Irradiated Single Crystals for High Temperature Measurements in Space Applications
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Irradiated Single Crystals for High Temperature Measurements in Space Applications Alex A. Volinsky1, V.A. Nikolaenko2, V.A. Morozov2, V.P. Timoshenko3 1 University of South Florida, Department of Mechanical Engineering, Tampa FL 33620 USA [email protected]; http://www.eng.usf.edu/~volinsky 2 Russian Research Center “Kurchatov Institute”, Moscow, Russia 123182 3 Molniya-T, Moscow, Russia 123459 ABSTRACT While spacecrafts experience temperatures from -120 to 110°C on the orbit, their surface reaches extremely high temperatures, well above 1000 °C, during descent into the atmosphere due to aerodynamic heating. Sophisticated insulation systems are designed for thermal protection. One of the steps in designing a protection system is experimental temperature measurements. Neutron flux induces point defects formation and accumulation in diamond and SiC single crystals, which causes overall lattice expansion. During thermal annealing this process is reversed, so the annealing temperature and time result in the “reduced” lattice parameter (measured by X-Ray diffraction), which allows determining the maximum temperature, if the exposure time is known. This paper describes the use of irradiated single crystal high temperature sensors for measuring temperatures in thermal protection systems during spacecraft descent, as well as other space applications. These additional applications include measuring the furnace temperature during single crystal growth in space at zero gravity, and measuring the rocket combustion chamber turbo pump temperature. INTRODUCTION New efficient engine and thermal protection systems design is the major tasks for the space industry. Engine efficiency increases with its operating temperature, which is limited by materials. New high-temperature materials are being developed, and include high-temperature alloys, composites, and ceramic materials. Since materials strength decreases with temperature, it is essential to develop adequate cooling systems. As the maximum operating temperature is normally just under a hundred degrees below the maximum allowed for a particular material, it is extremely important to gain knowledge of temperatures reached in operating devices. While predictive thermal models exist, the trusted temperature data can be obtained only experimentally. Accurate experimental temperature measurement techniques become especially useful during the engine fine tuning, although measuring high temperatures in operating engine is challenging, since: 1) the operating temperatures are high; 2) normally, large temperature gradients are present, and need to be accounted for; 3) the geometry of engine elements is complex; 4) new generation engine elements become smaller and smaller; 5) engine elements should stay intact during testing, i.e. the thermal sensor should not cause engine parts damage; 6) sensor should not affect tested material thermal properties; 7) getting readings from sensors installed in an operating engine is complicated.
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All experimental temperature measureme
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