The first Venus investors

I have limited the Unobtainium required to install a self-sufficient Venus colony. It relies upon several components working together: including a mountain kingdom (i.e., a Bond Villain Lair) and a 50 km unsnappable chain. All that, requires investors. These investors currently live on Earth. I don't assume they be immoderately villainous, but they will like to get paid after a few Venus-Conjunction synods.

We need a first mission to Venus proper that might offer a short(ish)-term Return On Investment.

That would start with the Venus-crossing asteroids, starting with coörbitals. The prerequisite would be mining operations on Earth-crossers and coörbitals, and certainly an Earth-orbiting refining base - the L4 and L5 points fore and aft our own Moon look like winners (thanks Hop David).

First, we sic some miners onto one of those Venus-bound orbiting rocks. Wikipedia led me to 2013 ND15, which lists also as of 2014: 2001 CK32, 2002 VE68, 2012 XE133.

2001 CK32 (19) and 2002 VE68 (20.6) are the high-magnitude ones, which is how they were known as the only ones for a decade. They'd be the whales, that investors would start with. If 0.2 albedo is assumed the estimator calculates 470 m mean diameter for 2001 CK32, and 236 m for 2002 VE68 - that is, visible area 1475 m² and 740 m², as seen when it's tumbling. By contrast the Saturn V cylinder at 10 x 110 m had a visible area of 1100 m² if seen side-on, more like 32 m² if seen front-on.

Most useful for any electronics and even humans at an inner-system asteroid, would be the stone, to protect from the radiation involved in a Mercury-crossing orbit. So I suggest 2001 CK32 first. This mission will need to bring its own refinery, solar panels, and 3D printers; and some means to catch the sun's escaping ions. I expect it will be an Earth-region space base simply moved into this new orbit, to dock with the rock.

The stone, I think, will contain some oxygen; and especially in the "Sunshine" peak there is an opportunity to catch solar hydrogen and helium ions. Energy will be solar: Venus gets insolation 2620 Wm^-2. Oxygen and hydrogen, of course, make up water; also simple propellant. Also during this time, the rock is repurposed to shield the habitat and important electronics. Over the rest of the 583-4 day synodic, sufficient propellant should be collected for a return to Earth on Hohmann.

Those on schedule to go home: helium, other precious metals they won't need over Venus, and workers who've done with their shift and also want paid. A reusable craft should have been sent four weeks ago with their resupply and replacements; that first crew can return with a clear conscience, if they leave sufficient propellant behind them.

When the rarer-earths are fished out, for any given 'stroid, the now-shielded original craft moves into the orbit crossing Venus' ionic coma: oxygen, hydrogen, helium. I recommend L2 for protection. These components are assembled there into larger and more-efficient stations that can (re)capture those ions - which isn't done in L2, that's done over Venus proper. The rock is also sent over and reassembled, to be combined into an even bigger stone shield for humans who DON'T want to be bathing in ions. Smaller rocks like 2013 ND15 and 2012 XE133 and probably 2002 VE68 too might as well just get cracked into bits where they're at, and have their pieces pushed over to Venus by robot to be worked in orbit.

Voilà. A Venus orbital station. These four asteroids - and whatever else might traipse in on a Venus-crossing trajectory - should be able to supply a few decent-sized, shielded, and 8.66 g habitats over Venus for awhile. I'd set a permanent darkside icedepot in Venus' umbra.

Some can move on to supply more-stable L4 and L5 stations... and, in the meantime, to pay the Earthers. These stations, therefore, exist first as energy-cheap refineries for Venus-crossing asteroids (just like their models back home!), and for helium catchment.

Over a few synodic years, we will see the first Venus-based investors. They'll be the ones looking at the great chemical-factory that is Venus' low cloud-bank. That's where "ISRU" kicks in. And thence to Maxwell Montes and long-term farming communities.