Development of a thermal vacuum system for application in space hardware environmental testing
Schwendtner, Daniel Thomas.
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Since 2001 the Space Science and Engineering Lab (SSEL) at Montana State University has designed and built a variety of space hardware, as well as developed the facilities necessary for environmental testing of flight hardware. In late 2005, the SSEL began developing a system to simulate the vacuum environment of near-space which would allow for rudimentary outgassing testing as well as thermal testing of electronics and spacecraft components. To truly test hardware and validate hardware analysis and design, the ability to cycle between the expected temperature extremes in a vacuum environment was essential. The usage and operation of thermal vacuum systems was investigated, requirements for a thermal vacuum system were defined, and possible design options were considered. A Finite Element Analysis (FEA) was performed to predict the heat load in Watts on the system when a 40 kg nanosatellite (50 cm x 50 cm x 60 cm) was cycled between -40°C and +80°C at rates of temperature change from 1°C/min to 5°C/min. Additional research, analysis, and design was performed on a thermal shroud surrounding the same nanosatellite and operating under identical conditions. Radiation heat transfer between the satellite on the shroud's inside and the vacuum chamber on the shroud's outside was calculated using the radiation network approach. The LU decomposition method was used to solve the resulting set of simultaneous equations. From the results, a design was selected for the system base plate on which the nanosatellite rested, with the capability of sinking or sourcing 833 W of heat power. Similarly, the thermal shroud was designed to sink or source up to 704 W through the shroud body, and up to 229 W through the shroud top. Testing was performed to validate both the FEA model and the physical hardware. Temperature measurements were taken during system testing to validate the design, and as a means to compare the FEA model of the base plate and the radiation heat transfer calculations with the performance of the system hardware. The results indicated that the system functioned as designed, that it met the design requirements, and that it was capable of completely and safely testing satellites and other space hardware.