Wednesday, November 23, 2011

‘Space Elevators’ in Fact and Fiction

• The Fountains of Paradise (Arthur C. Clarke, 1979): Engineers construct a space elevator on a mountain peak in the fictional island country of Taprobane.
• The Web Between the Worlds (Charles Sheffield, 1979): Here ‘The King of Space’ embarks upon the most spectacular construction project ever - a space elevator. As a short story, this concept had been rejected by sci-fi editors at least twice, on the grounds that a space elevator was not believable. (As opposed to the far more credible little green men from Mars who ran rampant through their publications.) The editor who finally did buy the story made Sheffield write an accompanying article explaining the thing.
You may have noticed that both these stories were published in the same year. Clarke’s was first. On learning of Sheffield’s upcoming novel, Clarke graciously wrote an open letter to The Science Fiction Writers of America stating that coincidence, not plagiarism, lay behind the fact that the two books had such strikingly similar themes. Besides the space elevator, each book had as its main character the world's leading bridge-builder, and each employed a device known as a Spider. (Source: Author’s intro to The Web Between the Worlds.)
• Friday (Robert A. Heinlein, 1982): Here the space elevator is called ‘The Nairobi Beanstalk’. 
• Red Mars (Kim Stanley Robinson, 1993): Colonists build a space elevator on Mars, which is later sabotaged.
• Jumping Off the Planet (David Gerrold, 2000): This space elevator, referred to as a ‘beanstalk’ (as Heinlein did), is more fanciful than the other entries here, skipping as it does from the Earth to the moon to the planets - and eventually to the stars. Gerrold (famous for, among other things, Star Trek’s ‘Trouble with Tribbles’ episode) also explores some industrial uses of a mature space elevator technology.
• Here is a more comprehensive listing of space elevators in fiction.
• 1895: Russian scientist Konstantin Tsiolkovsky, inspired by the Eiffel Tower, described a tower that reached an altitude of 35,790 kilos (22,238 miles) above sea level. He noted that a ‘celestial castle’ at the top would orbit Earth in a geostationary orbit (it would remain over the same spot on Earth's surface). 
A tower or similar structure was soon shown to be an unrealistic approach for a space elevator, since no known material was (or is) strong enough to build an Earth-based structure tall enough to reach the heights needed. Subsequent concepts would involve a tether, rather than a building.
• 1959: Yuri N. Artsutanov, another Russian scientist, offered a more feasible proposal. Artsutanov suggested lowering a cable from geostationary orbit to the surface of Earth. The other end of the cable would be attached to a counterweight beyond geosync orbit, leaving the center of gravity at geosync height. Ever since its introduction, this is the concept that has been most commonly proposed. Almost every design now includes a base station, a cable, climbers, and a counterweight.
• 1966: Isaacs, Vine, Bradner and Bachus, four American engineers, reworked the concept, calling it a ‘Sky-Hook’ and publishing their analysis in Science. They determined that a space elevator cable would require twice the strength of the strongest existing material of that time, including graphite, quartz, and diamond.
• 1975: Jerome Pearson, an American scientist, took a crack at it. His analysis was published in Acta Astronautica. He designed a tapered cable that would be thickest at the geostationary orbit level, where the tension was greatest, and narrowest at the ends to reduce weight. He suggested using a counterweight that would be slowly extended out to 144,000 kilometers (90,000 miles, almost half the distance to the Moon) as the lower section of the elevator was built. 
The weight of the material needed to build his elevator would have required thousands of Space Shuttle trips, although part of the material could be transported up a partially-completed elevator or manufactured in space from asteroidal or lunar ore.
• 1977: Hans Moravec published an article called ‘A Non-Synchronous Orbital Skyhook’ which proposed a variation of a space tether transportation system.
• 1990s: David Smitherman, a NASA engineer, realized that the high strength of recently-developed carbon nanotubes might make an orbital skyhook feasible. He invited scientists and engineers to the Marshall Space Flight Center to discuss concepts and compile plans for an elevator. He compiled information from the workshop into the publication ‘Space Elevators: An Advanced Earth-Space Infrastructure for the New Millennium’, which summarizes the state of the technology at that time.
• 2003 [approx]: Bradley C. Edwards, an American scientist, suggested creating a 100,000 km (62,000 mi) long paper-thin ribbon using a carbon nanotube composite material. Supported by the NASA Institute for Advanced Concepts, his work was expanded to cover the deployment scenario, climber design, power delivery system, orbital debris avoidance, anchor system, construction costs, schedule, and environmental hazards. The main obstacle to the design is the technological limit of the tether material: It still, as of the early 21st century, cannot be made strong enough. One of his books on the subject, Leaving the Planet by Space Elevator (with Philip Ragan, 2008), was published in Japan and made their best-seller list. 
• 2005: Competitions (with prizes) to encourage space elevator development emerge. These include (or have included) Elevator: 2010, the Robogames Space Elevator Ribbon Climbing Competition, NASA’s  Centennial Challenges program, and the European Space Elevator Challenge.
• 2005: The LiftPort Group of space elevator companies announced that it will build 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 mile) space elevator, this move will allow it to make money in the short term and conduct research and development into new production methods. The goal was a space elevator launch in 2010. In 2006 the company announced that they had tested a mile of ‘space-elevator tether’ made of carbon-fiber and fiberglass tape.
• 2008: Japan announced its intent to build a Space Elevator. Leo Lewis, Tokyo correspondent of England’s ‘The Times’ reported on plans by Shuichi Ono, chairman of the Japan Space Elevator Association. Lewis said: "Japan is increasingly confident that its sprawling academic and industrial base can solve those [construction] issues, and has even put the astonishingly low price tag of a trillion yen ($8 billion) on building the elevator.”
Main source: Wikipedia. See also their articles on the lunar space elevator, tether propulsion, and on space elevator construction, economics, and safety.
‘Space elevator’ books on Amazon
There are also other theoretical options for rocketless space launches, including launch loops, lightcraft, space guns, space fountains and space shafts.
from The Patriots of Mars [Postscripts & Essays]

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