Saturn C-5N

The Saturn C-5N was a conceptual successor to the Saturn V launch vehicle which would have carried a nuclear thermal third stage in place of the S-IVB used on the Saturn V. That single change would have raised the payload of the standard Saturn V to low Earth orbit from 118,000 kg to 155,000 kg. It was designed as an evolutionary successor to the Saturn V for the planned crewed mission to Mars by 1980, which it would have cut to a transit of about four months, instead of the eight to nine months of chemical rocket engines. The Mars mission, along with all work on the evolutionary successors of the Saturn V, was cancelled in 1972 and 1973 by the Nixon Administration. The ground testing of the NERVA nuclear thermal engines intended for its in-space third stage still holds a number of combined thrust and specific impulse records, and the concept influenced Project Timberwind in the 1990s.