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The emergence of fuel cell systems and hybrid fuel cell systems requires the evolution of analysis strategies for evaluating thermodynamic performance. A gas turbine thermodynamic cycle integrated with a fuel cell was computationally simulated and probabilistically evaluated in view of the several uncertainties in the thermodynamic performance parameters. Cumulative distribution functions and sensitivity factors were computed for the overall thermal efficiency and net specific power output due to the uncertainties in the thermodynamic random variables. These results can be used to quickly identify the most critical design variables in order to optimize the design and make it cost effective. The analysis leads to the selection of criteria for gas turbine performance.

A new NASA approach to Launch Vehicle (LV) design and development is recommended, which will increase human rated LV reliability in the future. At its core, the new approach includes probabilistic modeling and simulation methods, which will enable the low design margins and large loading uncertainties inherent in LV's to be quantified and addressed, like they have not been on past LV programs.In order to implement the new approach, NASA will need to emphasize probabilistic modeling and simulation in its new Vision for Space Exploration (VSE) programs, like Crew Exploration Vehicle (CEV), Cargo Launch Vehicle (CaLV), and Crew Launch Vehicle (CLV), in order to move towards more reliable systems. This will require increased investment in probabilistic modeling and simulation analysis upfront. Unfortunately, the current approach to fielding these new systems in NASA is to use heritage hardware, which inherently has unquantified low design margins and large loading uncertainties, due to the way past programs have been implemented. The current approach unmodified will result in LV systems that have the same low reliability as past fielded systems. Therefore, it is recommended that NASA increase its investment in probabilistic modeling and simulation for the new VSE programs, CEV, CLV, and CaLV.One possible solution to increasing the NASA investment in probabilistic modeling and simulation for the VSE, in times of limited budget, is to obtain support from the Aeronautics Research Mission Directorate (ARMD), where the current Associate Administrator, Lisa Porter, is emphasizing probabilistic modeling and simulation. It is recommended that the ARMD probabilistic modeling and simulation expertise and Research & Technology be focused on the VSE program needs, in order to assure the development of more reliable LV systems in the future.

A combustor liner was computationally simulated and probabilistically evaluated in view of the several uncertainties in the aerodynamic, structural, material and thermal variables that govern the combustor liner. The interconnection between the computational fluid dynamics code and the finite element structural analysis codes was necessary to couple the thermal profiles with structural design. The stresses and their variations were evaluated at critical points on the liner. Cumulative distribution functions and sensitivity factors were computed for stress responses due to the aerodynamic, mechanical and thermal random variables. It was observed that the inlet and exit temperatures have a lot of influence on the hoop stress. For prescribed values of inlet and exit temperatures, the Reynolds number of the flow, coefficient of thermal expansion, gas emissivity and absorptivity and thermal conductivity of the material have about the same impact on the hoop stress. These results can be used to quickly identify the most critical design variables in order to optimize the design and make it cost effective.