Theoretical Megastructure

1 theoretical

1.1 stellar scale
1.2 planetary scale
1.3 orbital structures
1.4 trans-orbital structures

theoretical

a number of theoretical structures have been proposed may considered megastructures.

stellar scale

a cut-away diagram of idealized dyson shell—a variant on dyson s original concept—1 au in radius.

most stellar scale megastructure proposals designs make use of energy sun-like star while possibly still providing gravity or other attributes make attractive advanced civilization.

the alderson disk theoretical structure in shape of disk, outer radius equivalent orbit of mars or jupiter , thickness several thousand miles. civilization live on either side, held gravity of disk , still receive sunlight star bobbing , down in middle of disk.
a dyson sphere (also known dyson shell) refers structure or mass of orbiting objects surrounds star make full use of solar energy.
a matrioshka brain collection of multiple concentric dyson spheres make use of different wavelengths of light.
a stellar engine either uses temperature difference between star , interstellar space extract energy or serves shkadov thruster.
a shkadov thruster accelerates entire star through space selectively reflecting or absorbing light on 1 side of it.
topopolis (also known cosmic spaghetti) large tube rotates provide artificial gravity.
a ringworld (or niven ring) artificial ring encircling star, rotating faster orbital velocity create artificial gravity on inner surface. non-rotating variant transparent ring of breathable gas, creating continuous microgravity environment around star, in eponymous smoke ring.

related structures might not classified individual stellar megastructures, occur on similar scale:

a dyson swarm dyson sphere made of separately orbiting elements (including large habitats) rather single continuous shell.
a dyson bubble dyson sphere in individual elements statites, non-orbital objects held aloft pressure of sunlight.

planetary scale

a bishop ring, halo or orbital space habitat similar smaller niven ring. instead of being centered on star, in orbit around star , diameter typically on order of magnitude of planet. tilting ring relative orbit, inner surface experience conventional day , night cycle. due enormous scale, habitat not need enclosed stanford torus, instead atmosphere retained solely centripetal gravity , side walls, allowing open sky.
globus cassus hypothetical proposed project transformation of planet earth bigger, hollow, artificial world ecosphere on inner surface. model serves tool understand world s real functioning processes.
shell worlds or paraterraforming inflated shells holding high pressure air around otherwise airless world create breathable atmosphere. pressure of contained air supports weight of shell.
completely hollow shell worlds can created on planetary or larger scale contained gas alone, called gravitational balloons, long outward pressure contained gas balances gravitational contraction of entire structure, resulting in no net force on shell. scale limited mass of gas enclosed, shell can made of mundane material. shell can have additional atmosphere on outside.

orbital structures

an orbital ring dynamically elevated ring placed around earth rotates @ angular rate faster orbital velocity @ altitude, stationary platforms can supported excess centripetal acceleration of super-orbiting ring (similar in principle launch loop), , ground-tethers can supporter stationary platforms.
the bernal sphere proposal space colony maximum diameter of 16 kilometers.
rotating wheel space stations, such stanford torus, wheel-like space station produce artificial gravity rotation. typical designs include transport spokes central hub used docking and/or micro-gravity research.
the related concepts, o neill , mckendree cylinders, both pairs of counter-rotating cylinders containing habitable areas inside , creating 1g on inner surfaces via centripetal acceleration. scale of each concept came estimating largest 1g cylinder build steel (o neill) or carbon fibre (mckendree).
hollowed asteroids (or bubble worlds or terraria) spun on axis simulated gravity , filled air, allowing them inhabited on inside. in concepts, asteroid heated molten rock , inflated final form.

trans-orbital structures

one concept space elevator has tethered mobile seagoing platform.




a skyhook long tether hangs down orbit.
a space elevator tether fixed ground, extending beyond geostationary orbital altitude, such centripetal force exceeds gravitational force, leaving structure under slight outward tension.
a space fountain dynamically supported structure held momentum of masses shot top @ high speeds ground.
a launch loop (or lofstrom loop) dynamically supported 2000 km long iron loop projects in arc 80 km ridden maglev cars while achieving orbital velocity.
startram generation 2 maglev launch track extending ground above 96% of atmosphere s mass, supported magnetic levitation.
a rotovator rotating tether lower tip moving in opposite direction tether s orbital velocity, reducing difference in velocity relative ground, , hence reducing velocity of rendezvous; upper tip likewise moving @ greater orbital velocity, allowing propellantless transfer between orbits. around airless world, such moon, lower tip can touch ground 0 horizontal velocity. momentum exchange tether, orbital energy gained or lost in transfer.




^ shell worlds - approach terraforming moons, small planets , plutoids , k. l. roy; r. g. kennedy iii; d. e. fields, 2009, jbis, 62, 32-38
^ dani eder [1]
^ ederworld analyzed (concentric gravity balloons maximize volume)
^ o neill, gerard k. (1977). high frontier: human colonies in space. william morrow , company. isbn 0-688-03133-1. 
^ mckendree, thomas lawrence (november 9–11, 1995). implications of molecular nanotechnology technical performance parameters on defined space system architectures. fourth foresight conference on molecular nanotechnology. palo alto, california. 
^ cole, dandridge m.; cox, donald w. (1964). islands in space: challenge of planetoids. philadelphia: chilton book co. asin b0007dzsr0. 
^ niven, larry (1974). bigger worlds . hole in space. new york: ballantine books. pp. 111–126. asin b002b1ms6u. 
^ tether transport leo lunar surface , robert l. forward, 1991, 27th joint propulsion conference, aiaa 91-2322