That's the only way to get anywhere with space travel. The ships that would be required for space travel would be way too large to take off from the surface. I don't think this tech is quite there yet. Don't get me wrong, the printers are there, there's a place near me that has one that the military uses. I went to see it for work, couldn't see it, classified BS, but he said most 3D printers, once it prints something, you have to file off the imperfections. However with the one they have, he said it's ready for use as soon as it comes out, nothing it wasted and it can print in almost any material, metals included. Pretty cool stuff, too bad I couldn't see it. Anyway he said it was a massive machine, had to be to be able to print in so many materials. So I think it would be difficult to get one to space, but not impossible, but I don't think the robots are quite there yet. I mean does NASA even have any robots that can make repairs unattended? Give it a 3D printer, if it messes up, it could be life or death, just like those cars that can brake on it's own, very dangerous if the computer malfunctions.