It’s a decent explanation for a phenomena that is not intuitively obvious just by looking at a diagram of the solar system. I wonder just how much fuel is needed to go directly without gravitational slingshots.
For high-efficiency chemical propulsion (e.g. hydrogen - which, note, non-storable!) that's about 3.5-4x the exhaust velocity, meaning around 98-99% of your spacecraft's mass needs to be fuel.
For electric propulsion (which has issues because of low thrust and electrical power requirements), it's only about 0.5-1x the exhaust velocity, so only maybe 50-70% of spacecraft mass needs to be fuel.
Yeah, people tend to pretty easily understand how the rocket equation is exponential in the required ∆V, but the way it's inversely exponential in exhaust velocity is less well understood.
Good specific impulse plus good thrust is a combo that requires nuclear-explosion-scale energy, ie Project Orion or Nuclear Salt Water Rockets (an option that is, shockingly, even more insane than Orion).
