Not targeting to stable S2_6 as there's a risk this causes AI not to defend well enough while running spacerace. Those hard-coded flag want values of military advisor rally ought to go...
Out of dozens of cities, one or two occasionally builds some space part.
At least in the game I'm looking at, the leading nation (only one building spaceship) seems to do so only in one city, that is also filled with Wonders built earlier. So I assume it's AI's wonder city. It's probably building space parts only because AI does not like to build non-essential things in wonder city (it wants to reserve it for wonder building), so space parts do not need to compete with those. That information sets general space want value to a new light. It probably would need increasing too - but I'm leaving that to another ticket.
In testing: Patch here does not help with making more cities to build space parts - assuming the want is still far too low for that. In fact, in my reference game it causes space race to finish *later*. Probably the increased want makes AI to research further space techs (instead of something more beneficial in the current situation)
In civ2civ3, cities need Factory, Library, University and Research Lab in the city in order to build space parts. The reason was to discourage players from selling all science related buildings while building the spaceship (since tech tree is almost finished at that point). I was also hoping to encourage AI to build more of those buildings in their cities.
Now that tech upkeep is enabled, I think this is no longer needed, and it'd be possible to reduce the requirements to just Factory as classic rules, if it helps the AI to build more space parts.
Or even remove the Factory requirement, because I have noticed in my games that AIs do not use to build Factories, nor other production related buildings. I guess because production bonus was halved in civ2civ3, and AI is calibrated for classic values.
https://www.hostedredmine.com/issues/773268 has a savegame attached, that might be handy in checking AI spacerace behavior.
Rebased patch.
The "one city" AI usually builds space parts was the wonder city, which avoids building some other targets. That has been addressed separately already.
We've increased AIs general wants for spacerace victory several times over last couple of years. Now it usually does do run for spacerace, but it still does so in a really half-heartedly. Out of dozens of cities, one or two occasionally builds some space part. Maybe we should not increase general want at the moment (so not to increase want to start spacerace), but to increase want to proceed in spacerace when already running.