[geoschmo]

The only way that will work is if your sacrificial ship manages to damage one of the enemies engines, or if they expend enough supply in combat to run out before they get to where they are going. A fleet moving at a speed of 6 can move 6 sectors during one simultaneous turn and engage in combat in all six sectors.

There is one other way, but it's not something you have control over so it won't help you in this situation. If the enemy has orders to seek after your ship, or a planet, and the target they are seeking after can manage to survive an entire 30 combat rounds, they will use another movement point in a second (or third, etc) round of combat trying to kill the target.