Nope. The energy cost is trivial. The cost of joules for a vacation to Europa is within upper middle class aspirations. It only costs so much because our lif

Nope. The energy cost is trivial. The cost of joules for a vacation to Europa is within upper middle class aspirations. It only costs so much because our lifters are hideously inefficient. The reason rockets are so inefficient is that we don't know how to keep cracks from spreading through our structural materials, so we have to derate their strength by huge factors to get reliability. Nano- and micro-composite materials look like they will be able to vastly improve this situation (and indeed already are in the latest jetliners), and the rocket equation gives big big cost savings for weight savings. High strength materials are also good for rotovators and other semi-passive lifters. Another big opportunity is to shift some of the propulsion to the ground. It should be straightforward to shine launch lasers up the tail of a standard rocket and reduce its propellant requirement by many percent, which the rocket equation then multiplies into a large cost savings. Exclusively laser launched vehicles are also possible but speculative at this point (they need visible light lasers to get range but those are still too inefficient). Most of the necessary technology exists or can easily be built. All we lack is the optimism to make the investment. As for getting metal back, the asteroid belt is energetically close despite the distance. A small nuclear reactor and patience will do the job.