Rocket Science

Over on the Rec.Models.Rockets newsgroup, Jesse asked:
"How come on real rockets they always have funnel like things on the back of the thruster thingo?"

To which Peter Alway* replied:
"Because the hot flamey stuff that comes out of the thruster thingo is accelleratized to the fastness of that noisy stuff you hear by passing through an other-way funnel-like thingy before it reaches the funnel-like things you see, and by going through the funnel-like things it embiggens, which acceleratizes it to several times faster than that noisy stuff you hear. The faster the flamey stuff leaves the thruster thingo, the faster the rocket travels when it runs out of the gunk it burns."

He's absolutely right you know.

*Peter Alway wrote Rockets of the World and its many supplements as well as historical reference and scale modelling data books. He also raises rabbits and teaches astronomy at a college in the midwest.