[zackmorris]

If anyone wants breadcrumbs, I just did a deep dive and there are a couple of promising technologies that could terraform Venus on roughly a human timescale of 100 years:

* Sun shade/sail near L1 tipped up to 35 degrees to remain still: 5 micron polymer film (1.5-3.5 billion tons or 10-25 million SpaceX Starship launches at 150 tons each) or 50 layer graphene (15 thousand tons or 100 launches). Liquid CO2 ocean forms at 31 C or 88 F, or dry ice glaciers at -78 C or -108 F result in nitrogen atmosphere dropped from 92 times pressure to close to Earth's pressure. Shade rotation can simulate a 24 hour day.

* Comets to increase water and spin rate: 50-100 100 km diameter comets from Kuiper Belt at 30 AU, nuclear rocket using 1% of water to gravitationally slingshot comets by planets over 20-100 years to impact at equator, resulting in 50 day retrograde or 64 day prograde rotation (down from 243 days). Decreases temperature and sulphuric acid enough for microbes to start fixing CO2 and acid.

The "hard" parts are getting bots into orbit to blow graphene bubbles to form a honeycomb, and inventing open-ended fusion rockets to avoid containment issues.

5 cm by 50 cm graphene sheet grown in 20 minutes:

https://www.nature.com/articles/srep21152.pdf (warning PDF)

Direct fusion drive:

https://www.sciencedirect.com/science/article/pii/S009457652... (PDF available)

Magnetic mirror concept for open-ended fusion rocket:

https://en.wikipedia.org/wiki/Magnetic_mirror

Magnetic reconnection thruster:

https://www.youtube.com/watch?v=caM94mem5K4

I think the sun shade is probably how we'll slow global climate change until we can plant the 1-10 trillion trees it will take to reverse it (mechanical carbon capture can't be scaled enough practically), but I digress.

Note that the blocker is actually getting to low Earth orbit (LEO) since delta V is straightforward with ion engines. That will arguably be a solved problem once big "dumb" rockets like Starship scale. I'm a big fan of JP Aerospace's airship to orbit concept and other magnetohydrodynamic (MHD) craft, but it's unclear if they will be able to achieve heavy lift. Aerospike engines and exotic rockets are being evolved by AI currently.

[WalterBright]

Mechanical carbon capture is a joke. There's no way it can scale enough to be measurable. It also requires energy - coming from where?

Trees, on the other hand, can scale, and they get their energy from the sun.

[a_t48]

Wind! Venus is full of it. (Making it so that your wind power can survive corrosion and the high speeds is an exercise left to the reader)

[WalterBright]

In order for a windmill to work, it has to be anchored. There's no wind if you're floating in it.

[a_t48]

Spitballing here, you might be able to use some sort of floating wind turbine, and trail it out on a long enough cable to catch a different windstream. There's all sorts of reasons why it's a pretty terrible idea.

[nine_k]

Forgotten: genetically modified algae-like organisms that would float at the habitable-ish altitude due to having a gas bubble. These organisms should consume sunlight and transform gaseous substances into something more solid/liquid to rain it down onto the surface, thus making the atmosphere less thick and more transparent. Bonus points for binding and removing chlorine and leaving oxygen intact.