toy model:<p>I, the spaceship, would like to accelerate through space. I take up some fuel and hurl it in the opposite direction, which requires me to apply force to the fuel I&#x27;m ejecting. It goes off into space at some rate determined by the impulse I applied and the mass of fuel I applied it to.<p>Newton&#x27;s third law means that when I hurl the fuel, it applies a symmetrical impulse to me, accelerating me in the opposite direction.<p>In this model, the acceleration I get from the fuel doesn&#x27;t depend in any way on the mass of the fuel I eject, only on the force I apply to it. What&#x27;s wrong with the model?