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,[1] often depicted in science fiction. The main component would be a cable (also called a tether) anchored to the surface and extending into space. An Earth-based space elevator cannot be constructed with a tall tower supported from below due to its 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 (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 (crawlers) could repeatedly climb up and down the tether by mechanical means, releasing their cargo to and from orbit.[2] The design would permit vehicles to travel directly between a planetary surface, such as the Earth's, and orbit, without the use of large rockets.
The concept of a tower reaching
Available materials are not strong and light enough to make an Earth space elevator practical.[4][5][6] Some sources expect that future advances in carbon nanotubes (CNTs) could lead to a practical design.[2][7][8] Other sources believe that CNTs will never be strong enough.[9][10][11] Possible future alternatives include boron nitride nanotubes, diamond nanothreads[12][13] and macro-scale single crystal graphene.[14]
The concept is applicable to other planets and celestial bodies. For locations in the Solar System with weaker gravity than Earth's (such as the Moon or Mars), the strength-to-density requirements for tether materials are not as problematic. Currently available materials (such as Kevlar) are strong and light enough that they could be practical as the tether material for elevators there.[15]
History
Early concepts
The key concept of the space elevator appeared in 1895 when Russian scientist Konstantin Tsiolkovsky was inspired by the Eiffel Tower in Paris. 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 (22,236 miles), the height of geostationary orbit.[16] He noted that the top of such a tower would be circling Earth 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.
Both the tower and cable ideas were proposed in David E. H. Jones' quasi-humorous Ariadne column in New Scientist, December 24, 1964.
In 1966, Isaacs, Vine, Bradner and Bachus, four American engineers, reinvented the concept, naming it a "Sky-Hook", and published their analysis in the journal Science.[19] They attempted 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, quartz, and diamond.
In 1975, an American scientist,
After the development of
In 2000, another American scientist,
21st century
To speed space elevator development, proponents have organized several
In 2005, "the LiftPort Group of space elevator companies announced that it will be building a carbon nanotube manufacturing plant in Millville, New Jersey, to supply various glass, plastic and metal companies with these strong materials. Although LiftPort hopes to eventually use carbon nanotubes in the construction of a 100,000 km (62,000 mi) space elevator, this move will allow it to make money in the short term and conduct research and development into new production methods."[8] 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 5 cm (2.0 in) wide and 1 mm (0.039 in) (approx. 13 sheets of paper) thick, lifted with balloons.[29] 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.[30]
In 2007,
In 2012, the Obayashi Corporation announced that it could build a space elevator by 2050 using carbon nanotube technology.[34] The design's passenger climber would be able to reach the GEO level after an 8-day trip.[35] Further details were published in 2016.[36]
In 2013, the International Academy of Astronautics 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.[37][38][self-published source?]
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 strand longer than a meter. They thus put the project in "deep freeze" and also keep tabs on any advances in the carbon nanotube field.[39]
In 2018, researchers at Japan's Shizuoka University launched STARS-Me, two CubeSats connected by a tether, which a mini-elevator will travel on.[40][41] The experiment was launched as a test bed for a larger structure.[42]
In 2019, the International Academy of Astronautics published "Road to the Space Elevator Era",[43] 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[14] with higher specific strength than carbon nanotubes.
In fiction
In 1979, space elevators were introduced to a broader audience with the simultaneous publication of
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. Because the counterweight, above GEO, is rotating about the Earth faster than the natural orbital speed for that altitude, it exerts a centrifugal pull on the cable and thus holds the whole system aloft.
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:[44]: Table 1
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:[44]: p. 126
This is 35,786 km (22,236 mi) above Earth's surface, the altitude of geostationary orbit.[44]: Table 1
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, 35,786 km (22,236 mi) 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 35,786 km (22,236 mi). 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 35,786 km (22,236 mi) 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 (i.e., the tension per unit of cross sectional area) is constant along the length of the cable.[44][45] 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.[46] 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.[46] 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:[44]
where
Safety margin can be accounted for by dividing T by the desired safety factor.[44]
Cable materials
Using the above formula, the ratio between the cross-section at geostationary orbit and the cross-section at Earth's surface, known as taper ratio, can be calculated:[note 1]
Material | Tensile strength (MPa) |
Density (kg/m3) |
Specific strength (MPa)/(kg/m3) |
Taper ratio |
---|---|---|---|---|
Steel | 5,000 | 7,900 | 0.63 | 1.6×1033 |
Kevlar | 3,600 | 1,440 | 2.5 | 2.5×108 |
Single wall carbon nanotube | 130,000 | 1,300 | 100 | 1.6 |
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 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. Oceanic anchor points are also typically in international waters, simplifying and reducing the cost of negotiating territory use for the base station.[2]
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.[17] 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 that 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.[47]
The cable would need to be made of a material with a high
For comparison, metals like titanium, steel or aluminium alloys have
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.
In 2014, diamond nanothreads were first synthesized.[12] Since they have strength properties similar to carbon nanotubes, diamond nanothreads were quickly seen as candidate cable material as well.[13]
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.[53]
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
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.[46]
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: 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.[53] Space elevators and their loads would be designed so that the center of mass is always well-enough above the level of geostationary orbit[56] 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.[57]
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.[58] At the speed of a very fast car or train of 300 km/h (190 mph) it will take about 5 days to climb to geosynchronous orbit.[59]
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 provide energy to the climber:
- Transfer the energy to the climber through wireless energy transferwhile 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[60]
Wireless energy transfer such as
Yoshio Aoki, a professor of precision machinery engineering at Nihon University and director of the Japan Space Elevator Association, suggested including a second cable and using the conductivity of carbon nanotubes to provide power.[33]
Counterweight
Several solutions have been proposed to act as a counterweight:
- a heavy, captured asteroid[16][61]
- a space dock, space station or spaceport 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.[46]
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
At the end of Pearson's 144,000 km (89,000 mi) cable, the tangential velocity is 10.93 kilometers per second (6.79 mi/s). That is more than enough to
Extraterrestrial elevators
A space elevator could also be constructed on other planets, asteroids and moons.
A Martian 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.[63] 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 an areostationary space elevator; on the other hand, 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 near Mars. This could provide readily available resources for future colonization on Mars.
The Earth's
Rapidly spinning asteroids or moons could use cables to eject materials to convenient points, such as Earth orbits;
A space elevator using presently available engineering materials could be constructed between mutually tidally locked worlds, such as Pluto and Charon or the components of binary asteroid 90 Antiope, with no terminus disconnect, according to Francis Graham of Kent State University.[70] 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.[2] 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.[2]
Prior to the work of Edwards in 2000,
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.[2][21][73] 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 payed 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.[2] 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
A space elevator would present a navigational hazard, both to aircraft and spacecraft. Aircraft could be diverted by
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.[citation needed]
Economics
With a space elevator, materials might be sent into orbit at a fraction of the current cost. As of 2022, conventional rocket designs cost about US$12,125 per kilogram (US$5,500 per pound) for transfer to geostationary orbit.[75] Current space elevator proposals envision payload prices starting as low as $220 per kilogram ($100 per pound),[76] 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 for an orbital airship system.[77]
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."[78]
International Space Elevator Consortium (ISEC)
The International Space Elevator Consortium (ISEC) is a US Non-Profit
ISEC coordinates with the two other major societies focusing on space elevators: the Japanese Space Elevator Association[85] and EuroSpaceward.[86] ISEC supports symposia and presentations at the International Academy of Astronautics[87] and the International Astronautical Federation Congress[88] 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.[89]
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 published an article in 1977 called "A Non-Synchronous Orbital Skyhook" describing a concept using a rotating cable.[90] 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
The aerovator is a concept invented by a Yahoo Group discussing space elevators, and included in a 2009 book about space elevators. It would consist of a >1000 km long ribbon extending diagonally upwards from a ground-level hub and then levelling out to become horizontal. Aircraft would pull on the ribbon while flying in a circle, causing the ribbon to rotate around the hub once every 13 minutes with its tip travelling at 8 km/s. The ribbon would stay in the air through a mix of
Other concepts for non-rocket spacelaunch related to a space elevator (or parts of a space elevator) include an orbital ring, a space fountain, a launch loop, a skyhook, a space tether, and a buoyant "SpaceShaft".[95]
Notes
- ^ Specific substitutions used to produce the factor 4.85×107:
See also
- Gravity elevator
- Orbital ring
References
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- ^ a b c d e f g h i j k Edwards, Bradley Carl. The NIAC Space Elevator Program (Report). NASA Institute for Advanced Concepts. Archived from the original on May 12, 2008. Retrieved November 24, 2007.
{{cite report}}
: CS1 maint: bot: original URL status unknown (link) - ^ Hirschfeld, Bob (January 31, 2002). "Space Elevator Gets Lift". TechTV. Archived from the original on June 8, 2005. Retrieved September 13, 2007.
The concept was first described in 1895 by Russian author K. E. Tsiolkovsky in his 'Speculations about Earth and Sky and on Vesta.'
- ^ Fleming, Nic (February 15, 2015). "Should We give up on the dream of space elevators?". BBC. Retrieved January 4, 2021.
'This is extremely complicated. I don't think it's really realistic to have a space elevator,' said Elon Musk during a conference at MIT, adding that it would be easier to 'have a bridge from LA to Tokyo' than an elevator that could take material into space.
- ^ Donahue, Michelle Z. (January 21, 2016). "People Are Still Trying to Build a Space Elevator". Smithsonian Magazine. Retrieved January 4, 2020.
'We understand it's a difficult project,' YojiIshikawa says. 'Our technology is very low. If we need to be at 100 to get an elevator built – right now we are around a 1 or 2. But we cannot say this project is not possible.'
- ^ "Why the world still awaits its first space elevator". The Economist. January 30, 2018. Retrieved January 4, 2020.
The chief obstacle is that no known material has the necessary combination of lightness and strength needed for the cable, which has to be able to support its own weight. Carbon nanotubes are often touted as a possibility, but they have only about a tenth of the necessary strength-to-weight ratio and cannot be made into filaments more than a few centimetres long, let alone thousands of kilometres. Diamond nanothreads, another exotic form of carbon, might be stronger, but their properties are still poorly understood.
- ^ a b "Space Elevators: An Advanced Earth-Space Infrastructure for the New Millennium", NASA/CP-2000-210429, Marshall Space Flight Center, Huntsville, Alabama, 2000 (archived)
- ^ a b Cain, Fraser (April 27, 2005). "Space Elevator Group to Manufacture Nanotubes". Universe Today. Retrieved March 5, 2006.
- ^ Aron, Jacob (June 13, 2016). "Carbon nanotubes too weak to get a space elevator off the ground". New Scientist. Retrieved January 3, 2020.
Feng Ding of the Hong Kong Polytechnic University and his colleagues simulated CNTs with a single atom out of place, turning two of the hexagons into a pentagon and heptagon, and creating a kink in the tube. They found this simple change was enough to cut the ideal strength of a CNT to 40 GPa, with the effect being even more severe when they increased the number of misaligned atoms... That's bad news for people who want to build a space elevator, a cable between the Earth and an orbiting satellite that would provide easy access to space. Estimates suggest such a cable would need a tensile strength of 50 GPa, so CNTs were a promising solution, but Ding's research suggests they won't work.
- ^ Christensen, Billn (June 2, 2006). "Nanotubes Might Not Have the Right Stuff". Space.com. Retrieved January 3, 2020.
recent calculations by Nicola Pugno of the Polytechnic of Turin, Italy, suggest that carbon nanotube cables will not work... According to their calculations, the cable would need to be twice as strong as that of any existing material including graphite, quartz, and diamond.
- ^ Whittaker, Clay (June 15, 2016). "Carbon Nanotubes Can't Handle a Space Elevator". Popular Science. Retrieved January 3, 2020.
Alright, space elevator plans are back to square one, people. Carbon nanotubes probably aren't going to be our material solution for a space elevator, because apparently even a minuscule (read: atomic) flaw in the design drastically decreases strength.
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During the last ten years, the assumption was that the only power available would come from the surface of the Earth, as it was inexpensive and technologically feasible. However, during the last ten years of discussions, conference papers, IAA Cosmic Studies, and interest around the globe, many discussions have led some individuals to the following conclusions: • Solar Array technology is improving rapidly and will enable sufficient energy for climbing • Tremendous advances are occurring in lightweight deployable structures.
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Further reading
- A conference publication based on findings from the Advanced Space Infrastructure Workshop on Geostationary Orbiting Tether "Space Elevator" Concepts Archived March 28, 2015, at the Wayback Machine (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" HTML PDF, John Hickman, Ph.D. Journal of Evolution and TechnologyVol. 4 – November 1999
- A Hoist to the Heavens By Bradley Carl Edwards
- Ziemelis K. (2001) "Going up". In New Scientist 2289: 24–27. Republished in SpaceRef Archived January 12, 2022, at the Wayback Machine. Title page: "The great space elevator: the dream machine that will turn us all into astronauts."
- The Space Elevator Comes Closer to Reality. An overview by Leonard David of space.com, published March 27, 2002
- Krishnaswamy, Sridhar. Stress Analysis – The Orbital Tower (PDF)
- LiftPort's Roadmap for Elevator To Space SE Roadmap(PDF)
- Shiga, David (March 28, 2008). "Space elevators face wobble problem". New Scientist.
- Alexander Bolonkin, "Non Rocket Space Launch and Flight". Elsevier, 2005. 488 pgsISBN 978-0-08044-731-5.
External links
- The Economist: Waiting For The Space Elevator (June 8, 2006 – subscription required)
- CBC Radio Quirks and Quarks November 3, 2001 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? Archived February 1, 2020, at the Wayback Machine. 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