“reduce the time to reach Pluto from 9.5 years to just 4”
Has anybody considered what effect that would have on people?
Locked inside a sterile environment for 4 years, each way may not go over too well with even the most laid back personalities.
No one needs to “go to Pluto” direct from Earth. Do Mars first, see how that goes.
Intermediate steps - mine the asteroids, perhaps some sort of habitat on a Jupiter moon. Farther than that, there’d need to be a realistic reason with a commercial payback.
Actually, do the Moon (again) first lol