Sorry to be late, an0n.
It takes more fuel to decellerate than accellerate? What?!
The Newtonian physics model is really really simple. You only use fuel to change speed or direction. If you're moving 80m/s, you'll keep moving at that speed if you cut the engines. The only way you'll stop is by firing the engines on the exact opposite course for the exact same amount of time as it took to get up to speed.
Freespace, as you'll notice, doesn't do this. It has an inertial drop off (you coast to a stop when you cut engines) and no instant inertial damping (changine directions is instantaneous). Call it 'arcade physics'.
I prefer Independence War's psuedo newtonian model because it makes the game less twitch oriented and it allows you to pull off some really nifty stunts. On the other hand, it doesn't let you pull off a Return of the Jedi Death Star Mk2 reactor run quite as easily (You're likely to carom off the walls). Mostly, however, I like the IW model because you can turn it on or off at will.
