If you click on the nuke silo, it will tell you that nuke scientists build pieces of the rocket there with 100 steel and 2 nucleum. After 5 pieces the nuke gets built and you can launch it, sorry for the pain, we actually forgot to add a lot of information to some buildings like the robots charging and the nucleum recipe to the nucleum plant so it was a bit of a "find it out urself".
Thanks for playing our game for so long, but sorry for the frustration