Mine those asteroids: Strathclyde team finds easy 12

Aug 13, 2013 by Nancy Owano report
Schematic representation of the four categories of motion near the L2 point (represented by the set of axes in the figure): periodic motion around L2 (i.e., halo orbit), hyperbolic invariant manifold structure (i.e., set of stable hyperbolic invariant manifold trajectories), transit trajectory and non-transit trajectory. Credit: arXiv:1304.5082 [math.DS]

(Phys.org) —Researchers at the University of Strathclyde in Glasgow have identified twelve easily retrievable objects among the population of near earth objects (NEOs). In their paper published this month in Celestial Mechanics and Dynamical Astronomy, authors D. García Yárnoz, J. P. Sánchez, and C. R. McInnes discuss the 12 asteroids that could be easily mined for valuable resources using existing spacecraft technology. Their article, "Easily Retrievable Objects Among the NEO Population," focuses on near earth objects, about which other researchers tend to discuss in terms of the threats these pose in destruction. Authors of this paper, however, are concerned about being able to harness the positive benefits if the objects can be successfully exploited.

"Asteroids and comets are of strategic importance for science in an effort to understand the formation, evolution and composition of the Solar System. Near-Earth Objects (NEOs) are of particular interest," they said, "because of their accessibility from Earth, but also because of their speculated wealth of material resources."

While they are not the first team to talk about how NEO resources may be exploited, the authors are pointing out that, out of these NEOs, they can identify a family of EROs—Easily Retrievable Objects. These EROs can be transported from "heliocentric orbits into the Earth's neighborhood at affordable costs." The problem to transfer an to an Earth or Moon centered can be decoupled into the initial phase of inserting the asteroid into a stable invariant manifold, they said, and then provide the maneuvers required to continue the transit into the Earth system.

The Strathclyde team searched through a database of about 9,000 NEOs for candidates and they found 12 that could be retrieved by changing velocity by less than 500 meters per second.
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The authors said that the approach they would use for retrieval may also serve as a robust search and ranking methodology for future retrieval candidates that can be automatically applied to the growing survey of NEOs. "The possibility of capturing a small NEO or a segment from a larger object would be of great scientific and technological interest in the coming decades," they stated. "It is a logical stepping stone towards more ambitious scenarios of asteroid exploration and exploitation, and possibly the easiest feasible attempt for humans to modify the Solar System environment."

As MIT Technology Review pointed out in discussing their findings, "None of the 12 ERO asteroids are new to astronomers; in fact one of them became briefly famous when it was found to be temporarily orbiting the Earth until 2007. But until now nobody had realized just how easily these bodies could be captured."

The authors of the article stated that "The paper presents a list of 12 EROs, with a total of 25 trajectories to periodic orbits near L2 and 6 near L1 below a cost of 500 m/s, and the number of these objects is expected to grow considerably in the coming years."

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More information: Easily Retrievable Objects among the NEO Population, arXiv:1304.5082 [math.DS] arxiv.org/abs/1304.5082

Abstract
Asteroids and comets are of strategic importance for science in an effort to understand the formation, evolution and composition of the Solar System. Near-Earth Objects (NEOs) are of particular interest because of their accessibility from Earth, but also because of their speculated wealth of material resources. The exploitation of these resources has long been discussed as a means to lower the cost of future space endeavours. In this paper, we consider the currently known NEO population and define a family of so-called Easily Retrievable Objects (EROs), objects that can be transported from accessible heliocentric orbits into the Earth's neighbourhood at affordable costs. The asteroid retrieval transfers are sought from the continuum of low energy transfers enabled by the dynamics of invariant manifolds; specifically, the retrieval transfers target planar, vertical Lyapunov and halo orbit families associated with the collinear equilibrium points of the Sun-Earth Circular Restricted Three Body problem. The judicious use of these dynamical features provides the best opportunity to find extremely low energy Earth transfers for asteroid material. A catalogue of asteroid retrieval candidates is then presented. Despite the highly incomplete census of very small asteroids, the ERO catalogue can already be populated with 12 different objects retrievable with less than 500 m/s of {Delta}v. Moreover, the approach proposed represents a robust search and ranking methodology for future retrieval candidates that can be automatically applied to the growing survey of NEOs.

via Arxiv Blog

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antialias_physorg
3.3 / 5 (7) Aug 13, 2013
500 m/s seems an awful lot of momentum needed given the mass of an asteroid (OK, there's no rush so using solar sails that is probably doable within the foreseeable future)

Question is: Do these asteroids really contain valuable minerals to mine (in significant quantities to make it worth the expense of retreiving them) or are they just rocks?
The paper talks about diameters 2-30meters and 10E6kg masses (is that worth it?). At one point it seems to demand propulsion methods orders of magnitude better than what we have today, but the conclusions state that this is within today's technological abilities (?).

In any case getting first hand experience with moving asteroid would be valuable. For the day when we need to move one away fom us.
Egleton
1.9 / 5 (9) Aug 13, 2013
Park them at L4 for building material later.
Don't waste their potential energy by dropping them down the gravity well.
tscati
1 / 5 (1) Aug 13, 2013
Now, was that 500 m/sec or 500 ft/sec he said? errrm....oops, bye-bye New York!
IMP-9
3.7 / 5 (3) Aug 13, 2013
500 m/s seems an awful lot of momentum needed given the mass of an asteroid.


If you did the math you would see that's only about 12 tonnes of propellant for a NEXT thruster. That is doable, probably multiple spacecraft are needed but it is not "orders of magnitude better than what we have today". If you read it the paper goes into some detail about this and how it's feasible.
antialias_physorg
3.7 / 5 (6) Aug 13, 2013
If you did the math you would see that's only about 12 tonnes of propellant for a NEXT thruster.

As they note in their article: that (the fuel alone) is already an order of magnitude heavier than the types of probes we're currently sending to those kinds of distances. So we're not talking about a cheap mission (i.e. several hundred million dollars).
And when all is said and done: moving the asteroid (with all the ancillary costs of mission control, capturing it and then mining/refining it) must be done. Then you need to calculate how much money you get out of it by selling the material to make it worth it.

Currently iron sells for 9-11ct per kg. The upper bound for their asteroids are 1000 tonnes. If all of that is 100% iron (and there is no reason to suspect that it is) than that would be worth 100000$ (under optimum conditions).
Looks like this is still missing 3 orders of magnitude to break even (not even considering risk of failure - which is large with space missions)
Aaron1980
2 / 5 (10) Aug 13, 2013
we can use them to protect the earth from NEOs found to be heading to strike earth. Rather than trying to fire things at them from the ground we can more easily change the trajectories of the EROs to knock the NEOs out of harms way. Cosmic Billiards anyone?
IMP-9
4.4 / 5 (5) Aug 13, 2013
that (the fuel alone) is already an order of magnitude heavier than the types of probes we're currently sending to those kinds of distances. So we're not talking about a cheap mission (i.e. several hundred million dollars).


But that's very different from "propulsion methods orders of magnitude better than what we have today". It's just a matter of fuel. The paper is not trying to sell asteroid mining. There is more than iron on an asteroid, I don't believe it is economically viable but that's not a fair assessment. Planetary resources estimate there is 25 to 50 billion dollars worth of platinum in a 30m of some types of asteroids. Their estimate is likely much higher than what could actually be extracted but there are other metals too, the point is there is scope.

Lastly they don't need to be talking about metals at all. One of the most interesting space mining efforts is extracting water for use in space. This is widely beloved to be economically sound.
javjav
4.5 / 5 (4) Aug 13, 2013
Currently iron sells for 9-11ct per kg.


The price of some materials on NEO is multiplied 1000 times what they cost on earth surface. Iron is a valuable material on orbit, but initially the most profitable material could be water ice, which is free of cost on earth surface but very valuable on orbit, where it can be split into Oxygen and Hydrogen and sold as fuel. Missions to moon and mars would be much affordable with these resources already available on earth obit.

Regarding the orbit insertion issue, it could be easy if we use part of the mass of the asteroid to produce ions for an ion engine (or electromagnetic gun) attached to it. Earth orbit insertion would take several years, but we would not need to bring fuel for it. Also useful for deep space missions. We would only need to improve the technology of these engines to be more flexible about their fuel, but apart from that it does not sound to be expensive.
antialias_physorg
3.6 / 5 (5) Aug 13, 2013
But that's very different from "propulsion methods orders of magnitude better than what we have today"

Since the NEXT thrusters haven't been used outside the lab one could argue that we don't have them yet. (Though they are cool, and I fully expect them to live up to expectations).
Planetary resources estimate there is 25 to 50 billion dollars worth of platinum in a 30m of some types of asteroids.

As I said: That's a very bold estimate based on no observation whatsoever. Currently we just don't know what largish asteroids are made of or what types of variability they show in their makeup. Certainly no pure platinum asteroids have impacted on Earth in the recent past for us to substantiate that kind of conjecture.

A science mission to probe/prod a few is in order before we think about moving/mining them - don't you think?
IMP-9
4.4 / 5 (5) Aug 13, 2013
NEXT thrusters aren't orders of magnitudes beyond what is in space today either.

That's a very bold estimate based on no observation whatsoever. Currently we just don't know what largish asteroids are made of or what types of variability they show in their makeup. Certainly no pure platinum asteroids have impacted on Earth in the recent past for us to substantiate that kind of conjecture.


Nobody is talking about pure platinum asteroids, and we can look at their make up from spectra and the numerous spacecraft that have visited them. Their estimate is almost certainly an exaggeration, yours is just as wrong. Nobody is going to space to bring back iron.
gopher65
2.5 / 5 (4) Aug 13, 2013
That's a very bold estimate based on no observation whatsoever. Currently we just don't know what largish asteroids are made of or what types of variability they show in their makeup.

The other thing to consider is that on Earth water slowly creates "veins" of material like platinum. We don't know if the differentiating forces on a small asteroid are great enough to achieve something similar... but probably not.

If that is the case, and the various materials that make up the asteroid are basically evenly distributed, mining will be a far more complex - though still ultimately achievable - process. Most people don't seem aware of this particular extraction difficulty.
TheGhostofOtto1923
2.7 / 5 (7) Aug 13, 2013
NEXT thrusters are flight-capable and are only awaiting the appropriate missions

"The NASA Evolutionary Xenon Thruster project at Glenn Research Center aims to build an ion thruster about three times as powerful as the NSTAR used on Dawn and Deep Space 1. By 2008, flight qualification models of the thruster were available."
missing 3 orders of magnitude to break even
-Compare that to the amount of money and effort already spent on learning how to confine and manipulate bulk plasmas in tokamaks.

These small rocks provide essential practice. By the time we are ready to move economically viable asteroids we should be pretty good at it. We should have the confidence that we can do it safely.

And we should know a lot more about how these things can be used as weapons, and how to counter that threat. Because it is a very serious threat indeed. One that rivals nuclear proliferation.

And like the promise of limitless power, the public may want to pay for limitless platinum.
Jeddy_Mctedder
1.5 / 5 (8) Aug 13, 2013
once the rough estimate of the minimum amount of inertia is established ----which also requires a specific and detailed calculation of those asteoids masses-----then a specific mechnism can be developed for providing this inertia at the highest impulse possible. my believe is a specific set of ion engines that are small , and lightweight, will be developed that can be anchored to the surface of the asteroid and provide the thrust required over time. those engines will probably not be very powerful, but they will be efficient.

the most optimal solution, thought probably impractical. is to develop a nuclear powered thruster capable of 'mining' the surface of the asteroid for propellant, further decreasing the initial weight cost of launching the mission from earths gravity well, and increasing the amount of propellant that will be available to provide thrust.

call this the 'lewis and clark' approach.
xX_GT_Xx
3 / 5 (4) Aug 13, 2013
Seems like a fun but thoroughly impractical thought exercise. So what if you can nab an asteroid? Now what?

Nobody answers that. "Mine it" they say. Yes, but how? What's the big plan to grind up a 30m asteroid in space?
kcameron
not rated yet Aug 13, 2013
It makes no sense to bring an asteroid to be mined in an Earth orbit. At most, one might expect a few percent of an asteroid to be valuable. If we ever mine extraterrestrial bodies, I'm sure we'll refine the minerals in place before sending them to Earth.
Restrider
2 / 5 (5) Aug 14, 2013
It makes no sense to bring an asteroid to be mined in an Earth orbit. At most, one might expect a few percent of an asteroid to be valuable. If we ever mine extraterrestrial bodies, I'm sure we'll refine the minerals in place before sending them to Earth.


As far as I know, certain types of asteroids contain far higher concentrations of heavier metals than Earth's crust and thus contain more valuable elements than you would find on Earth.

Furthermore, a few people seem to misconceive the entire idea behind space mining. Gathering metals, water and other elements in space could be used as sources for fuel (hydrogen/oxygen) or even as resources for an entire manufacturing industry in zero gravity in Earth's orbit. Essentially reducing the cost for space exploration, exploitation and even colonisiation significantly, since you would have to send far less mass into space.
TheGhostofOtto1923
1 / 5 (4) Aug 14, 2013
Seems like a fun but thoroughly impractical thought exercise. So what if you can nab an asteroid? Now what?

Nobody answers that. "Mine it" they say. Yes, but how? What's the big plan to grind up a 30m asteroid in space?
What makes you think that many scientists and engineers haven't seriously been studying this for a long time?
http://en.wikiped...d_mining

-And what makes you think that people would be looking for asteroids to mine if they didn't have an understanding based on research and study, that they very possibly COULD be mined?

And what makes you think you could post such a thoughtless comment without getting trashed for it?
antialias_physorg
5 / 5 (2) Aug 14, 2013
As far as I know, certain types of asteroids contain far higher concentrations of heavier metals than Earth's crust

It looks like the ideas for mining are still very vague. And the proposed mining mechanism on the wikipedia entry for asteroid mining sound less stellar in terms of efficiency and/or hardware availability - especially the more hardware intensive ways that would require fantastically maintenance-free mining gear.
Maintenance is traditionally a big issue for mining operations.

(And self-replicators? Seriously? I mean: yeah, great concept. But we're still a ways away from making self replicators on Earth with all available materials - let alone in space under harsh conditions and limited material availability)
TheGhostofOtto1923
1 / 5 (4) Aug 14, 2013
Well let's do a little more research. Here's a company with Branson as a member that is committing dollars to the effort:
http://www.planet...hnology/

-It will necessarily entail exploring the potentials on many fronts, which is what is happening; accessing, assaying, mining, processing, and moving, all of which depend on what is available and where it is.

'Self-replicators' initially may be factory units which produce purpose-built machines such as dozers, drillers, and haulers using local materials.

Per maintenance, we are already learning much about function and durability with landers and rovers. It may be more practical in some applications to turn out many disposable worker bots onsite.

But again I think that major govt concerns are with how easily space rocks can be used as weapons. Mining may VHS a convenient excuse for exploring this potential.

Will rogue govts have the potential to launch robotic probes to steer these things in 20 years? Most likely.
xX_GT_Xx
5 / 5 (1) Aug 15, 2013
And what makes you think you could post such a thoughtless comment without getting trashed for it?


Dunno. Call it optimism. Same thing that makes you think you have a different Wikipedia than I do.

Still no mention of how. Vaporize material? Dig a shaft? Hope that the asteroid is pebbly enough so you can just scoop up whatever's laying around? They can, and do, all that now, on Earth. Figure out a way to do it in microgravity.

Here's an experiment you could try: Fill a sock with dirt and swing it around your head in a nice, stable orbit. Now poke a hold in the sock so dirt dribbles out as you spin it, representing mining, i.e. altering the orbiting body's mass. What happens to your orbit?
Lurker2358
2 / 5 (4) Aug 18, 2013
antialias_physorg:

Rare Earths and precious metals are the only thing worth mining and bringing back to Earth. I also assumed the drop-pods for the extremely valuable metals were made in space from the iron or slag left-overs from the mining process.

Gold and Platinum are worth a lot more than Iron, but you are right, iron will never pay for itself.

What you need is each load needs enough Gold and Platinum to pay for it's costs, since they are lately fluctuating somewhere around $1600 per Troy ounce, which is tens of thousands of times more than Iron. Then maybe if you have left-over space put some other materials on it together.
TheGhostofOtto1923
1 / 5 (2) Aug 18, 2013
Still no mention of how
Still no indication that you did any research whatsoever. I know, it's easier just to make stuff up.

Lots of scientists and engineers have explored many options and you can read about some of their work on the Internet.
are the only thing swirth mining and bringing back to earth
Lurker forgets about helium 3. Lurker forgets about lots of stuff.

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