The Seven

From ' The Jack Vance Treasury' ..... Sail 25 , with the marvelous character Henry Belt, an experienced spacer who is the captain of a small training craft called Sail 25. The propulsion for this craft comes from light pressure (also called radiation pressure) from the sun upon this sail made of extremely lightweight material. The story is about a training cruise, in which six cadets are taken on a simple little training cruise to Mars.