Hi Tiberiu,
Full disclosure, I played the last 30 turns twice. I don't usually go for science victory (I almost always play domination), so I needed to figure out the optimal strategy to bulbing my scientists, and getting to satellites for hubble, which I thought would be the key to winning this game. I settled my cities maximizing the resources available and terrace farms, not thinking about observatories. I wasn't at that point fully aware of this map structure.
Early game gold and happiness were a major challenge at the start. At one point I had to farm barbarian encampments for gold to keep from taking deficit gold science penalty (I wasnt perfect at this so a few turns I lost science). I only met Songhai, Greece, America, Germany and Brazil. I settled the fifth (southermost) town with a goal to defend against an eventual Songhai attack, and this proved to be critical eventually.
Mid game once I realized that the only victory condition possible was science, the challenge was that Germany and America both went rationalism, but that fact that both of them did I think helped me actually be able to win. Once the nukes started flying between them all their border towns were glowing for the rest of the game.
I was first to modern era but already behind by many techs vs America and Germany. I was also third in selecting ideology, America went Order, Germany Autocracy, so I selected Freedom. This was risky but their tourism output was fairly low. I was able to build Eiffel tower for the tourism. Tiwanaku in that location is a production monster. I was able to get Statue of Freedom as well. Freedom tier 3, buying spaceship parts was also a key. I was able to scrape enough gold from my friend Brazil to buy the final part.
America and I were friendly until the ideology selections. He settled those towns near me pretty late. Once he was belligerent towards me I bribed Germany to attack America, and America to attack Greece and Germany once they peaced out. I also donated to America a copy of a luxury to get the "You've traded recently" modifier. I watched the border closely to see if he is amassing units, but he never did. It may have helped at the end when I liberated Wittenberg repeatedly from the Songhai, but I am not sure if that gives you a diplomatic boost or not (I doesn't show as a modifier).
For an army I had 1 warrior,1 spearman, 5 or 6 archers/machine guns, I may have sold at the end or lost one or two to the Songhai attack on Wittenberg. He was really annoying with the paratrooper drops behind my lines. I also didn't want to spend resources on building planes, so he had air superiority. But this was just a nuisance, as the actual game came down to this:
The situation at turn 252 (see tech picture)
I had 5 scientists on standby, enough faith to buy 1 most scientist, 3 more scientists will generate before end of the game, I can get 2 more from hubble.
I also have rationalism finisher coming due in 6 turns.
My techs (55), American has 67, Germany 66. I know someone has Advanced Ballistics already from the research costs.
I played this end part twice.
First time I bulbed now to get to hubble as quickly as possible, worried about one of them getting there before me. I think I lose that on turn 290 to American space victory (I only played it to turn 287 but I could spy him building the final part in the capital). I was nowhere close to finishing as I was out of scientists and needed to hard research the final tech.
Second time I really min-maxed my science output in each town. Also delayed starting the bulbing until after I finished electronics but before rationalism finisher (which I use on satellites).
There is a lot of moving part here, so there is probably a more optimal way to play these last turns to get there before 295.
The last 3 turns are bulb final tech, buy part, launch. I don't know the exact rules around bulbing the getting the tech immediately vs having to wait a turn even though you have enough science.
Ultimately I am not really sure what changed on the second play through that made Washington not launch on 290. I could see his second last spaceship part sitting in a city 6 tiles to the east of my capital and not moving. His capital is much further to the north. It may be that the path to the north is blocked by German nukes or paratroopers? Or maybe just luck. As I launch they are both still ahead of me in techs.
