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NASA is considering a space based Variable Gravity Research Facility to study the biomedical effects and habitability of various gravity levels encountered as humans venture from Earth. This paper identifies the human factors in the design and use of the V6RF. This includes both the human studies that should be conducted in the VGRF and the design of the VGRF for human habitation. Designers must consider human factors early in the VGRF development to ensure its success.

This paper discusses the process by which the initial system concept design for a remotely operated Tumbling Satellite Retrieval System (TSRS) was developed. This kit, when attached to the Orbital Maneuvering Vehicle (OMV), will retrieve spacecraft whose motion or interfaces prevent direct capture by standard OMV attachment hardware. The system concept design, which was defined by mission, system, and functional requirements, was developed under a NASA/MSFC contract, the objective of which is the development of an evaluation test article. (Detailed design and validation tests will follow.) The process started with the development of twelve “design reference mission” (DRM) retrievals. The twelve DRMs were developed from analysis of the physical and dynamic characteristics of existing and planned spacecraft. Potential TSRS configurations were then developed for accomplishing each DRM.

A new type of oxygen sensor is being developed for potential use in future manned space missions. This sensor incorporates two independent measurement schemes using dual electrochemical cells formed in a common body of solid electrolyte-zirconia. A combination of potentio-metric and coulometric measurements yields accurate and fast response to cabin atmosphere oxygen. Means for self-calibration, fault detection and diagnosis by computer operation are discussed.

A dynamic simulation model has been developed for a vapor-cycle cooling system designed for aircraft applications using the latest technology developments. The heat exchanger models use multiple-, lumped-parameter, fixed-length elements based on coupled thermal and mass storage effects, and flow equations that incorporate the effects of thermal expansion and contraction. This model is developed to include the two-phase constant pressure temperature gradient unique to refrigerant mixtures. The full system model incorporates global mass conservation which is essential for accurate pressure levels and, thus, dynamic response and steady state performance. Phase boundary-based coordinate transformations on the nonazeotropic refrigerant mixture property data result in improved accuracy and computation efficiency. The simulation is developed with modular components with causality defined to minimize connection states and thus execution time.

Environmental Control System (ECS) features to improve reliability and to reduce maintenance of fighter aircraft are presented. The features are intended to overcome support-ability problems of current fighter aircraft ECS, and to reduce supportability requirements for ECS designs in future aircraft. They have the potential to achieve very significant reductions in failure rates, maintenance, and logistics support for fighter aircraft ECS. Two features offer the highest reliability and maintainability improvements. These are use of digital ECS controls integrated with an aircraft maintenance management system, and the use of more rugged bleed air components to reduce maintenance and logistic support. If these and other improvements are installed, ECS downtime can be reduced by 79% from that of the best in current fighter aircraft.

Long duration activities by man in space requires a regenerable CO2 removal system. Current systems under study include those based on the oxygen/hydrogen fuel cell and an amine resin. Both approaches are based on well-known acid-base chemistry of CO2. Our efforts are directed at the development of electroactive CO2 carrier molecules that are capable of binding CO2 when in the reduced form and releasing CO2 in the oxidized form. The successful development of these carriers would provide the chemical basis for a more efficient CO2 removal system and offers other potential advantages as well. The general requirements and advantages of electroactive CO2 carrier molecules are discussed. In addition, studies on carrier molecules which demonstrate the feasibility of this approach are described.

The relative importance of life sciences in spaceflight depends on the nature of the: mission. For brief missions to low earth orbit, such as Shuttle flights, issues involving health concerns, life support, or crew factors present fewer challenges than would longer flights, e.g., those planned for Space Station. For missions of exploration, such as a Mars expedition, the life sciences are not only important to the safety and success of the mission, they are on the critical path to being able to embark on the mission at all. This paper presents a brief history of the role of life sciences in the space program and describes the characteristics of exploration missions that impact life sciences requirements. It concludes by outlining what needs to be done if the very demanding life sciences requirements of exploration missions are to be supported.

The G198A generalized environmental control and life support system (ECLSS) simulation computer program has a library of ECLSS component and subsystem subroutines that can be used to model the complexity of planned ECLSS's for advanced manned spacecraft. The G189A program has successfully provided the necessary mathematical modeling functions for the Skylab and the Space Shuttle orbiter. This paper presents developments at Rockwell International concerning the preparation of the user-friendly computer program (PrepG189) for facilitating G189A program schematics and input data preparation. The two major subprograms in PrepG189 are the schematic processor and the panel processor. The program is operated on a VAX computer terminal. A high level of maneuverability has been achieved in moving between the subordinate portions of the program that participate in numerical data and schematic preparation.

Regenerative physical-chemical technologies for closing major life support functions will play a vital role in reducing the resources needed to support future long duration human space missions in which resupply would not be feasible or desirable. An approach to chemical process research and technology development, as well as systems level research, which can be provided by current state-of-the-art and anticipated advances in computerized modelling and simulation techniques, are discussed. Such techniques will provide a set of fundamental analytical tools for NASA's proposed Pathfinder Physical-Chemical Closed Loop Life Support Program to be used for guiding the specific research and the management of the program.

This paper discusses new technology developments in carbon dioxide (CO2) detection using Non-Dispersive Infrared (NDIR) techniques. The method described has successfully been used in various applications and environments. It has exhibited extremely reliable long-term stability without the need of routine calibration. The analysis employs a dual wavelength, differential detection approach with compensating circuitry for component aging and dirt accumulation on optical surfaces. The instrument fails “safe” and provides the operator with a “fault” alarm in the event of a system failure. The NDIR analyzer described has been adapted to NASA Space Station requirements and a breadboard furnished under NASA contract NAS9-17612.

This paper will review the design approach and hardware involved with the long-term telerobotic support of a deepwater subsea completion complex. The key to a successful design involves matching the design of the subsea equipment and interfaces with the capabilities of the telerobot support system while simultaneously maximizing simplicity, maintainability, reliability and expandability.

This paper describes the operational principles of a hybrid capillary pumped loop in general, and results on testing of a high power hybrid system in particular. A hybrid capillary pumped loop is a thermal control system which consists of a capillary pumped loop and a mechanical pump which is placed in series with the capillary evaporators in the liquid return line. The hybrid loop can be operated in either a passive capillary mode, or in a pump-assisted mode, whereby the mechanical pump augments the heat transport capability of the capillary evaporators. The high power hybrid system was built to demonstrate the feasibility of such a hybrid loop concept. Test results verified that a hybrid loop could be operated in either mode, and that transition between these two modes of operation required opening or closing a single valve on the liquid line.

There is a great need for reliable environmental sensors that can monitor the concentrations of gases and vapors such as oxygen, carbon dioxide, carbon monoxide, water vapor and other contaminants of the cabin air in a manned space station. Honeywell has developed a new class of electrochemical gas sensors based on nonaqueous electrolytes. Sensors with three electrode configuration and gold sensing electrodes have been fabricated and used for monitoring both carbon dioxide and oxygen with the capability to monitor water vapor using linear scanning voltammetry. Sensors with platinum sensing electrodes have been used to monitor low concentrations of toxic gases such as carbon monoxide and nitrogen oxides with potential capability to monitor organic contaminants. Experimental results obtained with these low-power and microprocessor-based sensors will be presented.

High-power heat transport systems for large space platforms such as Space Station require the use of complex fluid loops to effectively and efficiently move waste heat energy from source to sink. In particular, use of two-phase heat acquisition and transport systems offers significant advantages such as reduction of pump power, automation of control systems, constant sink temperatures at the load, and flexible load placement. Analytical tools are needed for design analysis and performance prediction of these systems. Moreover, environmental considerations and insulation systems need to be taken into account, especially when subcooling and superheating become important parameters in the overall design. This paper will discuss the development and use of FLOSIN, a system-level, two-phase fluid loop analyzer. It will explain the modeling approach for systems utilizing a Rotary Fluid Management Device (RFMD), Back Pressure Regulating Valve (BPRV), and cavitating Venturis.

Space Station water recovery involves five separate reprocessing loops: potable water from cabin humidity condensate and carbon dioxide reduction water, hygiene water from crew hygiene activities, hygiene water from crew urine, animal cage wash water and experiment waste water. The magnitudes of the separation tasks involved differ substantially, as do the waste and product water qualities. Three different phase change water recovery technologies are being considered for Space Station use. They include Air Evaporation, Thermoelectric Integrated Membrane Evaporation and Vapor Compression Distillation (VCD). The potential application of these technologies to each reprocessing loop is considered. Comparisons are drawn for urine processing based on a range of evaluation criteria, including product water quality, specific energy, percent recovery, power, weight, resupply needs, reliability, technological maturity, zero-gravity compatibility and contamination potential.

In an effort to reduce the weight of medical supplies that must be sent into space to support the Health Maintenance Facility (HMF) of the Space Station, a disposable cartridge (SWIS) is being developed which will purify the Space Station potable water to USP XXI(1) Water for Injection (WFI) quality. This water will subsequently be mixed with concentrates to reconstitute intravenous solutions such as Ringer's Lactate, which would be used in emergency situations for treatment of ill or injured crew members. The SWIS purification process train will consist of particulate prefiltration, carbon adsorption, mixed bed deionization, ultrafiltration, and sterilizing microfiltration. The present concept envisions a device that will be passive in nature, requiring only tap pressure as the driving force for filtration. The SWIS is being designed to produce at least 6 liters of WFI at a flow rate of 6 liters/hour.

Thermal management systems are currently being developed for application on large orbiting platforms, specifically the Space Station. Based upon its thermodynamic properties, ammonia was selected as a working fluid suitable to handle the power and heat rejection requirements of these systems. The Space Station's 30-year design life, minimum maintenance requirement, maximum reliability, and ammonia working fluid have led to new material compatibility issues. Although ammonia is a well understood fluid for ground-based refrigeration uses, it produced some unexpected results when applied to space-based heat transport systems.

Preprotype air revitalization and water reclamation subsystems (Mole Sieve, Sabatier. Static Feed Electrolyzer, Trace Contaminant Control, and Thermoelectric Integrated Membrane Evaporative Subsystem) were operated and tested independently and in an integrated arrangement. During each test, water and/or gas samples were taken from each subsystem so that overall subsystem performance could be determined. The overall test design and objectives for both subsystem and integrated subsystem tests were limited, and no effort was made to meet water or gas specifications. The results of chemical analyses for each of the participating subsystems are presented along with other selected samples which were analyzed for physical properties and microbiologicals.

An experiment was performed to observe flow regimes and measure pressure drops of two-phase (liquid/vapor) flow and condensation in reduced gravity. Testing was conducted aboard the NASA-JSC KC-135 reduced gravity aircraft using a prototype two-phase thermal management system for large spacecraft. A clear section of two-phase line enabled visual and photographic observation of the flow regimes. The two-phase mixture was generated by pumping nearly saturated liquid refrigerant 114 through an evaporator and adding heat through electric heaters. The resultant two-phase flow was varied by changing the evaporator heat load, creating qualities from 0.05 to 0.80. Visual and photographic observation of vapor condensation was also made through a clear cover on the system condenser. During the flight tests, the experiment hardware was exposed to gravitational acceleration ranging from near-zero to 1.8 g's.