 What is the “space cafard” that Si describes?
There on the long, long haul to the Jupiter satellites, fearfully checking the symptoms of space cafard, the madness compounded of claustrophobia, monotony, boredom and free fall. He was drafted into the working force reserves, served his time, and is now free from toil for the balance of his life. Law prevented him from ever being called up for contributing to the country's labor needs again. The only fair thing was to let the technologically unemployed remain unemployed, with their Inalienable Basic stock as the equivalent of unemployment insurance, while the few workers still needed put in a reasonable number of hours a day, a reasonable number of weeks a year and a reasonable number of years in a life time.
 It’s the isolation that spacemen feel working alone in space, with only computers as company
 It’s the isolation that spacemen feel working alone in space, with only computers as company  It’s the public’s adverse opinion of space exploration that Gubelin tries to hide.  It’s the desire to return home from a long voyage.  It is the current system of operations for spacecraft, where people man ships with only one person.