The brown rocks are asteroids, which naturally destroy your ship on impact - somewhat like what you can do if you purchase the upgrade to remove your anti-collision programming, and use your ship to ram others. If you can outrun the asteroids, you shouldn't have a problem - they have about 2 shields, or armor, not sure which, so you can destroy them with the weakest weapon in the game (laser cannon?). If you play at 300%, I understand that you either have a slow system or are an excellent pilot, so you shouldn't have trouble with these, but the easiest way is to run away for a bit, so they're following you in a more or less straight line, and not coming in from every direction, then open fire. Martin Turner gave them very large 'crews' so that destroying them will boost your combat rating very quickly, rather than steeping your hands in blood destroying many ships with people on board in the traditional manner. At least that's what I understand. Once you've destroyed the main group of asteroids in the system, you should have time to board the ship, just watch out for stray asteroids that will appear from time to time. Hope that helps!
One question - you did play The Frozen Heart first?
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