Hi, I have a question that has been bugging me for ages now. It concerns acceleration up to the speed of light. I know that if an attempt is made to accelerate a spaceship/particle up to the speed of light from the outside, it is not possible to get it to the speed of light because the energy requirement to accelerate the spaceship/particle gets exponentially larger as the speed of light is approached, and tends to infinity at the speed of light. However, what if you are propelling the spaceship/particle from the inside instead? For example, what if you are inside a spaceship that has its own propulsion system, and is accelerating towards the speed of light? You would experience that the spaceship remains at its rest mass energy, as you are in the inertial frame of the spaceship at all times. Therefore there should be no exponential increase of energy required to accelerate the spaceship as it approaches the speed of light, right? Or am I missing something here? I figure I must be missing something because otherwise it appears to me that a craft can accelerate up to the speed of light under its own propulsion, which surely is impossible?