Launch loops ( https://en.m.wikipedia.org/wiki/Launch_loop ) are most commonly discussed at orbital-class scale ... 2,000 km long runways to throw stuff (and possibly, people) into space, assembly-line style.<p>Problem is, it's one of those huge, hypothetical mega-projects that seems perfectly feasible on paper, but quickly bogs down as soon as anyone starts talking about <i>actually</i> building one.<p>But unlike most space launch mega-projects, launch loops scale. You can build a working hobby-sized one in your basement.<p>So I've been kicking around the idea of picking one of the mega-bridge (or mega tunnel) projects under consideration, and building a launch loop instead ... intended as a viable pilot project for one day building a full-scale orbital launcher ... or just a viable replacement for really long bridges.<p>So, question is, is it feasible at this scale? Energy requirements? How much traffic could one handle? Special challenges for building a closely linked pair (for two-way traffic)? Risks?<p>Addendum: John Knapman developed a more adaptable version, called a space cable ( http://www.spacecable.org.uk/index.html ). He includes many smaller-scale, alternative applications for it ... but nothing there about use as a mega-bridge, so my question stands.