A space elevator is a proposed type of space transportation system. The main
component would be a cable (Composed of Carbon nanotubes) anchored to the surface and extending into space. The design would permit vehicles to travel along the cable from a planetary surface, such as the Earth’s, directly into space or orbit, without the use of large rockets.
An Earth-based space elevator would consist of a cable with one end attached to the surface near the equator and the other end in space beyond geostationary orbit (35,800 km altitude). The competing forces of gravity, which is stronger at the lower end, and the
outward/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 cable deployed, climbers could repeatedly climb the cable to space by mechanical means, releasing their cargo to orbit. Climbers could also descend the cable to return cargo to the surface from orbit.
The concept of a space elevator was first published in 1895 by Konstantin Tsiolkovsky. 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 structures, with the weight of the system held up from above by centrifugal forces. In the tensile concepts, a space tether 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. To construct a space elevator on Earth the cable material would need to be both stronger and lighter (have greater specific strength) than any known material.
Development of new materials which could meet the demanding specific strength requirement is required for designs to progress beyond discussion stage. Carbon Nanotubes (CNTs) have been identified as possibly being able to meet the specific strength requirements for an Earth space elevator. Other materials considered have been Boron Nitride Nanotubes, and Diamond NanoThreads which were first constructed in 2014.
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 used as the tether material for
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 35,790 kilometers, the height of geostationary orbit. He noted that the top of such a tower would be circling Earth as in a geostationary orbit. Objects would attain horizontal velocity 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”).
Advancement of 21st Century:
To speed space elevator development, proponents have organized several competitions, 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, 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.” 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 (approx. 13 sheets of paper) thick, lifted with balloons.
In 2007, Elevator:2010 held the 2007 Space Elevator games, which featured US$500,000 awards for each of the two competitions, (US$1,000,000 total) as well as an additional US$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.In 2008 the book Leaving the Planet by Space Elevator by Dr. Brad Edwards and Philip Ragan was published in Japanese and entered the Japanese best-seller list. This led to Shuichi Ono, chairman of the Japan Space Elevator Association, unveiling a space-elevator plan, putting forth what observers considered an extremely low cost estimate of a trillion yen (£5 billion/ $8 billion) to build one.
In 2012, the Obayashi Corporation announced that in 38 years it could build a space elevator using carbon nanotube technology. At 200 kilometers per hour, the design’s 30-passenger climber would be able to reach the GEO level after a 7.5 day trip. No cost estimates, finance plans, or other specifics were made. This, along with timing and other factors, hinted that the announcement was made largely to provide publicity for the opening of one of the company’s other projects in Tokyo.
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 strength-to-weight ratio within 20 years. The fouryear 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 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 few more years , may this project came into Existence, which reduce the time as well as cost to travel in Space at a Specific altitude of 35,790 kilometers.