Spotlight: Asteroid/Moon Mining and Water Propulsion
There's been a lot of excitement lately in the space industry, and specifically in the private sector, about mining in outer space. Although launch prices have been coming down drastically thanks to innovative launch companies like SpaceX, commercial exploitation of space has been held back by high launch costs that have limited space enterprises to highly profitable, unique services such as communications satellites. However, these same dropping launch prices are enabling a wider range of business activities in space, coupled with NASA opening the ISS to business [link], and multiple companies seeking to start their own private space stations for business opportunities (i.e. Axiom Space, Bigelow Aerospace).
Looming business prospects in low Earth orbit will require basic resources such as oxygen, water, and propellant, as well as raw materials for orbital industries. Additive manufacturing has already been demonstrated in space, and has the potential to create extremely high quality products that can best be made in zero-G and/or vacuum, such as solar sails, telescopic lenses, microchips and fiber optic cables. While launch costs have plummeted, it is still too expensive to launch resources into orbit and make a significant profit. However, if they can harvested from outside of Earth's gravity well, it can be quite a bit cheaper.
Where To Get Resources
The Moon is the most immediate answer. The lunar poles, particularly Shackleton Crater at the south pole, have many "permanently-shadowed craters" that never see the light of the Sun, and have been proven to contain thousands and thousands of tons of water ice. Additionally, many scientists believe there is more water ice buried under the surface all over the Moon (although not as accessible). Water ice can be melted into water to be used for human life support, greenhouses, or water propulsion; it can also be electrolyzed into hydrogen and oxygen, which can also be used as highly efficient rocket fuel, or the oxygen can be used for life support and the hydrogen for various industries as a reactant.
The Moon also contains a LOT of ilmenite, which is a titanium-iron oxide, and is very important commercially on Earth. It also traps hydrogen from solar wind, so breaking it down would yield titanium, iron, hydrogen, and oxygen - all extremely useful to any orbital or lunar industries.
Silicon also abounds, making up 20% of the Moon by weight. Although more difficult to refine, it would be an essential ingredient for those high-powered Made in Space semiconductors.
The Moon also contains rare earth metals, which although far fewer in total quantity, are still believed by NASA to be profitable, if not definitely useful to any in-space manufacturing.
The basic idea is to fly a high-isp robotic spacecraft out to an appropriately sized asteroid, pick it up in a doggie bag, then fly it back to lunar orbit for an Orion spacecraft to inspect up close. As you can see in step 1 of the yellow track, it takes multiple orbits of apogee burns to finally escape Earth's orbit, plus a gravity slingshot around the Moon - this is due to the extremely low thrust of the ion engines it would use. Now imagine coming back with the weight of the asteroid... It was impossible for Orion to do it itself, because the Orion service module is severely underpowered (which partly led to the LOP-G currently being developed). There were a few other concepts, but the idea of bagging the asteroid is interesting, in the context of mining. Asteroids have negligible gravity, so if you drill or do anything to extract resources, the excavated material will just fly off into space. Bagging the asteroid also opens up additional possibilities, as we'll see below
The Players
Planetary Resources is probably the most well-known company looking to exploit the stars. They started with the ambitious goal of mining asteroids in 2009, but so far have only launched a few survey demonstration satellites; in addition to this, they used COTS solutions to map out all the most profitable asteroids in the neighborhood of Earth. They realized that the infrastructure is not there to make it profitable, although they did take advantage of the air-launched LauncherOne, which was probably the first affordable smallsat launcher. Unfortunately, it appears that the company failed to procure funding in 2018 and had to lay off many of its employees and was bought out by a blockchain company.
(PR's process for getting at asteroid resources)
Another well-known(-ish) company is Deep Space Industries, started by space business pioneer Rick Tumlinson. It also appears to have to gone defunct, but they also realized they needed additional infrastructure to make it work. So their first big development (besides some cool concept art of asteroid processing facilities) was water propulsion, which is becoming more and more common now with CubeSats as a green, non-toxic, easily handled propellant. The idea behind it is to use water extracted from asteroids as a quasi-infinite propellant to maneuver the asteroid back to a more permanent processing facility to extract the rest of the minerals from it.
(DSI Fuel Processor Concept from space.com)
The third company I'd like to talk about is TransAstra. While public products of Planetary Resources seem to be limited to finding asteroids, and Deep Space Industries got hung up on propulsion, TransAstra got as far as a NASA Innovative Advanced Concepts (NIAC) Phase III grant, the first ever, to test a prototype of their mining equipment on an asteroid simulant in low Earth orbit [Official][Commentary]. Notably, they're using a Momentus Vigoride spacecraft bus, which is basically a smallsat bus powered by water plasma thrusters. The gist of TransAstra's plan is to deploy these small-ish robotic "Worker Bees" (literally what they're called) to go to asteroids, bag them ARM-style, and evaporate the water ice using optical mining. They've already demonstrated optical mining on the ISS, so this is a pretty advanced proof-of-concept for them to go into orbit, pick up a fake asteroid, and then suck the life out of it just like it would with a real asteroid.
(TransAstra APIS or Honey Bee)
The big benefit of optical mining, aside from their already-proven results with it on the ISS, is that it doesn't require converting solar energy into electricity, then back into heat, while also requiring a container of sufficient material strength to contain all that. It just directs the concentrated light beam to a point on the asteroid, evaporates the volatiles, then sucks them into another bag for storage. Sounds easy! My opinion is that the solar concentrators and "piping" will be the most difficult part, both to get into orbit and to manufacture, since the water propulsion, the asteroid bag, and the optical mining have already been proven. I think another downside of their business model is reliance on low-efficiency water propulsion. Water as a propellant, while avoiding the massive energy costs and difficulty of storage that comes with liquid hydrogen, takes a massive hit on efficiency. Using water as a propellant basically means throwing away 2/3 of your fuel (TransAstra claims 360 seconds [src], but other water thrusters get about 130 seconds), so unless the spacecraft itself is extremely light (which could be done if its all plastic and built in space), you're gonna spend most of your asteroid mother lode just getting home. On the plus side, it uses no electricity for propulsion, just reflected solar energy to heat the water, which will cut on weight significantly. It'll also take a long time, but that's fine with thousands of mini robotic worker bees doing the work incrementally. As a plus, it can harvest for fuel on the go, and when it gets back, the dry husk can be mined by more specialized equipment to get the metal resources as well.
How To Get Resources
Looming business prospects in low Earth orbit will require basic resources such as oxygen, water, and propellant, as well as raw materials for orbital industries. Additive manufacturing has already been demonstrated in space, and has the potential to create extremely high quality products that can best be made in zero-G and/or vacuum, such as solar sails, telescopic lenses, microchips and fiber optic cables. While launch costs have plummeted, it is still too expensive to launch resources into orbit and make a significant profit. However, if they can harvested from outside of Earth's gravity well, it can be quite a bit cheaper.
Where To Get Resources
The Moon is the most immediate answer. The lunar poles, particularly Shackleton Crater at the south pole, have many "permanently-shadowed craters" that never see the light of the Sun, and have been proven to contain thousands and thousands of tons of water ice. Additionally, many scientists believe there is more water ice buried under the surface all over the Moon (although not as accessible). Water ice can be melted into water to be used for human life support, greenhouses, or water propulsion; it can also be electrolyzed into hydrogen and oxygen, which can also be used as highly efficient rocket fuel, or the oxygen can be used for life support and the hydrogen for various industries as a reactant.
The Moon also contains a LOT of ilmenite, which is a titanium-iron oxide, and is very important commercially on Earth. It also traps hydrogen from solar wind, so breaking it down would yield titanium, iron, hydrogen, and oxygen - all extremely useful to any orbital or lunar industries.
Silicon also abounds, making up 20% of the Moon by weight. Although more difficult to refine, it would be an essential ingredient for those high-powered Made in Space semiconductors.
The Moon also contains rare earth metals, which although far fewer in total quantity, are still believed by NASA to be profitable, if not definitely useful to any in-space manufacturing.
All this talk about the Moon, but what about the asteroids? There are some pros and cons to the asteroids: first, is getting there. NASA tried to do the Asteroid Redirect Mission in the early 2010s, where they would send an Orion to capture a small asteroid and bring it back to lunar orbit for study. They also had concepts to do the same thing with a much bigger Copernicus nuclear thermal rocket. Budgetary constraints (and practicality) aside, ultimately what killed the concept was that NASA couldn't find a near-Earth asteroid to capture! That said, some companies, such as TransAstra [I think, no source] believe that it can take significantly less delta-V to reach an asteroid than the surface of the Moon. If the orbits line up right, mining asteroids will always cut out the landing portion, which is not insignificant in fuel costs and required equipment.
There are several classes of asteroids [link], but three stand out. C-group, or carbonaceous, asteroids contain carbon compounds, as well as other volatiles like water, and are very common. While not full of valuable minerals like iron, titanium, or platinum, they contain ingredients essential for life and other biological processes. The Moon lacks carbon, and it's necessary for many chemical reactions.
S-group, or silicaceous, asteroids are composed primarily of silicates (rock). These can be used as construction materials, or for refining silicon.
Finally, M-type asteroids contain lots of iron and nickel. The biggest advantage of M-type asteroids from our Earthly perspective is that they are undifferentiated. Earth, with its active geological history and hot core, has slowly but steadily precipitated out all the heaviest elements to its center where they are completely inaccessible to us. Asteroids are too small and too cold to have ever done that, so everything they have is on display, ready to mine. There are some estimates that
The NASA Precedent: The Asteroid Redirect Mission
Asteroid mining is especially interesting because it's the only space industry concept that NASA made serious plans to advance. There's been a lot of debate about the merits of NASA's current Artemis program and it's convoluted framework for putting a person on the Moon again, as well as it's lack of plans to utilize lunar resources. Compare this to Moon Direct and other plans to set up ISRUs to produce return fuel immediately [Read more about Moon Direct here]. However, NASA's ARM plan, while it soon devolved into make-believe and was quietly cancelled, set a viable framework for asteroid mining that left its legacy in commercial plans today.
(NASA Asteroid Redirect Mission infographic)The NASA Precedent: The Asteroid Redirect Mission
Asteroid mining is especially interesting because it's the only space industry concept that NASA made serious plans to advance. There's been a lot of debate about the merits of NASA's current Artemis program and it's convoluted framework for putting a person on the Moon again, as well as it's lack of plans to utilize lunar resources. Compare this to Moon Direct and other plans to set up ISRUs to produce return fuel immediately [Read more about Moon Direct here]. However, NASA's ARM plan, while it soon devolved into make-believe and was quietly cancelled, set a viable framework for asteroid mining that left its legacy in commercial plans today.
The basic idea is to fly a high-isp robotic spacecraft out to an appropriately sized asteroid, pick it up in a doggie bag, then fly it back to lunar orbit for an Orion spacecraft to inspect up close. As you can see in step 1 of the yellow track, it takes multiple orbits of apogee burns to finally escape Earth's orbit, plus a gravity slingshot around the Moon - this is due to the extremely low thrust of the ion engines it would use. Now imagine coming back with the weight of the asteroid... It was impossible for Orion to do it itself, because the Orion service module is severely underpowered (which partly led to the LOP-G currently being developed). There were a few other concepts, but the idea of bagging the asteroid is interesting, in the context of mining. Asteroids have negligible gravity, so if you drill or do anything to extract resources, the excavated material will just fly off into space. Bagging the asteroid also opens up additional possibilities, as we'll see below
The Players
Planetary Resources is probably the most well-known company looking to exploit the stars. They started with the ambitious goal of mining asteroids in 2009, but so far have only launched a few survey demonstration satellites; in addition to this, they used COTS solutions to map out all the most profitable asteroids in the neighborhood of Earth. They realized that the infrastructure is not there to make it profitable, although they did take advantage of the air-launched LauncherOne, which was probably the first affordable smallsat launcher. Unfortunately, it appears that the company failed to procure funding in 2018 and had to lay off many of its employees and was bought out by a blockchain company.
(PR's process for getting at asteroid resources)
Another well-known(-ish) company is Deep Space Industries, started by space business pioneer Rick Tumlinson. It also appears to have to gone defunct, but they also realized they needed additional infrastructure to make it work. So their first big development (besides some cool concept art of asteroid processing facilities) was water propulsion, which is becoming more and more common now with CubeSats as a green, non-toxic, easily handled propellant. The idea behind it is to use water extracted from asteroids as a quasi-infinite propellant to maneuver the asteroid back to a more permanent processing facility to extract the rest of the minerals from it.
(DSI Fuel Processor Concept from space.com)
The third company I'd like to talk about is TransAstra. While public products of Planetary Resources seem to be limited to finding asteroids, and Deep Space Industries got hung up on propulsion, TransAstra got as far as a NASA Innovative Advanced Concepts (NIAC) Phase III grant, the first ever, to test a prototype of their mining equipment on an asteroid simulant in low Earth orbit [Official][Commentary]. Notably, they're using a Momentus Vigoride spacecraft bus, which is basically a smallsat bus powered by water plasma thrusters. The gist of TransAstra's plan is to deploy these small-ish robotic "Worker Bees" (literally what they're called) to go to asteroids, bag them ARM-style, and evaporate the water ice using optical mining. They've already demonstrated optical mining on the ISS, so this is a pretty advanced proof-of-concept for them to go into orbit, pick up a fake asteroid, and then suck the life out of it just like it would with a real asteroid.
(TransAstra APIS or Honey Bee)
The big benefit of optical mining, aside from their already-proven results with it on the ISS, is that it doesn't require converting solar energy into electricity, then back into heat, while also requiring a container of sufficient material strength to contain all that. It just directs the concentrated light beam to a point on the asteroid, evaporates the volatiles, then sucks them into another bag for storage. Sounds easy! My opinion is that the solar concentrators and "piping" will be the most difficult part, both to get into orbit and to manufacture, since the water propulsion, the asteroid bag, and the optical mining have already been proven. I think another downside of their business model is reliance on low-efficiency water propulsion. Water as a propellant, while avoiding the massive energy costs and difficulty of storage that comes with liquid hydrogen, takes a massive hit on efficiency. Using water as a propellant basically means throwing away 2/3 of your fuel (TransAstra claims 360 seconds [src], but other water thrusters get about 130 seconds), so unless the spacecraft itself is extremely light (which could be done if its all plastic and built in space), you're gonna spend most of your asteroid mother lode just getting home. On the plus side, it uses no electricity for propulsion, just reflected solar energy to heat the water, which will cut on weight significantly. It'll also take a long time, but that's fine with thousands of mini robotic worker bees doing the work incrementally. As a plus, it can harvest for fuel on the go, and when it gets back, the dry husk can be mined by more specialized equipment to get the metal resources as well.
How To Get Resources
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