By Evan Gough,
Published by Universe Today, 21 June 2022
The earliest mention of asteroid mining might be in a story from 1898 titled “Edison’s Conquest of Mars,” by Garrett Serviss. In that story, Martians attack Earth, killing tens of thousands and destroying New York City. Earth retaliates and sends an armada to Mars. While travelling, the armada comes across an asteroid that the Martians are mining. The asteroid is a rubble pile of gold nuggets.
A conversation breaks out among the crew.
“Phew! Won’t we be rich?” exclaimed a voice.
“How are we going to dig it and get it back to earth?” asked another.
“Carry it in your pockets,” said one.
“No need of staking claims here,” remarked another. “There is enough for everybody.”
Their conversation was a prescient hint of things to come.
The idea to mine asteroids incubated in the background until more modern times, when the realities of the space-faring age brought the idea into focus.
Starting in the 2000s, asteroid mining—or at least its potential—gained momentum. Private companies were starting to send spacecraft into Earth orbit, though it was tentative at first. People started to wonder about mining asteroids. Who owned them? How could it be done?
Japan’s Hayabusa brought a sample of asteroid Itokawa back to Earth in 2010. Wealthy people formed companies with the intent to mine asteroids. In 2015, the US Congress passed the Space Act that gave US companies the right to mine asteroids and other bodies in space, though it stopped short of claiming sovereignty over any bodies in space.
Companies popped up and talked about mining asteroids. They calculated the value of asteroids and started developing robotic explorers to operate on asteroids. One company called the Asteroid Mining Corporation worked with a Japanese University to develop the Space Capable Asteroid Robotic Explorers (SCAR-E).
The initial fervour of the past couple of decades has died down, but the idea is still there. And as our knowledge of asteroids grows and our space-flight capabilities advance, the idea of asteroid mining will never disappear.
There are a number of reasons why asteroid mining is desirable. The materials in asteroids represent an enormous financial value, which always attracts capitalist activities. Some materials needed for our modern technological devices are in short supply on Earth but are available on asteroids. And mining on Earth carries an environmental burden that mining on dead asteroids doesn’t.
One day asteroid mining might be possible, profitable, or even necessary. We’re not there yet, but scientists are still thinking ahead about how it could work, even though there are a whole host of obstacles in the way. We’re accustomed to spacecraft being launched on far-flung missions into the Solar System. But space travel is complicated, risky, and expensive. Even sampling asteroids is challenging.
How can asteroid mining be brought out of the realm of science fiction and into reality?
In a new paper, a trio of researchers suggest that some of the obstacles could be overcome by using Mars orbit as a base of operations.
The paper is “Phobos and Mars orbit as a base for asteroid exploration and mining.” The lead author is Anthony Taylor from the University of Wisconsin-Madison. The paper is published in the journal Planetary and Space Science.
NEO asteroids are not the target. Their number and their value are limited. At some point in our asteroid-mining, space-faring future, we’ll want to develop the asteroids in the main belt between Mars and Jupiter. There’s nearly-immeasurable wealth and resources there. The asteroid Davida alone may be worth 27 quintillion US dollars. One calculation says there’s $100 billion dollars in mineral wealth for every person on Earth in the main asteroid belt.
The main obstacle, according to the paper, is the energy required to reach the main belt and rendezvous with asteroids. In spaceflight that energy is quantified as Delta V, where V is velocity and Delta is change. Launching and maneuvering require changes in delta-v, and those changes require energy. “Most MBAs are energetically too hard to reach with present technology from low Earth orbit. An alternative is to use Mars orbit as a base from which to conduct MBA research, prospecting, and mining.”
Even the easiest-to-reach MBA is difficult to reach from Low Earth Orbit (LEO) because of the delta-v. The Near-Earth Asteroids are much easier to reach in comparison. It requires “… a minimum delta-v ~7 km s-1 to rendezvous from low Earth orbit (LEO) with the easiest to reach MBA, compared with ~4 km s-1 needed for the easiest to reach near-Earth asteroids (NEOs) from low Earth orbit.”
It follows that reaching MBAs is easier if you start from Mars orbit. The delta-v will be far lower. The difference between ~7 km s-1 and ~4 km s-1 might not sound like much, but the fuel requirements scale exponentially with delta-v.
The team wrote some code that allows them to find the delta-v needed to reach and rendezvous with any asteroid in the main belt from either Earth or Mars orbit. For Mars, they use Phobos’ orbit, which is about 9,000 km (5,600 miles) above the planet, and for Earth they used LEO. “We used PARC (Python Asteroid Rendezvous Code) to investigate whether Phobos-like orbits around Mars at altitudes of ~9000 km are more energetically favourable and useful locations from which to dispatch missions to MBAs.”
The short answer is “Yes they are.”
The available mass in the MAB and the MC (Mars Crosser) asteroid populations dwarfs that of the NEO asteroids. So in terms of large-scale delta-v needed to reach more resources, the Phobos Mars Orbit idea wins again. “Most known MBAs + MCs are bigger than the largest NEO, (1036) Ganymed, at ~50 km diameter. Therefore, the accessible mass of MBAs + MCs increases more quickly than an equivalent number of NEOs at a given delta-v requirement.”
In the figure above, the large asteroids Ceres, Pallas, and Vesta skew the results a little. They require a large delta-v to reach, though it’s still lower from PMO than from LEO. “But operationally it is the low delta-v tails that are of particular interest,” the authors write.
The authors point out that for a particular delta-v, more MAB material is accessible from PMO. In fact, it’s not even close. “We find that PMO provides access to ~7 x 1015 tonnes of material within ?v < 4 km s-1,” they write. Over 99.9% of that material is in MABs and MCs, while the insignificant remainder is in LEOs. On the other hand, “From LEO, only ~3 x 106 tonnes of material are accessible within ?v < 4 km s-1 and are entirely found in NEOs.”
Of course, there’s more to mining MBAs from Mars Phobos Orbit than just the ?v required to get there. The effort to even get equipment to MPO requires fuel and resources and time. The authors acknowledge that, and emphasize that their study is focused on reaching asteroid resources from an already established base. There are all kinds of other variables depending on the mass of the equipment sent to asteroids, where and how it’ll be processed, what will be done with the waste, and where the extracted resources will go.
One team of researchers can’t answer all these questions. Their paper simply shows how it takes fewer resources to reach the bulk of the Solar System’s asteroidal material from MPO than it does from LEO. Whether or not asteroid mining ever makes sense depends on a whole bunch of factors.
That’s where the Phobos delta-v penalty comes in. It’s the price a spacecraft pays to maneuver in and out of orbit around Mars. The planet’s gravity well extracts its own price.
“Whether the Phobos delta-v penalty is economically disadvantageous depends on the masses to be moved, both of raw and beneficiated (refined) ore, and of mining and processing equipment,” the authors explain. “If the beneficiating equipment is massive then the simplified raw material gathering spacecraft that will undertake the Phobos to asteroid journey may be of significantly lower mass.”
Mining the MAB wouldn’t happen in a vacuum (sorry.) Facilities on Mars would likely be part of the endeavour. Maybe the structural materials in the asteroids, like iron, would be used to manufacture other facilities in the MAB or in Mars orbit. But none of these considerations changes the raw fact that more MAB material is within reach from MPO than from LEO. “We find that there is a far larger population of known asteroids accessible to current technology from Phobos orbit than from low Earth orbit, by a factor of 300 in number and a factor 109 in mass for a delta-v of 4 km s-1,” the paper concludes.
Phobos itself could play an advantageous role, according to the authors.
“Phobos is a convenient site for emplacing massive ore-refining equipment. Phobos has properties that aid in extracting ore from raw asteroid material, as it provides some gravity, an inertial platform, and radiation shielding. Phobos may then serve as a useful forward operating base for the exploration and mining of the Main Belt.”
If this idea ever comes to fruition, then it’s likely that Mars itself will be a part of it. “The presence of
large-scale operations in Mars orbit may also lead to routine access to Mars’ surface,” they write.
The rest is left to our imaginations. Would human beings lead the mining operation? If so, then Mars could act as a kind of lifeboat in case of problems. Evacuating a damaged mining spacecraft and landing on Mars, where we can extract oxygen, fuel, and water, and store food and other supplies, seems like a natural emergency backup plan.
Or maybe there’d be very little need for flesh and blood humans. Maybe robots could do most of the work. Robotic technology is growing in leaps and bounds and there’s no reason to think it won’t keep advancing.
Asteroid mining is really in-situ resource utilization writ large. If humanity is ever going to expand out into the Solar System, the resources in the MAB will play a role. Only time will reveal exactly what that role is.
See: Original Article