REM@MIT-MC@sri-unix (09/20/82)
From: Robert Elton Maas <REM at MIT-MC> I'll give you one good reason for building in space instead of on Luna. It's damned hard to build large massive things in gravity. Things keep falling. Things have to be supported against falling. But things break and structures collapse and a cascade of disaster happens with one thing knocking another apart and something else collapses and heavy objects crush people to death. Supporting against gravity, girders have to be strong to support the basic stuff that just be held up, but those girders are massive themselves and that merely compounds the problem. There's some limit beyond which it's virtually impossible to build anything bigger. Witness the limit that even pieces of rock can't rise more than about 29 thousand feet above sea level; they get crushed under their own weight. In space we can build things arbitrarily large providing we're sufficiently far from tidal forces of planets (including moons etc.). At L-5 (or in LEO for that matter) we can build much larger than on Moon, and much more cheaply materialwise. Even though many elements are available on the moon, some aren't. But in deepspace (L-5 or whereever) we can bring asteroids of desired composition nearby and raid them for materials. On Luna we'd have to somehow land those asteroids gently enough to avoid moonquaking the processing plant to shambles. Sure there'll be uses for moon bases, but the longrun picture is surely deepspace for a vast majority of large manufacturing and energy-producing facilities, and probably habitat as well.