A shellworld is any of several types of hypothetical

megastructure A megastructure is a very large artificial object, although the limits of precisely how large vary considerably. Some apply the term to any especially large or tall building. Some sources define a megastructure as an enormous self-supporting a ...

s: *A planet or a planetoid turned into series of concentric

matryoshka doll Matryoshka dolls ( ; rus, матрёшка, p=mɐˈtrʲɵʂkə, a=Ru-матрёшка.ogg), also known as stacking dolls, nesting dolls, Russian tea dolls, or Russian dolls, are a set of wooden dolls of decreasing size placed one inside ano ...

-like layers supported by massive pillars. A shellworld of this type features prominently in Iain M. Banks' novel ''

Matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ultimately composed of atoms, which are made up of interacting subatomic partic ...

''. *A megastructure consisting of multiple layers of shells suspended above each other by

orbital ring An orbital ring is a concept of an artificial ring placed around a body and set rotating at such a rate that the apparent centrifugal force is large enough to counteract the force of gravity. For the Earth, the required speed is on the order of 1 ...

s supported by hypothetical mass stream technology. This type of shellworld can be theoretically suspended above any type of stellar body, including planets, gas giants, stars and black holes. The most massive type of shellworld could be built around

supermassive black hole A supermassive black hole (SMBH or sometimes SBH) is the largest type of black hole, with its mass being on the order of hundreds of thousands, or millions to billions of times the mass of the Sun (). Black holes are a class of astronomical obj ...

s at the center of

galaxies A galaxy is a system of stars, stellar remnants, interstellar gas, dust, dark matter, bound together by gravity. The word is derived from the Greek ' (), literally 'milky', a reference to the Milky Way galaxy that contains the Solar System. ...

. *An inflated canopy holding high pressure air around an otherwise airless world to create a breathable atmosphere."Shell Worlds - An Approach To Terraforming Moons, Small Planets and Plutoids"
K. L. Roy; R. G. Kennedy III; D. E. Fields, 2009, JBIS, 62, 32-38 The pressure of the contained air supports the weight of the shell. * Completely hollow shell worlds can also be created on a planetary or larger scale by contained gas alone, also called bubbleworlds or gravitational balloons, as long as the outward pressure from the contained gas balances the gravitational contraction of the entire structure, resulting in no net force on the shell. The scale is limited only by the mass of gas enclosed; the shell can be made of any mundane material. The shell can have an additional atmosphere on the outside.

References

External links

Shellworlds
* * * *{{cite web, url=http://www.orionsarm.com/eg-article/464f869fc12cb, title=Orion's Arm - Encyclopedia Galactica - Dynamic Orbital Rings, website=orionsarm.com, accessdate=2018-08-09 Megastructures Exploratory engineering Terraforming