 Saturn C-5N

The Saturn C-5N was a conceptual successor to the Saturn V launch vehicle which would have had a nuclear thermal third stage instead of the S-IVB used on the Saturn V. This one change would have increased the payload of the standard Saturn V to Low Earth orbit from 118,000 kg to 155,000 kg.The conceptual Saturn C-5N was designed as an evolutionary successor to the Saturn V, intended for the planned crewed mission to Mars by 1980, it would have cut crewed transit times to Mars to about 4 months, instead of the 8–9 months of chemical rocket engines.