[ghost8772]

The catapult was a mass driver. Rail gun more specifically. they had the original, but its location was iffy and likely well known to officials on earth. they did build a secondary one as backup with no data on earth of its location.

Escape velocity from Moon is small, escape velocity from earth is much larger, no numbers on hand, but moon is listed as 1/6th gravitational acceleration. no an item on the moon is not going to be drawn to earth, if that was the case there would be a continuous flow of moon dust from the moon to earth's atmosphere. the moon has its own gravitational field, the point of separation is closer to the moon than earth, but its not on or really near the surface.

Yes most authors describe building colonies INTO the rock of a mostly airless planet. it does take more effort to open rock than multiple wall constructs. as I recall the only point in this book that was not dug into the surface was "the old dome" which they worried about taking collateral damage (no point could withstand a direct nuke attack)

the foodstuff sent to earth was compressed more to ship as little air and water, as well as most produce per package. larger profit per firing.