As question states, I start and then stop a spaceship in vacuum by using orientable thrusters. In the acceleration phase, I am doing positive work, but in the deceleration phase I am doing negative work. These two should cancel out and I would do zero net work.
Seems kind of strange that I do zero net work although it make sense because the spaceship's kinetic energy didn't change overall. The space ship used up a bunch of chemical potential energy which is now transferred to the "thruster dust" floating about in space.
Does this make sense?