I agree with "Jerry." It's a very underrated space movie (of course, how many good low-budget ones AREN'T underrated?) If I remember correctly, the solution to the mystery was a sort of variation (but not "rip-off") of 2001, because the computer controlling the spaceship had actually been a man, who had somehow been turned into a computer. And like HAL, they tried to disconnect his "mind", but not the mechanical parts of him, and as with HAL, it led to disaster. There is at least one funny moment. When the Christopher Cary character, who can't find any food, finds the abandoned pet bird, there's a kind of ominous moment, but then the obvious thing doesn't happen after all.