Publication Date


Document Type


Committee Members

Ramana Grandhi (Advisor), Ramana Grandhi (Committee Member), Ronald Taylor (Committee Member), Scott Thomas (Committee Member)

Degree Name

Master of Science in Engineering (MSEgr)


Due to the inherent natural variability of parameters with reusable launch vehicles, design considerations without use of a reliability or safety index may be unreliable and vulnerable to vehicle failures. Generally in preliminary air vehicle design little information is known regarding design variable uncertainties, consequently requiring a technique that can quantify epistemic uncertainties. Evidence Theory is employed to accomplish this task resulting in a reliability bound of belief and plausibility. Due to the discontinuous nature of the belief and plausibility function it is necessary to implement a continuous function known as plausibility decision to be used to calculate sensitivities that can be implemented in a gradient-based reliability-based design optimization algorithm. This research develops a new plausibility decision approximation that calculates sensitivities with respect to uncertain design variables without introducing extra computational cost or numerical integration. This new metric was demonstrated in a sensitivity analysis as well as a reliability based design optimization of the aeroelastic flutter reliability of a reusable launch vehicle's wing.

Page Count


Department or Program

Department of Mechanical and Materials Engineering

Year Degree Awarded