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. He noted that the top of such a tower would be circling Earth as in a geostationary orbit. 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. The key concept of the space elevator appeared in 1895 when Russian scientist Konstantin Tsiolkovsky was inspired by the Eiffel Tower in Paris. Currently available materials (such as Kevlar) are strong and light enough that they could be practical as the tether material for elevators there. 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. The concept is applicable to other planets and celestial bodies. Possible future alternatives include boron nitride nanotubes, diamond nanothreads and macro-scale single crystal graphene. Other sources believe that CNTs will never be strong enough. Some sources expect that future advances in carbon nanotubes (CNTs) could lead to a practical design. The cable thickness is adjusted based on tension it has its maximum at a geostationary orbit and the minimum on the ground.Īvailable materials are not strong and light enough to make an Earth space elevator practical. This structure is held in tension between Earth and the counterweight like an upside-down plumb bob. In the tensile concepts, a space tether reaches from a large mass (the counterweight) beyond geostationary orbit to the ground. 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. Like all buildings, Tsiolkovsky's structure would be under compression, supporting its weight from below. His proposal was for a free-standing tower reaching from the surface of Earth to the height of geostationary orbit. The concept of a tower reaching geosynchronous orbit was first published in 1895 by Konstantin Tsiolkovsky. With the tether deployed, climbers could repeatedly climb up and down the tether by mechanical means, releasing their cargo to and from orbit. 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. An Earth-based space elevator cannot be constructed with 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 (35,786 km altitude). 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. The main component would be a cable (also called a tether) anchored to the surface and extending into space. A free-flying satellite (green dot) is shown in geostationary orbit slightly behind the cable.Ī 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. Examples from a number of countries provide evidence of how civil society is put under pressure – and what counter-strategies are being developed.Space elevator in motion rotating with Earth, viewed from above North Pole. The present dossier provides analyses and background information about how civil societies' spaces are being restricted and highlights various facettes. These developments, known as "shrinking space" or "closing space", have become a global trend. Furthermore, civil society actors are targets of defamation, threats and violence. In many countries, state authorities are taking more and more systematic measures, aimed to restrict the work of civil society. It can shape political processes, successfully oranise political participation, uncover corruption and human rights abuses – and it will demand accountability from state actors.īut all across the world, civil society is under pressure. Civil society is part and parcel of all political processes, be they national or international.
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