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> 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 constr

> 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 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.

Nomentatus 4y ago
Costs for both paths will go down steeply over time. But launch costs can only go down so far given the sheer amount of fuel necessary to launch anything into orbit from earth. Remember maintainance robots will come, not just more reliable and cheaper printers that are very lightweight (used at the end of a long flexible arm.) 3D printing aluminum isn't, you know, rocket science.
- manholio 4y ago
  You don't seem to resonate witn the basic premise of this discussion: the mass of the structure must stil be lifted into orbit in the form of raw materials, printer fillament, etc. We were debating the finer points of wheter the high cost of space fabrication is covered by space optimized design that will never need to experince atmospheric drag, gravity, launch forces, vibrations and volume constraints etc.
  - Nomentatus 4y ago
    No, soon enough the vast majority of mass will be catapulted from the lunar surface. There's oodles of aluminum in lunar soil.
    - manholio 4y ago
      > soon enough the vast majority of mass will be catapulted from the lunar surface 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.
      - Nomentatus 4y ago
        It's early days, but costs per pound to space are going down fast. The tech itself isn't science fiction we can sinter a cannonball from lunar dirt or extract aluminum and make a ball to put in a catapult. It's just plenty expensive as yet, but costs are coming down. 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.

Nomentatus 4y ago

Costs for both paths will go down steeply over time. But launch costs can only go down so far given the sheer amount of fuel necessary to launch anything into orbit from earth. Remember maintainance robots will come, not just more reliable and cheaper printers that are very lightweight (used at the end of a long flexible arm.) 3D printing aluminum isn't, you know, rocket science.

manholio 4y ago
You don't seem to resonate witn the basic premise of this discussion: the mass of the structure must stil be lifted into orbit in the form of raw materials, printer fillament, etc. We were debating the finer points of wheter the high cost of space fabrication is covered by space optimized design that will never need to experince atmospheric drag, gravity, launch forces, vibrations and volume constraints etc.
- Nomentatus 4y ago
  No, soon enough the vast majority of mass will be catapulted from the lunar surface. There's oodles of aluminum in lunar soil.
  - manholio 4y ago
    > soon enough the vast majority of mass will be catapulted from the lunar surface 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.
    - Nomentatus 4y ago
      It's early days, but costs per pound to space are going down fast. The tech itself isn't science fiction we can sinter a cannonball from lunar dirt or extract aluminum and make a ball to put in a catapult. It's just plenty expensive as yet, but costs are coming down. 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.