Following a recent discussion about Full Thrust being boring and predictable to play (something I don't agree with, incidentally) it seemed like a good idea to re-post an old house rule I've used on and off for years now. This is the latest iteration of it with some refinements from game play, and it's intended to be a "chaos enhancer" in games by adding another variable to play and breaking up formation maneuvering. Like all house rules you should get your opponent's approval before playing with it.
Knocked Off Course:
Severe damage will sometimes result in sudden unexpected changes in a ship's course. This may be the result of sheer kinetic impact, damaged drives flaring and sputtering wildly, an unbalanced spaceframe as parts of the hull are blown off, or the ever popular "dying helmsman falls on his controls" trope.
Whenever a ship takes a threshold check, roll one extra die to see if the vessel's course is affected by the damage. This check uses the same target number as the threshold checks (6 for the first check, 5-6 for the second, etc.) and therefore is more likely to occur as damage mounts. Modifiers are applied as normal, so for example a ship that goes completely past the first two threshold points in one volley would test on 4-6 (5-6 for the second thresh point +1 for the "skipped" first one). If the ship is affected it is said to be "Knocked Off Course" and the following procedure is used depending on whether you're using Cinematic or Vector movement rules.
Cinematic: The ship's course changes. Roll 1d6 and consult the following chart.
1: Change the ship's heading two points (60 degrees) to starboard.
2-3: Change the ship's heading one point (30 degrees) to starboard.
4-5: Change the ship's heading one point to port.
6: Change the ship's heading two points to port.
Vector: The ship's course changes AND the vessel tumbles wildly. First roll 1d6 and consult the following chart.
1-3: Move the ship's course arrow one point (30 degrees) to starboard.
4-6: Move the ship's course arrow one point to port.
After adjusting the course arrow, roll 1d12 and change the ship's facing to that direction on the clock face (with 12 o'clock being the current facing).
If you don't have a d12 (seriously? are you sure you're a gamer?) roll a 1d6 followed by a second 1d6. If the second roll is 1-3 add nothing to the first roll. If the second roll is 4-6 add 6 to the first roll. Treat the result as the d12 roll above.
Did I really need to tell anyone how to do that?
Any changes to heading and/or facing occur immediately, which may affect firing arcs if the ship hasn't fired yet this turn. A particularly unlucky ship might take several volleys causing threshold checks during a turn and possibly be knocked off course multiple times, with each incidence resolving independently.