Space afterburners =/= aircraft afterburners.
Assuming that FS2 ships use some type of plasma exhaust (which given that fusion reactors are alluded to, it is more than likely that this is the case), then all you really need for afterburners is to shoot MORE PLASMA through the engine, or perhaps heat the plasma hotter to eject it faster - both of which can be done from a dedicated reserve of charged plasma or a giant capacitor bank. That explains the little afterburner bar. When the plasma accumulators/capacitors are empty, you just need to recharge them. The on-board reactor takes care of that.
Chemical-burning rocket afterburners wouldn't function like this in the slightest.
If there are engines on the front/sides/top/bottom of the ships to maneuver and steer, then there is no real reason that lateral or reverse 'afterburners' are impractical. Calling it 'afterburner' is a little bit of a nomenclature error methinks, if they really are plasma thrusters - a more proper term would be 'overload' or 'overcharge'. It is very obvious that afterburners make things go faster, which is most likely why volition called it afterburner. It's instantly familiar to everyone.
My Singularity mod features lateral thrust and reverse thrust at half normal forward speed - because those thrusters are smaller. Forward is the obvious direction for afterburners. Backwards isn't much of a stretch. Full slide afterburners would require some pretty awesome maneuvering jets though. Although this part is really just personal preference for some semblance of realism along with the rule of cool.
