__________________________________________________________________ biased spamy incorrect defiant cnts required build space tethers long earth surface geostationary orbit space elevator space tethers orbit right minute made existing materials even boeing report quoted says possible existing materials upper limit length practical space tether built existing materials yes overall upper length limit non rotating skyhook still economically worthwhile probably around best knowledge one gone trouble actually determining upper limit simply time build one long better materials allow build even longer one good example suspension bridges longest build practical suspension bridge using steel cable tad one mile since made longer ones using carbon fiber cables even carbon fiber cables strong enough build suspension bridge across strait gibraltar matter degree current materials build non rotating skyhook length push need build one long make affordable space flight reality long non rotating skyhook lower endpoint velocity orbital velocity altitude upper endpoint velocity escape velocity altitude skyhook combined reusable single stage sub orbital launch vehicle orion spacecraft would give affordable access earth orbit near earth space space tourism asteroid mining satellite solar power stations space colonies would become possible system truth know make clearer