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One of the concerns for future spaceflight activities is the intermediate and/or long-term physiological or pathological complications which may develop in those individuals who engage in repetitive EVAs. Notwithstanding the thousands of exposures of individuals to decreased atmospheric pressures over the last 50 years, the syndrome of DCS still remains poorly understood, particularly as regards repeated exposure to pressure changes. The literature on the effects of repetitive exposure to low barometic pressures is confounding. Studies supporting an increased, decreased, and no change to susceptibility to DCS associated with repeated exposure to reduced pressures were found, and are discussed.

Vehicle longitudinal motion is decisively influenced by engine-control functions. The dynamics of the mixture formation in particular can lead to uncontrolled variations in the air/fuel ratio. This has a considerable adverse effect on ride comfort as well as exhaust emissions. Changes in the indicated torque following a throttle alteration are analysed, reaction sequences differing in time response are separated. Physics-based control functions can thus be established, achieving better results than a purely empirical method.

The otolith organs are the linear motion sensors of the mammalian system. As part of the vestibular system these small organs are located in the inner ear. Mathematically modeled, they consist of an overdamped second-order system with elastic, viscous damping, and mass elements. The governing equations of motion which describe the relative velocity of the mass with respect to the skull consist of a set of three coupled partial integral-differential equations. When these equations are nondimensionalized they yield three nondimensional parameters which characterize the dynamic response of the system. These nondimensional equations are solved numerically for the relative displacement of the otolith mass for various values of one of the three nondimensional parameters. The solutions generated are for a step change in skull velocity. These solutions indicate that the end organ long time response as well as limited maximum displacement requires a high degree of viscoelastic damping.

This report deals with a new exhaust emission concept, the idea of which is the reduction of raw exhaust emissions and improvement of fuel economy by operating a gasoline engine in its (HC+NOx)-minimum. This is accomplished with a smooth running control. Further components of this concept are a cylinder individual fuel injection system as well as a dual coolant circulation system.

For engines with rather fast changing load-cycles a simple system is proposed to cool the combustion air in the upper load-range and heat it in the lower range. This “levelling system” is self contained and works without any connection to the ambient air or to the cooling circuit of the engine. It relies basically on means, which enhance the thermal inertia of the inlet manifold in combination with an efficient heat exchange with the combustion air. Examples are given for different applications. Test results prove the advantages of the system and are compared with results of ordinary aftercooling systems. Furthermore it is shown that even aftercooled engines may benefit from a higher thermal inertia. The paper demonstrates that a levelling system is an economical and usefull means to improve the behaviour of ail types of supercharged engines.

Life sciences research facilities planned for the U.S. Space Station will accommodate life sciences investigations addressing the influence of microgravity on living organisms. Current projects within the Life Sciences Space Station Program (LSSSP), the Life Sciences Space Biology (LSSB) and Extended Duration Crew Operations (EDCO) projects, will explore the physiological, clinical, and sociological implications of long duration space flight on humans and the influence of microgravity on other biological organisms/systems. Initially, the primary research will emphasize certifying man for routine 180-day stays on the Space Station. Operational crew rotations of 180 days or more will help reduce Space Station operational costs and minimize the number of Space Transportation System (STS) shuttle flights required to support Space Station.

The basic structure of a new engine control system for highly accurate air-fuel ratio control is introduced. Improved engine power and decreased fuel consumption are required for today's engines. Better air-fuel ratio control must be attained to set the air-fuel ratio to that of the maximum power and minimum fuel consumption. In order to enhance the accuracy of the air-fuel ratio control, the air flow meter, air-fuel ratio sensor, and fuel supply device are improved in the new system. Accuracy is lost in conventional system owing to the sensors' deterioration over long-term use. So prevention of air flow meter deterioration and compensation of air-fuel ratio sensor deterioration are taken into consideration. Fuel atomization of the fuel supply device is improved in order to reduce the air-fuel ratio fluctuation in the transient operating state. High power and decreased fuel consumption over long-term use are made possible with the new system.

The utility of analog environments as sources of data for future, long duration space missions is discussed. The undersea habitat is evaluated on a point by point basis for similarities and differences with Space Station and a possible Lunar Base. The comparability of Antarctic wintering-over stations is also considered. Critical issues for research are described as well as the requirement that participants be involved in the conduct of meaningful work.

Conventional oxygen separation from gases has a low extraction efficiency and requires a large energy source. An innovative low power, efficient oxygen extractor could capture free oxygen from the Martian atmosphere for use in life support systems. It might also be used during the lunar oxygen separation process from the soil or a Space Station ECLSS (Environmental Control and Life Support System) for oxygen concentration and distribution. Aquanautics Corporation received a Small Business Innovative Research (SBIR) Grant from NASA's Johnson Space center to develop such a system. The contract began in January 1988. The technology has involved a substantial research effort that is now entering into the first phase of prototype development. This paper discusses the technology in general terms and the specific work which is being performed for NASA to determine the feasibility for Martian applications.

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.