Space elevator construction
Encyclopedia
The construction of a space elevator is considered to be a large project. Like other historical large projects it entails technical risk: some advances in engineering, manufacture and physical technology are required. Once a first space elevator is built, the second one and all others would have the use of the previous ones to assist in construction, making their costs considerably cheaper. Such follow-on space elevators would also benefit from the great reduction in technical risk achieved by the construction of the first space elevator.
has published a paper that identifies "Five Key Technologies for Future Space Elevator Development":
Two different ways to deploy a space elevator have been proposed.
, and simultaneously lowering one cable downwards towards the Earth's surface while another cable is deployed upwards directly away from the Earth's surface.
Tidal force
s (gravity and centrifugal force) 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 forces 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
s, an expensive proposition.
, former Director of Research for the Institute for Scientific Research (ISR), based in Fairmont, West Virginia
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 cable
s would be pulled up from the ground along it, repeatedly strengthening it until the elevator reaches the required mass
and strength
. This is much the same technique used to build suspension bridge
s.
If the cable provides a useful tensile strength of about 62.5 GPa 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 forces 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.
a) It would take 5 days to reach a geostationary
altitude of 36,000 km with this speed.
Overview
David Smitherman of NASANASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
has published a paper that identifies "Five Key Technologies for Future Space Elevator Development":
- Material for cable (e.g. carbon nanotubeCarbon nanotubeCarbon nanotubes are allotropes of carbon with a cylindrical nanostructure. Nanotubes have been constructed with length-to-diameter ratio of up to 132,000,000:1, significantly larger than for any other material...
and nanotechnologyNanotechnologyNanotechnology is the study of manipulating matter on an atomic and molecular scale. Generally, nanotechnology deals with developing materials, devices, or other structures possessing at least one dimension sized from 1 to 100 nanometres...
) and tower - TetherSpace tetherSpace tethers are cables, usually long and very strong, which can be used for propulsion, stabilization, or maintaining the formation of space systems by determining the trajectory of spacecraft and payloads...
deployment and control - Tall tower construction
- Electromagnetic propulsionElectromagnetic propulsionElectromagnetic propulsion , is the principle of accelerating an object by the utilization of a flowing electrical current and magnetic fields. The electrical current is used to either create an opposing magnetic field, or to charge a fluid, which can then be repelled...
(e.g. magnetic levitationMagnetic levitationMagnetic levitation, maglev, or magnetic suspension is a method by which an object is suspended with no support other than magnetic fields...
) - Space infrastructure and the development of space-based industrySpace-based industrySpace-based industry is a blanket term sometimes used to cover a variety of future forms of human activity in outer space, including asteroid mining, space manufacturing, space trade, construction performed in space such as the building of space stations, space burial, and space advertising.This...
and economy
Two different ways to deploy a space elevator have been proposed.
Traditional way
One early plan involved lifting the entire mass of the elevator into geostationary orbitGeostationary orbit
A geostationary orbit is a geosynchronous orbit directly above the Earth's equator , with a period equal to the Earth's rotational period and an orbital eccentricity of approximately zero. An object in a geostationary orbit appears motionless, at a fixed position in the sky, to ground observers...
, and simultaneously lowering one cable downwards towards the Earth's surface while another cable is deployed upwards directly away from the Earth's surface.
Tidal force
Tidal force
The tidal force is a secondary effect of the force of gravity and is responsible for the tides. It arises because the gravitational force per unit mass exerted on one body by a second body is not constant across its diameter, the side nearest to the second being more attracted by it than the side...
s (gravity and centrifugal force) 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 forces 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
Rocket
A rocket is a missile, spacecraft, aircraft or other vehicle which obtains thrust from a rocket engine. In all rockets, the exhaust is formed entirely from propellants carried within the rocket before use. Rocket engines work by action and reaction...
s, an expensive proposition.
Cable seeding design
Bradley C. EdwardsBradley C. Edwards
In space engineering, Bradley C. Edwards is a researcher who is notable for having worked on Space elevators. He received funding from NIAC from 2001 to 2003 to write a paper proposing a way in which one could be built...
, former Director of Research for the Institute for Scientific Research (ISR), based in Fairmont, West Virginia
Fairmont, West Virginia
Fairmont is a city in Marion County, West Virginia, United States. Nicknamed "The Friendly City". The population was 18,704 at the 2010 census...
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 cable
Cable
A cable is two or more wires running side by side and bonded, twisted or braided together to form a single assembly. In mechanics cables, otherwise known as wire ropes, are used for lifting, hauling and towing or conveying force through tension. In electrical engineering cables are used to carry...
s would be pulled up from the ground along it, repeatedly strengthening it until the elevator reaches the required mass
Mass
Mass can be defined as a quantitive measure of the resistance an object has to change in its velocity.In physics, mass commonly refers to any of the following three properties of matter, which have been shown experimentally to be equivalent:...
and strength
Strength of materials
In materials science, the strength of a material is its ability to withstand an applied stress without failure. The applied stress may be tensile, compressive, or shear. Strength of materials is a subject which deals with loads, deformations and the forces acting on a material. A load applied to a...
. This is much the same technique used to build suspension bridge
Suspension bridge
A suspension bridge is a type of bridge in which the deck is hung below suspension cables on vertical suspenders. Outside Tibet and Bhutan, where the first examples of this type of bridge were built in the 15th century, this type of bridge dates from the early 19th century...
s.
Loop elevator design
This is a less well developed design, but offers some other possibilities.If the cable provides a useful tensile strength of about 62.5 GPa 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 forces 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
Current technological status:| Parameter | Required | Achieved | Year | Notes |
|---|---|---|---|---|
| Tether | ||||
| Strength | 100,000 kN/(kg/m) | 7,100 N | 2010 | House-tether. |
| Climber | ||||
| Speed | 83 m/s (298.8 km/h) a | 18.3 m/s (65.9 km/h) 4 m/s (14.4 km/h) |
2010 2009 |
Battery-powered climber to a distance of 300m, Second Japan Space Elevator Technical & Engineering Competition. Beam-powered climber to an altitude of 1km, Space Elevator Games 2009. |
| Altitude | 36,000 km | 1km | 2009 | Speed over 4 m/s (14.4 km/h). |
| Payload | 10kg | 2009 | Estimated - climber dragged bottom stop about 30m up, with speed over 6 m/s (21.6 km/h), during the Space Elevator Games 2009. | |
| Laser power beaming | ||||
| Power beam | 1 kW | 2009 | Distance greater than 300 meters. | |
a) It would take 5 days to reach a geostationary
Geostationary orbit
A geostationary orbit is a geosynchronous orbit directly above the Earth's equator , with a period equal to the Earth's rotational period and an orbital eccentricity of approximately zero. An object in a geostationary orbit appears motionless, at a fixed position in the sky, to ground observers...
altitude of 36,000 km with this speed.
See also
- Space elevator economicsSpace elevator economicsSpace elevator economics compares the cost of sending a payload into Earth orbit via a space elevator with the cost of doing so with alternatives, like rockets.-Costs of current systems :...
discusses capital and maintenance costs of a space elevator. - Space elevator safetySpace elevator safetyThere are risks associated with never-before-done technologies like the construction and operation of a space elevator. A space elevator would present a navigational hazard, both to aircraft and spacecraft. Aircraft could be dealt with by means of simple air-traffic control restrictions...
discusses safety aspects of space elevator construction and operation. - Elevator:2010Elevator:2010Elevator:2010 is a competition with monetary prizes similar to the Ansari X Prize, but with the purpose of developing space elevator and space elevator-related technologies...
, Space elevator prize competitions - Space elevators in fictionSpace elevators in fictionThis is a list of occurrences of space elevators in fiction. Some depictions were made before the space elevator concept became fully established.-Novels and Fairy tales:* 2061: Odyssey Three, novel by Arthur C. Clarke...
- Lunar space elevatorLunar space elevatorA lunar space elevator is a proposed cable running from the surface of the Moon into space.It is similar in concept to the better known Earth space elevator idea...
- Non-rocket spacelaunchNon-rocket spacelaunchNon-rocket space launch is a launch into space where some or all needed speed and altitude is provided by non-rocket means, rather than simply using conventional chemical rockets from the ground. A number of alternatives to rockets have been proposed...