Charles S. Godfrey, 79, a physicist who worked on the early development of nuclear weapons. Born in San Francisco, Godfrey was educated at the Massachusetts Institute of Technology and UC Berkeley, where he later worked with the Lawrence Livermore Laboratory. He first designed small, tactical nuclear weapons that were tested at Eniwetok Atoll in the Pacific Ocean in the 1950s. He took time out from Livermore in the 1960s to co-found Physics International, which became the world leader in technology for studying radiation effects. Godfrey also designed tests for the U.S. space program on the effects of micro-meteorite collisions on space vehicles. He was a pioneer in uses of hydrodynamics software to simulate nuclear explosions, reducing the need for test blasts. On Jan. 31 in Berkeley of Alzheimer's disease.