Plans for asteroid mining

Arch2008

The trick is to create an industry to do this as you go. We already know how to launch spacecraft to NEO. Build a small fleet of more efficient Shuttle 2.0 craft and pay for the trips by carrying commercial satellites to orbit. The first missions also carry the modules of a modest space station where the deep space vehicles will be assembled by crewmembers. The space station could also have a space tourism hotel module to pay for itself. The booster pods for the now defunct shuttles were perfect for these kinds of constructs but were foolishly allowed to burn up upon re-entry. So the bottom line start up cost is relatively low and doesn’t require any new technology.

Next, a simple group of automated probes go do a recon of which asteroids you should mine first. This survey would then be followed by a larger probe that nudges the target asteroid into NEO where the raw materials are extracted. The probe could use pellets made from material on the asteroid itself and shot out of a rail-gun on the probe to provide the thrust. A solar sail could deploy the probe to the asteroid, so once again, low cost and existing tech. Silicon from the Moon can be fused in solar powered kilns on the space station to make ceramic re-entry tiles. A simple re-entry pod could be constructed in orbit and used once per cargo load sent to Earth. The tiles might even be sold as souvenirs, since they were “Moon rocks”. As the asteroid u-haul process gains momentum, more ambitious programs could be funded. Once it starts, there’s really no reason to stop at one trillion dollars. A ten mile diameter nickel-iron asteroid has more ore on it than has been mined on Earth in all of history.

Spaceward ho!

D H

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.

Ryan_m_b

AKA near-verbatim reiterations of the Mars Trilogy

Higgs Boson

Sooooo ... exercising one's imagination is verboten around here, these days, Delta Hotel?

redrum419_7

Apparently so.

Ryan_m_b

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

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

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

No. Nobody sane is discussing the concept of de-orbiting an asteroid. Think about it.

SHISHKABOB

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

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

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

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 m_i, final mass m_f, effective exhaust velocity v_e, and velocity change v:

v = v_e * log(m_i/m_f)

Relation to specific impulse: v_e = I_sp*g_E, where I_sp is the specific impulse, and g_E 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)*g_E.

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

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

It will take a Dutch metallurgical genius to solve this problem. Someone who loves goooooold.

Aidyan

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

remind me of how much asteroid was left after the Tunguska event