Newton's first law of motion states that "In an inertial reference frame, an object at rest will remain at rest and an object in motion will remain in constant motion unless a net force is applied." Space is an inertial reference frame, so when a space craft such as the X-Wing flies through space it only needs enough force on it to reach a desired speed and then take that force away.




As you see in most of the movies when the space craft flies through space it seem like their engines are always on. Applying Newton's first law, a body or in this case the X-Wing will keep on moving with constant velocity if no force acts on it. By having the engines constantly running and applying a force, the X-Wing will keep on accelerating. So there is no reason why they would always have it on, or propelling it through space.



Also, the X-Wing flies through space just like a jet fighter would fly in the sky. The Next page will address this issue of why this cannot happen, and if it could what would it take to mimic the actions of a jet fighter.