In 1957, in response to Sputnik and in advance of NASA, a small group of scientists and engineers at a startup named General Atomic launched an attempt to build an interplanetary spaceship powered by nuclear bombs. They aimed to reach Mars by 1965 and Saturn by 1970, in 4,000-ton ships carrying payloads of 1,000 tons. Project Orion, based on hundreds of hours of interviews and thousands of pages of declassified documents, reveals their story firsthand. This expanded edition includes a revision of the long out-of-print 2002 text (with updated notes, references, index, and a chronological listing of technical reports), a new foreword by Freeman Dyson, a new afterword, 52 pages of illustrations, and 12 previously unpublished manuscript calculation sheets.