“Minimum energy trajectory: “
Everything is ‘green’ these days. What a joke.
“Minimum energy” means “maximum payload”.
No launching payloads into space is extraordinarily expensive. Virtually all missions are on nearly minimum energy trajectories. New Horizons was an exception because it would have taken so long that the crew that launched it would have been retired by the time it arrived, and the power for its instruments mostly gone.
Voyager took advantage of an exceptional (like once in 175 years) alignment of the outer planets to execute a series of gravity assists. New Horizons also got a big gravity assist from Jupiter.