[Flatus I. Maximus]

Yep, it's a cool idea. Which is why Heinlein used it almost 65 years ago.

[The SISU kid]

Beat me to it! ;-)

[BeauBo]

Wasn’t this also the basis for the launchers (”catapults”) that the Moon colony used to threaten Earth, to gain their Independence, in Heinlein’s Libertarian classic “The Moon is a Harsh Mistress”?

TANSTAAFL!