Your questions answered: asteroid mining
Our expert panel answers your questions on whether the costs and challenges of mining asteroids be overcome to create new space-based industries?
Mining asteroids for resources to sustain a space-based economy is a scenario taken straight from the pages of numerous science-fiction stories set in the distant future.
But several companies are hoping to literally launch this new industry within the next decade. We put your questions on just how such a grand plan might become a viable commercial reality to a panel of experts:
- Ian Crawford, professor of planetary science and astrobiology at Birkbeck, University of London, an expert on space exploration who has helped develop instruments to look for minerals on the moon.
- David Gump, CEO of Deep Space Industries (DSI), a US firm hoping to launch several small spacecraft to look for suitable asteroids and developing microgravity manufacturing technologies.
- Chris Lewicki, president and chief engineer of Planetary Resources, another US firm whose investors include Google bosses Larry Page, Eric Schmidt and film director James Cameron, and which is developing a space telescope, the Arkyd 100, to seek prospective asteroids to mine.
- Sara Seager, professor of planetary science and physics at the Massachusetts Institute of Technology (MIT), an expert on planets outside our solar system who has advised Planetary Resources.
What evidence is there for large enough extra-terrestrial mineral deposits to make space mining a realistic proposition?
Prof Sara Seager, MIT: The evidence is in the small asteroids or pieces of asteroids that fall to Earth as meteorites. Tens of thousands of meteorites have been collected and studied in sophisticated detail. Planetary scientists therefore know, in general, what asteroids are made of and that asteroids contain valuable metals.
Chris Lewicki, Planetary Resources: We’ve been able to connect our knowledge of the meteorite population to more modern things such as telescopic observations and taking spectra of these objects, and things such as radars that tell you even more about properties of ones that cross very close to the Earth. In the best case we’ve had several missions now that have gone to asteroids, taken up-close measurements and in one case even returned samples from them. All that says that there are really a lot of these resources out there. It’s an excellent amount of information to be starting our kind of business from.
David Gump, DSI: The very idea of mineral deposits is based on familiar (and largely irrelevant) experience on Earth, where cyclic geochemical extraction and concentration processes produce small, highly concentrated ore deposits in the Earth’s crust. But asteroids are mostly undifferentiated bodies that have never separated into core, mantle and crust. For this reason, there is no need to seek out mineral deposits because the entire body is an ore.
Source: Planetary Resources
How can you determine which asteroids would be worth exploiting?
Prof Ian Crawford, Birkbeck:
Information on the chemical composition of asteroids is obtained mainly from their optical and infrared spectra. Quite large telescopes are required to obtain spectra of the smallest objects because they are so faint, and the establishment of observatories dedicated to NEA detection and characterisation would greatly assist in creating an inventory of economically exploitable asteroids in near-Earth orbits. Metallic asteroids may additionally be detected from their very strong reflectance of radar signals transmitted towards them.
SS: The most relevant factor is “orbital economics”: which asteroids are easiest and hence most cost-effective to reach with a spacecraft and to land on and take off from. Of particular interest are asteroids with a low velocity relative to Earth and low surface gravity. Near-Earth asteroids (NEAs) numbering in the several thousands are the most accessible as they cross Earth’s orbit and can come close to Earth. Ideally we would like to know in advance what the interior of a prospective asteroid is made of. In practice we can’t precisely connect the exterior (as observed by telescopes) to the interior composition because of a surface layer of dust and space weathering. The ultimate goal to link an asteroid to meteorites recovered on Earth has remained elusive, hence a concept of deploying many autonomous small spacecraft which could land on candidate asteroids and determine their interior composition before sending out a fleet of mining-capable spacecraft. In the meantime we can classify some asteroids as metal-rich and those would be the place to start.
Source: Planetary Resources
What minerals are valuable enough to make this worthwhile?
IC: Metallic asteroids consist of essentially pure nickel-iron alloy. Although Earth has significant reserves of both these elements, and extra-terrestrial sources of them will probably not be required for the foreseeable future, such asteroids also contain several hundred parts per million of gold and platinum-group metals (PGMs). As a result, it has been estimated that a single small metallic asteroid about 200m across could be worth $30bn dollars at today’s prices. Other types of asteroids offer potentially exploitable materials. Carbonaceous chondrites (which make up 10–15 per cent of the NEA population) are relatively rich in volatiles. While probably not of significant value to the Earth’s economy, these could nevertheless be of great value to a future space economy, by providing water, hydrogen, and oxygen for use by future human and robotic space missions without the need to haul these materials out of Earth’s gravity.
A 500m-diameter asteroid that’s platinum-rich could have as much platinum in it as has been mined in the history of mining
Chris Lewicki, Planetary Resources
CL: There’s a valuation that a 500m-diameter asteroid that’s platinum-rich actually has as much platinum in it as has been mined in the history of mining. And the platinum-group metals are materials that we’re designing out of things because they’re so expensive: $1,600 an ounce. But for us, the material is valuable not just because it’s scarce here on Earth but because it is an incredibly useful element. It has wonderful catalytic properties, it’s used for high-temperature crucibles etc. Aluminium used to be one of the rarest metals that we knew in the 1800s and today it is ubiquitous. So we’d like to be able to help create that transition for the platinum group elements.
DG: We believe that PGMs will only ever be profitable as byproducts from refining of asteroidal regolith, after a mature industry has developed. We believe gold is a non-starter. And, to quote a very old bit of mining industry advice, the very first thing you need to know about rare earth elements, is that they are not rare. Certain carbonaceous chondrite meteorites show assay values in the order of 10 per cent water, 10 per cent reduced metal and five per cent metal sulphides. IF we can recover such material from chosen target asteroids, bring it to high Earth orbit, and refine it to directly useful feedstock (fuel, metal sheet, etc.) then that recovered asteroidal material has an imputed value of $1,000,000 per ton. Such material might characteristically also contain 50 parts per million PGMs, which can readily be calculated to be worth something like $2,000 per ton when returned to Earth. The key question now on retrieval missions is the subject of our ongoing review: ‘how small can you go to get started and still make money?’
The costs involved with space mining are going to be huge. What sort of value proposition could possibly make this feasible?
DG: Actually, it is the cost of terrestrial mining that is huge, with major projects often requiring tens of billions of dollars to bring on line. Initially, asteroid mining will be more of a boutique operation, producing very high-value products in modest quantities for in-space markets. The high-grade ore in a tiny five-metre asteroid is worth $200m to $500m. The first one returned should more than pay back the development and launch costs required to retrieve and process it. The ‘value proposition’ is that a developing in-space economy will seek to access useful resources from space rather than from Earth so as to avoid some fraction of the presently massive Earth-launch cost, which now ranges between $10,000/kg and $40,000/kg.
What mining process do you think would be most effective for gathering materials from asteroids?
DG: Asteroids come in several basic types. For a rubble pile of loosely held gravels and boulders, the steel metal grains can be collected with a magnet skimming the surface. Alternatively, we may use scoops, augers and active grabs to gather surface materials. The carbonaceous meteorites are mostly composed of water-bearing clay minerals and magnetite loosely stuck together by organic polymers (“plastics”). A magnet can also pick them up. Dormant comets likely have an outer layer of dust covering a weakly competent bituminous roadbase layer around a core of volatiles, silicates and carbonaceous materials (the “icy mudball”). Drilling, “moles” and other techniques are being considered to reach the core of dormant comets. Thus only some objects have buried layers that need to be accessed using terrestrial techniques. Material gathered at asteroids will be far richer than terrestrial ores, so beneficiation and refining processes will be different. Processes appropriate for low gravity and a good vacuum are relevant to asteroids, but most have no counterpart on Earth.
It is the cost of terrestrial mining that is huge. Initially, asteroid mining will be more of a boutique operation.
How much of the technology that you would need for space mining exists in some form already and in what additional areaswould you need to develop new capabilities?
SS: Technology already exists for spacecraft to travel to an asteroid, get into an orbit around an asteroid, land on an asteroid and touch down for sample return. [But] while much technology exists, we now have the tremendous task to enable a much faster and cheaper process. Even more significant is developing a cost-efficient asteroid mining process, one that works robotically in microgravity.
DG: Many of the techniques we need for asteroid mining and processing are far more rudimentary than those needed to extract useful products from ores on Earth. We rely heavily on basic physics and chemistry with which we are already very familiar and in which we have hundreds of years of practical experience. Of course we will learn as we go, and novel extraction and processing techniques appropriate to particular asteroids will develop as needed. Of crucial importance is the need for robustness and essentially zero maintenance. Mining-machine autonomous control, with only high-level human input, will be important due to the round-trip signal latency of possibly tens of minutes. Very significant advances in mining-machine automation and autonomous control have been achieved over the last few years. We will certainly need advances in machine AI and are in conversations with developers in these areas.
Do you envisage the material being returned to Earth in its raw form or would it more likely by refined and used for manufacturing in space, and why?
CL: I think the vast majority of it will be used in space and, much like we mine and refine materials on Earth, you do as much as you can near the site of the mine. There are transportation costs in space just as there are transportation costs on Earth, so if we are dealing with structural metals we’ll want to have reasonably pure metals before we start moving them around. And one of the reasons that water and volatiles are so early in our roadmap is that it is relatively easy to get to near 100 per cent purity in that particular resource, so you’re just shipping the stuff that matters.
DG: The value of water and metals from asteroids is highest in geosynchronous orbit and beyond, due to launch costs. Water or metal in high orbit is worth $17m/ton; brought back to Earth, steel sells for $700/ton. The easiest-to-reach asteroids, in terms of energy required, generally take the longest for their orbits to match up again with that of Earth – as much as 20–50 years. Waiting decades for a mining operation to pass by Earth again isn’t practical. We therefore will bring back small asteroids in the five to 10-metre range to a parking orbit near Earth, such as around the moon or to an Earth-moon Lagrange point. These will mass 200 to 1,500 tons, providing plenty of high-grade ore to process.
Within what timescale do you realistically think viable spacemining operations could be established?
DG: DSI will launch prospecting spacecraft in late 2015 and will likely launch retrieval missions in 2019–20 that deliver commercial quantities of ore back to Earth’s orbit by 2021–22. Therefore, within a decade, DSI will be producing asteroid-derived water, propellant and metals for in-space markets. The prospecting phase starts in late 2015 with 25kg FireFly spacecraft that perform asteroid fly-bys. Then slightly larger DragonFlies upgrade the prospecting campaign with the ability to acquire 25–50kg samples and return them to Earth for detailed analysis of their value. The first sample should be on its way back to the home planet in 2017. The retrieval phase requires a large Harvestor spacecraft with 40–100kW of solar-electric power to feed its ion engines for a two- to three-year round trip starting in 2019–20. In parallel, DSI will continue developing the processing technologies that we will launch into orbit to meet the first returning Harvestor.
CL: We are building our business to make money from day one and we’ve actually been successful in doing that in that many of the technologies that we’re developing to prospect and develop asteroid resources are technologies that are useful to people today in commercial markets and in government research. Having said that, we are aggressively working on the prospecting task and we’ll be putting our first spacecraft for remote sensing of asteroids up in early 2015 and maybe even some technology demos prior to that. Within a few years after that we’ve got our sights set on a number of near- Earth asteroid targets that we’d like to start to survey, with the goal at the beginning of the next decade of extracting our first small amounts of water and scaling that up.
What advice would you give to engineers interested in getting involved in this nascent industry?
DG: First readMining the Sky by John S. Lewis and sign up to receive DSI announcements and newsletters. Then begin considering how your specialty would be differently applied in space. In the absence of gravity, materials stayed mixed even with different densities – metal alloys impossible on the ground can be achieved in orbit, oil and water do mix, etc. New resources available to space engineers include the highest-quality vacuum at no cost. Solar power is reliable, available 24/7. Solutions to many problems will be different in space and there will be opportunities that require innovative thinking to realise.