[shirro]

Clipper is a massive payload for a planetary science mission as well. SLS was the only other operational US vehicle with the payload capacity.

[njarboe]

The Clipper was planned to be launched on the SLS, but due to delays in the SLS program and its massive cost ($2+ billion per launch), it was decided to use the Falcon Heavy to launch it even though the Falcon Heavy is a bit smaller and it will take 5 years instead of 3 to get to Jupiter.