The addendum is a line from "In the Bottom of a Hole" that ought to be tattooed inside every federal official's eyes, as in stamped on their retinas so it's overlaid on everything they see, forever:
There's everything in space. [...] Metal. Vacuum for the vacuum industries. A place to build cheap without all kinds of bracing girders. Free fall for people with weak hearts. Room to test things that might blow up. A place to learn physics where you can watch it happen.And the correction is, I overstated our ability to do interstellar flight; turns out our currently available nuclear rockets would have to be more than 99% propellant tank to get up to .1c. I calculated the delta-v myself. But you might be able to refuel them in-flight using electrostatic (not electromagnetic) ramscoops. And one day we'll be able to make fusion rockets, and full-fledged RAIR (ram-augmented interstellar rockets) will be within our grasp.