Rama

I only found out about Project Rho last night - where have you been all my life. Anyway: thanks to that, I bumped into Throne of Salt's blog. This in its turn has introduced me to the O'Neill Cylinder. That's a habitat "20 miles" long and "5 miles" in radius, rotating at "2.8 degrees" per second. Again, we're not prioritising internal physical space; O'Neill is offering low Coriolis.

The idea had been bumping along for some decades already when Gerard O'Neill proposed this (formally) in 1976. Arthur C Clarke's Rendezvous with Rama had already (1973) mooted a simpler version, which travelled between stars; Infocom would reuse that version for the 1982 game Starcross. I do believe that George O Smith had preceded Clarke back in the early 1940s, for his Venus Equilateral at Venus L4; Clarke was a superfan of Smith. But these earlier plans had a problem: orbiting around the Sun, you want them pointed at the Sun. Clarke himself may have worried about this, hence why "Rama" was interstellar.

O'Neill's innovation, as far as I know, was to make this one fit for the Solar System; which Smith's wasn't, yet. O'Neill had it spin both ways. This, he proposed for a "third island" - third generation, after two earlier generations of smaller habs.

Under the five mile / 2.8 degree specifications SpinCalc is telling me that Venereans and Earthlings should be residing in the 8.67-9.8 g tier, 3.6-4.1 km from the axis, not 8 km. I take it that, outside that tier, we're sowing many meters of loam and, below that, hull and shielding.

Venus would dispense with the 9.8 tier entirely and just set the floor at 8.67 g, 3.6 km from the axis. Earthling visitors can take the lift down to the basements. Someone hoping for Proxima Centauri planet's dark side will likely want higher g and a lower basement.

NOTE 1/6: I am not, yet, assuming that we build this sucker from scratch (or, from metallic scrap). For our hard-SF purposes a honeycombed spinning mining-asteroid (a "Reagan", for Jovian Republic afficionados) will work fine. Especially if where we've built it and where we're sending it aren't the same.

Also, Rho referred to an "L5 colony". They're talking Earth's L5 or maybe the Moon's L5 relative to Earth. I think this derives from where the Stanford group proposed to park its (earlier-"island") Torus.

WHERE TO PUT IT 12/22: Mostly inner planets, but safe from Earth. The spinning asteroid is better shielded but will be absolutely forbidden Earth.