 What was considered a downside to the space exploration by Si?
They also had a banquet for him, complete with speeches by such bigwigs of the Department of Space Exploration as Academician Lofting Gubelin and Doctor Hans Girard-Perregaux. He'd had plenty of time to figure it out, there alone in space on the Moon run, there on the Venus or Mars runs. His explanation was that a phobia against having his eyes touched prohibited either surgery to remould his eyeballs and cure his myopia, or contact lenses. If it is admitted that our organization has degenerated to the point that we haven't a single pilot, then it might well be that the Economic Planning Board, and especially those cloddies on Appropriations, will terminate the whole Department of Space Exploration."
 The fear of contracting space cafard.
 The inability to start of family of his own due to being away for long periods of time.  The fear of contracting space cafard.  His fear of being in the ship itself.  Becoming too used to being along for long periods of time.