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Global Reach, Global Power is the stated goal of the U. S. Air Force. The repositioning and restructuring of the Air Force requires bold new approaches to assure the goal is not denied. Improvements in aircraft propulsion, thermal management, and secondary power play key interacting roles in attaining the goal. Resource limitations dictate R&D investments seek solutions that promote synergism and address multiple problems. Increased collaboration between the user and the technologists is recommended to develop versatile and complementary solutions.

Aircraft subsystem and engine heat loads are increasing at a rapid rate.1 Fuel is used in integrated aircraft thermal management systems to cool aircraft subsystems and the engine lubricating oil. All current U. S. fighter aircraft circulate fuel on the airframe to match heat loads with available heat sink. Future aircraft will be required to circulate fuel in excess of that required for propulsive energy through the airframe and engine to assure component life and integrity. These thermal stresses push current fuels JP-4 and JP-8 to bulk fuel temperatures as high as 163°C at the inlet to the mainburner fuel nozzles and to wetted wall temperatures of 205°C inside the fuel nozzle passages.2 At these conditions, engine fuel nozzles, afterburner spray assemblies and manifolds are plugging, causing increased maintenance and cost. In some instances fuel degradation changes the spray pattern in the combustor or afterburner leading to damage to engine components.

The Water Supply Assembly (WSA) is part of the Liquid Management Section (LMS) of the Hermes Environmental Control and Life Support Subsystem (ECLSS) (see ref. [1] and [2]). The WSA has to provide pure water for drinking and food preparation (rehydratation of dry food and beverage powder) and to provide pure water for hygiene purposes (oral hygiene and towel wetting). To obtain different desired temperatures (as well as different quantities of water to be dispensed), a heating device, using electrical foils, and a cooling device, using a water/water heat exchanger have been designed with regard to the critical mass and power requirements. Two dispensers are used to fill food/beverage or hygiene (towels) containers. As part of the Hermes C1 phase, breadboard models of the heating device (heater) and of the cooling device (chiller) have been manufactured and functionally tested.

This paper presents results of new development work carried out in the context of the Water Conditioning Assembly (WCA) which is part of the Liquid Management Section (LMS) of the Hermes Environmental Control and Life Support Subsystem (ECLSS) (see ref [1] and [2]). Its task is to condition and monitor the quality of highly pure water which has been produced in two fuel-cell stacks by the oxidation of hydrogen. This water will be used for different cooling elements (e.g. water evaporator, water sublimator) and as potable water for drinking and food purposes. The assembly consists mainly of: a hydrogen separator, providing for removal of dissolved and gaseous residual hydrogen from the fuel-cell water.

The complex nature of the challenge as humans embark on exploration missions beyond Earth orbit will require that, in the early stages, simulation facilities be established at least on Earth. Suitable facilities in Low Earth Orbit and on the Moon surface would provide complementary information of critical importance for the overall design of a human mission to Mars. A full range of simulation campaigns is required, in fact, to reach a better understanding of the complexities involved in exploration missions that will bring humans back to the Moon and then outward to Mars. The corresponding simulation means may range from small scale environmental simulation chambers and/or computer models that will aid in the development of new materials, to full scale mock-ups of spacecraft and planetary habitats and/or orbiting infrastructures.

A simulation campaign, EXEMSI, organized by the ESA Long Term Programme Office was held from Sept. 7th to Nov. 6th 1992 in Germany. The crew- three men and one woman- was placed in confined and isolated living conditions in an hyperbaric chamber, thus simulating a space environment. During this two-month period, a nutritional investigation was conducted with a twofold objective: from an operational standpoint, to define and setup the food system; from a scientific standpoint, to collect data on the spontaneous nutritional behavior of the crew. In this scope, a well-defined food system was implemented. For food management and on line nutritional data collection, dedicated software has been developed. This software based on using barcodes permitted an accurate recording of food consumption for each crewmember. Nutritional assessments were then performed daily for each crewmember -or EMSInaut- by summing the nutritional values of all the foods consumed.

The results of a study of interaction effectiveness in the crew under isolation in the ESA EXEMSI 92 campaign are presented. The complexity and original character of the group structure was investigated using the bioengineering system known as the Homeostat apparatus. Even though the crew exhibited complex interaction, it is shown that the Homeostat is suitable for on-line inferring of the crew interaction effectiveness in simulation experiments.

This paper deals with the Functions Effectiveness Model (FEM) for Design of the Integrated Regenerative Life Support Systems (IRLSS) based on the physico-chemical methods of the crew metabolic–waste products transformation to controlled components of human environment and intended for the initial problem solution of the IRLSS technology synthesis. The Functions Effectiveness Model of the IRLSS is utterly based on the conceptual model of the Manned Orbital Station Ecologic–Technical System (1), which includes the IRLSS and links of environment: the Space Station Design, the Spaceship crew (CREW), the Space Cabin Atmosphere (SCA), the Thermal Control System (ThCS), the Energetic-Support System (ESS) and the Auxiliary Systems (AS).

The products of thermodegradation of fluorocarbon polymers (found in electrical insulation) will be toxic to space habitat crews, and the monitoring and detection of such contaminants are important to space environmental health. Experiments are therefore being performed on the thermodegradation of a liquid perfluoroalkane mixture (consisting of perfluorohexanes, C6F14, and −5% perfluoropentane, C5F12), similar in structure to polytetrafluoroethylene (PTFE - Teflon), in atmospheres of varying oxygen concentration. PTFE is a common material used on space vehicles for insulation of wires. When PTFE is thermally degraded, such as from the overheating of a wire and subsequent smoldering of the insulation, it may produce toxic compounds ranging from carbonyl fluoride and hydrogen fluoride through perfluorinated aromatic compounds to ultrafine particles.

An Infrared (IR) carbon dioxide (CO2) transducer has been designed, developed, and produced for space applications. This transducer provides measurement of partial pressure of CO2 in life support applications, including the Extravehicular Mobility Unit (EMU), Space Shuttle Orbiter and Spacehab. The electrochemical sensor presently used for these applications has a slow response time and has reliability concerns due to the electrolyte. The new microprocessor based unit has a fast response time and can be tailored to other space applications.

Microscopy aboard Space Station Freedom poses many unique challenges for in-flight investigations. Disciplines such as materials processing, plant and animal research, human research, environmental monitoring, health care, and biological processing have diverse microscope requirements. The typical microscope not only does not meet the comprehensive needs of these varied users, but also tends to require excessive crew time. To assess user requirements, a comprehensive survey was conducted among investigators with experiments requiring microscopy. The survey examined requirements such as light sources, objectives, stages, focusing systems, eye pieces, video accessories, etc. The results of this survey and the application of an Intelligent Microscope Imaging System (IMIS) may address these demands for efficient microscopy service in space.

An event in which electronic insulation consisting of polytetrafluoroethylene undergoes thermodegradation on the Space Station Freedom is considered experimentally and theoretically from the initial chemistry and convective transport through pulmonary deposition in humans. The low-gravity environment impacts various stages of event simulation. Vapor-phase and particulate thermodegradation products were considered as potential spacecraft contaminants. A potential pathway for the production of ultrafine particles was identified. Different approaches to the simulation and prediction of contaminant transport were studied and used to predict the distribution of generic vapor-phase products in a Space Station model.

The pump and flow control subassembly (PFCS) is an orbital replacement unit (ORU) on the Space Station Freedom photovoltaic power module (PVM). The PFCS pumps liquid ammonia at a constant rate of approximately 1170 kg/hr while providing temperature control by flow regulation between the radiator and the bypass loop. Also, housed within the ORU is an accumulator to compensate for fluid volumetric changes as well as the electronics and firmware for monitoring and control of the photovoltaic thermal control system (PVTCS). Major electronic functions include signal conditioning, data interfacing and motor control. This paper will provide a description of each major component within the PFCS along with performance test data. In addition, this paper will discuss the flow control algorithm and describe how the nickel hydrogen batteries and associated power electronics will be thermally controlled through regulation of coolant flow to the radiator.

This paper presents an overview of the design and operation of the internal thermal control system (ITCS) developed for Space Station Freedom by the NASA-Johnson Space Center and McDonnell Douglas Aerospace to provide cooling for the resource nodes, airlock, and pressurized logistics modules. The ITCS collects, transports, and rejects waste heat from these modules by a dual-loop, single-phase water cooling system. ITCS performance, cooling, and flow rate requirements are presented. An ITCS fluid schematic is shown and an overview of the current baseline system design and its operation is presented. Assembly sequence of the ITCS is explained as its configuration develops from Man Tended Capability (MTC), for which node 2 alone is cooled, to Permanently Manned Capability (PMC) where the airlock, a pressurized logistics module, and node 1 are cooled, in addition to node 2.

This paper presents the integrated approach toward failure detection, isolation, and recovery/reconfiguration to be used for the Space Station Freedom External Active Thermal Control System (EATCS). The on-board and on-ground diagnostic capabilities of the EATCS are discussed. Time and safety critical failures, as well as noncritical failures, and the detection coverage for each provided by existing capabilities are reviewed. The allocation of responsibility between onboard software and ground-based systems, to be shown during ground testing at the Johnson Space Center, is described. Failure isolation capabilities allocated to the ground include some functionality originally found on orbit but moved to the ground to reduce on-board resource requirements. Complex failures requiring the analysis of multiple external variables, such as environmental conditions, heat loads, or station attitude, are also allocated to ground personnel.

It is well known that selection of the pressure/oxygen ratio for a human space habitat is a critical decision for the well-being and mission performance of astronauts. It has also been noted how this ratio affects the requirement for pre- and post-breathing and the type and flexibility of EVA/EHA astronaut suits. However, little attention has been paid to how these issues interact with various mission design strategies. Using the first manned mission to Mars as a baseline mission, we have separated the mission into its component parts as it relates to habitat type (i.e., the Earth-Mars interplanetary vehicle, the ascent/descent vehicle, the base, human rover vehicles, etc.) and have determined the oxygen resupply requirements for each part as they reflect a mission design strategy. These component parts form a matrix where duration of stay, loss of oxygen due to leakage and usage, and oxygen resupply needs are calculated.

The TOPEX/Poseidon S/C, a joint venture between NASA and CNES, was launched from Kourou, French Guyana aboard an Ariane 42P launch vehicle on 10 August 1992. The primary objective of the mission is to perform precise measurements of ocean surface topography utilizing radar altimetry from a precision circular orbit with an altitude of 1335 km and an inclination of 66.25°. The S/C consists of an Instrument Module, which houses the primary instruments and S/C support equipment, and the Multimission Modular Spacecraft Standard Bus. The thermal design of the S/C includes multi-layer insulation, fixed radiators, shielded and unshielded louvers, constant-conductance heat pipes, and thermostatically and proportionally controlled heaters. This paper assesses the performance of the TOPEX/Poseidon TCS from the start of pre-launch activities throughout the first 45 days in orbit.

This paper determines the feasibility of potential Active Thermal Control System (ATCS) growth paths by assessing thermal, integration, and implementation impacts. TRASYS/IRTRAN models were used to evaluate the effects of increased radiator temperature, increased radiator area, and radiator wing addition on Space Station Freedom (SSF) elements, including energy reflected back to the ATCS. SINDA/FLUINT models were used to determine the heat rejection capability of an ATCS loop with an integrated heat pump that operates with Electrical Power System (EPS) peak power. The effects of upgrading the ATCS by advanced technology ORU implementation during maintenance replacements was also evaluated. The study results presented lead to conclusions on which paths are best suited for different growth scenarios.

The embedded heat pipe radiator panel is the thermal foundation for the present and future-generation three-axis-stabilized, geosynchronous communications spacecraft. This paper discusses design guidelines and analyzes the thermal performance of some commonly used heat pipe/panel configurations. Among the designs considered are an in-plane design with heat pipes bonded to each other in overlapping sections, an in-plane design with heat pipes crossing on two levels, and externally mounted heat pipes. The thermal performance parameters are quantified and compared as a function of radiator area and weight.

This paper presents the analytical results of a thermal hydraulic study to determine an “optimum” two-phase heat pipe/heat exchanger radiator panel configuration for the Space Station Freedom. The study was based on using conventional axially grooved heat pipes in combination with integral two-phase heat exchangers. Various design parameters were traded to arrive at an optimized panel design that satisfied the thermal requirements. For two-phase flow across a radiator array consisting of eight panels with fourteen heat pipes per panel, small diameter lines acting as flow restrictions are needed at the exit of each heat exchanger to balance the flow across each panel and the radiator array. The paper also presents the test results with a representative subscale heat pipe/heat exchanger radiator panel. In general, the heat pipes exhibit transport capabilities that exceed the design requirements. Balanced flow across each heat exchanger was also demonstrated.