Mining the Asteroids: Our Gateway to Mars

The OASIS Lecture Series was honored to feature space mission developer Warren James on January 11, 2014 at the A-MAN International STEM Science and Conference Center, whose mission was described by an enthusiastic Technology Director Ira Munn before Warren’s talk. Warren is a co-investigator on a NASA Innovative Advanced Concepts study of asteroid mining. The study’s purpose was to determine the feasibility of asteroid mining and define a spacecraft and infrastructure to do so. The project goals are to use asteroid mining to supply resources for use in space and ultimately on the Earth. Warren then extended that work to show how those asteroid mining technologies could be used to dramatically reduce the cost of a human mission to Mars.

Warren opened his talk by asking why going to Mars has been regarded as so difficult. The first two proposed missions to Mars, both by Wernher von Braun in the 1950’s, predicted a Mars arrival within the same century. The other missions – even the most recently published plan (2010) – proposed landing on Mars 25 years after the start of their programs. Unfortunately, human missions to Mars have always been 25 years or more in the future, no matter when such projects have been discussed. Over such a long span, support of a given Mars program may change with the succeeding US Presidential administrations. The multi-hundred billion projected program cost puts such a mission in competition with other Congressional interests. In addition, those costs would have to be completely covered by the Mars Exploration Program, as no non-governmental infrastructure exists for interplanetary flight.

But does a mission to Mars necessarily have to cost this much? Are an entirely new infrastructure and technology necessary, as NASA has always planned? Warren pointed out that Christopher Columbus didn’t have new ships designed for his voyages. Neither does the National Science Foundation for their Antarctica research mission; they use commercial aircraft or military assets along with existing facilities and equipment, which cuts costs down considerably. If a mission to Mars were similarly designed, the only new technology needed would be a Mars lander and surface equipment, which NASA could develop. Warren proposed that commercial asteroid mining technology would provide the systems needed for manned Mars missions.

Warren began by introducing asteroids—their history and structure. The first discovery of an asteroid (Ceres) took place in 1801; by December 2013, the number discovered reached 380,000. The asteroids range in shape from spherical to ellipsoid to highly irregular, and in size from Ceres (just under 1,000 km) to the tiny 25143 Itokawa (0.5 x 0.3 x 0.2 km) and even smaller objects not much larger than a small car. (The figure on page 3 compares asteroid Itokawa with the International Space Station and the proposed asteroid mining vehicle.) Most (>75%) are C-type (similar to carbonaceous chondrite meteorites); they contain carbon, nitrogen and water. S-types (stony) comprise approximately 17% of the asteroids.

While M-types (metallic) make up the minority (6%-8%), Warren described them as the treasure chest of the Solar System, bearing iron, nickel, aluminum, platinum/palladium group (PPG) metals, and rare earth elements. Just one M-type asteroid 1 km in diameter could contain nearly 4 times the amount of metal mined in all of human history. Approximately 1,200 Near Earth asteroids of at least that size have been detected (as well as 140,000 of 100 m or larger) Furthermore, an asteroid 10 km in diameter could contain 4,000 times the total mineral wealth mined from the earth. Warren calculated the potential revenue from a single spherical asteroid 25 m in diameter (28,634 tons) with a density of 3.5 g/cm3 containing 10% recoverable water (2,863 tons) and 0.5% PPG (143 tons). Assuming water sells for $8,000/kg and PPGs for $50,000/kg, the revenue would be considerable: $22 billion from water and from PPGs, $7 billion.

The asteroids that are likely to be mined first are the Near Earth Asteroids (NEAs), whose orbits bring them within 0.3 Astronomical Units of the Earth. Approximately 20% of these objects are easier to reach than the Moon. Moreover, roughly 30% of these objects are expected to eventually impact the Earth.

Asteroid-mined resources would have multiple uses in space: water as life support and propulsion, metals for large scale construction, silicon for solar panels. Asteroid mining would support space industry and lower its costs. However, there is not yet a market for use of asteroid mined materials in space.

Such markets do exist on Earth. PPGs are used in “green” technologies, rare earth elements in electronics, titanium in high-temperature metallurgy, and nickel in steel production. Prices and market demand are known, and PPGs mined on Earth command very high unit prices. With asteroid mining, environmental and energy costs and constraints would be lower, thus easing political concerns. At the same time, there is competition with existing market with established vendors. In addition, as the supply of PPGs increases, their price will fall, and likewise profits; at the same time, this can support new uses and markets. Warren gave aluminum, now cheap and in common use, as a historical example. It was once reserved for the most expensive flatware at the court of Napoleon III in France, and the Washington Monument was built with an aluminum cap to signify the wealth of the United States.

Warren then dove into more specifics on the economics of asteroid mining. He evaluated the cost of asteroid-mined material delivery to an Earth-Moon Lagrange (EML) staging location. The first product would be water, used to support traffic leaving cis-lunar space and trans-lunar flight operations. He first described the transport of water from Earth to EML1 as a comparison, assuming a Falcon 9 Heavy lifting 50 tons for $125M, a LOX/LH2 third stage for another $75M, and a net payload of 16,250 kg. Water delivery would cost $12,500/kg.

Warren then outlined a scenario in which asteroid mining could beat that cost and return a profit. Operations would be out of an EML1 Gateway station, with a fleet of four mining ships bearing an operations cost of $200M, development cost of $2.5B, and production cost per ship of $900M (the latter not including $375M for initial deployment to the station). Mining missions would be launched a year apart; each would take 4 years and return 150 tons of water, sold at $8,000/kg. Aggregated project expenses would be charged 2.5% interest per year and net earnings would accrue interest income at the same percentage per year. Under these assumptions, asteroid-mined water would not be sold until year 11 of the project and the total expenses would reach $9.5B by year 12. However, by year 19, all project research and development and production expenses would be repaid; water sales would reach $18B and the profit $6.2B, with water cost per kg dropping to $5,200 by year 25 and possibly lower than $1,250 upon the amortization of startup, research and development, and production costs. So the answer is Yes—eventually, asteroid mining of water will be more profitable than transport of water from Earth to EML1 and it could even be less expensive to return asteroid resources to EML1 than to deliver cargo to Low Earth Orbit (LEO).

In the near term, water would be the main product of asteroid mining. Later, metals would be mined for large scale construction in space, and silicon for solar panels. In the far term—in space and on Earth alike—PPGs, nickel, titanium and aluminum would be added to the list.

Warren next described the mining technology. He showed a diagram of the proposed robotic asteroid mining spacecraft (see inset). The spacecraft approaches an asteroid along its rotational axis and then rotates in sync with the asteroid. The containment vessel opens and arms within close around the asteroid, which is then restrained by airbags and anchors. The vessel closes and processing begins; upon completion, the mining debris is released. Solar collectors would power the spacecraft. Warren noted that in situ asteroid processing would be more practical than bringing an entire asteroid back to earth. Most of an asteroid’s mass is regolith, not useful except for radiation shielding; and perhaps not even that because high energy galactic cosmic ray impact leads to emission of secondary radiation. Thus, bringing back an entire asteroid would mean that over 90% of the returned mass would just be low-value mining debris and this would raise the effective cost of the valuable materials to a level that would make asteroid mining uneconomical.

And…asteroid mining can send us to Mars!

The EML1 staging base for asteroid mining operations could be used as a base for Mars mission operations, greatly reducing the necessary Delta V for the mission when compared to that which would be required when staging from LEO. Further reductions would be possible with lunar and/or Earth swing-by maneuvering, as would adding a phasing segment to the departure orbit that would lengthen the potential launch period. Furthermore, according to a sizing comparison Warren showed, EML1 staging would cut departure mass by 75% and launch cost by 45% compared with departure from LEO.

In addition, asteroid mining would give access to low-cost propellant and life support consumables. The technology could be used for in situ resource utilization (ISRU) on Phobos and Deimos. Both are essentially carbonaceous chondrite asteroids: rich in carbon, hydrogen, oxygen, and water. Generating return propellant (LOX/LH2) from Phobos ISRU would reduce LEO launch cost by 17%, and EML staging costs by 14%. L1 staging would be 60% lighter and 30% cheaper than the LEO option.

However, one needs to account for the mass of radiation shielding needed by the crew, not just for solar storms but for galactic cosmic rays. A large volume of water will be needed to protect the crew: at the very least, 0.5 meters. Assuming the crew cabin is 12 m long and 6 m in diameter, this means 161,000 kg of shielding water, driving up the cost of launching from LEO with LOX/LH2 fuel from nearly $4 billion to approaching $14 billion, or completely unaffordable! Here, a solar-thermal propulsion system (STPS) that would use water as reaction mass came “to the rescue”. This system, which was baselined for use by the asteroid mining spacecraft, has several advantages: first, since water is far denser than hydrogen or oxygen, the fuel tanks can be smaller, and water is easier to work with than cryogenics. Making the fuel tanks flexible to wrap around the crew module would provide over half-a-meter-thick radiation shielding. Second, independent of the propellant’s shielding, the crew cabins would be in a storm shelter surrounded by 10 cm of water, which could also be used for life support. Third, using asteroid-mined or Phobos/Deimos ISRU water would eliminate the cost of producing LOX/LH2. Fourth, the solar collectors that power the propulsion system can also provide heat for asteroid resource extraction during asteroid mining missions. Fifth, while the STPS has a lower specific impulse than a LOX/LH2 system, this can be advantageous in that the larger required propellant mass gives a higher amount of shielding. And while the STPS also has less thrust, this did not faze Warren—he noted that the mission design task would be “more challenging and thus more fun”. A comparison of an STPS mission with a launch from LEO with LOX/LH2 showed a nearly fourfold cheaper mission—and the crew will survive to explore other worlds.

Furthermore, as asteroid mining technology matures, costs will become even lower. The propellant cost at EML1 ($1,500/kg) and Phobos ($750/kg) will be less than that at LEO. Warren’s calculations showed a twofold drop in the total launch cost from early asteroid mining technology from EML1 to maturity. In fact, the final cost will be only 13% of the cost without asteroid-mined propellant.

Warren summed his talk by reiterating how a piloted Mars spacecraft could be derived from the asteroid mining spacecraft, with a crew module from the EML servicing station. In fact, everything for a mission to Mars could come from an asteroid mining program: the crew module, interplanetary transport, Phobos/Deimos ISRU, and an EML-located staging base. Only the Mars lander and surface equipment would have to be developed especially for the Mars mission. Warren closed by describing the asteroids as our gateway to Mars…and beyond.

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