Here's a simple guide on how to farm for Ration Seals and other resources on chapter 9 (Optional Mission: Supply Depot).
If this helps you out then please rate, comment and subscribe and I'll keep you updated for more tips and tricks in the future.
~Pete
Weapon Crafting guide for the Plasma Cutter I used in this vid.
http://www.youtube.com/watch?v=70hHmWjr_wo
