[ft] ship turning

my last word on ship turn rates.

i have now got the maths straight, and it turns out that the angular
acceleration of a ship (ie, the rate of turn) is:

- inversely proportional to the ship's length
- inversely proportional to the ship's mass
- proportional to the force generated by the drive

since the last two will cancel out for ships with the same fraction of their
mass in drives, we are left with the first. therefore, small ships turn
faster, the exact opposite of my previous conclusion. oh well. sorry for any
inconvenience. mail me if you want to see the maths.

Tom