NASA's ratings for space launches are at their lowest ever, so to raise public interest, they decide to find a "blue-collar slob" to go on their latest mission. NASA offer both Homer and Barney the chance to be an astronaut, and a competition ensues. Homer is the winner by default and goes into space.
Out in space, Homer spills a bag of potato chips, and while trying to clear up the mess, he smashes into an ant farm. James Taylor, who has dropped by to sing for the astronauts, suggests opening the door of the spacecraft to create a vacuum. They do so, but Homer nearly gets sucked out, breaking the door handle.
Homer manages to hold the door shut with an inanimate carbon rod, allowing the spacecraft to return safely to Earth.