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Plans for asteroid mining

by thorium1010
Tags: asteroids, google, mining space, ross perot
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Ryan_m_b
#37
Apr25-12, 04:08 PM
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Quote Quote by D H View Post
This thread (and this site) is not the place for fanciful scifi dreams.
AKA near-verbatim reiterations of the Mars Trilogy
Higgs Boson
#38
Apr26-12, 10:34 PM
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Quote Quote by D H View Post
The subject of this thread, Planetary Resources, is not talking about mining nickel or iron. Mining nickel or iron simply is not feasible yet, and won't be for a long, long time.

This thread (and this site) is not the place for fanciful scifi dreams.
Sooooo ... exercising one's imagination is verboten around here, these days, Delta Hotel?
redrum419_7
#39
Apr27-12, 01:14 AM
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Quote Quote by Higgs Boson View Post
Sooooo ... exercising one's imagination is verboten around here, these days, Delta Hotel?
Apparently so.
Ryan_m_b
#40
Apr27-12, 03:16 AM
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Quote Quote by redrum419_7 View Post
Quote Quote by Higgs Boson View Post
Sooooo ... exercising one's imagination is verboten around here, these days, Delta Hotel?
Apparently so.
Of course not, speculation and imagination are welcomed. So long as they stay within the rules. Arch's post would have been acceptable if he backed anything he said up with some actual science to validate his points rather than just wishy-washy SF claims. For example: what are the potential candidates for a space shuttle replacement and is there a business argument for their production? Could a single space tourist module on a small space station pay for the program? What are the energy costs of propelling large fuel tankers to space and how are they suitable for space craft construction? etc etc etc.
lpetrich
#41
Apr27-12, 10:59 PM
P: 518
Asteroid mining? Seems like a nonstarter. I seriously suspect that there won't be much by way of ore deposits in the asteroid belt, because of the lack of geological activity in most asteroids. To see why, let's review how how ore bodies form. Geologists have now gotten a good understanding of that, and we can use that understanding to see what one can expect of elsewhere.

Ore genesis - Wikipedia
Processes of Ore Formation
  • Fractional crystallization of magma bodies.
  • Sorting of immiscible components of magma bodies.
  • Hydrothermal processes: water dissolving some minerals in hotter rocks and those minerals precipitating out in cooler rocks.
  • Diffusion of minerals into cracks and the like ("lateral secretion").
  • Precipitation from bodies of water, like salt being left behind when water evaporates.
  • Mechanical sorting.
  • Being left behind by other materials getting leached away by water flowing through.
  • Release by volcanoes.
Most of these processes require liquid water, and only the Earth and Mars have such processes near their surfaces. There is even some evidence of such processes on Mars, in the form of evidence of carbonates and sulfates.

So we are stuck with igneous processes, rock melting. By the square-cube law, only a relatively large object can have such processes, so have any asteroids had them? The evidence, surprisingly, is yes. Certain meteorites, the "HED meteorites", have spectra similar to Vesta's surface, meaning that they likely came from Vesta.


So the smaller asteroids are unlikely to contain useful ores, except perhaps if they are fragments of some larger one that had had magma differentiation.


One could get the rarer elements by chewing through large quantities of asteroid, but it would be cheaper to do that with Earth rocks or seawater. But there *might* be some elements where mining asteroids might be worthwhile: the rarer "siderophiles". These are elements with a chemical affinity for iron, like gold and the platinum-group elements. The Earth's crust is depleted in them relative to stony and especially to iron asteroids, so one could mine gold by chewing through some iron asteroids.
Goldschmidt classification - Wikipedia
Mineralogy Notes 3
Abundances of the elements 3.1.3
Aidyan
#42
Apr29-12, 02:30 PM
P: 92
But would it not be less costly to mine a very small asteroid (say only few dozens of meters wide) ON Earth than mining it in space? One has to de-orbit it, splash it into the ocean and retrive it. Then we can mine it easily at home. Obviously safety is the big issue here, if it wrongly hits a city it is a disaster. But I think atmospheric reentry is a complex but not impossible science.
D H
#43
Apr29-12, 03:34 PM
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Quote Quote by Aidyan View Post
But would it not be less costly to mine a very small asteroid (say only few dozens of meters wide) ON Earth than mining it in space? One has to de-orbit it, splash it into the ocean and retrive it.


No. Nobody sane is discussing the concept of de-orbiting an asteroid. Think about it.
SHISHKABOB
#44
Apr29-12, 04:08 PM
P: 614
basically: you'd need A LOT of energy to take something going many km/s and slow it down to zero along with the energy needed to compensate for gravitational potential energy

it'd be silly
thorium1010
#45
Apr30-12, 11:09 AM
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Quote Quote by D H View Post


No. Nobody sane is discussing the concept of de-orbiting an asteroid. Think about it.
It maybe a silly/insane question .why is it impossible to bring small asteroids back to earth?
would it destabilise the asteroid belt or we cannot control the velocity it enters earths atmosphere. Or the energy required is too great for it to viable.
SHISHKABOB
#46
Apr30-12, 12:48 PM
P: 614
Quote Quote by thorium1010 View Post
It maybe a silly/insane question .why is it impossible to bring small asteroids back to earth?
would it destabilise the asteroid belt or we cannot control the velocity it enters earths atmosphere. Or the energy required is too great for it to viable.
it's because you're talking about taking a GIGANTIC ROCK from *space* to the *ground* without it just crashing and blowing some stuff up

we don't even have our spacecraft re-enter the atmosphere at slow speeds. How do you suggest we give an asteroid a "soft landing"? It's a totally unpractical idea.

also: no it wouldn't destabilize the asteroid belt, the only thing stabilizing the asteroid belt is the sun
lpetrich
#47
Apr30-12, 09:07 PM
P: 518
It's possible to work out the numbers -- soft-landing an asteroid is TOTALLY impractical. Let's see what one needs to do.

-

This asteroid will be accelerated by the Earth's gravity, and when it reaches the Earth's atmosphere, it will be traveling at a little over the Earth's escape velocity, about 11.2 km/s. How much propellant will one need to consume to soft-land it?

Over a century ago, Konstantin Tsiolkovsky showed how to find how much. His rocket equation, for initial mass mi, final mass mf, effective exhaust velocity ve, and velocity change v:

v = ve * log(mi/mf)

Relation to specific impulse: ve = Isp*gE, where Isp is the specific impulse, and gE is the acceleration of the Earth's gravity at its surface, about 9.81 m/s^2.

So to avoid consuming much more propellant than asteroid, the rocket must have an exhaust velocity more than the Earht's escape velocity.

-

The asteroid must be supported by the rocket engines as it makes its landing. That requires that the thrust be greater than (asteroid mass)*gE.

So for a thousand-ton asteroid, that requires a thrust of a million kilograms-force or 10 million newtons. Bigger asteroids require more thrust, of course. I won't get into English-system mass and force units.

-

So let's see what's available. Spacecraft propulsion - Wikipedia has a big compendium of numbers in its "Propulsion methods" table, and Wikipedia's articles on various rocket engines often list the engines' numbers.

The highest-thrust engines that have been successfully run are chemical-combustion ones, at 1 to 2 million newtons, and hydrogen-oxygen ones can get about 4.5 km/s of exhaust velocity. Ones with non-cryogenic propellants can get as much as 3 km/s. Because of the nature of their energy sources, it's difficult to get much more exhaust velocity than that.

So they are unsuitable.

One can get more energy per unit mass with nuclear reactions, and thus greater exhaust velocity, but there are problems here also. A nuclear reactor heating hydrogen can get around 9 km/s or thereabouts, which is still too low to be suitable. It cannot get much more than that without melting the reactor. Nuclear-bomb propulsion can get greater exhaust velocity, but it has certain other problems. Inertial confinement fusion would also get high exhaust velocity, but that mechanism has yet to produce energy breakeven in the lab.

So they are unsuitable also.

In contrast to these thermal systems, there are various nonthermal propulsion systems, like ion engines, that are in various stages of development. The Dawn spacecraft, currently at Vesta, has 3 ion engines, each with exhaust velocity 30 km/s and thrust 0.09 newtons. Most other nonthermal engines have similarly low thrust.

These are still more unsuitable ones.

So there's no way that soft landing an asteroid is going to work.
Higgs Boson
#48
Apr30-12, 10:37 PM
P: 10
Quote Quote by lpetrich View Post
So there's no way that soft landing an asteroid is going to work.
Unless someone engineers a really big catcher's mitt.

(Sorry, had to throw a little humor in there.)

Seriously though, from what I have read it appears to me, (and this remains no less feasible imho), that their intention is to manipulate said asteroid into some sort of orbit where it may be mined in space.

It is pie in the sky scifi though, I agree.
Antiphon
#49
Apr30-12, 11:55 PM
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It will take a Dutch metallurgical genius to solve this problem. Someone who loves goooooold.
Aidyan
#50
May1-12, 12:34 AM
P: 92
Why making things complicate? De-orbit slightly a NEO asteroid between the Earth and the Sun so that it takes the path towards Venus (not much thrust needed for that), 'aereobrake' it in Venus' atmosphere such that inserts itself into a synchronous orbit with the Earth + a component for Venus-Earth orbit transferal, and then, once it reaches Earth (at zero orbital velocity) let the thing simply fall freely and splash somewhere in a safe place in the ocean. It would be something like a Tunguska event, but at thousands of miles away from any inhabitated region. Maybe there is a problem with a Tsunami wave, but I think that if the asteroid is not too big, it will not harm. So, why not?
SHISHKABOB
#51
May1-12, 12:37 AM
P: 614
Quote Quote by Aidyan View Post
Why making things complicate? De-orbit slightly a NEO asteroid between the Earth and the Sun so that it takes the path towards Venus (not much thrust needed for that), 'aereobrake' it in Venus' atmosphere such that inserts itself into a synchronous orbit with the Earth + a component for Venus-Earth orbit transferal, and then, once it reaches Earth (at zero orbital velocity) let the thing simply fall freely and splash somewhere in a safe place in the ocean. It would be something like a Tunguska event, but at thousands of miles away from any inhabitated region. Maybe there is a problem with a Tsunami wave, but I think that if the asteroid is not too big, it will not harm. So, why not?
remind me of how much asteroid was left after the Tunguska event
Aidyan
#52
May1-12, 12:46 AM
P: 92
Quote Quote by SHISHKABOB View Post
remind me of how much asteroid was left after the Tunguska event
It was too small. Choose an asteroid with the right size.
D H
#53
May1-12, 07:30 AM
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Quote Quote by Aidyan View Post
Why making things complicate? De-orbit slightly a NEO asteroid between the Earth and the Sun so that it takes the path towards Venus (not much thrust needed for that),
Do the math. A lot of thrust is needed for that.

'aereobrake' it in Venus' atmosphere such that inserts itself into a synchronous orbit with the Earth + a component for Venus-Earth orbit transferal, and then, once it reaches Earth (at zero orbital velocity)
Zero orbital velocity? Try again. That meteor will hit the Earth's atmosphere with a speed of 13.7 kilometers per second.

let the thing simply fall freely and splash somewhere in a safe place in the ocean. It would be something like a Tunguska event, but at thousands of miles away from any inhabitated region. Maybe there is a problem with a Tsunami wave, but I think that if the asteroid is not too big, it will not harm. So, why not?
Maybe? There is a huge problem with a tsunami. There is also a huge problem with the asteroid breaking up in the atmosphere. If the asteroid is 100% gold, that breakup is definitely not a desirable outcome. There is also a huge problem with the impact. Water is downright solid to an object hitting it at 13+ km/s. Whatever is left of the asteroid after the atmospheric breakup will most likely vaporize.

If the asteroid is iron/nickel there isn't enough value to pay back the huge cost of your maneuvers. Iron and nickel are too cheap. You need something extremely valuable to justify bringing the outputs of space mining down to Earth. Even gold and platinum are dubious. If this is done, it won't be accomplished by splashing the asteroid in the ocean. It will be accomplished instead by mining the asteroid in space and carrying the precious cargo as payload in a vehicle designed for re-entry.

There is potential future value in iron/nickel asteroids, but that value would be realized by mining the asteroid in space and utilizing the resultant resources in space. That requires an in-space manufacturing capability. This might happen eventually, but that is not the subject of this thread.
SHISHKABOB
#54
May1-12, 08:59 AM
P: 614
Quote Quote by Aidyan View Post
It was too small. Choose an asteroid with the right size.
bigger asteroid means bigger impact event

we don't want big impact events


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