Hey i played the campaign, as far as it is right now. I found really many weapons, but no useful big thrusters ( not in shop not in planets ).
At the end of the campaign i got lucky and could buy some jump thrusters.
The game should balance the randomness of finding stuff a bit. Like no big thruster in galaxy #3 jet => increased chance of finding those...
Btw. the campaign is awesome. I guess i play a couple more hours just go get my ship growing a bit more ...