Search Results

Aerospatiale's activities in the field of Active Thermal Control have led to the definition, manufacture and test of a new generation of radiators. The fluid loop radiator study, engaged under the Hermes programme requirements, has resulted in the definition of large radiative panels that have low mass, low manufacturing cost constraints and various possible shapes. The hybrid radiator study, with respect to the Heat Exchanger, has provided a data base of results on the wet and dry concepts. A prototype model has been defined after a “trade-off analysis” and the choice of the dry contact solution has been selected. With respect to the two phase active thermal control concept, a complete loop is under development studies. The problems of “on-ground” testing have been analysed, particularly on the condenser section; the goal being the flight performance prediction of a space radiator.

Thermal control design of Columbus pressurised modules has evolved throughout phases B and C0 of the program leading to the C/D proposal emission. Proposal comments by the European Space Agency (ESA), negotiation of interfaces between Space Station Freedom (SSF) partners, possible advantageous design commonalities among the attached pressurised modules and MTFF reconfiguration are ongoing activities. This paper discusses the design solutions presented in the thermal control subsystem C/D proposal including modifications deriving from updated ESA requirements and preliminary feedback from negotiation of interfaces.

EURECA (EUropean REtrievable CArrier) has been designed as a multi-purpose carrier with a dedicated payload for different experiments (microgravity, astronomy, earth observation, solar physics and technology mission application) to be used during several missions. The EURECA Thermal Control design is subdivided in an “active” thermal control and a “passive” thermal control. The active thermal control is based on a Freon Fluid Loop composed of By-Pass valve, Cold Plates, Radiators and its scope is to guarantee a limited temperature range excursion for some P/L equipments and particular spacecraft units (e.g. Batteries). The passive thermal control composed of MLI blankets and MLI radiators, TCU (Thermal Control Unit), heaters, paints and tapes is instead devoted to maintain the temperature level of the overall carrier components within an acceptable value. Special attention was dedicated to the Hydrazine lines, tanks and thrusters to fulfil the stringent STS safety requirements.

The advent of permanently operating space laboratories as part of the International Space Station Freedom raises challenging requirements also for the thermal and environmental control of those laboratories. Enhanced crew size, power dissipation due to a broad range of experiments, flexibility with respect to payload reconfiguration and rack interchangeability, to name only a few, typically are such requirements. The paper is devoted to the analysis of these requirements and related conceptual design solutions in the light of overall system aspects with special emphasis on the permanently Attached Laboratory of the European Columbus Programme. In particular the following subjects will be addressed: loops concept factors like parallel /serial /multi loop/single loop and reconfiguration of water cooling and air cooling loops.

The Fluid Heat Transport Systems (FHTS) extension to the ESATAN thermal analyser was released to industry in 1989. A significant as effort has been directed towards obtaining, far as possible, an error free code which gives results in reasonable agreement with reference data. The first steps to ensure confidence in FHTS have been taken by system testing during software acceptance and by means of a comparison with RETRAN, a US code unique in possessing a US safety evaluation report for reactor licensing applications. RETRAN output data was taken as the a priori reference data to verify FHTS. Two sets of test cases have been defined, one concerning single-phase problems (basically the Columbus water loop), the second set containing models with two-phase conditions (a simple idealised loop and boundary conditions). The paper highlights the difficulties encountered during the comparison work, presents the major results and discusses the main issues involved in FHTS verification/validation.

The system of diffusion equations generated by SINDA is solved by an eigenmethod. This avoids the current numerical integration and its instability problems. The nonlinear terms such as radiative coupling are treated as forcing functions, and their rates of change determine the time steps, which are automatically set to yield any desired accuracy. The method can be significantly faster than the current methods. An example problem is solved in sufficient detail to allow a programmer to install the method in SINDA, so that its use would be just as convenient as calling for the Crank-Nicholson method. Existing SINDA models could be run without change, and the modelling advantages of SINDA are retained.

The “new generation” of large satellites like ERS-1 requires modular thermal balance testing due to the physical size. The purpose of this paper is to outline the experience gained from the ERS-1 Payload Thermal Balance Test. The first part of the paper highlights the test set-up, the earthshine compensation and the selected test phases. The second part describes the temperature uncertainty approach and test correlation criteria defined for the thermal analyses and tests. The third part concentrates on the test correlation with emphasis on the thermo-optical properties of the Optical Solar Reflectors (OSRs) in the Xenon light of the simulated sun and the temperature dependent linear conductance of the honeycomb core material which played a crucial role in explaining a temperature level offset. The paper is understood as complement to the paper presented in 1987 - Thermal Control and Design of the ERS-1 Payload -.

For thermal mathematical models, the heat sources of nodes representing payload elements are usually modelled in the form of time-dependent bivariate input data arrays. Each node night represent an experiment or a package consisting of a number of small experiments, which can be lumped together considering location, thermal mass, heat rejection mode, thermal dissipation timeline and anticipated temperature levels. The electrical power consumption of the individual experiments is usually given in the form of an electrical power timeline indicating identification, switch times and power levels provided by the planning authorities. The electrical energy consumption of the equipment, however, is converted to a certain degree into thermal dissipation to be rejected to the environment at a certain rate and time.

The ISO-satellite consists of a Service and a Payload Module, the latter being essentially made up of the Cryostat. The present paper describes the current status of this cryostat. The general structural and thermal layout, the He-flow schematic and safety system and the general cover layout are described together with an overview on the existing hardware. Some first test results are as well reported.

A failure during the Liquid Apogee Engine (LAE) firing with Thermal Shield, forced Selenia Spazio to critically review the thermal design concept of the LAE/Shield Assembly of ITALSAT Program. This review led to: the change of Thermal Shield design criteria (in order to increase the safety margin on the LAE firing temperatures); the identification of thermal failure modes of the utilized LAE (together with the contribution of many other US and European LAE utilizers and of LAE Supplier as well); the definition and implementation of a LAE Firing Control Strategy. This Paper describes the performed efforts and the resulting engineering considerations.

Space Shuttle astronauts are exposed to both the “trapped” radiation and the galactic cosmic radiation environments. In addition, the sun periodically emits high-energy particles which could pose a serious threat to flight crews. NASA adheres to federal regulations and recommended exposure limits for radiation protection and has established a radiological health and risk assessment program. Using models of the space radiation environment, a Shuttle shielding model, and an anatomical human model, crew exposure estimates are made for each Shuttle flight. The various models are reviewed. Dosimeters are worn by each astronaut and are flown at several fixed locations to obtain in-flight measurements. The dosimetry complement is discussed in detail. A comparison between the premission calculations and measurements is presented. Extrapolation of Shuttle experience to long-duration exposure us explored.

The effectiveness of a proposed concept for shielding a manned Mars vehicle using a confined magnetic field configuration is evaluated by computing estimated crew radiation exposures resulting from galactic cosmic rays and a large solar flare event. In the study the incident radiation spectra are transported through the spacecraft structure/magnetic shield using the deterministic space radiation transport computer codes developed at Langley Research Center. The calculated exposures unequivocally demonstrate that magnetic shielding could provide an effective barrier against solar flare protons but is virtually transparent to the more energetic galactic cosmic rays. It is then demonstrated that through proper selection of materials and shield configuration, adequate and reliable bulk material shielding can be provided for the same total mass as needed to generate and support the more risky magnetic field configuration.

Several underwound families of topoisomers of the plasmid pIB130 were irradiated with fission neutrons at 28 C in TE buffer. Form I DNA followed the expected exponential dependence on dose, and was greater for those DNA molecules characterized by larger linking numbers. The radiation sensitivity was found to be linearly related to average linking difference. We tentatively attribute this enhanced radiation sensitivity to the increased number of transient open states that closed DNA experiences with increasing superhelicity. Radioprotectants enhance decrease in the DNA linking number in the presence of topoisomerase I, suggests that some of the protection conferred may be due to decreases in DNA superhelicity.

One of the unique aspects of the Space Station is that it will be a totally encapsulated environment and the air and water supplies will be reclaimed for reuse. The Environmental Health System, a subsystem of CHeCS (Crew Health Care System), must monitor the air and water on board the Space Station Freedom to verify that the quality is adequate for crew safety. Specifically, the Water Quality Subsystem will analyze the potable and hygiene water supplies regularly for organic, inorganic, particulate, and microbial contamination. The equipment selected to perform these analyses will be commercially available instruments which will be converted for use on board the Space Station Freedom. Therefore, the commercial hardware will be analyzed to identify the gravity dependent functions and modified to eliminate them.

The process used to identify, select and design an approach to the isolation and concentration of volatile organic compounds from a water sample prior to chemical analysis in a microgravity environment is described. The Volatile Organics Concentrator (VOC) system described in this paper has been designed for attachment to a gas chromatograph/mass spectrometer (GC/MS) for analysis of volatile organics in water on Space Station. In this work, in order to rank the many identified approaches, the system was broken into three critical areas. These were gases, volatile separation from water and water removal/GC/MS interface. Five options involving different gases (or combinations) for potential use in the VOC and GC/MS system were identified and ranked. Nine options for separation of volatiles from the water phase were identified and ranked. Seven options for use in the water removal/GC column and MS interface were also identified and included in overall considerations.

Because of gastrointestinal discomfort associated with the ingestion of gas-loaded water in microgravity, it is important to monitor the gas content of the potable water onboard Space Station Freedom. A major potential constituent of this gas is nitrogen, which cannot be detected in aqueous solution by electrodes or by spectrophotometric methods. This paper concerns Lockheed's work in behalf of McDonnell Douglas Space Systems Company for NASA's Space Station Work Package 2. As part of the environmental monitoring subsystem for the Crew Health Care System, Lockheed is developing an Optical Water Quality Analyzer. An important feature of this instrument is the ability to unload and measure the gas content of the water sample.

The development of a high sensitivity, compact monitor for the measurement of total organic carbon (TOC) in water with no gravity-dependent components is discussed. The system is based on a combination of photo-catalzyed oxidation of organic compounds to form carbon dioxide, which is selectively measured using a gas permeable membrane and conductometric detection. This unique combination permits the development of a TOC analyzer with significant advantages over existing methods for TOC analysis including high sensitivity (i.e., detection limits at low parts per billion TOC concentrations), a linear response over a wide range of TOC concentrations (at least four orders of magnitude), long-term stable calibration, compact design, and performance with minimal maintenance for semi-continuous and continuous monitoring capabilities. The results from our preliminary investigations on the development of the TOC monitor are presented.

Several compounds in the ersatz humidity condensate do react with iodine to form iodine-substituted organic compounds (TOI), most notably phenol, acetaldehyde, ethanol, and sodium formate. Iodination of the ersatz humidity condensate produced 3.0 to 3.5 mg/L of TOI within 24 hours. The TOI that was produced by the passage of the ersatz humidity condensate through the first iodinated resin (IR) in the adsorption system was removed by the granular activated carbon that followed. TOI detected in the final effluent was formed by the reaction of the non-adsorbable condensate compounds with the final IR in the treatment series. The activated carbon bed series in the adsorption system performed poorly in its removal of TOC. The rapid breakthrough of TOC was not surprising, as the ersatz humidity condensate contained several highly soluble organic compounds, alcohols and organic acids.

Microbial proliferation in the STS potable water system is prevented by maintaining a 2-5 ppm iodine residual. The iodine is added to fuel cell water by an iodinated ion exchange resin in the Microbial Check Valve (MCV). Crew comments indicated excessive iodine in the potable water. To better define the problem, a method of in-flight iodine analysis was developed. Inflight analysis during STS-30 and STS-28 indicated iodine residuals were generally in the 9-13 ppm range. It was determined that the high iodine residual was caused by MCV influent temperatures in excess of 120 °F. This is well above the MCV operating range of 65-90 °F. The solution to this problem was to develop a resin suitable for the higher temperatures. Since 8 months were required to formulate a MCV resin suitable for the higher temperatures, a temporary solution was necessary. Two additional MCV's were installed on the chilled and ambient water lines leading into the galley to remove the excess iodine.

LiquidChromatogry/Mass Spectrometry (LC/MS) can improve Freedom water recovery systems testing by providing analytical information about non-volatile organic contaminants not amenable to conventional analytic techniques. A preliminary liquid chromatography method has been developed for organic acids in human urine. Using this method over twenty organic acids and related compounds can be resolved. Some of these compounds have not been reported previously from Environmental Control and Life Support System hardware testing.