> It’s not necessarily cheaper energetically to get stuff from an asteroid than from Earth. You’d have to accelerate stuff from a wildly different orbit, and then steer it and slow it down.
Delta V from just about anywhere in the solar system is lower than launching from the surface of Earth. You could launch stuff from Mars and bring it back to Earth orbit with less energy than launching it from Earth. The rocket equation is really punishing.
Right. The alternative is not to send materials from Earth for processing in space, that would be stupid. We send finished stuff, which were manufactured on the ground. But you don’t mine finished widgets from asteroids. You mine ore that needs refining and processing before being used to manufacture things. This ore is orders of magnitude heavier than the finished products, never mind all that’s required to do anything useful with it.
Delta V from just about anywhere in the solar system is lower than launching from the surface of Earth. You could launch stuff from Mars and bring it back to Earth orbit with less energy than launching it from Earth. The rocket equation is really punishing.