Which Ray Bradbury story has a space ship from Earth which will have to spend decades in space to reach the nearest star system? But early in the voyage it encounters a faster-than-light alien ship early and the captain turns the ship around and heads back to Earth. He figures that since it was now clear the technology existed it made no sense to spend decades in suspended animation. After all, even if it took humanity 20 years to figure out the techonology, humans would still get there faster than chugging along with conventional rockets. Is it “R is for Rocket”?