Read an article in IEEE Spectrum recently titled, 4 Products it makes sense to manufacture in space. The 4 products identified in the article include:
1) Metal alloys – because of micro-gravity, the mixture of metals that go into metal alloys should be much more even and as a result, should create a purer mixture of the metal alloy at the end of the process.
2) Fibre optical cables – the article says, ZBLAN, which is a heavy-metal fluoride glass fibre could have 1/10th the signal loss of current cable but is hard to manufacture on earth due to micro-crystal formation. Apparently, when manufactured (mixed-drawn) in micro-gravity, there’s less of this defect in the glass.
3) Printed human organs – the problem with printing biological organs, hearts, lungs, livers, etc. is they require scaffolding for the cells to adhere to that needs to be bio-degradeable and in the form of whatever organ is needed. However, in micro-gravity there should be less of a need for any scaffolding.
4) Artificial meat – similar to human organs above, by being able to build (3D print) biological products, one could create a steak or other cuts of meat that biological #D printing.
Problems with space manufacture
One problem with manufacturing metal alloys and fibre optic cable in space, is the immense heat required. Glass melts at 1400C, metals anywhere from 650C to 3400C. Getting rid of all that heat in space could present a significant problem. Not to mention the vessels required to hold molten materials weigh a lot.
And metal and glass manufacturing processes can also create waste, such as hot metal/glass particulates that settle on the floor on earth, but who knows where in space. To manufacture metal or glass on ISS would require a very heat tolerant, protected environment or capsule, lots of power to provide heat and radiator surfaces to release said heat.
And of course, delivering raw materials for metals and glass to space (LEO) would cost a lot (SpaceX $2.7K/kg , Atlas V $13.2K/kg). As such, the business case for metal alloy manufacturing in space doesn’t appear positive.
But given the reduced product weight and potentially higher prices one can charge for the product, fibre pptical glass may make business sense. Especially, if you could get by with 1/10th the glass because it has 1/10th the signal loss.
And if you don’t have to ship raw materials from earth (using the moon or asteroids instead), it would improvesboth business cases. That is, assuming raw material discovery and shipping costs are 1/6th or less as much as shipping from earth.
As for organs, as they can’t be manufactured on earth (yet), it could be the “killer app’ for made in space. But it’s sort of a race against time. Doing this in space may be a lot easier today but more research is going on to create organs on earth than in space. But eventually, manufacturing these on earth could be a lot cheaper and just as effective.
But I don’t see a business case for meat in space unless it’s to support making food for astronauts on ISS. Even then, it might be cheaper to just ship them some steak.
Products hard to make in space
I would think anything that doesn’t require gravity to work, should be easier to produce in space.
But that eliminates distillation, e.g., fossil fuel refining, fermentation, and many other chemical distillation processes (see Wikipedia article on Distillation).
But gravity is also used in depositing and holding multiple layers onto one another. So manufacturing paper, magnetic/optical disk platters, magnetic tapes, or any other product built up layer by layer, may not be suitable for space manufacture.
Not sure about semiconductors, as deposition steps can make use of chemical vapors. And that seems to require gravity. But it’s conceivable that in the absence of gravity, chemicals may still adhere to the wafer surface, as it’s an easier location to combine with than other surfaces in the chamber. On the other hand, they may just as likely retain their mixture in the vapor.
Growing extremely pure silicon ingots may be something better done in space. However, it may suffer from the same problems as metal alloy manufacturing. Given the need for extreme purity and the price paid for pure silicon, I would think this would be something to research ahead of metal alloys.
For further research
But in the end, if and when we become a space fairing people, we will need to manufacture everything in space. As well as grow or find raw materials easier than shipping them from the earth.
So, some research ought to be directed on how to perform distillation and multi-layer product manufacturing in space/micro-gravity. Such processes could potentially be done in a centrifuge, if they truly can’t be gone without gravity.
It’s also unclear how to boil any liquid in 0g or micro-g without convection (see Bizarre Boiling NASA Science article). According to the article, it creates one big bubble that stays where it is formed. Providing some way to extract this bubble in place would seem difficult. Boiling liquids in a centrifuge may work.
In any case, I’m sure the ISS crew would be more than happy to do any research necessary to figure out how to brew beer, let alone, distill vodka in space.