@Max that could be fun, but the test unit is set to leave earth soon to test it in real space conditions. Of course, there are many steps between that and working out a sustainable plan for 3D printing necessary items, but I do think they will get there eventually.
@Max, yes, I'm very optimistic about it. While on earth it's often used just for novelty items, it can also be amazingly useful in medicine, aviation, and industry. And in space, as I said, it can prove a real game-changer for supply chain planning.
I would agree that it's ultimately going to be necessary to build things in space, we'll still need the raw material. So something will have to get shipped up there regardless. And it goes without saying, any manufacturing will involve waste, so the weight of the raw material will be more than what you'd ship up as finished parts. If we're talking about a station on the moon or Mars, at least in principle, one might think of using raw material from those locations.
What I'd really like to see is space vehicles or space stations that create a 1g environment for people, before talk about staying up there for extended periods of time. These structures can still provide the 0g environments, if these are needed. But really, people do need that 1g if they expect to spend any significant time out there, and still hope to come back to earth.
@_HM no one is suggesting that we pollute space. What is printed on the test run will be returned to the earth. And what is printed in future is meant to be put to use -- the same way equipment manufactured on earth would be.
@Bert22306 Currently, 3D printing can be done with a number of materials, but moon dust is not one of them, as far as I know. Taking the materials from the moon, etc., might open one to charges of plundering space bodies, so I'm not certain they want to go there at this point. For now, the idea is that if you take the substances that can be 3D printed, which include plastics, as well as metals and ceramics, you'd have options to make what you need even if you did not foresee needing it years before when the original supply list was put togehter for the expedition.
In 2007 the ISS Solar Array Alpha Rotary Joint (Sarj) Bearing failed, disabling sun-tracling motion of half of the solar panels. The joint was redesigned, and replacement parts were manufactured on earth, they were installed on a later flight to restore full electrical power, and a special grease was applied to improve lubrication. For a realistic test, try fabricating replacement parts for this rotary joint. The joint is metal, so it will have to be done with the improved printer. Incidently, this is a large joint. The entire assembly including bearings, gears, motor to rotate the panels has long dimension of about 10 feet.