMR) to reduce carbon dioxide with hydrogen to methane and water, a gas-liquid separator to remove product water from the methane, and a Carbon Formation Reactor (CFR) to pyrolyze methane to carbon and hydrogen. The hydrogen is recycled to the SMR, while the produce carbon is periodically removed from the CFR. The SMR is well-developed, while the CFR is under development. In this paper, the fundamentals of the SMR and CFR processes are presented and results of Breadboard CFR testing are reported.

In planning for Exploration missions and developing the required suite of environmental monitors, the difficulty lies in down-selecting a multitude of technology options to a few candidates with exceptional potential. Technology selection criteria include conventional analytical parameters (e.g., range, sensitivity, selectivity), operational factors (degree of automation, portability, required level of crew training, maintenance), logistical factors (size, mass, power, consumables, waste generation) and engineering factors such as complexity and reliability. Other more subtle considerations include crew interfaces, data readout and degree of autonomy from the ground control center. We anticipate that technology demonstrations designed toward these goals will be carried out on the International Space Station, the end result of which is a suite of techniques well positioned for deployment during Exploration missions.

This paper details the analysis and design of the Temporary Sleep Station (TeSS) environmental control system for International Space Station (ISS). The TeSS will provide crewmembers with a private and personal space, to accommodate sleeping, donning and doffing of clothing, personal communication and performance of recreational activities. The need for privacy to accommodate these activities requires adequate ventilation inside the TeSS. This study considers whether temperature, carbon dioxide, and humidity remain within crew comfort and safety levels for various expected operating scenarios. Evaluation of these scenarios required the use and integration of various simulation codes. An approach was adapted for this study, whereby results from a particular code were integrated with other codes when necessary.

The aim of this study was to explore if fingernail delamination injury following EMU glove use may be caused by compression-induced blood flow occlusion in the finger. During compression tests, finger blood flow decreased more than 60%, however this occurred more rapidly for finger pad compression (4 N) than for fingertips (10 N). A pressure bulb compression test resulted in 50% and 45% decreased blood flow at 100 mmHg and 200 mmHg, respectively. These results indicate that the finger pad pressure required to articulate stiff gloves is more likely to contribute to injury than the fingertip pressure associated with tight fitting gloves.

Procedures that have been developed as part of the NASA JSC-sponsored pre-prototype Checkout, Servicing and Maintenance (COSM) program for pre- and post-EVA airlock operations are described. This paper addresses the accompanying pressure changes in the airlock and in the Advanced Extravehicular Mobility Unit (EMU). Additionally, the paper focuses on the components that are checked out, and includes the step-by-step sequences to be followed by the crew, the required screen displays and prompts that accompany each step, and a description of the automated processes that occur.

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).

Two simulated spacecraft water systems are being used to evaluate the effectiveness of iodine for controlling microbial contamination within such systems. An iodine concentration of about 2.0 mg/L is maintained in one system by passing ultrapure water through an iodinated ion exchange resin. Stainless steel coupons with electropolished and mechanically-polished sides are being used to monitor biofilm formation. Results after three years of operation show a single episode of significant bacterial growth in the iodinated system when the iodine level dropped to 1.9 mg/L. This growth was apparently controlled by replacing the iodinated ion exchange resin, thereby increasing the iodine level. The second batch of resin has remained effective in controlling microbial growth down to an iodine level of 1.0 mg/L. Scanning electron microscopy indicates that the iodine has impeded but may have not completely eliminated the formation of biofilm.

The Shuttle Orbiter humidity control and carbon dioxide removal system for extended duration missions presently uses a solid amine called HS-C. This August, on board STS-62, a new solid amine called HS-C+ will be used. HS-C+ uses the same amine and the substrate material, but a different preparation process. Forty-seven breakthrough tests have been conducted to characterize the performance of HS-C+. CO2 partial pressure, bed temperature, and H2O partial pressure were varied. Eleven HS-C breakthrough tests were also run to provide a direct comparison. Under all conditions tested, HS-C+ outperformed HS-C. Both materials adsorb all CO2 and H2O available at the start of a test when the beds are fully desorbed. As the bed becomes partially loaded, the CO2 and H2O adsorption rates decrease rapidly. HS-C+ continues adsorbing all CO2 and H2O available for a longer time. Greater surface area on HS-C+ may cause the improved performance.

The Early Human Testing Initiative (EHTI) Phase I Human Test, performed by the Crew and Thermal Systems Division at Johnson Space Center, demonstrated the ability of a crop of wheat to provide air revitalization for a human test subject for a 15-day period. The test demonstrated three different methods for control of oxygen and carbon dioxide concentrations for the human/plant system and obtained data on trace contaminants generated by both the human and plants during the test and their effects on each other. The crop was planted in the Variable Pressure Growth Chamber (VPGC) on July 24, 1995 and the test subject entered the adjoining airlock on day 17 of the wheat's growth cycle. The test subject stayed in the chamber for a total of 15 days, 1 hour and 20 minutes. Air was mixed between the plant chamber and airlock to provide oxygen to the test subject and carbon dioxide to the plants by an interchamber ventilation system.

The incidence of decompression sickness (DCS) in space appears to be less than that predicted to occur on the basis of ground based altitude chamber trials. Our current work uses six hours of chair rest adynamia and likewise produces fewer gas bubbles when compared to standing in a cross over study. Mild exercise during oxygen prebreathe is also very efficacious in reducing DCS and bubble formation (measured by Doppler ultrasound). The effect is postulated to be the result of the alteration in the populations of tissue micronuclei such that the radii are reduced. Surface tension then becomes too great for bubble growth from the existing inert gas partial pressures.

Supply of oxygen (O2) and hydrogen (H2) by electrolyzing water in space will play an important role in meeting the National Aeronautics and Space Administration's (NASA's) needs and goals for future space missions. Both O2 and H2 are envisioned to be used in a variety of processes including crew life support, spacecraft propulsion, extravehicular activity, electrical power generation/storage as well as in scientific experiment and manufacturing processes. Life Systems, Inc., in conjunction with NASA, has been developing an alkaline-based Static Feed Electrolyzer (SFE). During the development of the water electrolysis technology over the past 23 years, an extensive engineering and scientific data base has been assembled.

During the period July 2001 to March 2002, the performance of a water-jacketed high intensity discharge lamp of advanced design was evaluated within a lamp test stand at The University of Arizona (UA), Controlled Environment Agriculture Center (CEAC) in Tucson, Arizona. The lamps and test stand system were developed by Mr. Phil Sadler of Sadler Machine Company, Tempe, Arizona, and supported by a Space Act Agreement between NASA-Johnson Space Center (JSC) and UA. The purpose was for long term testing of the prototype lamp and demonstration of an improved procedure for use of water-jacketed lamps for plant production within the close confines of controlled environment facilities envisioned by NASA within Bioregenerative Life Support Systems. The lamp test stand consisted of six, 400 watt water-cooled, high pressure sodium HID lamps, mounted within a framework.

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.

Development of new air revitalization system (ARS) technology can initially be performed in a subscale laboratory environment, but in order to advance the maturity level, the technology must be tested in an end-to-end integrated environment. The Air Revitalization Technology Evaluation Facility (ARTEF) at the NASA Johnson Space Center (JSC) serves as a ground test bed for evaluating emerging ARS technologies in an environment representative of spacecraft atmospheres. At the center of the ARTEF is a hypobaric chamber which serves as a sealed atmospheric chamber for closed loop testing. A Human Metabolic Simulator (HMS) was custom-built to simulate the consumption of oxygen, and production of carbon dioxide, moisture and heat by up to eight persons. A variety of gas analyzers and dew point sensors are used to monitor the chamber atmosphere and the process flow upstream and downstream of a test article. A robust vacuum system is needed to simulate the vacuum of space.

Future NASA manned missions to the moon and Mars will require development of robust regenerative life support system technologies which offer high reliability and minimal resupply. To support the development of such systems, early ground-based test facilities will be required to demonstrate integrated, long-duration performance of candidate regenerative air revitalization, water recovery, and thermal management systems. The advanced life support Systems Integration Research Facility (SIRF) is one such test facility currently being developed at NASA's Johnson Space Center (JSC). The SIRF, when completed, will accommodate unmanned and subsequently manned integrated testing of advanced regenerative life support technologies at ambient and reduced atmospheric pressures.

Among the many firsts which will occur on STS-49, the maiden voyage of the Space Shuttle Endeavour, a Space Station Freedom (SSF) experiment entitled Assembly of Station by Extravehicular Activity (EVA) Methods (ASEM) promises to test the boundaries of EVA operational capabilities. Should the results be favorable, station and other major users of EVA stand to benefit from increased capabilities. Even the preparation for the ASEM experiment is serving as a pathfinder for complex SSF operations. This paper reviews the major tasks planned for ASEM and discusses the operational analogies investigators are attempting to draw between ASEM and SSF. How these findings may be applied to simplify station assembly and maintenance will also be discussed.