[actionfromafar]

To be fair, in Star Trek only thrusters etc seem to generate force vectors, and the thrusters seem able to accelerate the ship in any direction. Only the warp drive seems to fling the ship just "forward". But yeah, it's wizard retcon turtles all the way down...

[dragonwriter]

Thrusters and impulse engines seem to generate force vectors, and warp drive usually doesn't but the continuity is not very strong on that point and it is sometimes implied, and at one point in Voyager fairly explicitly stated to create accelerations (in Voyager, this was in reference to requiring the inertial dampeners to be functioning to go to warp without plastering the crew into a thin paste on the wall.)