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Practically getting an asteroid full of platinum down to Earth


SomeGuy12

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I would separate the metals in orbit. Fashion an aerodynamic cone, like a capsule, of the cheapest materials, knowing they would ablate/melt to a certain degree and not care... Put the precious metals on the inside... And bolt on some standard automatic parachutes.

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-Develop a spray-on ablative heat shield

-Capture the asteroid into earth orbit. Doesn't have to be a particularly close orbit, just enough to give us some time. You'd need anything from 100 to 400 m/s of delta-V, depending on the asteroid in question. This means you need about 0.5 to 1% of the asteroid's mass in fuel, if you are using a high-efficiency engine, like a VASIMR or nuclear salt water rocket.

-Put in a small industrial facility on the asteroid. Either chunk up the asteroid, or refine the precious metals out of it, whichever is more cost-effective. Coat the chunks in ablative shielding, and fire them back to earth using a magnetic railgun.

However, I'm guessing your margins on this are not going to be great.

Edit: 20% enriched uranium costs about $25/gram, which means a 2% solution used for fuel in a NSWR will cost 50c/gram, or $500/kg. That's without adding the $5000-odd per kg it would currently take to put it in earth orbit, so we're already presupposing ISRU, and that the water is essentially free of charge.

You would need 1kg of fuel to put 200kg of asteroid in earth orbit, assuming an ISp of 5,000 and a delta-V requirement of 200 m/s.

Platinum costs about $30,000/kg.

To even recoup your fuel costs, you would need the asteroid contain 0.0085kg of platinum per 100kg of mass. This is 85ppm.

Most estimates I've seen put the best-case scenario at between 90 and 200ppm for platinum-group metals in the most lucrative asteroids.

So before you even take into account the R&D, production, mission control, cost of extraction, recovery of the precious metals, you are talking about blowing 50% of your budget just buying fuel to put your asteroid in an extremely high earth orbit.

I don't think we're going to make a profit on this any time soon.

Edited by peadar1987
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-Develop a spray-on ablative heat shield

-Capture the asteroid into earth orbit. Doesn't have to be a particularly close orbit, just enough to give us some time. You'd need anything from 100 to 400 m/s of delta-V, depending on the asteroid in question. This means you need about 0.5 to 1% of the asteroid's mass in fuel, if you are using a high-efficiency engine, like a VASIMR or nuclear salt water rocket.

-Put in a small industrial facility on the asteroid. Either chunk up the asteroid, or refine the precious metals out of it, whichever is more cost-effective. Coat the chunks in ablative shielding, and fire them back to earth using a magnetic railgun.

However, I'm guessing your margins on this are not going to be great.

Edit: 20% enriched uranium costs about $25/gram, which means a 2% solution used for fuel in a NSWR will cost 50c/gram, or $500/kg. That's without adding the $5000-odd per kg it would currently take to put it in earth orbit, so we're already presupposing ISRU, and that the water is essentially free of charge.

You would need 1kg of fuel to put 200kg of asteroid in earth orbit, assuming an ISp of 5,000 and a delta-V requirement of 200 m/s.

Platinum costs about $30,000/kg.

To even recoup your fuel costs, you would need the asteroid contain 0.0085kg of platinum per 100kg of mass. This is 85ppm.

Most estimates I've seen put the best-case scenario at between 90 and 200ppm for platinum-group metals in the most lucrative asteroids.

So before you even take into account the R&D, production, mission control, cost of extraction, recovery of the precious metals, you are talking about blowing 50% of your budget just buying fuel to put your asteroid in an extremely high earth orbit.

I don't think we're going to make a profit on this any time soon.

Yea, LEO is not the place to mine asteroids.

If you can mine in solar orbit, however, you can use dross material and foam it into a heatshield for the payload, do a slight course correction for earth intercept, and aerobreak the cargo into an earth capture orbit.

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What about feeding dust from the asteroid to a rotor arm that would eject it a high velocity (this idea isn't original with me, btw; IIRC I first saw it in Gerard O'Neil's book 'The High Frontier'), poweredby solar power, or a nuclear theraml generator (or both)? If you've got a mining and ore processing unit there then you've already got something that can crush rocks, so anything that isn;t teh desired material (in this case platinum) can be reaction mass.

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What about feeding dust from the asteroid to a rotor arm that would eject it a high velocity (this idea isn't original with me, btw; IIRC I first saw it in Gerard O'Neil's book 'The High Frontier'), poweredby solar power, or a nuclear theraml generator (or both)? If you've got a mining and ore processing unit there then you've already got something that can crush rocks, so anything that isn;t teh desired material (in this case platinum) can be reaction mass.

It's hard to get stuff like that up to a reasonable speed, which means your ISp is going to be rubbish: https://what-if.xkcd.com/85/

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It's hard to get stuff like that up to a reasonable speed, which means your ISp is going to be rubbish: https://what-if.xkcd.com/85/

Granted, but that was talking about getting a dv of about 3km/s. IIRC there are rocks out there that might be of interest where you wouldn't need so much dV to get them captured by the Earth-Luna system. What I am not sure of is what's the minimal amount of dV you'd need in order to be useful, bearing in mind a very large reaction mass supply, nor whether a rock/dust flinger could realistically achieve that much.

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Break the asteroid into pieces that are small enough not to cause significant damage, but big enough so they survive mostly intact when entering the atmosphere, and alter their trajectory so they crash in a desert somewhere. Then it's just a matter of locating the stuff, loading it onto a truck and taking it to a reprocessing facility.

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