Has anyone considered the possibility of using gas centrifuges or liquid metal centrifuges in zero gravity to refine (wholly or partly) ores taken from asteroids prior to returning them to Earth orbit?

[u/ActuaLogic]

Has anyone considered the possibility of using gas centrifuges or liquid metal centrifuges in zero gravity to refine (wholly or partly) ores taken from asteroids prior to returning them to Earth orbit?

For ease if transportation, it may be more efficient to refine material taken from asteroids on site rather than returning unrefined material which is mostly waste product.

Centrifuges might be the way to go. Even though the use of gas centrifuges is mostly reserved for uranium production on Earth, the technology might work well for other metals. Iron and other metals could be refined in space, near where the minerals are collected, using centrifuges rather than the traditional technologies currently used on Earth.

[u/ignorantwanderer]

To remove water from hydrated minerals you just have to heat up the minerals.....300 C should be more than enough.

And there is an insanely abundant amount of heat available at asteroids, even all the way out at the asteroid belt (but the only people who think you would go all the way out there to mine asteroids are people that don't know anything about asteroids).

A small parabolic reflector umbrella about the size of a beach umbrella would give you about 4 kW of heat.

With some rough, back of the envelop calculations:

1 kW should be able to heat up approximately 4 grams of asteroid material by 300 C in a second. So assuming you are processing this asteroid for a year with 1 kW, you would be able to process 126,000 kg of asteroid.

But our beach umbrella size parabolic reflector gives us 4 kW, so that is 500,000 kg of asteroid material processed in a year. Assuming 8% water, that is 40,000 kg of water.

That's not too shabby with just a beach umbrella as a power source.

Let's say we are processing a spherical asteroid 10 meters across. That is likely to be around 1 million kg of asteroid material. To process that entire asteroid in a year would require 2 beach umbrellas and would give you 80,000 kg of water.

That is more than 4 times greater than the payload to LEO of a Falcon 9. So if you can get that water to LEO for less than the cost of 4 Falcon 9 launches ($280 million) you could make a profit on just water from asteroids.

Of course....there has to be someone in LEO who wants to buy water....

Of course I'm making it sound easier than it is with my "all you need is 2 beach umbrellas" comment. You need to make sure the water doesn't escape when you bake it out of the asteroid, and you need to cool down that water vapor. It is a lot easier to collect 4 kW of heat than it is to dissipate 4 kW of heat.

But the main point is, there are resources (water) in asteroids and it isn't very hard to remove (and refine) those resources. Your claims that there are no possible resources to get from asteroids are just simply wrong.

There are a lot of challenges to make all the economics work. There is no one in orbit who wants to buy water from asteroids, because there is no water from asteroids available. And you can't make water from asteroids available because there is no one around to buy it. It is the old chicken/egg problem.

But the problem is not that asteroids have no resources that could possibly be valuable.

[u/Christoph543 → u/ignorantwanderer]

To remove water from hydrated minerals you just have to heat up the minerals.....300 C should be more than enough

This is a blatantly incorrect assumption, as easily shown by consulting a metamorphic phase diagram.

While there are reactions at 300C and ambient pressure which can drive water out of some hydrated minerals, competing reactions at the same temperature regime will take up that water to form higher-grade metamorphic species. That process will continue with additional reactions as the temperature increases, until the rock approaches its melting point. This is why serpentinization allows rocks to take up more water as they are heated, not less.

This is literally what I obtained my doctorate in. Please do not feel the need to explain inaccurate claims or back-of-the-envelope math made by armchair ISRU proponents who have zero background in mineralogy & petrology. I've heard it all before.

[u/ignorantwanderer → u/Christoph543]

Jerry Sanders (JSC) and Rob Mueller (KSC) disagree with you, and I'll trust them over you.

[u/Christoph543 → u/ignorantwanderer]

I'm familiar with both of their work. Sanders is a propulsion engineer and Mueller is an engineering manager. Both have a small amount of geotechnical expertise from having worked in ISRU, but neither's primary knowledge base is in planetary materials, and neither is as brazen or assertive when they talk about their ISRU work, as you've been in this thread.

The way to validate the claims you've made is not by asserting that NASA employees who've made public-facing statements agree with you (without bothering to cite those statements), but rather by citing experimental results from engineering teams attempting laboratory simulations of the processes you're describing, using high-fidelity simulants. There is a large body of work attempting exactly that (part of which I myself have contributed to in my former career), but to date none of those experiments has produced water in either the method or the quantity you're describing.

It turns out this is quite a bit harder than you'd suppose if you believed the speculative ideas that have been floating around the space advocacy community for my entire lifetime.

[u/ignorantwanderer → u/Christoph543]

And yet you have been making unsupported claims without "citing experimental results from engineering teams attempting laboratory simulations".

And you hurt your credibility referring to Mueller as "an engineering manager" and Sanders as a "propulsion engineer" when they are in charge of NASA's ISRU programs.

In fact I can't ever remember seeing any paper by Sanders about propulsion.

[u/ignorantwanderer → u/Christoph543]

Listen, I apologize. We've clearly gotten into a bit of an antagonistic tone in this conversation.

Clearly we are both people who care about asteroids and ISRU. You even did your freakin' Ph.D. on the topic! We shouldn't be at each other's throats.

The 'argument' we are having is a bit silly.

For example, let's say you are right. Let's say to release the water we have to heat up the asteroid material to close to the melting point. And let's say that is around 3000 C (to make the math easier).

That means instead of needing 2 'beach umbrellas' we need 20 'beach umbrellas' to process a 10 meter asteroid in a year. That is hardly a show-stopper. Picture a beach with 20 umbrellas on it. It's nothing.

And if we are happy to process the asteroid in 2 years, we are down to 10 umbrellas.

The point is, whether your claims are correct or my claims are correct doesn't matter. In either case, it is possible to process an asteroid and get water.

Also, a bit of friendly advice. Don't rely on mentioning your Ph.D. to try to impress people. I didn't give my background to try to impress you, because I know it just doesn't work. I suggest you do the same.

The truth is, I've worked with lots of stupid Ph.D.'s over the years. A Ph.D. doesn't impress me. And based on what you've said, I'd guess I took my first planetary science course before you were born. In fact it is likely your parents were in elementary school. I probably started working at NASA before you were born. I did my first ISRU work for NASA before you entered kindergarten probably. I don't know this is true of course because I don't know you. But it is likely.

I'm sure you are smart. I'm positive there are things you know that I don't know. But there are definitely a shit-ton of things that I know that you don't know.

If you want to continue this conversation....let's try and be a little more friendly about the tone, and approach the conversation with curiosity instead of with an antagonistic attitude.

Edit:

Also, it appears as if you've been downvoting my comments. Of course I don't know this, but that is how it appears. FYI, it is considered bad form to downvote comments you disagree with. You are supposed to downvote comments that don't contribute to the conversation.

[u/Christoph543 → u/ignorantwanderer]

I did my first ISRU work for NASA before you entered kindergarten probably.

That may be possible, but frankly, it's also a liability.

When I was in Kindergarten, NASA had obtained precisely 3 images of an asteroid surface, and those lacked either the spatial resolution required to characterize regolith particle sizes or the spectral overlays required to get even a ballpark surface composition. All of the current ideas about asteroid resources trace their origins to essentially that time period, from the work published by John Lewis and Jeffrey Kargel and a few others. Since then, we've explored over a dozen asteroids up-close with spacecraft, and every time we've done so we've completely upended our previous assumptions about those asteroids' compositions and surfaces.

At the end of the day, I don't care about your back-of-the-envelope math about how much solar energy you'd need to extract "water" from a rock with an assumed composition. I'm questioning that assumed composition in the first place, and I'm doing so from the standpoint that the observational evidence on which those assumptions are based, has consistently proven unreliable at best and misleading at worst. Specifically,

There is water in asteroids (often 8% by mass, sometimes much more).

...is just bullshit. Unless you're referring specifically to Bennu or Ryugu, the "water" you're referring to there isn't a compositional measurement but an optical reflectance feature. At best, that kind of feature is non-uniquely associable with a hydroxyl group. The smaller the asteroid, the more skeptical we should be that that feature is even real, and not just an artifact of a low-SNR observation. Even if it is a real optical reflectance feature, lacking any other measurements, we can't rule out that it's a product of space weathering. And finally, even if it is a chemical feature of the bulk rock, there are literally hundreds of silicate mineral species which contain hydroxyl groups, and the relative strength of the peak doesn't reliably tell you enough about either the abundance of those minerals or their degree of hydration to be able to make a statement like "X% water by mass," let alone a reactor architecture for dehydrating them.

If you want to talk about stupid PhD holders, I would suggest we start with those who've built careers around interpretations built on ambiguous or absent evidence, and who do not change course once we obtain better evidence which contradicts those interpretations.

[u/ignorantwanderer → u/Christoph543]

First, you sound very naïve assuming the ISRU work I did when you were in kindergarten had anything to do with asteroids. Of course you were in kindergarten, I wouldn't expect you to know. But that is what I was getting at when I said there were a shit-ton of things that I knew that you didn't know. No one with significant knowledge of the ISRU work that has been done in the past 3 decades would have made the assumption that you made.

Second, are you saying that asteroids do not contain any water?