While the main problems of a functioning starship are commonly known such as energy requirements and radiation I have realized another problem when near the speed of light. The dynamic Casimir effect occurs when a reflecting object reaches relativistic velocities. Therefore a starship with a reflective bow will produce photons when the velocity approaches c. So a drag will occour as the ship speeds up. This drag could be used to slow the ship down but just like an airplane it must be overcome with force from the engine. I don't know if this is the correct section to post in or even if my idea is right (I haven't done the math yet) but I just wanted you all to know of this possible problem.