Three basic approaches for constructing a space elevator have been proposed: First, using in-space resources to

manufacture Manufacturing is the creation or production of goods with the help of equipment, labor, machines, tools, and chemical or biological processing or formulation. It is the essence of secondary sector of the economy. The term may refer to a ra ...

the whole cable in space. Second, launching and deploying a first seed cable and successively reinforcing the seed cable by additional cables, transported by climbers. Third, spooling two cables down and then connecting the ends, forming a loop.

Early construction concepts

There are two approaches to constructing a

space elevator A space elevator, also referred to as a space bridge, star ladder, and orbital lift, is a proposed type of planet-to-space transportation system, often depicted in science fiction. The main component would be a cable (also called a tether) an ...

. Either the cable is manufactured in space or it is launched into space and gradually reinforced by additional cables, transported by climbers into space. Manufacturing the cable in space could be done in principle by using an

asteroid An asteroid is a minor planet of the Solar System#Inner solar system, inner Solar System. Sizes and shapes of asteroids vary significantly, ranging from 1-meter rocks to a dwarf planet almost 1000 km in diameter; they are rocky, metallic o ...

Near-Earth object A near-Earth object (NEO) is any small Solar System body whose orbit brings it into proximity with Earth. By convention, a Solar System body is a NEO if its closest approach to the Sun (perihelion) is less than 1.3 astronomical units (AU) ...

.Hein, A.M.
Producing a Space Elevator Tether Using a NEO: A Preliminary Assessment
International Astronautical Congress 2012, IAC-2012, Naples, Italy, 2012 One early plan involved lifting the entire mass of the elevator into geostationary orbit, and lowering one cable downwards towards the Earth's surface while simultaneously another cable is deployed upwards directly away from the Earth's surface.Pearson, J. (1975). The orbital tower: a spacecraft launcher using the Earth's rotational energy. Acta Astronautica, 2(9), 785-799.
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Tidal force The tidal force is a gravitational effect that stretches a body along the line towards the center of mass of another body due to a gradient (difference in strength) in gravitational field from the other body; it is responsible for diverse phenom ...

s (

gravity In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the str ...

and

centrifugal force In Newtonian mechanics, the centrifugal force is an inertial force (also called a "fictitious" or "pseudo" force) that appears to act on all objects when viewed in a rotating frame of reference. It is directed away from an axis which is parallel ...

) would naturally pull the cables directly towards and directly away from the Earth and keep the elevator balanced around geostationary orbit. As the cable is deployed,

Coriolis force In physics, the Coriolis force is an inertial or fictitious force that acts on objects in motion within a frame of reference that rotates with respect to an inertial frame. In a reference frame with clockwise rotation, the force acts to the ...

s would pull the upper portion of the cable somewhat to the West and the lower portion of the cable somewhat to the East; this effect can be controlled by varying the deployment speed. However, this approach requires lifting hundreds or even thousands of tons on conventional

rocket A rocket (from it, rocchetto, , bobbin/spool) is a vehicle that uses jet propulsion to accelerate without using the surrounding air. A rocket engine produces thrust by reaction to exhaust expelled at high speed. Rocket engines work entire ...

s, an expensive proposition.

Cable seeding design

Bradley C. Edwards Bradley C. Edwards is an American physicist who has been involved in the development of the space elevator concept. Biography Dr Edwards received his PhD degree in Physics from the University of Wisconsin–Madison in 1990. His thesis work wa ...

, former Director of Research for the Institute for Scientific Research (ISR), based in

Fairmont, West Virginia Fairmont is a city in and county seat of Marion County, West Virginia, United States. The population was 18,313 at the 2020 census. It is the principal city of the Fairmont Micropolitan Statistical Area, which includes all of Marion County, a ...

proposed that, if nanotubes with sufficient strength could be made in bulk, a space elevator could be built in little more than a decade, rather than the far future. He proposed that a single hair-like 20-ton 'seed' cable be deployed in the traditional way, giving a very lightweight elevator with very little lifting capacity. Then, progressively heavier cables would be pulled up from the ground along it, repeatedly strengthening it until the elevator reaches the required

mass Mass is an intrinsic property of a body. It was traditionally believed to be related to the quantity of matter in a physical body, until the discovery of the atom and particle physics. It was found that different atoms and different element ...

and

strength Strength may refer to: Physical strength *Physical strength, as in people or animals *Hysterical strength, extreme strength occurring when people are in life-and-death situations *Superhuman strength, great physical strength far above human ca ...

. This is much the same technique used to build

suspension bridge A suspension bridge is a type of bridge in which the deck is hung below suspension cables on vertical suspenders. The first modern examples of this type of bridge were built in the early 1800s. Simple suspension bridges, which lack vertical ...

s. The length of this cable is 35,786 km or 35,786,000 m. A 20-ton cable would weigh about 1.12 grams per m.

Loop elevator design

This is a less well developed design, but offers some other possibilities. If the cable provides a useful tensile strength to density of about 48.1 GPa/(kg/m³) or above, then a constant width cable can reach beyond geostationary orbit without breaking under its own weight. The far end can then be turned around and passed back down to the Earth forming a constant width loop, which would be kept spinning to avoid tangling. The two sides of the loop are naturally kept apart by

coriolis force In physics, the Coriolis force is an inertial or fictitious force that acts on objects in motion within a frame of reference that rotates with respect to an inertial frame. In a reference frame with clockwise rotation, the force acts to the ...

s due to the rotation of the Earth and the loop. By increasing the thickness of the cable from the ground a very quick (exponential) build-up of a new elevator may be performed (it helps that no active climbers are needed, and power is applied mechanically.) However, because the loop runs at constant speed, joining and leaving the loop may be somewhat challenging, and the carrying capacity of such a loop is lower than a conventional tapered design.

Current status

Currently, the cable seeding design and the space manufacturing design are considered. The space manufacturing design would use a carbonaceous

near-Earth object A near-Earth object (NEO) is any small Solar System body whose orbit brings it into proximity with Earth. By convention, a Solar System body is a NEO if its closest approach to the Sun (perihelion) is less than 1.3 astronomical units (AU) ...

for mining its material and producing a

carbon nanotube A scanning tunneling microscopy image of a single-walled carbon nanotube Rotating single-walled zigzag carbon nanotube A carbon nanotube (CNT) is a tube made of carbon with diameters typically measured in nanometers. ''Single-wall carbon nan ...

cable. The cable would then be transported back to geostationary orbit and spooled down. Although this approach shifts the construction complexity away from the use of climbers in the cable seeding design, it increases the complexity of the required in-

space infrastructure Human presence in space is about humanity in space, particularly about all anthropogenic presence in space and human activity in space, that is in outer space and in a broader sense also on any extraterrestrial astronomical body. Humans have ...

. The cable seeding design could be rendered infeasible in case the material strength is considerably lower than was projected by Brad Edwards. Current technological status of the cable seeding design: a) It would take 5 days to reach a geostationary altitude of 36,000 km with this speed. Space elevator#Climbers

References

External links

The Space Elevator Reference

{{Space elevator

Construction Construction is a general term meaning the art and science to form objects, systems, or organizations,"Construction" def. 1.a. 1.b. and 1.c. ''Oxford English Dictionary'' Second Edition on CD-ROM (v. 4.0) Oxford University Press 2009 and ...

Transportation engineering