#à/explorer : https://en.wikipedia.org/wiki/In_situ_resource_utilization It just needed the initial push, which might be: - A mining setup on an asteroid - An energy extraction (hydrogen) using Jupiter flybys (how? what about the friction from the atmosphere? (is has to be so fast that it doesn't fall down... but then, how do you capture the gas?)) - An energy extraction from ice mining hydrolysis (extracting H${}_2$ and O${}_2$, although we would need the same energy to separate them than the energy it would give... maybe we flyby the sun to separate them?) We currently have 3d printing. What would be needed to 3d print in space? - A way to make a long filament of alloy - A way to make alloy - The requisite metals - A way to refine the said metals - Another machine to spin the allow in a filament - A strong source of energy to weld said filament