They spawn on their own over time randomly assuming there are blueprints set to Enemy Usable in the Catalog. Also you can shoot pirate stations to make them spawn as well.
Not sure on the loot part but causing them to overheat does make them drop loot.
Also if you want to expand your selection of enemies to fight against just look up
ZimmTech on the forums. They had a competition recently to try and make some more up to date enemies.