What might prevent metal “blowing” and other forms of shaping from working if gravity was not a factor? Let’s handwave-ignore the extremes of temperature as it relates to techniques and the present primitive space habitats and craft.
Is it possible to suspend a pool of molten metal, with a tube inside, spin while adding a gas to shape a container, and form more complex shapes through additional heat cycles in a repeatable process?
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You can work glass and plastic the way you can because at a certain temperature range their plasticity and viscosity are conducive to working them in that manner.
Iron has plasticity at a temperature, but lacks the viscosity until it gets too hot to have the plasticity needed. If you had a molten blob of iron in space and tried to inflate it, the material would get a hole blown in the side instead of inflating and stretching out because the working properties aren’t right.
What if the substance was only one part iron?
That would no longer be iron, then. It would be an alloy. Steel is the most common example of an iron alloy and it exhibits different properties based on the ratio of carbon and other elements.
Ditto goes for most alloys. Glass-like properties aren’t typical, otherwise metal blowing would be a thing.
There might be alloys that can do this, but not the usual ones. Some of the low-melting ones can be gooey-seeming, off the top of my head.
An alloy would have to have the working properties needed, but all “metals” have the same problem of viscosity and plasticity not overlapping.
Why would you need to go to space to try this? And since you’re thinking in space, how would you cool it down?
I have not invented antigravity. If you have any pointers, I’m all ears. /s
Why does it need to be in no gravity? Glass blowing isn’t done in no gravity.
Intuitively, when I have handled molten metals, they are deceptively heavy and viscous. There is very little time when they are in a mushy slushy state or like Taffy in the way that glass behaves. I thought, perhaps if the pool of molten metal were somehow suspended in an environment without gravity, it might be possible to apply glass blowing techniques for shaping.
I know centrifugal casting is a thing and used a lot by gold smiths in jewelry making. It was just a moment of curious imagination this morning thinking perhaps someone one day in the future might manually work metal in space like how glass in worked on Earth. I’ve been thinking about how things might be manufactured differently in a distant future when most of humanity lives in cislunar space habitats. This post was just a half curious passing shower thought.
Space is cold, the question is how would you keep it hot?
Sure, but temperature is useless in a vacuum. The heat has nowhere to go. There is some ambient radiation in space, but not enough. Temperature regulation is a serious thing for astronauts.
Things still do cool in shaded space, though, it just takes longer. The James Webb took like a month or two to get down to cryogenic IIRC.
I have a feeling OP was worried about gravity, which isn’t usually helpful here, but isn’t actually a dealbreaker. Glass is heavy too.
Metal has excellent heat capacity, why wouldn’t it stay hot on earth?
Are you saying things won’t stay hot in space? The exact opposite is true! It’s very hard to keep things from over heating if you have a heat source.
Something similar to what you are describing is called hot metal forming where you heat up a metal tube ( like aluminum) and then pump it full of gas. I don’t have any experience with this method, I only learned about it theoretically, but some of the parts can get pretty complex.
It’s mainly used in aerospace, but I’ve also heard of it being used to make some HVAC stuff
Hydroforming is very common on bicycles now too. The most controlled of these forming applications is usually found on the highest end Cannondale CAAD bikes.
It would take substantially less energy to make metal molten in space. As air pressure drops, the temperature needed for materials to change states becomes lower. That’s why water boils much faster on a mountaintop than it does at sea level.
The metal would be manually workable at relatively low temperatures. Without air, you would need a tank of a gaseous substance to “blow” into the metal.
Melting point doesn’t work like boiling point. Otherwise, what would we make rockets out of? They get really hot in a vacuum, but need to (and do) stay solid.
If you go to really high pressures like in an ocean trench or deeper, melting points will raise too (or lower, in water or silicon’s case), but 1 vs. 0 atmospheres is negligible. I haven’t seen it even mentioned in any vacuum engineering stuff.
While it’s true that the relationship between melting point and boiling point differ from material to material, the melting point always remains below the boiling point until the triple point.
The triple point is when the ambient pressure is low enough that a substance can be solid, liquid, and vapor in equilibrium at the same time.
As for engines, they burn at temperatures hot enough to melt the steel they are made of, even while on Earth. Engineers employ regenerative cooling to prevent the housing from melting at such high temperatures.
They still get very hot, though.
Another example: Every incandescent lighbulb. The filament is stupid hot in there, under a rough vacuum, and doesn’t melt. I would be surprised if 1 bar even amounted to a full degree of change in melting/freezing point.
Water is volatile, and so it’s a better example of variability at familiar scales. You’ll notice the freezing point is pretty much vertical at 0C on the phase chart until 100s of bars. (And then gets lower because pressure pushes matter towards denser states, and ice I is, unusually, less dense than the liquid)
The triple point shows up when the boiling point lowers to meet the melting point, and liquid water ceases to exist as a stable substance. It’s at ~0C.
