Re: First Revenues: Asteroid or Moon Mining?

[Robotbeat]

Really, if you can get a metric ton of pure PGM, you've already won the war. I disagree with your premise. The other parts are going to be harder. Transportation costs are just easier to quantify (which is why we focus so much on them).

Please advise how to move ore cheaply.

SEP, for one. Or chemical, using ISRU propellant.

But anyway, those are just guesses. My real point is that extracting the ore is probably more difficult and we have less understanding of that part.

[jongoff]

Really, if you can get a metric ton of pure PGM, you've already won the war. I disagree with your premise. The other parts are going to be harder. Transportation costs are just easier to quantify (which is why we focus so much on them).

Please advise how to move ore cheaply.

SEP, for one. Or chemical, using ISRU propellant.

But anyway, those are just guesses. My real point is that extracting the ore is probably more difficult and we have less understanding of that part.

On the Moon I'd say use a mass driver (or any of the three or four other competing propellantless launch options) with a small, reusable circularization/delivery stage. I wouldn't be surprised if something like that could work for an asteroid too.

~Jon

[Danderman]

I guess the winner would be the company that manages to get beyond all the theoretical approaches laid out here in favor of an affordable system that would really work.

[Warren Platts]

I voted asteroid.

A single SEP tug (~20 tonnes fueled in LEO) could capture a 1000 tonne carbonaceous chondrite asteroid into high lunar orbit. 20% of that mass could then be extracted as water, simply by heating, which is not particularly complex given continuous sunlight. Lets guess another 20 tonnes in LEO for the ISRU plant. 40 tonnes in LEO gives at best 20 tonnes of useful payload at L2. From a pure mass in LEO perspective asteroid mining breaks even when 20 tonnes is extracted in cis-lunar space.

I am skeptical that SEP will provide the magic bullet that its boosters seem to think it represents. The problem is I don't see how it scales well. E.g., moving 1,000 mT with 20 mT propellant. What is everything?

What is the Isp?
What is the delta v?
What is the trust-weight ratio?
What is the propellant?
What is wattage?
What is the area of the solar array?
What is the dry mass?
What is the plan to deal with the torques that come with trying to rotate, and then stop rotating a 1 to 4 square kilometer array?

And extracting water from a carbonaceous chondrite isn't simply a matter of heating (which isn't trivial anyways) because it's chemically bound to minerals--it's not ice, in other words. Somehow you are first going to have to pulverise the entire thing in order to get the full 20% of water. How is that going to be accomplished? Blast and clear, like they do on Earth and will likely do on the Moon? Probably not.

20 mT for the ISRU plant is a vast underestimate.

Taking into account tug and ISRU plant development, extraction of about 50 tonnes of useful stuff (e.g. water) is needed to break even financially.

There's a contradiction here. If SEP truly is the panacea that its boosters assume it will turn out to be, then what is the point of going for chemical propellants?

In contrast lunar mining is much less defined.

I respectfully, but strenuously disagree. Where is an asteroid mining proposal that's even half as well worked out as Spudis and Lavoie's Lunar mining proposal? . Heck, where are even the threads on this forum that wargame an asteroid mining proposal in as much detail as I have wargamed Lunar gold and propellant mining? Where is an SEP architecture that is half as worked out as ULA's abundant chemical Moon/Mars architecture?

When you look at the nitty gritty details of just what is required to extract useful amounts of refined products from asteroids, whether propellant or PGM's, it's difficult to even know where to begin.

How do you go about surveying 1,000 to 10,000 NEA's to find that potential needle in the haystack? How are you going to confirm that it's got the potential to live up to the hoped for expectations? And most of all, how do you go about processing an entire asteroid in a weightless environment, and how do you deal with the orbital debris issues that will likely ensue?

On the Moon, we already possess maps showing magnetic anomalies that indicate likely impact sites of metallic asteroids. Moreover, on the Moon, we can use more or less conventional extraction techniques, thanks to the gravity well.

The Lunar environment seems less hospitable to mining as well. The best deposits seem to be in permanently shaded craters, which complicates water extraction. Lunar dust is very abrasive. A four week day night cycle gives great temperature extremes and makes use of solar power difficult.

This reflects an unfortunately typical misunderstanding of the Lunar ice deposits. Granted, the permashaded craters are among the coldest places in the solar system, but we already have materials in hand that can handle it, like certain nickel-iron alloys made by Inconel and Incolloy. Moreover, in the polar regions, the temperature extremes are pretty mild. There are quasi-permanently plateaus in the polar regions that are illuminated 80% of the time or more. There the temperature stays a relatively balmy minus 50 degrees, plus or minus 10, all year round. As for Lunar dust being abrasive, (a) that's no different from the dust that results from hard rock mining operations on Earth; (b) there's no reason to think that asteroidal dust is any less abrasive.

Any products of ISRU are at the bottom of a gravity well. OK, its only Lunar gravity, but that still adds to the cost, at best it doubles the cost and probably more like 3x or 4x the cost for resources delivered to L2.

I've worked the numbers: using a reusable SSTO tanker-lander, it takes 100 mT of LH2/LO2 (mass ratio 5) to deliver 40 mT to L1/L2 and still reserve enough propellant to get back to the Lunar propellant station. So if the incremental cost of the Lunar propellant is $100/kg ($1B/10,000 mT), then the cost at a L1/L2 depot $250/kg. So, yes, it is indeed the case moving propellant from Lunar surface to L1/L2 using conventional rockets increases the cost by a factor of 2.5. But so what? 2.5 times $100 or $200 per kg is chicken feed!

The question is: Can an asteroid mining operation deliver LH2/LO2 to L1/L2 for less than $500/kg?

Moreover, on the Moon it's easy to scale up production. With asteroids, after you're done with one, you've got to go find another golden egg and reel it in. On the Moon, just add more equipment or simply work your automated mining equipment more hours.

On the Moon, a single mine at a place like Whipple Crater 10,000 mT annual production would be extremely modest by Earthly standards (it would be somewhere on a scale from a local mom 'n' pop gravel pit to a small Appalachian coal strip mine of the sort where 3 or 4 guys chip a way and load a truck or two per day, depending on the water content). If the water content at Whipple Crater were 10%, there is enough in the crater floor to sustain 10,000 mT/year for well over 200 years. 10,000 mT/year manufactured on the Moon would enable the delivery of up to 4,000 mT/year to an L1/L2 depot system. More than we know what to do with, which would be a good problem to have for once.

[Robotbeat]

I voted asteroid.

A single SEP tug (~20 tonnes fueled in LEO) could capture a 1000 tonne carbonaceous chondrite asteroid into high lunar orbit. 20% of that mass could then be extracted as water, simply by heating, which is not particularly complex given continuous sunlight. Lets guess another 20 tonnes in LEO for the ISRU plant. 40 tonnes in LEO gives at best 20 tonnes of useful payload at L2. From a pure mass in LEO perspective asteroid mining breaks even when 20 tonnes is extracted in cis-lunar space.

I am skeptical that SEP will provide the magic bullet that its boosters seem to think it represents. The problem is I don't see how it scales well. E.g., moving 1,000 mT with 20 mT propellant. What is everything?

What is the Isp?
What is the delta v?
What is the trust-weight ratio?
What is the propellant?
What is wattage?
What is the area of the solar array?
What is the dry mass?
What is the plan to deal with the torques that come with trying to rotate, and then stop rotating a 1 to 4 square kilometer array?
...

A square kilometer array? When did Planetary Resources EVER mention something on that scale? (Essentially, they haven't ever done that. Such an array would be about a thousand times greater power than they've said they wanted.)

But actually, if you're really interested in the answers, I could answer all of them for you. Not that hard.

I have a feeling you're not that interested in the answers, though. You've employed the most annoying debate tactic, which is just to ask a butt-load of questions, so many that it'd be incredibly time-consuming for anyone to respond to them all. I could do the same thing, and but it'd be pointless.

These are just basic systems engineering questions which depend greatly on the details of the architecture, but most of the answers can be found here (though this is a more expensive way of doing this mission and I'm sure PR would end up doing something a little different): http://kiss.caltech.edu/study/asteroid/asteroid_final_report.pdf

The capabilities of SEP improve continually as technology progresses, thus the optimal Isp is constantly improving, unlike chemical rocket engine technology which hasn't really progressed in the last 30-40 years.

I do agree with your point about difficulty of extraction. That's a big question mark (and yes, it's still a big question for lunar exploitation as well).

And FWIW, SEP helps lunar exploitation as well.

PS, I appreciate your passion for lunar exploitation.

[Warren Platts]

The orbital refinery is somewhat necessary for lunar mining.

I respectfully disagree. If you mine on the Moon, you will do most of the refining on the Moon. If you're going for propellant, you refine LH2/LO2 and ship that. If you're going for Au or Pt, you produce gold and platinum bars--these wouldn't need to be "4-nines" pure (i.e., 99.99%), but they would be recognizable gold or platinum bars. Transportation costs are simply too high.

Although some respectable people (notably Spudis and Lavoie) suggest shipping plain water to orbit from the Moon and then processing it into LH2/LO2 in orbit, I can't see how much can be gained by doing that, since it will be necessary to produce propellant on the Lunar surface anyways in order to ship the plain water to orbit. Since a cracking and cryocooling plant designed for a weightless environment would be radically different from one made to operate in gravity, you're doubling your development costs for no good reason: yes, there is boil-off, but at L1/L2 the boiloff is less than the station keeping requirements so that is a non-issue. Meanwhile, if you're sending plain water, you've got freezing water pipes to deal with.

Once the depot exists at EML1/2, one then brings power, personnel, refining equipment to EML1/2, and then...drops it down into the gravity well?  And then builds a refinery in a gravity well?

Yep. The landers described in the ULA papers would be capable of landing 20 to 25 mT chunks of specialized cargo (about as much as can be hauled by a single semi-truck trailer).

[neilh]

Wow, just a couple weeks ago I never would have guessed that asteroid mining would surpass both SLS and commercial crew as the most heavily-debated topic on this forum.

Interesting times.

[MikeAtkinson]

The Lunar environment seems less hospitable to mining as well. The best deposits seem to be in permanently shaded craters, which complicates water extraction. Lunar dust is very abrasive. A four week day night cycle gives great temperature extremes and makes use of solar power difficult.

This reflects an unfortunately typical misunderstanding of the Lunar ice deposits. Granted, the permashaded craters are among the coldest places in the solar system, but we already have materials in hand that can handle it, like certain nickel-iron alloys made by Inconel and Incolloy.

Finding a material that can cope is <1% of the problems solved. If I had thought that finding alloys that can cope with low temperatures were a problem then I would have said so.

Moreover, in the polar regions, the temperature extremes are pretty mild. There are quasi-permanently plateaus in the polar regions that are illuminated 80% of the time or more. There the temperature stays a relatively balmy minus 50 degrees, plus or minus 10, all year round.

But these are not the places where the ice is are they? Sun-lit plateaus are not permanently shaded craters, some are within 10km of each other I believe.

As for Lunar dust being abrasive, (a) that's no different from the dust that results from hard rock mining operations on Earth;

Every serious study I've seen says lunar dust is almost uniquely abrasive and point to dust mitigation being a significant problem.

(b) there's no reason to think that asteroidal dust is any less abrasive.

Yes, there is, we have samples, Carbonaceous Condrites are much softer and less abrasive than lunar dust.

[sdsds]

Wow I am stunned by the current poll results:

Asteroids (51% chance or better)    25 (43.1%)
The Moon (51% chance or better)    10 (17.2%)
Neither    4 (6.9%)
It's a coin flip (50% chance for both)    19 (32.8%)
Total Voters: 58

I voted Moon, because the robotic, zero-g manipulation of materials which would be needed to create (non-token) quantities of anything from asteroids seems difficult to engineer. Gravity is apparently under-rated among NSF forum contributors!

[MikeAtkinson]

I voted Moon, because the robotic, zero-g manipulation of materials which would be needed to create (non-token) quantities of anything from asteroids seems difficult to engineer. Gravity is apparently under-rated among NSF forum contributors!

Extracting water vapor out of a gas is something we already do routinely in zero-g.

There are several methods that could be used, I'll let those more experienced that myself say which is best.

I suspect the same method(s) will be equally effective on the moon.

[Archer]

My real point is that extracting the ore is probably more difficult and we have less understanding of that part.

Rectification definitely would work. I'm not saying that it is the easiest/cheapest approach, it's just the first idea that I thought of.
I'am sure that something more optimal can be developed, though I'd love to create a machine that evaporates gold and platinum

For non-metals simple separator will do the trick. As far as I remember dust in zero-G behaves like liquid in normal conditions.

[Warren Platts]

1. My understanding is, on Earth, all the heavy metals were drawn to the core while the planet was still molten. What we mine on the surface was deposited by asteroids and comets after the crust hardened. I assume the same thing happened on the Moon. Might as well get the good stuff from the source.

Two points:

A. It's not necessarily the case that all of the Moon's heavy, siderophile elements sank to its core: the recent "Big Splat" theory hypothesizes that a second moon formed contemporaneously at one of the Moon's Trojan points. There it would have been dynamically stable for up to 10's of millions of years:

Companion moons are a common outcome of simulations of Moon formation from a protolunar disk resulting from a giant impact, and although most coplanar configurations are unstable, a ~1,200-km-diameter moon located at one of the Trojan points could be dynamically stable for tens of millions of years after the giant impact. Most of the Moon’s magma ocean would solidify on this timescale, whereas the companion moon would evolve more quickly into a crust and a solid mantle derived from similar disk material, and would presumably have little or no core. Its likely fate would be to collide with the Moon at ~2–3 km s−1, well below the speed of sound in silicates. According to our simulations, a large moon/Moon size ratio (~0.3) and a subsonic impact velocity lead to an accretionary pile rather than a crater, contributing a hemispheric layer of extent and thickness consistent with the dimensions of the farside highlands.

So it is likely that the farside is enriched with heavy metals compared to the nearside sampled by the Apollo missions.

B. The Moon has concentration mechanisms that don't exist on asteroids. The phenomenon whereby volatiles are concentrated in the polar cold traps is well known. Thus, it was extremely surprising that the LCROSS results reported high concentrations of metals such as zinc, manganese, vanadium--and gold. (Silver peaks were also prominent.) Gladstone et al. reported an upper limit of Au of 0.2% by weight (2,000 g/t); this is an extremely--I repeat--extremely high concentration of gold, and is very hard to believe, as a quick BOTE shows:

Apollo 12 (IIRC) samples of pristine rocks had average Au concentrations of around 5 ppb, whereas core samples of regolith showed an average of around 2 ppb. That leaves 3 ppb unaccounted for.

Now, when daylight/nighttime boundary (the "terminator") moves slowly around the moon, it causes a big electrical field with some high voltages, which causes the well known phenomenon of electrostatic dust movement. What is less appreciated is that this electrical field will then separate out any tiny particles of native metals. This process of electrostatic separation is well-known technique in the mining industry for separating out metals. Presumably, such particles would be accelerated to high speeds and travel ballistically until they landed somewhere, where they would be relaunched again and again, until they landed in one of the polar cold traps, where, since the Sun doesn't shine there, they would get trapped and concentrated.

So, the Moon's area is 3.8 x 10¹³ m². If the average depth of regolith is 10 m, and if regolith density is 2,000 kg/m³, then mass of gold liberated is 3.8 x 10¹⁴ m³ * 2,000 kg/m³ * 3 x 10^-9 = 2.3 x 10⁹ kg Au. If the area of the cold traps is 3.7 x 10⁹ m², then 0.6 kg Au/m² should have been deposited in the polar cold traps. If this amount of Au happened to be concentrated in the top two meters of regolith (about the depth that LCROSS sampled), that would be 0.6 kg Au / 4,000 kg regolith = 150 g/t (ppm).

150 g/t is huge by Earthly standards, but given the number reported by Gladstone et al., one is tempted to wonder if some other mechanism is at work that could produce higher concentrations than 150 g/t. Thus, lately I've been thinking that the Big Splat could provide a source rock that would jack up the concentration.

According to this geologist (Bernard Wood), there is enough gold in the Earth's core to cover the surface of the Earth to a depth of 1.5 feet (about half a meter). If you crunch the numbers, this works out to an average concentration of Au over the entire Earth of 0.75 g/t. Since the hypothesized Trojan moon would have formed during the giant impact, and since it was presumably relatively undifferentiated, and since it formed a carapace on the Lunar farside, then in theory, pristine rocks found on the Lunar farside could have a similar Au concentration of 0.75 g/t.

Assuming a similar 60% of this in the farside regolith were liberated due to electrostatic separation, then 10 m * 1.9 x 10¹³ m² * 2,000 kg/m³ * 0.75 x 10^-6 * 60% = 1.7 * 10¹¹ kg Au. If the cold trap area is 3.7 x 10⁹ m², then 46 kg/m² should have been deposited. Assuming the regolith in the cold traps is 10 m, and the Au uniformly distributed, then the predicted Au concentration would be (1.7 * 10¹¹ kg Au) / (3.7 x 10¹⁰ m³ * 2,000 kg/m) = ~2,300 g/t (ppm) which actually matches the reported LCROSS results of ~2,000 g/t (ppm) quite nicely. Compare this to the 80 g/t Pt found in a tiny minority of meteorites.

Thus, in other words, both theory and empirical data suggest that a single cubic yard of regolith from polar cold traps is worth on the order of $200,000 USD. Moreover, this is the gold market we are talking about, which is worth more than PGM's on a per kilgram basis, and is about an order of magnitude larger in terms of annual production and sales, so that a potential market on the order of $100B/year for a Lunar gold mining op would be possible without depressing the price of gold too much.

Thus, in terms of concentration of ore and absolute market size, when it comes to precious metals, the Moon beats asteroids hands down! (IMO YMMV)

2. Much less gravity well to soak up profit.

As the LCROSS results showed, there is also water in the polar cold traps. I've ran the numbers, and enough water would be produced in the process of mining gold to send the gold all the way back to Earth fully propulsively.

Rooting for both to succeed however!

Same here!

[go4mars]

The Moon has concentration mechanisms that don't exist on asteroids. The phenomenon whereby volatiles are concentrated in the polar cold traps is well known... As the LCROSS results showed, there is also water in the polar cold traps.

Why couldn't an asteroid (Ceres for example) also have polar cold traps? 

[Warren Platts]

But these are not the places where the ice is are they? Sun-lit plateaus are not permanently shaded craters, some are within 10km of each other I believe.

The floor of Whipple crater is less than 10 km from its north rim which is a big plateau of quasi-permanent illumination. The ore will be brought up on trucks like in conventional mines on Earth.

As for Lunar dust being abrasive, (a) that's no different from the dust that results from hard rock mining operations on Earth;

Every serious study I've seen says lunar dust is almost uniquely abrasive and point to dust mitigation being a significant problem.

The reason Lunar dust is relatively abrasive is because there is no weathering processes on the Moon, so the grains don't get much of a chance to round their edges. Hard rock mining on Earth must face similar difficulties: you're blasting into solid granite, dust is generated, it's not weathered, therefore, it is going to be abrasive, like Lunar dust is. Yet, somehow, Earth mining companies manage to deal with it and make profits.

(b) there's no reason to think that asteroidal dust is any less abrasive.

Yes, there is, we have samples, Carbonaceous Chondrites are much softer and less abrasive than lunar dust.

A chondrite is a meteorite that's fallen to Earth. Therefore, it doesn't have much to say about the dust that cloaks most sizable asteroids.

[LegendCJS]

1. My understanding is, on Earth, all the heavy metals were drawn to the core while the planet was still molten. What we mine on the surface was deposited by asteroids and comets after the crust hardened.

Almost correct, but not entirely accurate.  Elements that were heavy  and that do not naturally form compounds with lighter elements were indeed drawn to the core during planetary differentiation.  But many heavy elements such as iron, uranium,... often bond with light elements making molecules that have low density, keeping them in the crust. 

The PMG elements aren't very friendly with light weight elements, so they were removed from the Earth's crust during differentiation.  In fact the density stratification process that sent Earth's natural PMG supply to the core is the same concentration mechanism that makes them so present in iron meteorites/ asteroids.  These asteroids are the remnants of the differentiated cores of failed planetesimals.

Thus iron asteroids are the direct outputs of natures only known concentration mechanism for PMG elements.