Solar Trek: An Alternate Star Trek Setting

Bold proposal: Take the "stars" out of Star Trek. Make it a hard(ish) sci-fi alternate history setting taking place within our solar system. Yes, this would lose some of the mission statement of the voice over intro, but it would actually put it in line with Roddenberry's pitch noting similarities to Wagon Train and Horatio Hornblower (spoiler: neither series featured journeys to other worlds.). In modern high concept terms we could think of it as The Expanse meets Voyage to the Bottom of the Sea.

So, there would have been genetic supermen in the 90s, leading to advances in spaceflight technology unencumbered by democratic concerns. The supermen dictators would have sent out space probes, maybe even began colonies. (One of these expeditions would start the terraforming of Mars. Their colony of genetically modified individuals would centuries later provide the famous half-Martian first officer, Spock.) As the post-Eugenics War chaos ushered in World War III, some would flee the Earth to set up settlements elsewhere.

In the 23rd Century, some of these farflung colonies and societies are only now being re-contacted. Some have grown strange in isolation. Other have grown into military powers in their own right, like the bellicose totalitarian state lurking around Jupiter's moons, the Klingons, or the mysterious Romulans of the cold depths of beyond Uranus.

The solar system could be updated to modern science, or it might conform to the state of knowledge in the late 60s when Star Trek debuted. I suppose one could push in back even to the 50s science of Asimov's Lucky Starr series, if you just needed Venus with an ocean. Science fiction's knack in the era for coming up with creative ways life could be almost everywhere might prove instructive.