Really, every plot element was a matter of a simple design error or just engineering silliness. Why in truth would we send all that biomass to Jupiter/Saturn in the first place when an automated probe would be the simplest way to initially discover that Iapetus is blinking at us because of its yin/yang albedo cause by local dirt and orbital dynamics?
If you pick at the technical details, the story collapses. Either you appreciate it for the artiness (note the absurd motion of the pods around the ship, which bears little resemblance to realism) or you put the thing in the dustbin and move on.
Automated probes are great for reasonably well understood missions. That was not the mission of Discovery. The monolith, “its origin and purpose still a total mystery,” send a signal to Jupiter. What waited there was unknown. Would they really want a probe to make first contact, especially considering the long communication lag? Even HAL wasn’t flexible enough to handle such a job, and he was limited in his movements.
So a human mission made perfect sense.
