"Astronauts like to do launch" sounds like "astronauts like to do lunch" which means astronauts like to take lunch. An astronaut is someone trained to travel in a spacecraft. "Launch" is the verb used to describe a spacecraft that is being set in motion to leave Earth and head into outerspace. The joke is centered around the word "launch" which kind of sounds like word "lunch" to describe what astronauts like to do.
Astronauts like to do launch .