The early days of the S{sub n} method

From the beginning at Los Alamos National Laboratory (LANL), solutions to the transport equation were very important. Many long-forgotten approximate solution techniques, including one by Feynman, were developed to help design nuclear weapons. Most of these methods were based on the methods of mathematical physics familiar to the project physicists and predated the use of computers, but continued research and pressing need produced two new and powerful computer-based systems: Monte Carlo and the S[sub N] method. The healthy and long-term competition between the two LANL groups responsible for these quite different approaches was both stimulating and synergistic.