Did a spacecraft ever use an atmosphere to accelerate away from a planet? If a spacecraft enters flat enough into the Earth's, or another planet's, atmosphere it will bounce off the Earth at a higher speed. That method can be used if a spacecraft has not enough fuel to reach orbital or escape velocity by itself. Has any, man-dor-unman, spacecraft ever used that technique? If so, which one on what planet or moon? Perhaps I should tell that of course you need to have the engines on. If you enter an atmosphere by gliding it will bounce you off but you won't reach a higher speed, don't you? Your premise is incorrect. In no case does, skipping off the atmosphere, leave you going faster than you arrived, engines on or not.