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Planetary Resource Extraction and Disassembly
Technology > Application > Manufacturing
Technology > Application > Materials Technology
Technology > Application > Megascale Engineering
Technology > Application > Materials Technology
Technology > Application > Megascale Engineering
 Image from Steve Bowers | |
| This partially disassembled planet is surrounded by nearly-completed suprashell, which will serve to collect material for onward distribution while also serving as a radiator to emit waste heat. | |
Due to the proportionally high energy cost of material export compared to asteroids, planetary surfaces are not the most convenient source of raw material. Regardless, planets do possess enormous volumes of mass which can be a sizable contribution to larger construction projects. Other reasons to mine them may be to create a swarm of habitats that more efficiently utilize the bodies' mass, or they may simply want the mass gone.
Terrestrial and rocky worlds can be landed on and built upon; many world support a moderate or even large population. But to extract material from a planet for use elsewhere. the gravitational pull must be overcome, for which there are two main fundamental methods: propel the mass with direct thrust, or launch it with kinetic infrastructure. Propellant rockets are rarely utilized as they can be slow and energy expensive to operate, though they have the advantage of being able to launch from anywhere to any orbit. Kinetic infrastructure such as mass drivers is the preferred method, allowing for a constant flow of packaged material to be rapidly launched into orbit, but with the drawback of having a set launch vector - that being whichever direction into space the driver happens to be facing at the time - and requiring massive static infrastructure.
Gaseous bodies are a common source of resources for any system, their dense upper atmospheres hosting easily accessed resources. It is typical for any system to have arrays of scoopship infrastructure in elliptical orbits around gaseous worlds, bringing the ships through the atmosphere for material extraction which is then released on the aphelion of the orbit. The material can be processed onboard the ships, or sent to a local orbital facility for processing.
For total disassembly, worlds will see stages of disassembly techniques. The mass of the world is a primary concern in the decision to undertake this process, as planets vary considerably in mass and volume, and thus the energy and time needed to disassemble them. The techniques used will accommodate the challenges weighed against what the bodies performing the extraction intend to do with the material and the system at large. One method is to use systems of orbital rings or loops reaching down into the atmosphere, supporting pipes which compress and contain the material and lift it out against gravity. The world may be totally encompassed by a suprashell or similar structure, with arrays of rings or loops extending down from the inside of the shell.
The loop-extraction process may be supplemented or entirely replaced by more energy-hungry methods. Gas worlds can be spun up and rotated fast enough that the effective gravity on the equator is reduced, making extraction easier; at higher speeds material will begin to fly off on its own. The planet can also be targeted with focused heat to excite the atmosphere to the point it begins to "boil" and expand, again leading to easier or inherent extraction. These processes are generally used with a series of suprashells maintained at different temperatures, which gather the extracted material and radiate any waste heat (which can be considerable). Mass drivers attached to the suprashell, or supported by eccentric orbital loops, facilitate delivery of material to distant destinations.
Energy required for total disassembly
To totally disassemble a planet and transport its mass out of its own gravity well, it is necessary to overcome the gravitational binding energy of that planet. The amount of energy required to achieve this is very large; such large amounts of energy can be obtained either by collecting the luminosity of the local star (using a Dyson swarm or bubble), and/or by the use of fusion or conversion technology. In many cases a combination of all three sources of power are used.Assuming relatively efficient use of the total luminosity of a Sun-like star, an Earth-sized planet could be disassembled in approximately 22 standard days, given a gravitational binding energy of 2.18 ×10e32 Joules. A gas giant world the same size and mass as Jupiter could be disassembled in 563 standard years, and this timescale could be reduced if the matter could be utilised in a fusion or conversion reactor. Smaller worlds similar to Mercury could be disassembled in a matter of hours; however, this would not generally be possible because the Dyson swarm would not yet be available in the earliest stages of the process.
In practice, the process of building a Dyson swarm would start by disassembling a relatively small world near the local star, where energy is abundant. For example, the planet Mercury could be disassembled in about thirty standard days, starting from scratch and utilising self-replicating power collection systems that increase in surface area exponentially. This assumes very efficient technology of the kind which is widely available in the Current Era, but had not yet been developed earlier in the history of the Terragen Sphere.
One factor that affects the speed of disassembly is that the deconstruction technology will emit a lot of waste heat (especially towards the end of the process). Additionally the intrinsic heat of the planet's core will add to the excess heat as the planet is reduced in size, a factor which requires require the construction of ever larger radiation surfaces to maintain a reasonable operating temperature. For this and related reasons, the last stages of planetary disassembly are generally carried out by devices and operatives which are tolerant of very high temperatures. The last stages of the disassembly of a planet might resemble a miniature star, as the planet radiates heat and emits vapour which can be collected at a distance after it has cooled down sufficiently.
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Development Notes
Text by Alex Mulvey and Steve Bowers
Initially published on 20 April 2021.
Initially published on 20 April 2021.
Additional Information
More details and many useful tables are available in this essay; Planet Disassembly by Robert Bradbury
See also this paper by Stuart Armstrong and Anders Sandberg (especially section 4.2)
http://www.fhi.ox.ac.uk/wp-content/uploads/intergalactic-spreading.pdf
See also this paper by Stuart Armstrong and Anders Sandberg (especially section 4.2)
http://www.fhi.ox.ac.uk/wp-content/uploads/intergalactic-spreading.pdf
