With the recent studies done by the Dawn spacecraft, I decided to do my own analysis of how we could effectively mine and use the materials in the Asteroid belt. I’m not a rocket scientist, but here is my formulations based upon my personal study of rocketry and mining.
Ceres, a dwarf planet in the asteroid belt, has vast quantities of water, and a surface area the size of India. The asteroid belt is filled with materials from rare elements to current earth bound commodities that will eventually be scarce once our galactic infrastructure starts being developed. From the iron to build massive spacecraft and stations to water for fuel, we will be able to extract the resources we need from this region of the solar system.
Transporting an object between areas of the asteroid belt is not a very propellant intensive activity. However, carrying the propellant needed to then haul the object back to Earth or Mars from the mining location in the belt would be horribly inefficient. The fuel for the interplanetary journey, would require the spacecraft to use much more fuel just to reach the mining location. This is because the fuel would act just like cargo in terms of its effect on propellant needs.
The solution to this issue is to send small mining robots with minimal fuel to various asteroids to drill and collect resources, and then do a quick burn to return to Ceres. Small burns is all it would take to eventually reach Ceres if time isn’t crucial. Only a slight change in orbit is required to eventually “catch up to” or “fall back to” the dwarf planet. You can learn about how spacecraft rendezvous here.
To summarize this first part, Ceres will be the base of the operations and will manufacture the propellant needed to send materials Earth bound or process them in automated facilities. The mining bots need to only carry enough fuel to reach their target asteroid and then return to Ceres.
The second and equally crucial part is transporting material from Ceres to Earth and any colonies on Mars. This may in fact be very important in jump starting the Martian ecosystem. To create oceans and lakes, large amounts of water will be needed that Mars has currently lost. Ceres has as much water as Earth has fresh water, and could be a great source for hydrating the Martian surface.
However, these prospects likely won’t be fully realized for several centuries. What will be happening, and very likely within my lifetime, is the transport of precious metals from the belt. Ceres is a great location for hauling cargo directly to and from Earth, because unlike Mars’ launch windows which only occur every 24 months, Ceres has a launch window every 15 months. This means a direct Earth to Ceres flight can provide an effective near annual restocking of materials.
One other potential system that could work well for hauling massive amounts of cargo to any location in the solar system, is launching a series of, in effect, massive shipping containers. These large storage facilities would only need to expend propellant once to achieve their needed orbit. At this time they would move, in a similar fashion to a comet, around the sun in a highly regular and dependable time frame. They would be placed such that their orbits coalesced with Earth/Mars and Ceres every several decades or another reasonable time frame. Cargo would be launched from Ceres into these hangers inside of small shuttles. The shuttles would do appropriate burns to achieve the same velocity and direction as the freighters, so they wouldn’t slow the freighter they entered down. Cargo could also be launched from Earth to go to Ceres. If fuel wasn’t too scarce, the freighters could make comparatively small burns to intersect with Earth or Ceres more frequently.
The benefits of this would be that a cargo shipment would never have to slow down enough to orbit Earth or Ceres, or even worse, launch from the surface or land there. If time wasn’t important for particular deliveries these shipping containers filled with small rockets could work very effectively. However, this is a longer term development, and they way I envision the asteroid business developing, would be first mining highly valuable materials whose worth per mass is very high. This would make sending ships from Ceres to Earth loaded with a comparatively small amounts of material very worthwhile and profitable. This would then fund the development of systems to send less valuable items such as iron to Earth. Even with this preliminary step, launches to Earth would likely still be based off of Ceres, and mining could be done across many asteroids before being packaged together on Ceres for transport.
One modern technology that could work very well for this interplanetary transport is the VASIMR engine. This rocket technology has no chemical reactions unlike traditional spacecraft engines and no moving parts or exposed electrodes. Using only electricity, it can accelerate neutral gases at high velocities, and using only the rudimentary designs we have today, they can efficiently transport many tons of materials faster and better than chemical engines. Small nuclear reactors could power autonomous crafts using these engines. The thrust to weight ratio would be very high, and can work very well for sending massive payloads such long distances.
With the plethora of asteroid mining companies that have sprouted up, I fully expect to see many developments regarding this happen within my lifetime, and hopefully this system or one like it will be the backbone by which this development works.
It was a lot of fun thinking about the design of this transport system, and feel free to critique any of the scientific aspects of this plan in the comments.