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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 A tether is a cord, fixture, or flexible attachment that characteristically anchors something movable to something fixed; it also maybe used to connect two movable objects, such as an item being towed by its tow. Applications for tethers includ ...
) anchored to the surface and extending into space. The design would permit vehicles to travel up the cable from a planetary surface, such as the Earth's, directly into orbit, without the use of large rockets. An Earth-based space elevator could not feasibly be simply a tall tower supported from below, due to the immense weight - instead it would consist of a cable with one end attached to the surface near the equator and the other end attached to a counterweight in space beyond
geostationary orbit A geostationary orbit, also referred to as a geosynchronous equatorial orbit''Geostationary orbit'' and ''Geosynchronous (equatorial) orbit'' are used somewhat interchangeably in sources. (GEO), is a circular geosynchronous orbit in altitu ...
(35,786 km altitude). The competing forces of gravity, which is stronger at the lower end, and the upward centrifugal force, which is stronger at the upper end, would result in the cable being held up, under tension, and stationary over a single position on Earth. With the tether deployed, climbers could repeatedly climb up and down the tether by mechanical means, releasing their cargo to and from orbit.Edwards, Bradley Carl
"The NIAC Space Elevator Program"
NASA Institute for Advanced Concepts
The concept of a tower reaching
geosynchronous orbit A geosynchronous orbit (sometimes abbreviated GSO) is an Earth-centered orbit with an orbital period that matches Earth's rotation on its axis, 23 hours, 56 minutes, and 4 seconds (one sidereal day). The synchronization of rotation and orbita ...
was first published in 1895 by
Konstantin Tsiolkovsky Konstantin Eduardovich Tsiolkovsky (russian: Константи́н Эдуа́рдович Циолко́вский , , p=kənstɐnʲˈtʲin ɪdʊˈardəvʲɪtɕ tsɨɐlˈkofskʲɪj , a=Ru-Konstantin Tsiolkovsky.oga; – 19 September 1935) ...
. His proposal was for a free-standing tower reaching from the surface of Earth to the height of geostationary orbit. Like all buildings, Tsiolkovsky's structure would be under compression, supporting its weight from below. Since 1959, most ideas for space elevators have focused on purely
tensile In physics, tension is described as the pulling force transmitted axially by the means of a string, a rope, chain, or similar object, or by each end of a rod, truss member, or similar three-dimensional object; tension might also be described a ...
structures, with the weight of the system held up from above by centrifugal forces. In the tensile concepts, a
space tether Space tethers are long cables which can be used for propulsion, momentum exchange, stabilization and attitude control, or maintaining the relative positions of the components of a large dispersed satellite/spacecraft sensor system. Depending on ...
reaches from a large mass (the counterweight) beyond geostationary orbit to the ground. This structure is held in tension between Earth and the counterweight like an upside-down
plumb bob A plumb bob, plumb bob level, or plummet, is a weight, usually with a pointed tip on the bottom, suspended from a string and used as a vertical reference line, or plumb-line. It is a precursor to the spirit level and used to establish a verti ...
. The cable thickness is adjusted based on tension; it has its maximum at a geostationary orbit and the minimum on the ground. Available materials are not strong and light enough to make an Earth space elevator practical. Some sources expect that future advances in
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 na ...
s (CNTs) could lead to a practical design. Other sources believe that CNTs will never be strong enough. Possible future alternatives include
boron nitride nanotube Boron nitride nanotubes (BNNTs) are a polymorph of boron nitride. They were predicted in 1994 and experimentally discovered in 1995. Structurally they are similar to carbon nanotubes, which are cylinders with sub-micrometer diameters and micromete ...
s, diamond nanothreads and macro-scale single crystal
graphene Graphene () is an allotrope of carbon consisting of a Single-layer materials, single layer of atoms arranged in a hexagonal lattice nanostructure.
. The concept is applicable to other planets and Astronomical object, celestial bodies. For locations in the solar system with weaker gravity than Earth's (such as the
Moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...
or
Mars Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury. In the English language, Mars is named for the Roman god of war. Mars is a terrestrial planet with a thin at ...
), the strength-to-density requirements for tether materials are not as problematic. Currently available materials (such as
Kevlar Kevlar (para-aramid) is a strong, heat-resistant synthetic fiber, related to other aramids such as Nomex and Technora. Developed by Stephanie Kwolek at DuPont in 1965, the high-strength material was first used commercially in the early 1970s a ...
) are strong and light enough that they could be practical as the tether material for elevators there.


History


Early concepts

The key concept of the space elevator appeared in 1895 when Russian scientist
Konstantin Tsiolkovsky Konstantin Eduardovich Tsiolkovsky (russian: Константи́н Эдуа́рдович Циолко́вский , , p=kənstɐnʲˈtʲin ɪdʊˈardəvʲɪtɕ tsɨɐlˈkofskʲɪj , a=Ru-Konstantin Tsiolkovsky.oga; – 19 September 1935) ...
was inspired by the
Eiffel Tower The Eiffel Tower ( ; french: links=yes, tour Eiffel ) is a wrought-iron lattice tower on the Champ de Mars in Paris, France. It is named after the engineer Gustave Eiffel, whose company designed and built the tower. Locally nicknamed ...
in
Paris Paris () is the capital and most populous city of France, with an estimated population of 2,165,423 residents in 2019 in an area of more than 105 km² (41 sq mi), making it the 30th most densely populated city in the world in 2020. Si ...
. He considered a similar tower that reached all the way into space and was built from the ground up to the altitude of 35,786 kilometers, the height of
geostationary orbit A geostationary orbit, also referred to as a geosynchronous equatorial orbit''Geostationary orbit'' and ''Geosynchronous (equatorial) orbit'' are used somewhat interchangeably in sources. (GEO), is a circular geosynchronous orbit in altitu ...
. He noted that the top of such a tower would be circling
Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's sur ...
as in a geostationary orbit. Objects would acquire horizontal velocity due to the Earth's rotation as they rode up the tower, and an object released at the tower's top would have enough horizontal velocity to remain there in geostationary orbit. Tsiolkovsky's conceptual tower was a compression structure, while modern concepts call for a tensile structure (or "tether").


20th century

Building a compression structure from the ground up proved an unrealistic task as there was no material in existence with enough compressive strength to support its own weight under such conditions. In 1959, the Russian engineer Yuri N. Artsutanov suggested a more feasible proposal. Artsutanov suggested using a geostationary
satellite A satellite or artificial satellite is an object intentionally placed into orbit in outer space. Except for passive satellites, most satellites have an electricity generation system for equipment on board, such as solar panels or radioiso ...
as the base from which to deploy the structure downward. By using a
counterweight A counterweight is a weight that, by applying an opposite force, provides balance and stability of a mechanical system. The purpose of a counterweight is to make lifting the load faster and more efficient, which saves energy and causes less we ...
, a cable would be lowered from geostationary orbit to the surface of Earth, while the counterweight was extended from the satellite away from Earth, keeping the cable constantly over the same spot on the surface of the Earth. Artsutanov's idea was introduced to the Russian-speaking public in an interview published in the Sunday supplement of ''
Komsomolskaya Pravda ''Komsomolskaya Pravda'' (russian: link=no, Комсомольская правда; lit. " Komsomol Truth") is a daily Russian tabloid newspaper, founded on 13 March 1925. History and profile During the Soviet era, ''Komsomolskaya Pravda'' w ...
'' in 1960, but was not available in English until much later. He also proposed tapering the cable thickness in order for the stress in the cable to remain constant. This gave a thinner cable at ground level that became thickest at the level of geostationary orbit. Both the tower and cable ideas were proposed in
David E. H. Jones David Edward Hugh Jones (20 April 1938 – 19 July 2017) was a British chemist and author, who under the pen name Daedalus was the fictional inventor for DREADCO. Jones' columns as Daedalus were published for 38 years, starting weekly in 1964 in ...
' quasi-humorous ''Ariadne'' column in ''
New Scientist ''New Scientist'' is a magazine covering all aspects of science and technology. Based in London, it publishes weekly English-language editions in the United Kingdom, the United States and Australia. An editorially separate organisation publish ...
'', December 24, 1964. In 1966, Isaacs, Vine, Bradner and Bachus, four
American American(s) may refer to: * American, something of, from, or related to the United States of America, commonly known as the "United States" or "America" ** Americans, citizens and nationals of the United States of America ** American ancestry, pe ...
engineers, reinvented the concept, naming it a "Sky-Hook", and published their analysis in the journal ''Science''. They decided to determine what type of material would be required to build a space elevator, assuming it would be a straight cable with no variations in its cross section area, and found that the strength required would be twice that of any then-existing material including
graphite Graphite () is a crystalline form of the element carbon. It consists of stacked layers of graphene. Graphite occurs naturally and is the most stable form of carbon under standard conditions. Synthetic and natural graphite are consumed on la ...
,
quartz Quartz is a hard, crystalline mineral composed of silica ( silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical f ...
, and
diamond Diamond is a solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic. Another solid form of carbon known as graphite is the chemically stable form of carbon at room temperature and pressure, b ...
. In 1975, an American scientist,
Jerome Pearson Jerome Pearson (19 April 1938 - 27 Jan 2021) was an American engineer and space scientist best known for his work on space elevators, including a lunar space elevator. He was president of STAR, Inc., and has developed aircraft and spacecraft te ...
, reinvented the concept, publishing his analysis in the journal ''
Acta Astronautica ''Acta Astronautica'' is a monthly peer-reviewed scientific journal covering all fields of physical, engineering, life, and social sciences related to the peaceful scientific exploration of space. The journal is widely known as one of the top ae ...
''. He designed a cross-section-area altitude profile that tapered and would be better suited to building the elevator. The completed cable would be thickest at the geostationary orbit, where the tension was greatest, and would be narrowest at the tips to reduce the amount of weight per unit area of cross section that any point on the cable would have to bear. He suggested using a counterweight that would be slowly extended out to (almost half the distance to the
Moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...
) as the lower sections of the elevator were built. Without a large counterweight, the upper portion of the cable would have to be longer than the lower due to the way
gravitational 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 forces change with distance from Earth. His analysis included disturbances such as the gravitation of the Moon, wind and moving payloads up and down the cable. The weight of the material needed to build the elevator would have required thousands of
Space Shuttle The Space Shuttle is a retired, partially reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. Its official program n ...
trips, although part of the material could be transported up the elevator when a minimum strength strand reached the ground or be manufactured in space from asteroidal or lunar ore. After the development of
carbon nanotubes 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 na ...
in the 1990s, engineer David Smitherman of
NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeedin ...
/Marshall's Advanced Projects Office realized that the high strength of these materials might make the concept of a space elevator feasible, and put together a workshop at the
Marshall Space Flight Center The George C. Marshall Space Flight Center (MSFC), located in Redstone Arsenal, Alabama (Huntsville postal address), is the U.S. government's civilian rocketry and spacecraft propulsion research center. As the largest NASA center, MSFC's firs ...
, inviting many scientists and engineers to discuss concepts and compile plans for an elevator to turn the concept into a reality. In 2000, another American scientist, Bradley C. Edwards, suggested creating a long paper-thin ribbon using a carbon nanotube composite material.Bradley C. Edwards,
The Space Elevator
He chose the wide-thin ribbon-like cross-section shape rather than earlier circular cross-section concepts because that shape would stand a greater chance of surviving impacts by meteoroids. The ribbon cross-section shape also provided large surface area for climbers to climb with simple rollers. Supported by the NASA Institute for Advanced Concepts, Edwards' work was expanded to cover the deployment scenario, climber design, power delivery system, orbital debris avoidance, anchor system, surviving
atomic oxygen There are several known allotropes of oxygen. The most familiar is molecular oxygen (O2), present at significant levels in Earth's atmosphere and also known as dioxygen or triplet oxygen. Another is the highly reactive ozone (O3). Others are ...
, avoiding lightning and hurricanes by locating the anchor in the western equatorial Pacific, construction costs, construction schedule, and environmental hazards."Space Elevators: An Advanced Earth-Space Infrastructure for the New Millennium"
NASA/CP-2000-210429, Marshall Space Flight Center, Huntsville, Alabama, 2000
archived


21st century

To speed space elevator development, proponents have organized several
competitions Competition is a rivalry where two or more parties strive for a common goal which cannot be shared: where one's gain is the other's loss (an example of which is a zero-sum game). Competition can arise between entities such as organisms, indi ...
, similar to the Ansari X Prize, for relevant technologies. Among them are Elevator:2010, which organized annual competitions for climbers, ribbons and power-beaming systems from 2005 to 2009, the Robogames Space Elevator Ribbon Climbing competition, as well as NASA's Centennial Challenges program, which, in March 2005, announced a partnership with the Spaceward Foundation (the operator of Elevator:2010), raising the total value of prizes to US$400,000. The first European Space Elevator Challenge (EuSEC) to establish a climber structure took place in August 2011. In 2005, "the LiftPort Group of space elevator companies announced that it will be building a carbon nanotube manufacturing plant in
Millville, New Jersey Millville is a city in Cumberland County, in the U.S. state of New Jersey. As of the 2010 U.S. census, the city's population was 28,400, Their announced goal was a space elevator launch in 2010. On February 13, 2006, the LiftPort Group announced that, earlier the same month, they had tested a mile of "space-elevator tether" made of carbon-fiber composite strings and fiberglass tape measuring wide and 1 mm (approx. 13 sheets of paper) thick, lifted with balloons. In April 2019, Liftport CEO Michael Laine admitted little progress has been made on the company's lofty space elevator ambitions, even after receiving more than $200,000 in seed funding. The carbon nanotube manufacturing facility that Liftport announced in 2005 was never built. In 2007, Elevator:2010 held the 2007 Space Elevator games, which featured US$500,000 awards for each of the two competitions, ($1,000,000 total) as well as an additional $4,000,000 to be awarded over the next five years for space elevator related technologies. No teams won the competition, but a team from MIT entered the first 2-gram (0.07 oz), 100-percent carbon nanotube entry into the competition. Japan held an international conference in November 2008 to draw up a timetable for building the elevator. Lewis, Leo; News International Group; accessed September 22, 2008. In 2012, the Obayashi Corporation announced that it could build a space elevator by 2050 using carbon nanotube technology. The design's passenger climber would be able to reach the GEO level after an 8-day trip. Further details have been published in 2016. In 2013, the
International Academy of Astronautics The International Academy of Astronautics (IAA) is an independent non-governmental organization established in Stockholm (Sweden) on August 16, 1960, by Dr. Theodore von Kármán, and recognized by the United Nations in 1996. The IAA has electe ...
published a technological feasibility assessment which concluded that the critical capability improvement needed was the tether material, which was projected to achieve the necessary specific strength within 20 years. The four-year long study looked into many facets of space elevator development including missions, development schedules, financial investments, revenue flow, and benefits. It was reported that it would be possible to operationally survive smaller impacts and avoid larger impacts, with meteors and space debris, and that the estimated cost of lifting a kilogram of payload to GEO and beyond would be $500. In 2014, Google X's Rapid Evaluation R&D team began the design of a Space Elevator, eventually finding that no one had yet manufactured a perfectly formed
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 na ...
strand longer than a meter. They thus decided to put the project in "deep freeze" and also keep tabs on any advances in the carbon nanotube field. In 2018, researchers at Japan's Shizuoka University launched STARS-Me, two
CubeSat A CubeSat is a class of miniaturized satellite based around a form factor consisting of cubes. CubeSats have a mass of no more than per unit, and often use commercial off-the-shelf (COTS) components for their electronics and structure. CubeSats ...
s connected by a tether, which a mini-elevator will travel on. The experiment was launched as a test bed for a larger structure. In 2019, the
International Academy of Astronautics The International Academy of Astronautics (IAA) is an independent non-governmental organization established in Stockholm (Sweden) on August 16, 1960, by Dr. Theodore von Kármán, and recognized by the United Nations in 1996. The IAA has electe ...
published "Road to the Space Elevator Era", a study report summarizing the assessment of the space elevator as of summer 2018. The essence is that a broad group of space professionals gathered and assessed the status of the space elevator development, each contributing their expertise and coming to similar conclusions: (a) Earth Space Elevators seem feasible, reinforcing the IAA 2013 study conclusion (b) Space Elevator development initiation is nearer than most think. This last conclusion is based on a potential process for manufacturing macro-scale single crystal
graphene Graphene () is an allotrope of carbon consisting of a Single-layer materials, single layer of atoms arranged in a hexagonal lattice nanostructure.
with higher specific strength than
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 na ...
s.


In fiction

In 1979, space elevators were introduced to a broader audience with the simultaneous publication of
Arthur C. Clarke Sir Arthur Charles Clarke (16 December 191719 March 2008) was an English science-fiction writer, science writer, futurist, inventor, undersea explorer, and television series host. He co-wrote the screenplay for the 1968 film '' 2001: A Spac ...
's novel, ''
The Fountains of Paradise ''The Fountains of Paradise'' is a 1979 science fiction novel by British writer Arthur C. Clarke. Set in the 22nd century, it describes the construction of a space elevator. This "orbital tower" is a giant structure rising from the ground ...
'', in which engineers construct a space elevator on top of a mountain peak in the fictional island country of "Taprobane" (loosely based on
Sri Lanka Sri Lanka (, ; si, ශ්‍රී ලංකා, Śrī Laṅkā, translit-std=ISO (); ta, இலங்கை, Ilaṅkai, translit-std=ISO ()), formerly known as Ceylon and officially the Democratic Socialist Republic of Sri Lanka, is an ...
, albeit moved south to the Equator), and
Charles Sheffield Charles Sheffield (25 June 1935 – 2 November 2002), an English-born mathematician, physicist and science-fiction writer, served as a President of the Science Fiction and Fantasy Writers of America and of the American Astronautical Society. ...
's first novel, ''
The Web Between the Worlds ''The Web Between the Worlds'' is the second science fiction novel by Charles Sheffield. It was first published as a trade paperback by Ace Books in 1979, by the first UK edition in hardcover by Sidgwick & Jackson Ltd the following year. Further ...
'', also featuring the building of a space elevator. Three years later, in Robert A. Heinlein's 1982 novel ''
Friday Friday is the day of the week between Thursday and Saturday. In countries that adopt the traditional "Sunday-first" convention, it is the sixth day of the week. In countries adopting the ISO-defined "Monday-first" convention, it is the fifth d ...
'', the principal character mentions a disaster at the “Quito Sky Hook” and makes use of the "Nairobi Beanstalk" in the course of her travels. In
Kim Stanley Robinson Kim Stanley Robinson (born March 23, 1952) is an American writer of science fiction. He has published twenty-two novels and numerous short stories and is best known for his ''Mars'' trilogy. His work has been translated into 24 languages. Many ...
's 1993 novel '' Red Mars'', colonists build a space elevator on Mars that allows both for more colonists to arrive and also for natural resources mined there to be able to leave for Earth. In
Larry Niven Laurence van Cott Niven (; born April 30, 1938) is an American science fiction writer. His best-known works are '' Ringworld'' (1970), which received Hugo, Locus, Ditmar, and Nebula awards, and, with Jerry Pournelle, '' The Mote in God's E ...
's book '' Rainbow Mars'', Niven describes a space elevator built on Mars. In
David Gerrold David Gerrold (born Jerrold David Friedman; January 24, 1944)Reginald, R. (September 12, 2010)''Science Fiction and Fantasy Literature, Volume 2'' Borgo Press p. 911. Archived at Google Books. Retrieved June 23, 2013. is an American science fic ...
's 2000 novel, '' Jumping Off The Planet'', a family excursion up the Ecuador "beanstalk" is actually a child-custody kidnapping. Gerrold's book also examines some of the industrial applications of a mature elevator technology. The concept of a space elevator, called the Beanstalk, is also depicted in John Scalzi's 2005 novel, ''
Old Man's War ''Old Man's War'' is a military science fiction novel by American writer John Scalzi, published in 2005. His debut novel was nominated for the Hugo Award for Best Novel in 2006. ''Old Man's War'' is the first novel in Scalzi's ''Old Man's ...
.'' In a biological version,
Joan Slonczewski Joan Lyn Slonczewski is an American microbiologist at Kenyon College and a science fiction writer who explores biology and space travel. Their books have twice earned the John W. Campbell Memorial Award for Best Science Fiction Novel: '' A Door ...
's 2011 novel ''The Highest Frontier'' depicts a college student ascending a space elevator constructed of self-healing cables of anthrax bacilli. The engineered bacteria can regrow the cables when severed by space debris.


Physics


Apparent gravitational field

An Earth space elevator cable rotates along with the rotation of the Earth. Therefore, the cable, and objects attached to it, would experience upward centrifugal force in the direction opposing the downward gravitational force. The higher up the cable the object is located, the less the gravitational pull of the Earth, and the stronger the upward centrifugal force due to the rotation, so that more centrifugal force opposes less gravity. The centrifugal force and the gravity are balanced at geosynchronous equatorial orbit (GEO). Above GEO, the centrifugal force is stronger than gravity, causing objects attached to the cable there to pull ''upward'' on it. The net force for objects attached to the cable is called the ''apparent gravitational field''. The apparent gravitational field for attached objects is the (downward) gravity minus the (upward) centrifugal force. The apparent gravity experienced by an object on the cable is zero at GEO, downward below GEO, and upward above GEO. The apparent gravitational field can be represented this way: where At some point up the cable, the two terms (downward gravity and upward centrifugal force) are equal and opposite. Objects fixed to the cable at that point put no weight on the cable. This altitude (r1) depends on the mass of the planet and its rotation rate. Setting actual gravity equal to centrifugal acceleration gives: This is above Earth's surface, the altitude of geostationary orbit. On the cable ''below'' geostationary orbit, downward gravity would be greater than the upward centrifugal force, so the apparent gravity would pull objects attached to the cable downward. Any object released from the cable below that level would initially accelerate downward along the cable. Then gradually it would deflect eastward from the cable. On the cable ''above'' the level of stationary orbit, upward centrifugal force would be greater than downward gravity, so the apparent gravity would pull objects attached to the cable ''upward''. Any object released from the cable ''above'' the geosynchronous level would initially accelerate ''upward'' along the cable. Then gradually it would deflect westward from the cable.


Cable section

Historically, the main technical problem has been considered the ability of the cable to hold up, with tension, the weight of itself below any given point. The greatest tension on a space elevator cable is at the point of geostationary orbit, above the Earth's equator. This means that the cable material, combined with its design, must be strong enough to hold up its own weight from the surface up to . A cable which is thicker in cross section area at that height than at the surface could better hold up its own weight over a longer length. How the cross section area tapers from the maximum at to the minimum at the surface is therefore an important design factor for a space elevator cable. To maximize the usable excess strength for a given amount of cable material, the cable's cross section area would need to be designed for the most part in such a way that the
stress Stress may refer to: Science and medicine * Stress (biology), an organism's response to a stressor such as an environmental condition * Stress (linguistics), relative emphasis or prominence given to a syllable in a word, or to a word in a phrase ...
(i.e., the tension per unit of cross sectional area) is constant along the length of the cable. The constant-stress criterion is a starting point in the design of the cable cross section area as it changes with altitude. Other factors considered in more detailed designs include thickening at altitudes where more space junk is present, consideration of the point stresses imposed by climbers, and the use of varied materials. To account for these and other factors, modern detailed designs seek to achieve the largest '' safety margin'' possible, with as little variation over altitude and time as possible. In simple starting-point designs, that equates to constant-stress. For a constant-stress cable with no safety margin, the cross-section-area as a function of distance from Earth's center is given by the following equation: where Safety margin can be accounted for by dividing T by the desired safety factor.


Cable materials

Using the above formula we can calculate the ratio between the cross-section at geostationary orbit and the cross-section at Earth's surface, known as taper ratio:Specific substitutions used to produce the factor : The taper ratio becomes very large unless the specific strength of the material used approaches 48 (MPa)/(kg/m3). Low specific strength materials require very large taper ratios which equates to large (or astronomical) total mass of the cable with associated large or impossible costs.


Structure

There are a variety of space elevator designs proposed for many planetary bodies. Almost every design includes a base station, a cable, climbers, and a counterweight. For an Earth Space Elevator the Earth's rotation creates upward
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 paralle ...
on the counterweight. The counterweight is held down by the cable while the cable is held up and taut by the counterweight. The base station anchors the whole system to the surface of the Earth. Climbers climb up and down the cable with cargo.


Base station

Modern concepts for the base station/anchor are typically mobile stations, large oceangoing vessels or other mobile platforms. Mobile base stations would have the advantage over the earlier stationary concepts (with land-based anchors) by being able to maneuver to avoid high winds, storms, and
space debris Space debris (also known as space junk, space pollution, space waste, space trash, or space garbage) are defunct human-made objects in space—principally in Earth orbit—which no longer serve a useful function. These include derelict spacec ...
. Oceanic anchor points are also typically in
international waters The terms international waters or transboundary waters apply where any of the following types of bodies of water (or their drainage basins) transcend international boundaries: oceans, large marine ecosystems, enclosed or semi-enclosed region ...
, simplifying and reducing the cost of negotiating territory use for the base station. Stationary land-based platforms would have simpler and less costly logistical access to the base. They also would have the advantage of being able to be at high altitudes, such as on top of mountains. In an alternate concept, the base station could be a tower, forming a space elevator which comprises both a compression tower close to the surface, and a tether structure at higher altitudes. Combining a compression structure with a tension structure would reduce loads from the atmosphere at the Earth end of the tether, and reduce the distance into the Earth's gravity field the cable needs to extend, and thus reduce the critical strength-to-density requirements for the cable material, all other design factors being equal.


Cable

A space elevator cable would need to carry its own weight as well as the additional weight of climbers. The required strength of the cable would vary along its length. This is because at various points it would have to carry the weight of the cable below, or provide a downward force to retain the cable and counterweight above. Maximum tension on a space elevator cable would be at geosynchronous altitude so the cable would have to be thickest there and taper as it approaches Earth. Any potential cable design may be characterized by the taper factor – the ratio between the cable's radius at geosynchronous altitude and at the Earth's surface. The cable would need to be made of a material with a high tensile strength/density ratio. For example, the Edwards space elevator design assumes a cable material with a tensile strength of at least 100 gigapascals. Since Edwards consistently assumed the density of his carbon nanotube cable to be 1300 kg/m3, that implies a specific strength of 77 megapascal/(kg/m3). This value takes into consideration the entire weight of the space elevator. An untapered space elevator cable would need a material capable of sustaining a length of of its own weight ''at
sea level Mean sea level (MSL, often shortened to sea level) is an average surface level of one or more among Earth's coastal bodies of water from which heights such as elevation may be measured. The global MSL is a type of vertical datuma standardis ...
'' to reach a
geostationary A geostationary orbit, also referred to as a geosynchronous equatorial orbit''Geostationary orbit'' and ''Geosynchronous (equatorial) orbit'' are used somewhat interchangeably in sources. (GEO), is a circular geosynchronous orbit in altitud ...
altitude of without yielding. Therefore, a material with very high strength and lightness is needed. For comparison, metals like titanium, steel or aluminium alloys have breaking lengths of only 20–30 km (0.2–0.3 MPa/(kg/m3)). Modern
fiber Fiber or fibre (from la, fibra, links=no) is a natural or artificial substance that is significantly longer than it is wide. Fibers are often used in the manufacture of other materials. The strongest engineering materials often incorporate ...
materials such as
kevlar Kevlar (para-aramid) is a strong, heat-resistant synthetic fiber, related to other aramids such as Nomex and Technora. Developed by Stephanie Kwolek at DuPont in 1965, the high-strength material was first used commercially in the early 1970s a ...
,
fiberglass Fiberglass ( American English) or fibreglass (Commonwealth English) is a common type of fiber-reinforced plastic using glass fiber. The fibers may be randomly arranged, flattened into a sheet called a chopped strand mat, or woven into glass cl ...
and carbon/graphite fiber have breaking lengths of 100–400 km (1.0–4.0 MPa/(kg/m3)). Nanoengineered materials such as
carbon nanotubes 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 na ...
and, more recently discovered,
graphene Graphene () is an allotrope of carbon consisting of a Single-layer materials, single layer of atoms arranged in a hexagonal lattice nanostructure.
ribbons (perfect two-dimensional sheets of carbon) are expected to have breaking lengths of 5000–6000 km (50–60 MPa/(kg/m3)), and also are able to conduct electrical power. For a space elevator on Earth, with its comparatively high gravity, the cable material would need to be stronger and lighter than currently available materials. For this reason, there has been a focus on the development of new materials that meet the demanding specific strength requirement. For high specific strength, carbon has advantages because it is only the sixth element in the
periodic table The periodic table, also known as the periodic table of the (chemical) elements, is a rows and columns arrangement of the chemical elements. It is widely used in chemistry, physics, and other sciences, and is generally seen as an icon of ch ...
. Carbon has comparatively few of the protons and neutrons which contribute most of the dead weight of any material. Most of the interatomic bonding forces of any element are contributed by only the outer few electrons. For carbon, the strength and stability of those bonds is high compared to the mass of the atom. The challenge in using carbon nanotubes remains to extend to macroscopic sizes the production of such material that are still perfect on the microscopic scale (as microscopic defects are most responsible for material weakness). As of 2014, carbon nanotube technology allowed growing tubes up to a few tenths of meters. In 2014, diamond nanothreads were first synthesized. Since they have strength properties similar to carbon nanotubes, diamond nanothreads were quickly seen as candidate cable material as well.


Climbers

A space elevator cannot be an elevator in the typical sense (with moving cables) due to the need for the cable to be significantly wider at the center than at the tips. While various designs employing moving cables have been proposed, most cable designs call for the "elevator" to climb up a stationary cable. Climbers cover a wide range of designs. On elevator designs whose cables are planar ribbons, most propose to use pairs of rollers to hold the cable with friction. Climbers would need to be paced at optimal timings so as to minimize cable stress and oscillations and to maximize throughput. Lighter climbers could be sent up more often, with several going up at the same time. This would increase throughput somewhat, but would lower the mass of each individual payload. The horizontal speed, i.e. due to orbital rotation, of each part of the cable increases with altitude, proportional to distance from the center of the Earth, reaching low
orbital speed In gravitationally bound systems, the orbital speed of an astronomical body or object (e.g. planet, moon, artificial satellite, spacecraft, or star) is the speed at which it orbits around either the barycenter or, if one body is much more mas ...
at a point approximately 66 percent of the height between the surface and geostationary orbit, or a height of about 23,400 km. A payload released at this point would go into a highly eccentric elliptical orbit, staying just barely clear from atmospheric reentry, with the
periapsis An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. For example, the apsides of the Earth are called the aphelion and perihelion. General description There are two apsides in any elli ...
at the same altitude as LEO and the
apoapsis An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. For example, the apsides of the Earth are called the aphelion and perihelion. General description There are two apsides in any elli ...
at the release height. With increasing release height the orbit would become less eccentric as both periapsis and apoapsis increase, becoming circular at geostationary level. When the payload has reached GEO, the horizontal speed is exactly the speed of a circular orbit at that level, so that if released, it would remain adjacent to that point on the cable. The payload can also continue climbing further up the cable beyond GEO, allowing it to obtain higher speed at jettison. If released from 100,000 km, the payload would have enough speed to reach the asteroid belt. As a payload is lifted up a space elevator, it would gain not only altitude, but horizontal speed (angular momentum) as well. The angular momentum is taken from the Earth's rotation. As the climber ascends, it is initially moving slower than each successive part of cable it is moving on to. This is the
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 ...
: the climber "drags" (westward) on the cable, as it climbs, and slightly decreases the Earth's rotation speed. The opposite process would occur for descending payloads: the cable is tilted eastward, thus slightly increasing Earth's rotation speed. The overall effect of the centrifugal force acting on the cable would cause it to constantly try to return to the energetically favorable vertical orientation, so after an object has been lifted on the cable, the counterweight would swing back toward the vertical, a bit like a pendulum. Space elevators and their loads would be designed so that the center of mass is always well-enough above the level of geostationary orbit to hold up the whole system. Lift and descent operations would need to be carefully planned so as to keep the pendulum-like motion of the counterweight around the tether point under control. Climber speed would be limited by the Coriolis force, available power, and by the need to ensure the climber's accelerating force does not break the cable. Climbers would also need to maintain a minimum average speed in order to move material up and down economically and expeditiously. At the speed of a very fast car or train of it will take about 5 days to climb to geosynchronous orbit.


Powering climbers

Both power and energy are significant issues for climbers – the climbers would need to gain a large amount of potential energy as quickly as possible to clear the cable for the next payload. Various methods have been proposed to get that energy to the climber: * Transfer the energy to the climber through wireless energy transfer while it is climbing. * Transfer the energy to the climber through some material structure while it is climbing. * Store the energy in the climber before it starts – requires an extremely high specific energy such as nuclear energy. * Solar power – After the first 40 km it is possible to use solar energy to power the climber Wireless energy transfer such as laser power beaming is currently considered the most likely method, using megawatt-powered free electron or solid state lasers in combination with adaptive mirrors approximately wide and a photovoltaic array on the climber tuned to the laser frequency for efficiency. For climber designs powered by power beaming, this efficiency is an important design goal. Unused energy would need to be re-radiated away with heat-dissipation systems, which add to weight. Yoshio Aoki, a professor of precision machinery engineering at
Nihon University , abbreviated as , is a private research university in Japan. Its predecessor, Nihon Law School (currently the Department of Law), was founded by Yamada Akiyoshi, the Minister of Justice, in 1889. It is one of Japan's leading private universit ...
and director of the Japan Space Elevator Association, suggested including a second cable and using the conductivity of carbon nanotubes to provide power.


Counterweight

Several solutions have been proposed to act as a counterweight: * a heavy, captured
asteroid An asteroid is a minor planet of the 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 or icy bodies with no atmosphere. ...
; * a
space dock A space dock is a hypothesised type of space station that is able to repair or build spacecraft similar to maritime shipyards on Earth. They remove the need for new spacecraft to perform a space launch to reach space and existing spacecraft ...
,
space station A space station is a spacecraft capable of supporting a human crew in orbit for an extended period of time, and is therefore a type of space habitat. It lacks major propulsion or landing systems. An orbital station or an orbital space station ...
or
spaceport A spaceport or cosmodrome is a site for launching or receiving spacecraft, by analogy to a seaport for ships or an airport for aircraft. The word ''spaceport'', and even more so ''cosmodrome'', has traditionally been used for sites capable ...
positioned past geostationary orbit * a further upward extension of the cable itself so that the net upward pull would be the same as an equivalent counterweight; * parked spent climbers that had been used to thicken the cable during construction, other junk, and material lifted up the cable for the purpose of increasing the counterweight.Edwards BC, Westling EA. (2002) ''The Space Elevator: A Revolutionary Earth-to-Space Transportation System.'' San Francisco: Spageo Inc. . Extending the cable has the advantage of some simplicity of the task and the fact that a payload that went to the end of the counterweight-cable would acquire considerable velocity relative to the Earth, allowing it to be launched into interplanetary space. Its disadvantage is the need to produce greater amounts of cable material as opposed to using just anything available that has mass.


Applications


Launching into deep space

An object attached to a space elevator at a radius of approximately 53,100 km would be at
escape velocity In celestial mechanics, escape velocity or escape speed is the minimum speed needed for a free, non- propelled object to escape from the gravitational influence of a primary body, thus reaching an infinite distance from it. It is typically ...
when released. Transfer orbits to the L1 and L2
Lagrangian point In celestial mechanics, the Lagrange points (; also Lagrangian points or libration points) are points of equilibrium for small-mass objects under the influence of two massive orbiting bodies. Mathematically, this involves the solution of t ...
s could be attained by release at 50,630 and 51,240 km, respectively, and transfer to lunar orbit from 50,960 km. At the end of Pearson's cable, the tangential velocity is 10.93 kilometers per second (6.79 mi/s). That is more than enough to
escape Escape or Escaping may refer to: Computing * Escape character, in computing and telecommunication, a character which signifies that what follows takes an alternative interpretation ** Escape sequence, a series of characters used to trigger some s ...
Earth's gravitational field and send probes at least as far out as
Jupiter Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but slightly less than one-thousand ...
. Once at Jupiter, a gravitational assist maneuver could permit solar escape velocity to be reached.


Extraterrestrial elevators

A space elevator could also be constructed on other planets, asteroids and moons. A
Martian Mars, the fourth planet from the Sun, has appeared as a setting in works of fiction since at least the mid-1600s. It became the most popular celestial object in fiction in the late 1800s as the Moon was evidently lifeless. At the time, the pr ...
tether could be much shorter than one on Earth. Mars' surface gravity is 38 percent of Earth's, while it rotates around its axis in about the same time as Earth. Because of this, Martian stationary orbit is much closer to the surface, and hence the elevator could be much shorter. Current materials are already sufficiently strong to construct such an elevator. Building a Martian elevator would be complicated by the Martian moon Phobos, which is in a low orbit and intersects the Equator regularly (twice every orbital period of 11 h 6 min). Phobos and Deimos may get in the way of a geostationary space elevator, however, they may contribute useful resources to the project. Phobos is projected to contain high amounts of carbon. If carbon nanotubes become feasible for a tether material, there will be an abundance of carbon in Mars local region. This could provide readily available resources for the future colonization on Mars. Phobos is Synchronously orbiting Mars, where the same face stays facing the planet at ~6,028 km above the Martian surface. A space elevator could extend down from Phobos to Mars 6,000 km, about 28 kilometers from the surface, and just out of the
atmosphere of Mars The atmosphere of Mars is the layer of gases surrounding Mars. It is primarily composed of carbon dioxide (95%), molecular nitrogen (2.8%), and argon (2%). It also contains trace levels of water vapor, oxygen, carbon monoxide, hydrogen, and no ...
. A similar space elevator cable could extend out 6,000 km the opposite direction that would counterbalance Phobos. In total the space elevator would extend out over 12,000 km which would be below Areostationary orbit of Mars (17,032 km). A rocket launch would still be needed to get the rocket and cargo to the beginning of the space elevator 28 km above the surface. The surface of Mars is rotating at 0.25
km/s The metre per second is the unit of both speed (a scalar quantity) and velocity (a vector quantity, which has direction and magnitude) in the International System of Units (SI), equal to the speed of a body covering a distance of one metre in a ...
at the equator and the bottom of the space elevator would be rotating around Mars at 0.77 km/s, so only 0.52 km/s of
Delta-v Delta-''v'' (more known as " change in velocity"), symbolized as ∆''v'' and pronounced ''delta-vee'', as used in spacecraft flight dynamics, is a measure of the impulse per unit of spacecraft mass that is needed to perform a maneuver such a ...
would be needed to get to the space elevator. Phobos orbits at 2.15 km/s and the outer most part of the space elevator would rotate around Mars at 3.52 km/s. The Earth's
Moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...
is a potential location for a Lunar space elevator, especially as the specific strength required for the tether is low enough to use currently available materials. The Moon does not rotate fast enough for an elevator to be supported by centrifugal force (the proximity of the Earth means there is no effective lunar-stationary orbit), but differential gravity forces means that an elevator could be constructed through
Lagrangian point In celestial mechanics, the Lagrange points (; also Lagrangian points or libration points) are points of equilibrium for small-mass objects under the influence of two massive orbiting bodies. Mathematically, this involves the solution of t ...
s. A near-side elevator would extend through the Earth-Moon L1 point from an anchor point near the center of the visible part of Earth's Moon: the length of such an elevator must exceed the maximum L1 altitude of 59,548 km, and would be considerably longer to reduce the mass of the required apex counterweight. A far-side lunar elevator would pass through the L2 Lagrangian point and would need to be longer than on the near-side: again, the tether length depends on the chosen apex anchor mass, but it could also be made of existing engineering materials. Rapidly spinning asteroids or moons could use cables to eject materials to convenient points, such as Earth orbits; or conversely, to eject materials to send a portion of the mass of the asteroid or moon to Earth orbit or a
Lagrangian point In celestial mechanics, the Lagrange points (; also Lagrangian points or libration points) are points of equilibrium for small-mass objects under the influence of two massive orbiting bodies. Mathematically, this involves the solution of t ...
.
Freeman Dyson Freeman John Dyson (15 December 1923 – 28 February 2020) was an English-American theoretical physicist and mathematician known for his works in quantum field theory, astrophysics, random matrices, mathematical formulation of quantum m ...
, a physicist and mathematician, has suggested using such smaller systems as power generators at points distant from the Sun where solar power is uneconomical. A space elevator using presently available engineering materials could be constructed between mutually tidally locked worlds, such as
Pluto Pluto (minor-planet designation: 134340 Pluto) is a dwarf planet in the Kuiper belt, a ring of trans-Neptunian object, bodies beyond the orbit of Neptune. It is the ninth-largest and tenth-most-massive known object to directly orbit the S ...
and
Charon In Greek mythology, Charon or Kharon (; grc, Χάρων) is a psychopomp, the ferryman of Hades, the Greek underworld. He carries the souls of those who have been given funeral rites across the rivers Acheron and Styx, which separate the ...
or the components of binary asteroid
90 Antiope Antiope (minor planet designation: 90 Antiope) is a double asteroid in the outer asteroid belt. It was discovered on October 1, 1866, by Robert Luther. In 2000, it was found to consist of two almost-equally-sized bodies orbiting each other. At ...
, with no terminus disconnect, according to Francis Graham of Kent State University. However, spooled variable lengths of cable must be used due to ellipticity of the orbits.


Construction

The construction of a space elevator would need reduction of some technical risk. Some advances in engineering, manufacturing 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 lower. Such follow-on space elevators would also benefit from the great reduction in technical risk achieved by the construction of the first space elevator. Prior to the work of Edwards in 2000, most concepts for constructing a space elevator had the cable manufactured in space. That was thought to be necessary for such a large and long object and for such a large counterweight. Manufacturing the cable in space would be done in principle by using an
asteroid An asteroid is a minor planet of the 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 or icy bodies with no atmosphere. ...
or
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 (Apsis, perihelion) is less than 1.3 astronomical unit ...
for source material. These earlier concepts for construction require a large preexisting space-faring infrastructure to maneuver an asteroid into its needed orbit around Earth. They also required the development of technologies for manufacture in space of large quantities of exacting materials.Space Elevators: An Assessment of the Technological Feasibility and the Way Forward, Page 326, http://www.virginiaedition.com/media/spaceelevators.pdf Since 2001, most work has focused on simpler methods of construction requiring much smaller space infrastructures. They conceive the launch of a long cable on a large spool, followed by deployment of it in space. The spool would be initially parked in a geostationary orbit above the planned anchor point. A long cable would be dropped "downward" (toward Earth) and would be balanced by a mass being dropped "upward" (away from Earth) for the whole system to remain on the geosynchronous orbit. Earlier designs imagined the balancing mass to be another cable (with counterweight) extending upward, with the main spool remaining at the original geosynchronous orbit level. Most current designs elevate the spool itself as the main cable is paid out, a simpler process. When the lower end of the cable is long enough to reach the surface of the Earth (at the equator), it would be anchored. Once anchored, the center of mass would be elevated more (by adding mass at the upper end or by paying out more cable). This would add more tension to the whole cable, which could then be used as an elevator cable. One plan for construction uses conventional rockets to place a "minimum size" initial seed cable of only 19,800 kg. This first very small ribbon would be adequate to support the first 619 kg climber. The first 207 climbers would carry up and attach more cable to the original, increasing its cross section area and widening the initial ribbon to about 160 mm wide at its widest point. The result would be a 750-ton cable with a lift capacity of 20 tons per climber.


Safety issues and construction challenges

For early systems, transit times from the surface to the level of geosynchronous orbit would be about five days. On these early systems, the time spent moving through the Van Allen radiation belts would be enough that passengers would need to be protected from radiation by shielding, which would add mass to the climber and decrease payload. A space elevator would present a navigational hazard, both to aircraft and spacecraft. Aircraft could be diverted by
air-traffic control Air traffic control (ATC) is a service provided by ground-based air traffic controllers who direct aircraft on the ground and through a given section of controlled airspace, and can provide advisory services to aircraft in non-controlled airsp ...
restrictions. All objects in stable orbits that have
perigee An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. For example, the apsides of the Earth are called the aphelion and perihelion. General description There are two apsides in any el ...
below the maximum altitude of the cable that are not synchronous with the cable would impact the cable eventually, unless avoiding action is taken. One potential solution proposed by Edwards is to use a movable anchor (a sea anchor) to allow the tether to "dodge" any space debris large enough to track. Impacts by space objects such as meteoroids, micrometeorites and orbiting man-made debris pose another design constraint on the cable. A cable would need to be designed to maneuver out of the way of debris, or absorb impacts of small debris without breaking.


Economics

With a space elevator, materials might be sent into orbit at a fraction of the current cost. As of 2000, conventional rocket designs cost about US$25,000 per
kilogram The kilogram (also kilogramme) is the unit of mass in the International System of Units (SI), having the unit symbol kg. It is a widely used measure in science, engineering and commerce worldwide, and is often simply called a kilo colloquially. ...
(US$11,000 per pound) for transfer to geostationary orbit. Current space elevator proposals envision payload prices starting as low as $220 per kilogram ($100 per pound), similar to the $5–$300/kg estimates of the Launch loop, but higher than the $310/ton to 500 km orbit quoted to Dr.
Jerry Pournelle Jerry Eugene Pournelle (; August 7, 1933 – September 8, 2017) was an American scientist in the area of operations research and human factors research, a science fiction writer, essayist, journalist, and one of the first bloggers. In the 1960s ...
for an orbital airship system. Philip Ragan, co-author of the book ''Leaving the Planet by Space Elevator'', states that "The first country to deploy a space elevator will have a 95 percent cost advantage and could potentially control all space activities."


International Space Elevator Consortium (ISEC)

The International Space Elevator Consortium (ISEC) is a US Non-Profit
501(c)(3) A 501(c)(3) organization is a United States corporation, trust, unincorporated association or other type of organization exempt from federal income tax under section 501(c)(3) of Title 26 of the United States Code. It is one of the 29 types of ...
Corporation formed to promote the development, construction, and operation of a space elevator as "a revolutionary and efficient way to space for all humanity". It was formed after the Space Elevator Conference in
Redmond, Washington Redmond is a city in King County, Washington, United States, located east of Seattle. The population was 73,256 at the 2020 census, up from 54,144 in 2010. Redmond is best known as the home of Microsoft and Nintendo of America. With an ann ...
in July 2008 and became an affiliate organization with the National Space Society in August 2013. ISEC hosts an annual Space Elevator conference at the
Seattle Museum of Flight The Museum of Flight is a private non-profit air and space museum in the Seattle metropolitan area. It is located at the southern end of King County International Airport (Boeing Field) in the city of Tukwila, immediately south of Seat ...
. ISEC coordinates with the two other major societies focusing on space elevators: the Japanese Space Elevator Association and EuroSpaceward. ISEC supports symposia and presentations at the International Academy of Astronautics and the International Astronautical Federation Congress each year.


Related concepts

The conventional current concept of a "Space Elevator" has evolved from a static compressive structure reaching to the level of GEO, to the modern baseline idea of a static tensile structure anchored to the ground and extending to well above the level of GEO. In the current usage by practitioners (and in this article), a "Space Elevator" means the Tsiolkovsky-Artsutanov-Pearson type as considered by the International Space Elevator Consortium. This conventional type is a static structure fixed to the ground and extending into space high enough that cargo can climb the structure up from the ground to a level where simple release will put the cargo into an
orbit In celestial mechanics, an orbit is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an object or position in space such as ...
. Some concepts related to this modern baseline are not usually termed a "Space Elevator", but are similar in some way and are sometimes termed "Space Elevator" by their proponents. For example,
Hans Moravec Hans Peter Moravec (born November 30, 1948, Kautzen, Austria) is an adjunct faculty member at the Robotics Institute of Carnegie Mellon University in Pittsburgh, USA. He is known for his work on robotics, artificial intelligence, and writings ...
published an article in 1977 called "A Non-Synchronous Orbital Skyhook" describing a concept using a rotating cable. The rotation speed would exactly match the orbital speed in such a way that the tip velocity at the lowest point was zero compared to the object to be "elevated". It would dynamically grapple and then "elevate" high flying objects to orbit or low orbiting objects to higher orbit. The original concept envisioned by Tsiolkovsky was a compression structure, a concept similar to an aerial mast. While such structures might reach
space Space is the boundless three-dimensional extent in which objects and events have relative position and direction. In classical physics, physical space is often conceived in three linear dimensions, although modern physicists usually consi ...
(100 km, 62 mi), they are unlikely to reach geostationary orbit. The concept of a Tsiolkovsky tower combined with a classic space elevator cable (reaching above the level of GEO) has been suggested. Other ideas use very tall compressive towers to reduce the demands on launch vehicles. The vehicle is "elevated" up the tower, which may extend as high as above the atmosphere, and is launched from the top. Such a tall tower to access near-space altitudes of has been proposed by various researchers. Other concepts for
non-rocket spacelaunch Non-rocket spacelaunch refers to theoretical concepts for launch into space where much of the speed and altitude needed to achieve orbit is provided by a propulsion technique that is not subject to the limits of the rocket equation. Although al ...
related to a space elevator (or parts of a space elevator) include an orbital ring, a pneumatic space tower, a space fountain, a launch loop, a skyhook, a
space tether Space tethers are long cables which can be used for propulsion, momentum exchange, stabilization and attitude control, or maintaining the relative positions of the components of a large dispersed satellite/spacecraft sensor system. Depending on ...
, and a buoyant "SpaceShaft".Space Shaft: Or, the story that would have been a bit finer, if only one had known...
"Knight Science Journalism Tracker (MIT)", July 1, 2009.


Notes


References


Further reading


A conference publication based on findings from the Advanced Space Infrastructure Workshop on Geostationary Orbiting Tether "Space Elevator" Concepts
(PDF), held in 1999 at the NASA Marshall Space Flight Center, Huntsville, Alabama. Compiled by D.V. Smitherman, Jr., published August 2000. * "The Political Economy of Very Large Space Projects
PDF
John Hickman, Ph.D. '' Journal of Evolution and Technology'' Vol. 4 – November 1999.
A Hoist to the Heavens
By Bradley Carl Edwards * Ziemelis K. (2001) "Going up". In
New Scientist ''New Scientist'' is a magazine covering all aspects of science and technology. Based in London, it publishes weekly English-language editions in the United Kingdom, the United States and Australia. An editorially separate organisation publish ...
2289: 24–27
Republished in SpaceRef
Title page: "The great space elevator: the dream machine that will turn us all into astronauts."

An overview by Leonard David of space.com, published March 27, 2002. * Krishnaswamy, Sridhar. Stress Analysis �
The Orbital Tower
(PDF) *
LiftPort LiftPort Group is a privately held Washington state corporation. It was founded in April 2003 by Michael J. Laine. The company is focused on the construction of a space elevator using carbon nanotubes. History * April 2003, LiftPort Group fou ...
's Roadmap for Elevator To Spac
SE Roadmap
(PDF) * * Alexander Bolonkin,
Non Rocket Space Launch and Flight
. Elsevier, 2005. 488 pgs. .


External links


The Economist: Waiting For The Space Elevator
(June 8, 2006 – subscription required)

''Riding the Space Elevator''
Times of London Online: Going up ... and the next floor is outer space

''The Space Elevator: 'Thought Experiment', or Key to the Universe?''
. By Sir Arthur C. Clarke. Address to the XXXth International Astronautical Congress, Munich, September 20, 1979.
International Space Elevator Consortium Website

Space Elevator
entry at ''
The Encyclopedia of Science Fiction ''The Encyclopedia of Science Fiction'' (SFE) is an English language reference work on science fiction, first published in 1979. It has won the Hugo Award, Hugo, Locus Award, Locus and BSFA Award, British SF Awards. Two print editions appeared ...
'' {{DEFAULTSORT:Space Elevator Exploratory engineering Space colonization Spacecraft propulsion Spaceflight technology Vertical transport devices Space access Hypothetical technology Emerging technologies Articles containing video clips