The SLS option would have entailed a direct trajectory to Jupiter taking less than three years. ... The move to Falcon Heavy saved an estimated US$2 billion in launch costs alone. NASA was not sure an SLS would be available for the mission since the Artemis program would use SLS rockets extensively, and the SLS's use of solid rocket boosters (SRBs) generates more vibrations in the payload than a launcher that does not use SRBs.
