I disagree, I think it means if you have grade 3 upgrades, you can complete the mission (with a bit of skill) without a problem. The biggest help for me was not using the mouse to steer, use wasd to move and the mouse to aim. While you're shooting at stuff just use the keys to fly in a constant circle around the screen. This will save you a lot more health than any grade 5 shield would, seriously... Its impossible to do the last few space missions even with grade 5 stuff if you aren't good at dodging the lasers coming at you. Your shields are there just in case you don't dodge them all, but are not meant to take ALL the incoming damage.