So let's talk some other strategy stuff - just theoretically speaking, for now; I'll show my actual game later. In a space win, if you want to win as fast as possible, the goal is to get to communism and state property as fast as possible while conquering your way up to about 30-40 cities and 60-63% land area at the same time. I've covered the conquest, and I've easily gotten to communism pretty quick this game, so now let's get on to my civics, teching, and tile improvement choices lategame.
In terms of civics, I immediately switched to state property and free religion after the Taj golden age coincided with unlocking SP. However, I'm waiting to switch to rep and caste system until the next golden age. I only got constitution from Sitting Bull after the GA ended, and I need to whip a few more things regardless...no sense in spending 2-3 turns in anarchy; that's a huge loss at this point in the game. Representation is FAR better than universal suffrage because you won't have many towns, but you are guaranteed to have many many specialists by the end of the game.
The reason SP is so vital and I ignore stuff like universal suffrage or emancipation, is because the way to win space fast on standard speed/size pangaea maps, is the
hammer economy. You adopt SP and SPAM workshops/watermills/windmills everywhere. With caste, SP grassland workshops give 2f4h, which is basically a
plains hill mine that feeds itself. Meanwhile, fin watermill yields can get as ridiculous as 3f4h5c with a levee and golden age (yes, a TWELVE yield tile without even any resource on it...all you need is a river). Then you build factories and power them, to turn those 4 hammers into 8.5 from the production bonuses, before converting hammers into whatever resource you need (units, buildings, wealth, and of course research). This
vastly outshines towns because, even with emancipation, it takes a ridiculous 50 turns to grow a cottage into a town, and all the while you will have to build all the science AND money buildings to make that commerce as flexible of a resource as a yield from just workshops. By covering the land with them and then giving a factory to every city, I can quickly increase your beakers/turn by thousands in just a handful of turns, especially as my new conquests come online.
Now for techs - usually, you want to go AL or electricity, and only after getting both do you go railroad. Afterwards, it's straight for plastics for the Three Gorges Dam, superconductors for labs, fusion for a free Great Engineer to start your last golden age, rocketry for Apollo, and composites to genetics to ecology, to round out your last few spaceship techs, finishing your teching and wrapping up your building as the last golden age ends. You want 4 golden ages ideally - 1 from Taj, 3 from 6 assorted great people. In this game, I was lucky to get quite a few techs from other AIs, despite eventually leaving them all in the dust. Starting with Renaissance techs, I got: nationalism from Mansa; constitution, democracy, and biology from Sitting Bull; and astronomy and rifling from Augustus after capping him. In this case I went AL before electricity because I wanted to milk the ridiculous fin + Colossus combo for as long as I could. I traded for democracy just to build Statue of Liberty, which when combined with rep + caste gave me an extra 250 beakers/turn immediately from 30 cities on the continent...not bad!
A word on improvements: as much as it hurts to do, besides your buro/Oxford capital or some other highly cottaged cities you care about, you must ruthlessly bulldoze even villages and towns to make way for workshops. With the factory and power bonuses, as well as forge + SP - like I said, workshops actually outperform towns by a sizeable margin. And remember - you can't build spaceship parts with commerce, no matter how much of it you have, which is what the final dozen or so turns of the game comes down to.
On a more miscellaneous note, you may be asking - why TGD? Well, simply put, it's more efficient in a variety of ways. Coal plants cost an extra +2 unhealth for power, which means that they essentially limit your city size to 1 less than they could be. A missing grassland workshop being worked in every city is a pretty big loss that adds up quickly. Second, hammer-wise, coal plants for about 30 cities costs 4500 hammers, while TGD costs just 1750 hammers. But - and I've been thinking about this after being asked by several other forum members, about why that wonder just seems so dam good (ha) - the actual cost is far less. See, when you're building TGD, you ideally want to either build it in your buro capital or Ironworks city, and in a place that already has coal power. That means that the "hammers" you spend towards that wonder are +100% or even +150% more effective than the hammers you spend building power in each city individually. If you're industrious, like I am this game, that bonus further increases to +150% or up to +200%! What this means is - and I think the math works about this way - when building TGD in Cuzco like I do this game, every hammer is worth +210% (forge + factory + state property + buro + coal power + ind) instead of +60% (forge + factory + state property). With these bonuses in mind, 30 coal plants would cost 4500 / 1.6 = 2812.5 base hammers, but TGD is just 1750 / 3.1 = 564.5 base hammers. That means that TGD is
FIVE times as hammer-efficient as coal plants, and saves you 2248 base hammers, which when multiplied back with 1.6 would give you a net savings of 3600 hammers - more than a late-game great scientist bulb, and nearly equal to 1 entire turn of research if hammers = beakers.
Oh, right - by the end, we'll be making well over 3600 beakers/turn. Screenshots and the finale, putting all this into practice, coming up

.