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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.

The design and performance of the Space Station Freedom Photovoltaic (PV) Power Module Thermal Control System radiators is presented. The PV Radiator is of a single phase pumped loop design using liquid ammonia as the coolant. Key design features are described, including the base structure, deployment mechanism, radiator panels, and two independent coolant loops. The basis for a specific mass of 7.8 kg/m2 is discussed, and methods of lowering this number for future systems are briefly described. Key performance parameters are also addressed. A summary of test results and analysis is presented to illustrate the survivability of the radiator in the micrometeoroid and orbital debris environment. A design criterion of 95% probability of no penetration of both fluid loops over a 10 year period is shown to be met. Methods of increasing the radiator survivability even further are presented.

The Tethered Satellite System (TSS) is a Space Shuttle payload that was flown on July 31, 1992. Though anomalies prevented full deployment, the duration of the mission was approximately as planned, so it was possible to assess system thermal performance. The deployer, which supports the satellite and controls tether movement, has a thermal design that includes multilayer insulation, heaters, and the Spacelab Freon Loop. The Deployer Thermal Subsystem met all requirements, and there were no anomalies during the flight. This paper summarizes the TSS deployer thermal design and compares pre- and post-flight thermal analyses. It also describes simplified personal-computer thermal models of the TSS-1 and presents analysis results for the as-flown timeline.

Capillary pumped loops (CPLs) have undergone extensive development since the late 1970's, and represent a maturing technology that is beginning to appear in spacecraft designs (COMET, EOS AM). Perhaps because most CPL literature is intended for CPL and heat pipe developers, or perhaps because of the myriad of component design and layout options available, many thermal control designers are either unfamiliar with the capabilities offered by CPLs, or are confused about their limitations. This survey paper is targeted toward thermal control designers who must decide when and where to use CPLs, or having chosen a CPL solution, must deal with system-level integration and test issues.

The COMmercial Experiment Transporter (COMET) is a satellite will launch aboard the Conestoga rocket. COMET provides the United States Commercial research and development community with a dependable and economical means to access space. The COMET program is defined and funded by the NASA Centers for the Commercial Development of Space (CCDS). The Center of Space Transportation and Applied Research (CSTAR) was given the authority to establish and implement the COMET program. The COMET Service Module is designed, integrated and tested by Defense Systems Incorporated for Westinghouse Commercial Space. The Capillary Pumped Loop (CPL) was integrated into the Service Module by OAO Corporation for Defense Systems Incorporated. The Service Module's primary function is to carry payloads to space, providing them with utilities such as a tightly controlled thermal environment, electrical power, attitude control, data management, and communications while in orbit.

The fluid and thermal dynamics of the environment of plants in a small controlled-environment system have been modeled. The results of the simulation under two scenarios have been compared to measurements taken during tests on the actual system. The motivation for the modeling effort and the status of the modeling exercise and system scenario studies are described. An evaluation of the model and a discussion of future studies are included.

This paper is intended to address the process of System Analysis in the area of Advanced Life-Support Systems (ALSS). Particular attention is given to Controlled Ecological Life Support Systems (CELSS) architectures. The process of System Analysis is an iterative one in which “trade-offs” of various system elements are executed to evaluate system functionality and structure. In the process, consideration is given to factors such as system requirements, potential architectures and design concepts, integration issues and system operations. The emphasis of the paper is on developing a consistent framework for the analysis process. It is anticipated that by developing a formal framework, particularly for the systems analysis of a CELSS, comparisons of approaches and of quantitative assessments will be made easier.

The MELISSA (Microbial Ecological LIfe Support System Alternative) project has been set up to be a model for the studies on ecological life support systems for long term space missions. The compartmentalisation of the loop, the choice of the micro-organisms and the axenic conditions have been selected in order to simplify the behaviour of this artificial ecosystem and allow a deterministic and engineering approach. In this framework the MELISSA project has now been running since beginning 1989. In this paper we present the general approach of the study, the scientific results obtained on each independent compartment (mass balance, growth kinetics, limitations, compound conversions,..), the tests of toxicity already performed between some compartments and their effect on the growth kinetics. The technical results on instrumentation and control aspects, and the current status of the ESA/ESTEC hardware are also reviewed.

One way to increase thermal software performance has been developed at AEROSPATIALE Cannes by means of a condensation algorithm for conductive models (EQUIVALE). The benefit of this improvement is exportable to other software packages by developing specific interfaces. Therefore, two gateways are now available to perform ESATAN conductive models condensation: the first (ESAEQU) translates the initial ESATAN input deck into the different files required by EQUIVALE; the second (EQUESA) generates a new ESATAN input deck including the equivalent conductances provided by EQUIVALE. Three examples of application are described hereafter: the first (RADIATOR PANEL) illustrates the condensation processing coupled to ESATAN, the second (TV-SAT/TDF), more realistic, refers to a flight model in the frame of the AEROSPATIALE Thermal Software environment and the third (TÜRKSAT) shows the optimum use of EQUIVALE with the combination of both PLATEAU and EQUIVALE software packages.