Doing the exploration missions I sometimes enter systems that are called "Aid the Planet". I talk to the planet and they need, for instance, 10 shield generators. How do I complete these missions and where do I find these shield generators?
There's a vendor at Sol Space Dock (in the requisitions area) that sells those things. Buy them there, take them back to the planet. (I'd buy a surplus, so you have more for next time, if you have the EC to do so.)
Actually, the "Aid the Planet" missions never ask for anything you can't replicate directly from your ship. Just hit the "Replicator" button at the bottom of your inventory, replicate the amount requested and re-hail the planet to deliver the supplies.