I read this paperback in the late 70's or early 80's. I believe the spaceport was found on Mars (?). The spaceship seats were very uncomfortable to humans and they did not know exactly how to operate the ships. People knew enough to fire them up and send them off to pre-programmed destinations. Some journeys were splendors, others never returned and were presumed lost. It was the first sci-fi books i read and I'd like to read it again. Thanks!