123 Years

Poul Anderson, "The Troublemakers" IN Anderson, The Complete Psychotechnic League, Volume 2 (Riverdale, NY, February 2018), pp. 91-138.

"Centenarians were not uncommon these days. But very few reached 150. Nobody reached 200."

-"What Shall It Profit?," p. 79.

At the beginning of "The Troublemakers," Enrico Yamatsu states in his Starward! that:

the Pioneer, launched in 2126, will take 123 years to reach Alpha Centauri;

that this means five or six generations;

that it is longer than a long lifetime.

I would call it six generations, taking one generation as about twenty years, enough time for someone to be born and to become a young adult. If some people, however few, are reaching 150, then 123 years is shorter than a long lifetime. A baby, taken into the Pioneer before its launch could reach Alpha Centauri. Just. But there would still be six generations born in the ship. If such a ship were ever to be launched, then far better arrangements would have to be made for the lives, activities and sanities of its crew. Many would have to be scientists, their attention directed outwards, studying the universe as the ship passed through it. There would have to be libraries, audiovisual entertainment and virtual realities (if possible). The way the ship is organized and socially divided seems crazy to me.