Uniform circular motion requires a force perpendicular to the velocity. Therefore, the work done by such a force is zero because the dot product of the force and the path is zero. So there is no energy gain beyond the kinetic energy arising from its constant speed. But if I have a mass (rocket ship) traveling in a straight line in space with a constant speed, the only way I can get it to move in a uniform circle would be to have some sort of thruster acting perpendicular to the direction of movement. I am imagining a spaceship and thrusters being continually applied perpendicular to direction of motion. Energy would be depleted as the rocket fuel is used. If I stop using energy, by turning off the motor the ship stops its uniform circular motion and continues in a straight line. It seems energy must be continually expended to maintain uniform circular motion. However, this seems to contradict the accepted answer that no work is done on an object by the force that causes the uniform circular motion. What am I missing?