*** SPOILERS SPOILERS SPOILERS ***
I assume you're talking about teh mission right after you leave the Tau's. Tobias has left you and you, Juni, Sinclair and Quintaine cross a methane field. You end up taking on a fleet of ships which decloak right infront of you. Lots of Cruisers, gunboats, fighters and a battleship.
Tip 1: Let others worry about teh Battleship and the cruisers. You're probably not powerful enough to take them on. Worry about teh fighters and the gunboats and STAY AWAY FROM THE BATTLESHIP!!!
Tip 2: Get the biggest shield you can get your hands on.
any other tips depend on what ship you are flying and your loadout., basically, there's no chance you can take on that Battleship. If you absolutely want to, keep moving. use Strafe (A and D) to evade teh turrets and fire missiles at it. But the most important thing is to keep moving, use you thrusters and don't fly preditable, change your direction often.
Lastly, don't worry about Juni, Sinclair or Quintaine (especially Quintain), they will survive
Good luck and keep trying
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