Citadel of the Green Death

Joel lay back on his bunk, staring into the glowing square. Walls, floor and ceiling receded from consciousness. He was free of the prison as if like Alice he had stepped through a mirror into a world beyond.

"Sa Nels, a Martian of Terran descent, discovered the stellar drive in 4471," the narrator was saying. "The Republic organized an expedition to the trinary system of Proxima Centauri, Alpha Centauri A and B, our nearest neighbors; and Sa Nels was put in charge."