When a gunboat has intercepted a slave convoy of yours and has done damage to the two smaller transports, it is against the rules for the much larger transport accompanying them to use its cruise engines to put itself between the small transport and gunboat. Especially in an asteroid field. If you can't keep up with thrusters and keep getting bumped backwards by rocks, it's not allowed to use cruise, mmkay? I said this to the transport doing it, but he continued to use cruise in combat anyway.
Edited to add - I'd PM this, except it looks like only 2 of you have forum accounts.