433 Eros is a stony asteroid in a near-Earth orbit

Asteroid mining may soon be a method for gathering resources. The basic idea is that raw resources and minerals could be mined from an asteroid in space using a variety of methods. Even a relatively small asteroid with a diameter of one kilometer can contain billions of metric tons of raw materials.

In 1989 the world production of iron ore reached a peak of 928,054 metric tons prior to 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.

Asteroid selection

The Near-Earth asteroids orbit in close proximity 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.

The table below shows a comparison of delta-v requirements for various missions. In terms of propulsion energy requirements, a mission to a near-earth asteroid compares favorably to alternative mining missions. Low earth orbits (LEO) are those typically attained by Space Shuttle launches.

Note:

1. This is the typical amount. However much smaller delta-v asteroids exist

Mining

There are two options for mining:

1. Bring back raw asteroidal material.
2. Process it on-site to bring back only processed materials, and produce fuel propellant for the return trip.

Processing in situ for the purpose of extracting 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.

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 in order 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 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:

1. Material is successively scrapped 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.
2. 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.

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 automation 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 a shelter against radiation from solar flares. A habitat mounted on the asteroid and covered by surface material would provide suitable protection.

External links

• Asteroids Near Earth -- Materials for Utilization: Projects to Employ Resources of the Moon and Asteroids Near Earth in the Near Term
• How Asteroid Mining will Work - Howstuffworks
• [http://www.spacefuture.com/archive/the_technical_and_economic_feasibility_of_mining_the_near_earth_asteriods.shtml

The Technical and Economic Feasibility of Mining the Near-Earth Asteroids], M. J. Sonter.