By Abhinav Sukla

For thousands of years, humans have only been able to stare upward at the heavens. Hardly half a century ago, many scoffed at the notion of even leaving Earth’s atmosphere. Now, in an age where the space industry is being rapidly privatized and our brief, post–Cold War hiatus from space exploration has ended, the planets and stars have never been closer to our grasp.

Most of us, however, are still hyperfocused on observation alone. I think we should be a little more ambitious, and begin to think about how we can USE what we find in space. In order to do so, I’ve broken the future of space resource extraction into three rough categories: the short term (50–100 years from now), the mid term (100–1000 years from now), and the long term (several thousand years from now).

Short term

Although his political controversies make the news far more often than his extraterrestrial ambitions, Elon Musk has been a central figure in publicizing space resource extraction, specifically through his Mars settlement initiative. Mars settlements, like the one Mr. Musk proposes, would use Mars’ carbon dioxide rich atmosphere to produce methane fuel, allowing the planet to act like a fuel station for space missions in the area. In its flagship rocket, the Starship, SpaceX uses methane fuel for exactly this reason: if a Mars base is established, powering rockets with methane fuel could enable even more expansion. The engineering here is largely settled; what remains is a question of time and continued investment.

The moon also has similar potential to become a waypoint for rockets. The moon’s underground caverns are packed with ice, and this ice can be harvested, and the water molecules broken down into hydrogen and oxygen, which can then be synthesized into rocket fuel. Helium-3, a unique isotope of helium necessary for fusion power (power generated by fusing 2 atoms), is also found on the moon, although fusion power remains an open question, and may not be widely available for centuries even if it proves viable.

In the short term, we could also begin trying to capture asteroids and extract the materials from them. Many asteroids are filled with trillions in rare metals, but the precision maneuvering required to harvest them is still far out of our reach. That’s why it’s likely only limited, preliminary trials will occur during this period. In the mid term, however, asteroid mining might become a crucial part of our economy as the technology develops.

Mid term

Profitably mining asteroids would mean overcoming some steep challenges. We’d have to locate suitable targets and reach them across orbits that make the fuel logistics unpredictable, then anchor to them, and then begin to drill. A lot could go wrong, and the minuscule margin for error necessitates impeccable mining technology, a significant engineering obstacle. The payoff, though, could be enormous. Asteroids hold vast quantities of water, which can be split into rocket fuel, along with rare metals worth trillions. Rather than hauling these materials back to Earth, where they’d be costly to transport and would crash market prices anyway, they’d be most valuable left in space, supplying fuel depots, construction, and the broader off-world economy that the earlier stages of expansion would have already established.

The second idea is far simpler, and relies on well known physics that is already being applied here on Earth: solar panels. A massive “swarm” of millions of solar panels that orbit close to the sun, known as a Dyson Swarm, could be developed. Such a swarm could capture a significant fraction of the sun’s energy output, dwarfing anything achievable on Earth, and beam it back to power our civilization’s growing energy demands.

The mid-term goals above sit within the bounds of known physics and plausible engineering. The long-term ones are far more speculative, and require technological advances that are far from guaranteed.

Long term

Perhaps the most well known long term space resource extraction goal is the Dyson Sphere. The Dyson sphere holds a special place in the world of science fiction as an ambitious and awe-inspiring super structure. In essence, it is a scaled up version of a Dyson swarm — it involves encompassing an entire star in a shell made of solar panels in order to harvest its entire power output. Despite being by far the most prominent of all the devices mentioned in this section, the Dyson sphere is likely the least practical. For one, the premise relies on sheer scale to achieve massive power outputs, since solar panels are nowhere near the best way to extract energy. As a result, the amount of material needed to actually build this structure would require breaking down all of the solar system’s planets, including Earth, which is a completely unviable idea for the foreseeable future considering we are still living here. Although the next two proposals are extrasolar, they offer more elegant ways to extract power from stellar objects, and most of the challenges lie in transportation to these objects rather than the actual engineering behind the structures.

The Penrose process describes a theoretical mechanism for extracting the rotational energy of a black hole. The premise is simple: when Kerr (rotating) black holes consume matter through the Penrose process, they sacrifice a little bit of their rotational energy, so throwing matter into a Kerr black hole could potentially allow for its energy to be slowly extracted. Black holes have a region known as the ergosphere that is located just outside of their event horizons. A phenomenon known as frame-dragging occurs in this space: due to the powerful gravity of black holes, space-time itself is dragged in the direction of the black hole’s spin inside of the ergosphere. The Penrose process theorizes that if an object were sent into the ergosphere and broken into 2 pieces such that one piece was on a trajectory into the black hole while the other would skirt along the outside of the ergosphere and be able to leave, the remaining piece would be sped up by the frame-dragging, effectively having “stolen” a portion of the black hole’s rotational energy. The idea is that the piece being consumed has negative energy and angular momentum relative to an outside observer once it starts its descent, and the conservation of energy and momentum dictates that the other piece must escape with an increase in energy, which is drawn from the black hole’s own rotation, slowing it slightly as a result. The Penrose process has the potential to be a highly efficient energy production method, but there are a few glaring obstacles to implementing it, the most obvious being the logistical constraint. The closest Kerr black hole is located around 1560 light years away. Even assuming we may someday be able to construct rockets capable of traveling at ~25% the speed of light, a dubious proposition in itself, such a journey would require dozens or hundreds of generations to live out their lives in the depths of space in order to actually reach one of these black holes.

The final mechanism I am proposing is currently just as unfeasible as using the Penrose Process, but has similarly high power generation potential. It involves a special type of neutron star called pulsars. Neutron stars are hyper-compressed, magnetized, and rapidly rotating remnants of stars 8–20x the mass of our sun after they reach the end of their lives and go supernova. Pulsars are neutron stars that have misaligned magnetic and rotational axes. These pulsars are the most powerful spinning magnets in the universe, which means their rotation can create a massive change in the magnetic field within a conductive coil placed in orbit nearby. Such a system is known as a permanent magnet generator, or PMG, and could potentially generate billions of times the entire world’s current power usage when the magnet in question is an object as powerful as a pulsar. However, apart from the extreme heat and radiation emanating from neutron stars, this system would experience the Lorentz force, which acts on charged particles moving through magnetic fields. Since this force is proportional to the speed of the object (which is large due to the small radius of ~10km of neutron stars and their large mass) and to the strength of the magnetic field, there would be crushing structural pressure on the system as well as large torques that threaten to dislodge the coil’s orbit entirely. Thus, a pulsar based PMG may remain beyond our reach long after the advent of interstellar travel.

Some of the more speculative ideas on this list may never be actually constructed due to the unpredictability of technological progress. However, many of the short-term and mid-term propositions are achievable even with today’s technology. The only thing missing is incentive. Global investment in space has increased in recent years, but it remains focused on observation, communication, and defense rather than extraction. If priorities change, the first steps toward one of these plans might arrive sooner than we expect.