question:  Why did the Department hope that Si would continue for three more space missions?
context: What's more important—Man's conquest of space, or one spaceman's life? 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. It was better to retire on a limited crediting, on a confoundedly limited crediting, than to take the two or three more trips in hopes of attaining a higher standard. 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. His friend said drily, "Either of us could have volunteered for pilot training forty years ago, Lofting. His industrial aptitude dossier revealed him a possible candidate for space pilot, and it was you yourself who talked him into taking the training ... pointing out the more pragmatic advantages such as complete retirement after but six trips, added shares of Basic so that he could enjoy a more comfortable life than most and the fame that would accrue to him as one of the very few who still participate in travel to the planets. He was drafted into the working force reserves, served his time, and is now free from toil for the balance of his life. It will take months, possibly more than a year, to bring another novitiate pilot to the point where he can safely be trusted to take our next explorer craft out. Appropriations for our expeditions have been increasingly hard to come by—even though in our minds, Hans, we are near important breakthroughs, breakthroughs which might possibly so spark the race that a new dream to push man out to the stars will take hold of us. 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."
output:  It would take too long to train a new pilot to complete the explorations.
options:  He didn't complain about the explorations and enjoyed his time in space.  His required compensation was lower than the other pilots.  It would take too long to train a new pilot to complete the explorations.  He was the best of the best in the space exploration team.