Uncertainties associated with the design parameters of the Space Nuclear Propulsion System (SNPS) nozzle such as geometry, boundary conditions, material behavior, thermal and pressure loads, etc. are considered to assess its reliability. Preliminary assessment of the reliability is performed using NESSUS (Numerical Evaluation of Stochastic Structures Under Stress) computer code developed at NASA Lewis Research Center (LeRC). Probabilistic finite element analysis of the nozzle system is conducted and the sensitivity of reliability to the uncertainties in the random variables is quantified. For example the nozzle spatial geometry uncertainties have the most significant effect on the effective stress at low probabilities while the inner wall temperature has the most significant effect at higher probabilities.

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