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Published byChester Woods Modified over 9 years ago
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AAE 450 Spring 2008 Steven (“CJ”) Hiu 02/20/2008 Structural Analysis: Overpressure Safety MAT & FAM Coder – Structures CAD – Tanks, Intertank Couplers
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AAE 450 Spring 2008 Overpressure Safety Systems Purpose – prevent damage to rocket from overpressure (tanks, lines, injector) Sensors –Pressure Transducers, strain gauges Actuators –Pressure Relief Valves –Burst Disk (single use) – usually rated to high psi Use – on the ground, in gondola, during firing Feed Lines Oxidizer Tank (not critical, feed line may suffice) Pressurant Tank – vital, cryo LN 2 subject to heating LITVC (similar to oxidizer) Structures
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AAE 450 Spring 2008 Thermal Analysis of Pressurant Tank Assume constant velocity (terminal rise) Thermal Analysis based on conduction Conservative (Ignore phase change, no boundary layer) Findings –~30 K rise over 30 km –Pressure rises above critical tank allowable Solutions –Relief Valve on pressurant tank –Umbilical on Gondola Structures
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References Hart, G H, Grounding The Space Shuttle, NASA’s Foam Insulation Problem, www.insulation.org/articles/article.cfm?id=IO51204 www.insulation.org/articles/article.cfm?id=IO51204 http://www.efunda.org – Thermal properties of Aluminum http://www.efunda.org http://www.nist.gov/srd/fluids.htm - Thermal properties of Liquid Nitrogen http://www.nist.gov/srd/fluids.htm Acknowledgements Many thanks to all FAM team members for their dedication and perseverance AAE 450 Spring 2008 Structures
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AAE 450 Spring 2008 Backup Slide 1 Thermal Conductivity across tank wall Structures T a (function of Altitude) T f (Foam interface temp) T l (LN 2 temp) Ambient (Air) Foam Insulation Tank Wall Liquid Nitrogen
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Backup Slide 2 –Thermal Conductivity Values –Foam – assume constant f 0.161 BTU/hr.ft^2.F (1 in.) 0.023 W/m^2K –Aluminum – Al function of temperature AAE 450 Spring 2008 Structures
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AAE 450 Spring 2008 Backup Slide 3 Specific Heat of Liquid Nitrogen, 6 MPa AAE 450 Spring 2008 Structures
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Backup Slide 4 AAE 450 Spring 2008
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