Marion Zimmer Bradley 
The Colors of Space 

It was a week before the Lhari ship went into warp-drive, and all that time young Bart Steele had stayed in his cabin. He was so bored with his own company that the Mentorian medic was a welcome sight when he came to prepare him for cold-sleep. The Mentorian paused, needle in hand. ’Do you wish to be wakened for the time we shall spend in each of the three star systems, sir? You can, of course, be given enough drug to keep you in cold-sleep until we reach your destination.’ Bart felt tempted — he wanted very much to see the other star systems. But he couldn’t risk meeting other passengers.