Buy the Contact Gun as soon as possible. Ammo for it will start appearing around the ship. Sell all of the unneeded ammunition for it for 1,000 credits per unit.
Sell your Plasma Cutter at the store. It will fetch plenty of credits, but a new one is completely free. This is helpful for the max up challenge, because you can now buy about another seven nodes.
In Chapter 2, when you enter the Zero G Therapy area, there is a hole on the right side of the room along with debris blocking the hallway to other side and where you can see the planet. Once you go through the room on the left and get to the other side, back up to the debris. You can see something flashing outside in the direction of the planet--it is10,000 credits.