The raw materials would still need to be shot up into space. And what makes manufacturing and assembly in zero-g cheaper than on the Earth's surface?
Except for the massive byproducts created on earth to get through the "more expensive" phase. It would be deeply deceptive and cynical to sell that as "green", surpassing even today's deceptive selling of carbon capture and storage technology on fossil fuel power plants.
Fuel is a pretty small cost for rockets anyway so using more-expensive clean fuel wouldn't be prohibitive.
Hate to be the one to mention it, but the military may well be paying most of the freight to set most of this up (covertly or not) since space based you-name-it including hypersonic projectiles are going to be more and more useful as the decades pass.
Because why should we build things on the ground and deliver the finished products in orbit, when we can push an entire industrial chain into orbit and furnish it with the vast quantities of required inputs, while taking advantage of the vast nothingness that exists there, and the 100000 times more expensive labor. It's like Elon Musk's Mars city, but in vacuum, with zero in situ resource utilization.
In a large scale on orbit construction project, like a space based solar power station, we could manufacture complex interlocking units on the ground like space station modules on the ISS, and hope all the power routing, and docking, and everything else, will work together when launched… or we can build it the old fashioned way, but with robots or astronauts up in space… bolting, welding, wiring, cabling and routing everything up there from easily made standard parts that meet the requirements. Just like large photovoltaic solar farms are built on earth, with X units of photovoltaic panels, attached to structural support frames suitable for the location they are being installed at (wind loads, thermal range, etc) … and everything cabled together with hundreds of little plastic clips and miles of copper wire in weatherproof plastic conduit.
Now some things will obviously be different in space, like hundreds of plastic clips are obviously a space debris risk, so they probably won’t design cabling systems that need that sort of support. But they will need to manage lots of power and data cables which will need some level of protection from the slow but steady degradation by various forms of radiation and plasma from the Sun and deep space, and it turns out a few millimeters of plastic can get you years and years of protection from oxygen plasma which would could eat away at exposed wires and slowly increase the risk of short circuits. Yes it might need to be replaced regularly, but so will other things, and then you don’t need to use crazy specialised oxygen plasma resistant wire insulation…
Space is hard, but we build things for way more harsh environmental conditions on the ground all the time in industrial applications. What they don’t need that space currently does, is earth based industry doesn’t usually care about total weight. Starship will revolutionise space not by magic, but by slashing the cost per kilo and allowing us to use more normal engineering procedures and hardware where appropriate. Like panels and wiring and support structural girders. My point was that 3d printing lightweight plastic structural parts where they are needed, will be to space based solar power, what mixing concrete on a construction site is when compared to having everything transported to the site via cement mixers. Sometimes it makes sense for the project to mix on site, other times it won’t.
I’m not sure what there is to argue with about this thesis.
I argue that any kind of large scale structure fabrication is fundamentally different than the preparation of raw inputs, like your concrete example. A large orbital 3D printer is a complex industrial machinery that needs servicing, constant supervision and human involvement, it's more akin to the Hubble telescope than to an concrete mixer. The costs to operate it in space are orders of magnitude higher than on the ground even in the most optimistic orbit cost reduction scenario, short of space elevators and the like.
Until we have self replicating and selfrepairing orbital robots, any space project will need to contend with the fact that human labor in a spacesuit in orbit is inconceivably more expensive than a guy riding his bike to the factory in sweatpants, breathing the free air our planet seems to have aplenty and drinking the water that falls from the sky from time to time. And this is, I repeat, a fundamental stumbling block no matter how far launch vehicles advance, space will always be insanely hard compared to surface.
So you better have a damn good economic case for printing structures in orbit which are 1000x more expensive than the same structures built on earth. The savings from the support structure and the lack of foldable mechanisms necessary to deploy into orbit could be significant, but definitely less than a single order of magnitude.
3D printing aluminum isn't, you know, rocket science.
Other than naturally falling asteroids, to date we have managed to acquire about 400Kg of moon rock at a price point of roughly $200bln in today's money. That's about $500k per gram.
These speculative predictions about moon & asteroid mining imply technology advances that are so far into the future that they are basically mindless daydreaming. Things like self replicating robots, nuclear space-ships and other sci-fi staples.
We are decades or centuries away from that and the impact of such tech cannot be predicted - they will change society so much that we cannot even begin to imagine their impacts. Sort of like people in the 19th century imagined a future of personal balloons, not being able to imagine the impact of airplanes and the automobile.
You're right, according to me, about getting minerals from the asteroid belt, for earth use. That's not happening until the farther future: the delta is extreme, and down to earth itself not trivial. But extraction from the moon or mars moons (about the same delta to a lagrange point as the moon believe it or not) can be economical in bulk precisely because the cost to get to earth orbit can only go down so far (the cost of the fuel).
Fulton used to loiter around the fences around his steamship as it was being built; you should find and read all the scorn every single passerby had for the mad, doomed project that seems pretty ordinary now.
When I was young, maybe 1963, I had dreams in which people in the future were carrying around small devices with screens they kept looking at, about the size of my fathers pocket calender planner (3" by 6" maybe). Not a wholly original idea, Dick Tracy comics showed a TV watch back then.
My father, a very competent electronics engineer who was very well read, poured absolute scorn on the idea. He didn't just say that no known tech could do that, he said that the device was strictly impossible, and that no matter how long the world lasted, no such device would or could exist. His reason: you can't flatten a cathode ray tube that much. Time easily dispenses with our reasons why not.
Labor is extraordinary expensive, yes, at first. That is because our robotic technology isn't good enough and that people don't live and work in orbit yet. That will change with time as we begin space colonization.