Uranium, use the retrofit function. It should only take one turn rather than taking three for you to build all new ones. In fact, you can retrofit and continue building something at your space yard, so no problem you're only behind one turn.
<edit>Holy fuck you eager beavers, I process the turn last night and I wake up this morning and you've all uploaded your turns!

. I knew it, it's addictive isn't it.
I've e-mailed the PBW Admin in charge of mods, hopefully we get this automatic execution thing working again.</edit>
<edit>New, Necrodome Class Destroyer, featuring advanced warp technology, shield generators, and phase cannons! All the standards including a dedicated engineering staff, damage control, and orion slave girls! Bonus : advanced point-defense disruptors for whacking those annoying flies!
</edit>
Brian