“Early evidence suggests that there are trillions of dollars worth of minerals and

metals buried in asteroids that come close to the Earth. Asteroids are so close that

many scientists think an asteroid mining mission is easily feasible.”

 

 

Value of Materials

 

Launch cost of ANY material from the earth: $10,000 per kg.

 

“Note that the asteroidal materials we are talking about are, simply, water,nickel-iron metal, hydrocarbons, and silicate rock. Purified, and made

available in low earth orbit, they will be worth something like $500,000 per ton, under having avoided terrestrial gravity's "launch cost levy."

 

“These values are up there with optical glass, doped semiconductors, speciality

isotopes for research or medicine, diamonds, some pharmaceuticals, illicit drugs. On the mining scene, the only metal which has ever been so valuable was radium, which in the 1920s reached the fabulous value of $200,000 per gram!

 

Platinum Group Metals (which are present in metallic and silicate asteroids, as

proved by the "ground truth" of meteorite finds) have a value present in the order of $1,000 per ounce or $30 per gram. Vastly expanded use in catalysts and for fuel cells will enhance their value and PGM recovery from asteroid impact sites on the Moon is the basis of Dennis Wingo's book, “MoonrushValue” of Materials.

 

One NASA report estimates that the mineral wealth of the asteroids in the asteroid belt might exceed $100 billion for each of the six billion people on Earth. John S. Lewis, the author of the space mining book Mining the Sky, has said that an asteroid with a diameter of one kilometre would have a mass of about two billion tons. There are perhaps one million asteroids of this size in the solar system. One of these asteroids, according to Lewis, would contain 30 million tons of nickel, 1.5 million tons of metal cobalt and 7,500 tons of platinum. The platinum alone would have a value of more than $150 billion!

 

Professor John Lewis has pointed out (in Mining the Sky) that the resources of the

solar system (the most accessible of which being those in the NEAs) can permanently support, in the first-world comfort, some quadrillion people.

 

 

Mineral Content

Spectroscopic studies suggest, and ‘ground[1]truth' chemical assays of meteorites confirm, that a wide range of resources are present in asteroids and comets, including nickel-iron metal, silicate minerals, semiconductor and platinum group metals, water, bituminous hydrocarbons (Ralph: think OIL like materials), and trapped or frozen gases including carbon dioxide and ammonia.

 

Even a relatively small asteroid with a diameter of one kilometre can contain billions of metric tons of raw materials.

 

“In 1989 the world production of iron ore reached a local peak of 928,054 metric tons before the collapse of the Warsaw Pact. In comparison, a comparatively small M-type asteroid with a mean diameter of 1 km could contain more than 3 billion metric tons of iron-nickel ore or 3,000 times the annual production for 1989. (In other words, more iron ore than has ever been mined in human history.) A small portion of the extracted material would also contain precious metals, although these would likely be more difficult to extract.

 

Platinum Elements

 “As one startling pointer to the unexpected riches in asteroids, many stony and stony-iron meteorites contain Platinum Group Metals at grades of up to 100 ppm (or 100 grams per ton). Operating open-pit platinum and gold mines in South Africa and elsewhere mine ores of grade 5 to 10 ppm, so grades of 10 to 20 times higher would be regarded as spectacular if available in quantity, on Earth.”

 

Helium-3

 

“Researchers see helium-3 as the perfect fuel source: extremely potent, nonpolluting, with virtually no radioactive by-product. Proponents claim it's the fuel of the 21st century. The trouble is, hardly any of it is found on Earth. But there is plenty of it on the extraterrestrial bodies (the moon and asteroids). “  

 

“"Helium 3 could be the cash crop for the moon (and asteroids)," said Kulcinski, a longtime advocate and leading a pioneer in the field, who envisions the moon becoming "the Hudson Bay Store of Earth. "Today helium 3 would have a cash value of $4 billion a ton in terms

of its energy equivalent in oil, he estimates.

Water

 

Water is an obvious first, and key, the potential product from asteroid mines, as it is a highly prized resource in outer space. (Think Moon/Mars Colonies)

 

Water could also be broken down into hydrogen and oxygen to form rocket engine propellants. (not only what we need to get stuff back home, but also a very valuable commodity to sell to other space-faring companies.

 

Extraction and Processing

 

Mining

 

There are two options for mining:

¨ Bring back raw asteroid material.

¨ Process it on-site to bring back only processed materials, and

produce fuel propellant for the return trip.

 

Processing in situ to extract high-value minerals will reduce the energy requirements for transporting the materials to the point of manufacture. However, the processing facilities must then be transported to the mining site. Thus there is an economic trade-off.

 

Mining and processing an asteroid is much less massive an operation than Earth or

Moon mining. We do not need heavy mining and transport machinery. We don't need complex chemical processing on the Moon to get valuable materials, and waste disposal is achieved by just putting all waste into a big bag. However, the near zero-gravity space environment has its unique challenges as well.

A typical asteroid would probably be crumbly, consisting of silicate dirt embedded

with nickel-iron granules and volatiles. We can make this assumption for the

purposes of this analysis, but should be aware that the consistency from asteroid to

an asteroid can vary from pure metal to pure powder, and could also entail a mix of

consistencies.

 

Many different methods have been discussed for mining the asteroid. Conventional

methods include scraping away at the asteroid's surface (i.e., strip mining), and

tunnelling into the asteroid. Most Earth mining depends upon gravity to hold the

cutting edge against the ore. (However, for many Earth mining operations this is not enough, and other means are employed, e.g., cables and reels.) Scraping away at the surface of the asteroid requires holding the cutting edge against the outer surface of the asteroid. This would require either local harpoons or anchors embedded into the surface of the asteroid, or cables or a net around the asteroid for the cutter to hold onto.

 

Strip mining would result in a lot of dirt being thrown up. An unconventional space mining method sees this not only as a problem but also as an opportunity. A canopy around the mining site can be used to collect ore purposely kicking up, the canopy shaped and rotating to use the centrifugal force to channel the ore to the perimeter for collection, as this NASA artwork shows. If no canopy were put

up, a lot of debris would cloud and cover the mining environment and probably interfere with mining operations. (Mining without a canopy would certainly be unacceptable in Earth orbit. Companies will most probably use a canopy also because the canopy would be quite profitable in terms of the number of loose ore it would collect.)

 

A variation on this is to have a stationary canopy. A dust kicker goes down to the asteroid and just kicks up the ore at low velocity. When there's enough ore in the canopy, it's sealed off and moved to the processing site (where the ore can be collected by rotation or other mechanical means). It is simple and highly reliable, presenting minimal risk of breakdown of mining machinery.

 

Some studies adopted tunnelling to mine an asteroid. The cutter holds itself steady by the walls of the tunnel -- pushing against the walls or cutting into them. Tunnelling prevents the consumption of the entire asteroid, but desirable ore veins or cracks can be followed.

 

Another candidate process for extracting volatiles from within near-Earth asteroids which are dormant comets (currently estimated to be around 40% of near-Earth asteroids) is to drill into the asteroid, much like we do for oil and natural gas. Geological and Mining Consultant David L. Kuck of Oracle, Arizona, proposes in a long paper entitled "Exploitation of Space Oases" some highly automated methods of drilling and producing volatiles without the need for extraction of materials and thus without dealing with the crushing, grinding and tailings disposal.

 

 

 

 

Mining Mechanisms

 

One of the difficulties in mining an asteroid will be the rotation period of the body. It may be necessary to attach rockets to the asteroid to eliminate the spin before mining can commence. Alternatively, the mining operation can be placed at the pole of the asteroid, or asteroids with high rates of rotation can simply be avoided.

 

The mining operation will require special equipment to handle the extraction and processing of ore in outer space. The machinery will need to be anchored to the body, but once emplaced the ore can be moved about more readily due to the lack of gravity. Docking with an asteroid can be performed using a harpoon-like process, where a projectile penetrates the surface to serve as an anchor then an attached cable is used to winch the vehicle to the surface.

There are several options for material extraction:

 

¨ Material is successively scraped off the surface in a process comparable to strip mining. The digging machine will need to be anchored against the asteroid using a series of attachments, then cut into the surface using a blade. The drawback to this approach is the large amount of loose material that will collect in the low-gravity

environment about the asteroid.

¨ A mine can be dug into the asteroid, and the material extracted through the shaft. This eliminates the problem of producing loose material, but it would require a transportation system to carry the ore to the processing facility. Potentially the microgravity environment can be exploited to move the material to the surface.

¨ Ultrasonic/Laser Mining

Due to the distance from Earth to an asteroid selected for mining, the round-trip time for communications is likely to be on the order of a minute or more. Thus any mining equipment will either need to be highly automated, or a human presence will be needed nearby. Humans would also be useful for troubleshooting problems and for maintaining the equipment. So, at least until automated space mining technology improves sufficiently, the mining facilities would need to be accompanied by a sealed-environment habitat. The operation is also likely to be of long duration, so the health risks of weightlessness would need to be managed and the crew would require shelter against radiation from solar flares. A habitat mounted on the asteroid and covered by surface material would provide suitable protection.

 

Mining Equipment Postulates

 

The machinery will likely be solar-powered, to reduce the need for fuel that would have to be hauled to the asteroid by spacecraft.

The equipment will also have to be lightweight to transport it to the asteroid.

Some experts, including Lewis, have favoured using robotic equipment to limit the personnel needed to carry out the mining project. This would reduce the number of supplies, like food, required for a manned mission.

 

Miners on asteroids would use techniques similar to those used on Earth. The most likely method would be to scrape desired material off the asteroid, and tunnel into veins of specific substances. Scraping, or strip mining will pull out valuable ore that will float off the asteroid.

 

Because much of the ore will fly off, a large canopy might be used to collect it.

 

Asteroids have nearly no gravity, so the mining equipment, and the astronaut-miners who operate them, will have to use grapples to anchor themselves to the ground. However, the lack of gravity is an advantage in moving mined material around without having to use much power.

 

Once a load of material is ready to be sent to either Earth or a space colony, rocket fuel for a ferrying spacecraft could be produced by breaking down water from the asteroid into hydrogen and oxygen.

 

After an asteroid's minerals and resources have been exhausted by the mining project, the equipment can then be transported to the next asteroid.

 

Processing

 

Asteroidal material in general is exceptionally good ore requiring a minimum of

processing, since it has free metal already.

 

Only basic ore processing need to occur at the asteroid, producing free metal and volatiles (usually stored as ices), and perhaps selected minerals, glasses and ceramics. The required equipment is quite simple.

 

The following is a sample ore processing system, but is not the only one proposed to date.

 

At the input chute, the ore will be ground up and sieved into different sizes as the first step of a basic ore processing system. Most asteroids probably offer far more crumbly material than we could consume in one mining expedition.

 

Simple mechanical grinders, using a gentle rocking jaw arrangement for coarse crushing and a series of rollers for fine crushing could be arranged in a slowly rotating housing to provide centrifugal movement of the material. Vibrating screens are used to sift the grains for directing them to the properly sized grinders.

 

The streams of material are put through magnetic fields to separate the nickel-iron metal granules from the silicate grains. Alternatively, the streams can be dropped onto magnetic drums, whereby the silicates and weakly magnetic material deflect off the drum whereas the magnetic granules and pebbles stick to the magnetic drum until the scrape off point. Repeated cycling through the magnetic field and perhaps additional grinders can give highly pure bags of free nickel-iron metal.

 

An optional additional piece of equipment is an "impact grinder" or "centrifugal grinder" whereby a very rapidly spinning wheel accelerates the material down its spokes and flings it against an impact block. Any silicate impurities still attached to the free metal are shattered off. It's feasible to have drum speeds sufficient to flatten the metal granules by impact. A centrifugal grinder may be used after mechanical grinding and sieving, and before further magnetic separation. In fact, most of the shattered silicate will be small particles that could be sieved out

 

The nonmagnetic material is channelled into a solar oven where the volatiles are cooked out. In zero gravity and windless space, the oven mirrors can be huge and made of aluminium foil. The gas stream is piped to tanks located in a cold shadow of space. The tanks are put in series so that the furthest one away is coldest. This way, water condenses more in the first one, carbon dioxide and other vapours in the tanks downstream.

 

Rocket fuel for the delivery trip to Earth orbit can be produced by separating oxygen and hydrogen gases from the mix, or by electrolysis of water. Alternatively, the hydrogen could be chemically bonded with carbon to produce methane fuel. On the simpler end, simple steam rockets could be used.

 

Thin, relatively lightweight spherical tanks could be sent to store the frozen volatiles. Ultimately, tanks for storing frozen volatiles for sending to Earth orbit can be manufactured by some of the nickel-iron metal, by use of a solar oven for melting the nickel-iron metal. A cast can be made from sand or glass-ceramic material from melted leftover ore.

 

Some silicate material from the asteroid can be shipped back to Earth orbit to be used for making glass, fibreglass, ceramics, "astercrete", dirt to grow things in, and radiation shielding for habitats and sensitive silicon electronics.

 

Processing of glasses, ceramics, "astercrete" and the like is not discussed here, because it is discussed in the chapters on lunar material utilization and space manufacturing. If we were to not use lunar materials but use only asteroidal materials, processing asteroidal material to make glasses, ceramics and astercrete is analogous to the discussion on processing lunar materials for the same feedstocks and products.

 

Undesired material can be put in a big wastebag container, or "sandbags", or cast into bricks by a solar oven, used for shielding the habitat from space radiation, creating more cold shadows, or just removed from the mining operation's space. (If waste were simply ejected at escape velocity, it would not significantly increase the number of meteors in interplanetary space. However, it's cheaper to skip the ejector equipment and just bag it all.)

 

Finally, I should add that some studies consider processing all the asteroidal material by solar oven, skipping the magnetic separators, impact grinders, etc. This approach would utilize giant superlightweight mirrors to concentrate sunlight onto a cavity containing any matrix of material, to first extract the volatiles, and then raise the temperature to more than 1600C (2900F). Only the free metal would melt at the latter temperature. However, separating the molten metal from the silicate matrix seems a little tricky.

 

Near Earth Opportunities and Targets

 

Some of these near earth asteroid bodies have orbits that bring them very close to earth – allowing very low energy/effort to return production materials to earth/earth orbit.

 

“The most accessible group of NEAs for resource recovery is a subset of the Potentially Hazardous Asteroids (PHAs). These bodies (about 770 now discovered) approach to within 7.5 million km of earth orbit. The smaller subset of those with orbits which are earth-orbit-grazing give intermittently very low delta-v return opportunities (that is it is easy velocity wise to return to Earth). “

 

“The Near-Earth asteroids orbit close to the Earth and are considered likely candidates for early mining activity. Their low delta-v location makes them suitable for use in extracting construction materials for space-based facilities, greatly reducing the economic cost of transporting supplies into Earth orbit. “

 

“One potential source for an early asteroid mining expedition is 4660 Nereus. This body has a very low delta-v compared to lifting materials from the surface of the Moon. The velocity difference from low earth orbit is only 60 meters per second (compared to 9,000 meters per second to reach orbit from Earth.) However it would require a much longer round-trip to return the material. So most likely it would require an automated mining mission for economic reasons.

 

Launch Technologies

 

N.B. a large number of these objects are substantially closer to Earth than the

moon, and thus easier to reach at much lower expenditures of energy/cost.LiftPort

 http://www.liftport.com/

Think – space elevator.

  Transport :

                Rail Gun  

                Ion Drive  

                Self – Generated Propellant (out of Water)

 

Return to Earth – “About 10% of Near-Earth Asteroids are energetically more accessible (easier to get to) than the Moon (i.e. under 6 km/s from LEO), and a substantial minority of these have return-to-Earth transfer orbit injection delta-v's of only 1 to 2 km/s.

Return of resources from some of these NEAs to low or high earth orbit may therefore be competitive versus earth-sourced supplies.”

 

 

 

The Interplanetary Transport Network (requires Patience)

¨http://www.answers.com/main/ntquery;jsessionid=6mw7sycyvkqm?method=4&dsid=2222&dekey=Interplanetary+Transport+Network&curtab=2222_1&sbid=lc05b

¨ Uses gravity assist to create transport lanes throughout the solar system. Movement of materials through these lanes is slow, but also very cheap… setting up a steady stream of deliveries – first one wouldn’t arrive for some time, but after that they’d arrive in a continuous stream at regular intervals.

 

Competition

 

So far, the only competition I can find (other than NASA and other space

agencies having considered the feasability) is a company called SpaceDev.

 

http://www.spacedev.com/newsite/templates/homepage.php?pid=2

 

Conclusion

 

The possibility of space exploration and mining is inspiring millions of students and researchers and raising billions of dollars in investment worldwide. The question on everyone's lips: when will we build the first hydrogen fuel station on the Moon, dig the first asteroid mine or bring material back to Earth? Faragalli predicts it could be soon.

"Towards the end of the 2030s, which is roughly around the time that many are predicting that there should be people on Mars," said Faragalli, “I think that is when we might realistically see an industry bringing metals back to Earth.”

Stay tuned.