Orbital Shipyards is an structure that allows you to build vessels that are too large to be built on the planetary surface. This means they must be built in low orbit to ensure that shipyard doesn't float away.
For each level of Orbital Shipyards you build your Production will raise by 8. This is not based on an Astros stat so it will give the same for each of your bases. The amount of Orbital Shipyards you have can also affect which ships you are able to build, not just how fast. Your Economy will also raise by 2 credit an hour per level. They are required for all ships from Dreadnoughts onwards.
Dreadnoughts require at least level 1 orbital shipyards. Titans require level 3, Leviathans a level 5, and Death Stars need level 7. Energy consumption per level is 12, but they do increase the Economy by 2 per level.
Cybernetics 2 is required for the construction of orbital shipyards.