Dyson Shell 2.0
Any animate fan of science fiction is well acquainted with the concept of a Dyson Shell, often incorrectly referred to by it’s parent concept: the Dyson Sphere. While a Dyson Sphere can be defined as any one of three specific solar energy collecting megastructures, a Dyson Shell is unique because of it’s capability to collect 100% of a star’s energy output, fully encapsulating it in an opaque sphere of ultra-strong photovoltaic material. This shell is not only capable of serving an advanced species with a nearly limitless supply of power, but also providing it with a vast livable internal biosphere millions of times the surface area any rocky planet could offer. Dyson Spheres of all varieties are staples in both science fiction, as well as the actual search for extraterrestrial life in our universe.
A while back, I delineated the properties of the three types of Dyson Spheres, and the the actual feasibility of creating one ourselves in the distant future. While Dyson Swarms and Dyson Bubbles are not out of the realm of feasibility with semi-modern technology, traditional Dyson Shells will likely remain a technical improbability due to their sheer size, their insane dynamical properties, and their reliance on impossibly strong materials. Still, the idea of harnessing the entire power output of a star would be tantalizing to any rapidly advancing species looking to expand outwards into the cosmos. With the next nearest sources of power of this magnitude likely being light-years away, such a race may find the need to look towards another solution to the Dyson Shell, one which, despite being far more radical, is far simpler.
Before I delve into this solution, it is first prudent to go over what makes a traditional Dyson Shell so arduous. A traditional Dyson Shell would be constructed around a species’ home star at the distance of the star’s habitable zone. For our sun, this is about 1 AU. Even using every last shred of solid material in the Solar System (including the cores of the giant planets), such a shell would only have a thickness of about 48 centimeters; roughly the length of your arm. Considering this structure would be hundreds of millions of kilometers in diameter, this is an extremely thin-walled shell. Artificial gravity would then be created by rotating the structure around the star at extreme velocities, inducing a centrifugal force on anything within. This rotation is not trivial; a Dyson Shell with a radius of 1 AU around our Sun would need to be spun up to a velocity of 1,200 km/s (0.4% of the speed of light) to simulate the gravitational acceleration experienced here on Earth! For a shell boasting a thickness of 48 centimeters, this velocity engenders a material stress something on the order of 10²⁰ Pascals: 1.7 billion times the strength of diamond.
Though it seems a traditional Dyson Shell can likely be ruled out of technical feasibility, another form of Dyson Shell just might do the trick. Often referred to as a non-rotating Dyson Shell, this “Dyson Shell 2.0” could provide a solution to most, if not all of the technical difficulties exhibited by the traditional Dyson Shell. The design of a non-rotating Dyson Shell is very similar to that of its predecessor; a large, rigid sphere which completely encases a star for the purpose of energy collection. The difference is that while a traditional Dyson Shell produces gravity via rotation, the non-rotating Dyson Shell uses the star’s mass itself as the source of it’s gravity. The shell is built with a much smaller radius; the radius at which the star’s gravity at that distance is equal to the gravity of their home planet, encapsulating far less volume than a traditional Dyson Shell. Because of this, a civilization which utilizes a non-rotating Dyson Shell would instead live on the outside surface, where gravity pulls them downward.
Using this design, a species could make a Dyson Shell orders of magnitude thicker with the same amount of material, while not having to stress (pun intended) about creating a material stronger than physics deems possible. Pulverizing just the inner rocky planets into building material, our species could construct such a shell around our Sun 50 meters thick at the distance where the Sun’s gravity equals the Earth’s. This radius would be about 3.7 million km; 16 times closer to the Sun than Mercury’s orbit, and nearly 2 times closer than the Parker Solar Probe will pass at its closest approach to the Sun in 2025. Because the only stress imparted on the structure would be from the Sun’s gravity as opposed to extreme rotation, the material constraints of a non-rotating Dyson Shell are also much less stringent. With a 50 meter thickness, the megastructure would require a material with a strength of ~20,000 Gigapascals; just 20 times the maximum known yield strength of graphene. Given that such a structure will likely not be constructed for hundreds if not thousands of years, this is not an insurmountable feat.
To live on such a Dyson Shell, planet-sized “bowls” could be engineered into the outer surface of the shell capable of housing all the various biospheres from the species’ home planet, plus several bowls for the species themselves. These bowls could then be filled with breathable atmosphere, liquid water, and organisms, all confined to the inside of the bowls by the steady gravitational force from below. The various wildlife biospheres could be treated like National Parks and kept comparatively untouched, while the race could continue to advance and expand rapidly in the “developed” biospheres. All of the biospheres could be interconnected by a vast transit system running through the interior of the shell like the veins of a body.
The biggest challenges associated with a non-rotating Dyson Shell would be:
- Lack of sunlight for the biospheres,
- Extreme heat conducted through the shell’s surface, and
- Gravitational instability.
Because the biospheres would need to be constructed on the outside of the shell, there would obviously be no natural sunlight available to the species that builds it. This can be negated by one of two methods: artificial lighting, or reflective lighting. A species collecting the power output of an entire star can likely spare a few Watts to illuminate several planet-sized biospheres, no sweat. If they instead prefer natural lighting, a series of mirrors and channels could direct filtered sunlight from the shell’s interior to the biospheres using a bit of engineering magic.
Inhabitants of non-rotating Dyson Shells would be besieged by extremely high surface temperatures from below due to their required proximity to their host stars. The Parker solar probe negates this heat by using a highly reflective sunshield to redirect the continuous torrent of solar radiation out into space. This method would be futile for a Dyson Shell, however, because unlike the Parker Solar Probe, the inside of a Dyson Shell would not be reflecting this heat into space, but simply containing it within itself. This effect would destroy the radiative temperature gradient around the star, and probably cause the star to bloat until it either became too diffuse for fusion to continue in its core, or until it destroyed the shell itself. Not to mention that making the interior of the shell reflective defeats the whole purpose of building a Dyson Shell. Instead, the species could shield the undersides of their biospheres with insulative material to cause unwanted heat to flow around them, and out into space. A large scale active cooling system consisting of massive radiators could also help to mitigate this issue.
Finally, non-rotating Dyson Spheres would suffer from gravitational instabilities by the nature of their designs. In theory, the structure would be gravitationally stable only when its center of mass was placed exactly in line with the Sun’s, but the moment anything perturbs this system (like a tiny asteroid hitting one side or even interactions from the distant gas giants), the entire structure would destabilize and free fall into the Sun. An advanced active control system with powerful maneuvering thrusters would be required to maintain gravitational stability, and perhaps spinning the structure just a little bit might not hurt in this respect as well.
All Dyson Shells, of course, are not without other serious challenges. Both types of shells would require an extremely advanced manufacturing process, involving breaking up entire planets and transforming them into insanely rigid, solar collecting material. Both types would require an immense knowledge of power transfer as well, eons ahead of anything we can imagine today. Both would also need an effective asteroid deflection system, a highly accelerated understanding of orbital dynamics, and of course, an extreme knowledge of space as an manipulable environment. Building a Dyson Shell, non-rotating or otherwise, would be an extraordinary engineering and scientific feat.
Still, when push comes to shove, the Dyson Shell 2.0 may yet be the most effective solution to power collection for a rapidly developing species looking to spread out into the universe. Such a megastructure wouldn’t come without its hurdles, but one thing for certain is that life of all kinds has been known to seek out challenges and exploit them, any way they can. Our species today has just begun to harvest the awesome power of the Sun, our nearest celestial neighbor. The Sun continually emits enough free energy in 1 second to power the energy demands of our entire race for a week, and it doesn’t have any plans of stopping for the next 5 billion years. As we advance out towards the vast frontier of space, we would be foolish to look elsewhere than towards our own Sun for our ever-escalating power demands.
