Studied by Marshall Space Flight Center in 1968, the Saturn V-Centaur booster would have been used for deep space missions if it had flown. It consisted of an ordinary

Saturn V Saturn V is a retired American super heavy-lift launch vehicle developed by NASA under the Apollo program for human exploration of the Moon. The rocket was human-rated, with three stages, and powered with liquid fuel. It was flown from 196 ...

launch vehicle, except that the

Apollo spacecraft The Apollo spacecraft was composed of three parts designed to accomplish the American Apollo program's goal of landing astronauts on the Moon by the end of the 1960s and returning them safely to Earth. The expendable (single-use) spacecraft ...

would be replaced with a Centaur (known as the S-V in the plans) as a high-energy liquid-fueled fourth stage. This combination never flew.

References

Saturn (rocket family) {{rocket-stub