To take down larger ships, land on them and use grenades or pulsars. Drop ships can't reach you while you are positioned on top, standing between the automatic turrets. This strategy doesn't work against Fenrir, which has turrets that can fire on all sides, but otherwise it's a great technique that has the added benefit of allowing you to replenish your energy while you inflict damage. Just make sure that you fly away the second the ship is finally destroyed.