1. AAE 450 Spring 2008 Steven (“CJ”) Hiu 02/20/2008 Structural Analysis: Overpressure Safety MAT & FAM Coder – Structures CAD – Tanks, Intertank Couplers

2. 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

3. 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

4. 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

5. 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

6. 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

7. AAE 450 Spring 2008 Backup Slide 3  Specific Heat of Liquid Nitrogen, 6 MPa AAE 450 Spring 2008 Structures

8. Backup Slide 4 AAE 450 Spring 2008