Neutronics Models and Analysis of the Small Nuclear Rocket Engine (SNRE)

Abstract

The fundamental goal of the President’s Vision for Space Exploration announced in early 2004 is to advance U.S. scientific, security, and economic interest through a robust space exploration program. Human expeditions to Mars were one of the long-term activities identified in support of this goal. Although mission architecture, schedule, and preferred hardware have not yet been identified, crewed exploration missions will demand exceptional propulsion system performance. Past studies, in particular those in support of both the Strategic Defense Initiative (SDI) and Space Exploration Initiative (SEI), have shown nuclear thermal propulsion systems provide superior performance for high mass high propulsive delta-V missions. An extensive nuclear thermal rocket technology development effort was conducted from 1955-1973 under the Rover/NERVA Program. The Small Nuclear Rocket Engine (SNRE) was the last engine design studied by the Los Alamos National Laboratory during the program. At the time, this engine was a state-of-the-art design incorporating lessons learned from the very successful technology development program. Recent activities at the NASA Glenn Research Center have included upgrading and modernizing nuclear thermal propulsion system models and analysis methods. A highly detailed MCNP Monte Carlo transport model based on the SNRE was developed as a computational benchmark. Several simpler MCNP models were also developed and exercised. Results from the simpler models are compared to the benchmark model results and to available documentation for the SNRE. Results comparisons include engine reactivity (k-effective), control system reactivity worth, engine system energy balances, core interior component heating, and relative MCNP execution times.