Browsing by Keyword "Space and Planetary Science"
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Item Accurate calculation of conductive conductances in complex geometries for spacecrafts thermal models(2016-02-15) Garmendia, Iñaki; Anglada, Eva; Vallejo, Haritz; Seco, Miguel; CIRMETAL; MAQUINASThe thermal subsystem of spacecrafts and payloads is always designed with the help of Thermal Mathematical Models. In the case of the Thermal Lumped Parameter (TLP) method, the non-linear system of equations that is created is solved to calculate the temperature distribution and the heat power that goes between nodes. The accuracy of the results depends largely on the appropriate calculation of the conductive and radiative conductances. Several established methods for the determination of conductive conductances exist but they present some limitations for complex geometries. Two new methods are proposed in this paper to calculate accurately these conductive conductances: The Extended Far Field method and the Mid-Section method. Both are based on a finite element calculation but while the Extended Far Field method uses the calculation of node mean temperatures, the Mid-Section method is based on assuming specific temperature values. They are compared with traditionally used methods showing the advantages of these two new methodsItem Cements based on kaolinite waste(2018-08-10) García Giménez, Rosario; Vigil de la Villa Mencía, Raquel; Frías, Moises; Martínez Ramírez, Sagrario; Vegas Ramiro, Iñigo; Fernández Carrasco, Lucía; GENERALThe cement industry involves high-energy consumption that generates high CO2 emissions into the atmosphere. Environmental concerns can be addressed by replacing parts of Portland cement clinkers with pozzolanic materials in mortars and concrete. Slag, fly ash and silica fume are materials considered for the planned replacement. Research studies on clay minerals, such as kaolinite, are being followed with special attention by the scientific community and the cement industry. It is well known that these minerals require an activation process to transform kaolinite (K) into metakaolinite (MK). MK is an amorphous material from the transformation of K with high pozzolanic activity, which is its capacity to react with the portlandite released during the hydration of Portland cement, generating compounds such as C–S–H gels and some aluminum-phase hydrates. One of the MK production methods is heat treatment controlled by kaolinite at temperatures in the range of 600–900°C. Different residues have been used (coal mining, paper sludge and waste from a drinking water treatment plant) activated at 600°C for 2h to elaborate blended cements. Due to their good behaviour as future eco-efficient additions, this research is a study by x-ray fluorescence (XRF), x-ray diffraction (XRD) and scanning electron microscopy (SEM) of their influence on the performances of blended cement mixtures (binary and ternary one), with substitutions of pozzolan ratio at 28 days of hydration. The porosity of pozzolanic cements decreases because of the formation of hydrated phases during pozzolanic reaction.Item Innovative Thermal Management Concepts and Material Solutions for Future Space Vehicles(2016) Esser, Burkard; Bárcena, Jorge; Kuhn, Markus; Okan, Altug; Haynes, Lauren; Gianella, Sandro; Ortona, Alberto; Liedtke, Volker; Francesconi, Daniele; Tanno, Hydeyuki; Tanno, Hideyuki; EXTREMATWhen entering a planetary atmosphere, space vehicles are exposed to extreme thermal loads. To protect the vehicle’s interior, a thermal protection system is required. Future aerospace transportation demands solutions that exceed the performance of current systems and up-to-date material limits. Therefore, new and disruptive solutions must be envisaged to meet those extreme conditions. In the search of new solutions for sharp leading edges of future hypersonic reentry or transport vehicles, the THOR project, composed of eight European organizations (industries, research centers, and universities) and one Japanese Agency (Japan Aerospace Exploration Agency), is actively working on definition, design, implementation, and simulation of new passive and active thermal management solutions and their verification in relevant environments (high-enthalpy facilities). This paper provides an overview of the recent developments on the four concepts that are targeted in the project, applying different physical methodologies: 1) passive cooling using highly conductive carbon-based fibers, 2) passive cooling with intensive internal radiative exchange, 3) active cooling based on convection heat transfer using a ceramic sandwich/thermal protection system with ceramic foams/lattices, and 4) active transpiration cooling of external surfaces. Details on these thermal management concepts, requirements from end users, and test configurations, as well as results from experimental and numerical verification, are given.Item The vacuum tribology model (VTM) of tribolab(2003) Garmendia, I.; Landaberea, A.; Anglada, E.; Fernández-Sanz, R.; Santiago, R.; Herrada, F.; Encinas, J. M.; CIRMETALTriboLAB is a tribology instrument that is planned for installation in the EuteF Flight Segment Platform [1], along with several other European scientific instruments. Eutef will be fixed onto an Express Pallet Adapter (ExPA), which provides standard structural, mechanical, electrical and communications interfaces to the Columbus External Payload Facility of the International Space Station (ISS). As a part of the model philosophy, a vacuum tribological model (VTM) has been developed to generate "on ground" tribological data of selected lubricants. The idea is to compare the results obtained "on ground" with those that will be produced in the space, in order to investigate the different behaviors of same tribological films and to be able to compare the performance of specific lubricants in Low Earth Orbit (LEO) conditions. The VTM is composed of six double experiment cells that perform respectively ball bearing (BB) experiments (with liquid and solid lubrication) and pin-on-disk (PoD) tests of solid lubricants. Thin films of alloyed MoS 2 are being tested in the VTM under controlled vacuum conditions. In this work, the two sections of the VTM are described.