You go jumping down towards Blackwater City with rockets in a gigantic barrage at you. Be sure to especially avoid the red ones. The robots are very happy to see you - an attack starts immediately. Soon reinforcements come. You get 15,000 bolts for holding off the attack.

Part 2 - the bridge. You have to take out the ships as they come through the force field. 20,000

Part 3 - counterattack. Somebody has to get behind the Noids, i.e. you. Next they want the turrets to get knocked out of commission. When you take them both out, the enemies come up to join you. Now enemy saucers come down. 25,000.

You get gravity boots!

Ratchet and Clank 3 - Up Your Arsenal Walkthrough