A fix-up of five stories published 1961 to 1969
The Brain & Brawn Ship series is set in the future of our universe and in McCaffrey’s Federated Sentient Planets. The parents of babies with severe physical disabilities but fully developed and exceptionally talented brains may allow them to become “shell people” rather than to be euthanised. Taking that option, physical growth is stunted, the body is encapsulated in a titanium life-support shell with capacity for computer connections, and the person is raised for “one of a number of curious professions. As such, their offspring would suffer no pain, live a comfortable existence in a metal shell for several centuries, performing unusual service for Central Worlds.”
After medication and surgery, general education, and special training, shell children come of age with heavy debts which they must work off in order to become free agents. They are employed as the “brains” of spacecraft (“brainships”), hospitals, industrial plants, mining planets, and so on, even cities – in the books, primarily spaceships and cities.