Diagram of a space elevator
L’ascenseur spatial is a concept of space transportation between the surface and an orbit around the Earth (or another planet). It is based on the idea of a cable kept stretched by the force (The word force can designate a mechanical power over things, and also, metaphorically, a …) centrifugal due to the rotation of the Terre (Earth is the third planet in the Solar System in order of distance …) on herself. To be in balance, the cable must extend beyond thegeostationary orbit (The geostationary orbit, abbreviated GEO (geostationary orbit) is an orbit …) (36,000 km), from which the centrifugal force exceeds the force of gravitation (Gravitation is the phenomenon of physical interaction that causes attraction …). Once in place, nacelles going up along the cable would make it possible to reach theorbit (In celestial mechanics, an orbit is the trajectory that a body draws in space …) more economically than with a launcher (Pitcher, astronautics term Pitcher, baseball term) classic space like a rocket (Rocket may refer to 🙂.
The idea developed (In geometry, the evolute of a plane curve is the locus of its centers of …) in the 1950s came up against many technological constraints, and in the first place the non-existence of a material (A material is a material of natural or artificial origin that man shapes …) both light and strong enough to withstand the tension (Tension is a force of extension.) generated by the proper weight (Weight is the force of gravity, of gravitational and inertial origin, exerted by …) cable. The discovery in the years 1980-90 of nanotubes of carbone (Carbon is a chemical element of the crystallogen family, symbol C, …), whose mechanical properties theory could be sufficient, has revived a certain interest in the concept, which remains however for theinstant (The instant designates the smallest constituent element of time. The instant is not …) in the domain ofUtopia (Utopia (neologism of the English writer Thomas More), synthesis of Greek words …) or the science (Science (Latin scientia, “knowledge”) is, according to the dictionary …) fiction.
Birth of the concept
The concept ofascenseur spatial (The space elevator is a concept of space transportation between the surface and an orbit around the …) was invented by the Russian pioneer of theastronautics (Astronautics or spaceautics or cosmonautics, is made up of all the sciences …) Constantin Tsiolkovski (Constantine Edwardovich Tsiolkovsky (in Russian ?????????? ?????????? ????????????) was born in Russia …) in 1895. On the model of the Tour Eiffel (The Eiffel Tower, initially named the 300-meter tower, is a puddled iron tower …), which had just been completed in 1889, he imagined a tower of 36 000 km high, which would bring by a elevator (An elevator is a mobile device ensuring the movement of people (and objects) in …) charges in orbits.
If the concept of the space elevator was quickly relaunched by Iouri Artsoutanov in 1960, it was only introduced to the general public in 1978 by Arthur C. Clarke, in his novel by science-fiction (Science fiction, pronounced /sjɑ̃s.fik.sjɔ̃/ (abbreviated as …) The Fountains of Paradise. It is also called orbital tower (orbital tower in English).
Clarke describes the construction, from a space station (A space station, in the field of astronautics, is a space installation in orbit …), a gigantic tower intended to constitute a fixed link between the surface (A surface generally refers to the surface layer of an object. The term a …) terrestrial and a counterweight in geostationary orbit. The balance ofensemble (In set theory, a set intuitively designates a collection …) is ensured permanently, by building another tower element in the opposite direction. At total (Total is the quality of what is complete, without exception. From an accounting point of view, a …), it’s a kind of slingshot of 72,000 kilometers (The meter (symbol m, from the Greek metron, measure) is the basic unit of length of the System …) long that must be carried out.
As often, Clarke was inspired by real scientific work, in particular that of the Soviet Iouri Artsoutanov in 1957 and those that four Americans (John D. Isaacs, Hugh Bradner, George E. Backus du Scripps Institution of Oceanography, et Allyn C. Vine of Wood’s Hole Oceanography Institute) published on February 11, 1966, in the review Science (Satellite elongation into a true « Sky Hook »).
In 1975 another American, Jerome Pearson, proposes adopting a structure in the form of a long ribbon, one end of which would itself play the role of counterweight. It became a project (A project is an irreversible commitment of uncertain result, not reproducible a …) 144,000 kilometers (38% of the Earth – Moon distance) but it is no longer necessary to anchor the land base of the structure so firmly (in Clarke’s novel, the base of the tower is anchored several kilometers in the basement).
The system is in equilibrium because half of the cable is located above the geostationary orbit (about 36,000 km from the earth’s surface) while the other half is below. Thus the lower half “pulls” the whole downwards due to the weight of the cable while the upper part “pulls” upwards which creates a tension. The end of the cable which is in space is therefore not in orbit around (Around is the name that the avian nomenclature in French (updated) gives …) of the earth itself, because its speed (On distingue 🙂 actual is much higher than its orbital speed (The orbital speed of a celestial body, most often a planet, a natural satellite, a …). In fact if the cable was coupé (A coupe is a closed car, with two doors (sometimes three with hatchback or four as have …) it would eject into space because of the centrifugal force.
The ascent or descent of a cabin (On a boat, a cabin designates a living room for one or more people. One …) does not affect the balance of the system given the total weight of the cable and its very high tension, so tight that it would be as rigid as a Wall (A wall is a solid structure that separates or delimits two spaces.).
It is also possible to shorten the length (The length of an object is the distance between its two most …) of the cable by adding a counterweight at the end of the cable in space (which could be the launcher that originally threw the cable).
One has to imagine the titanic nature of the project, the length of a 72,000 km cable would correspond to six times the diameter (In a circle or a sphere, the diameter is a line segment passing through the center …) of the Earth, and a quarter of the Earth-Moon distance.
Arrival of nanotubes
For a long time, the idea seemed utopian, since there was no sufficiently resistant material. But the appearance of nanotubes, using fullerenes in particular, has given it some credit. So theEuropean Space Agency (The European Space Agency (ESA) is …) (ESA) and NASA are now seriously interested. The space elevator could take the form of a long cable on which shuttles circulate.
Brad Edwards of the California Foundation Eureka Scientific describes in detail a possible method of building such an elevator (see external link):
- All (The whole understood as the whole of what exists is often interpreted as the world or …) first, you launch a spacecraft into geostationary orbit.
- Then the latter sends a thin ribbon towards the Earth (1 micrometer (One micrometer (μm symbol) is equal to 10-6 = 0, 000,001 meters.) thick) with ad hoc mechanical characteristics (resistant and light). At fur (Fur is a small Danish island in the Limfjord. Fur has around 900 inhabitants. The island …) and as the cable descends, the vehicle (A vehicle is a mobile device, which makes it possible to move people or loads of a …) moves away from Earth to maintain balance. It thus reaches a distance of 72 000 km.
- Once the first cable is anchored to the ground, it is used to put in place others and constitute the final cable.
The potential advantage of such a system lies in its low operating cost. In some concepts, theenergy (In common sense, energy refers to anything that allows work to be done, to manufacture …) braking of a cab descending can even be salvaged to propel a cabin amount. Its main drawback is its vulnerability (In risk management, the vulnerability of an organization or an area …) meteorites, space debris, aircraft or even natural disasters.
Calculations were carried out, and showed that the cable of nanotubes in question should measure approximately one metre (The meter (symbol m, from the Greek metron, measure) is the basic unit of length of …) wide, be as thin as a sheet (The leaf is the organ specialized in photosynthesis in plants …) from paper (Paper (from Latin papyrus) is a material made from fibers …), and be able to withstand a tension of about 63 GPa, equivalent to a tug-of-war game between 100,000 people on each side.
Nicola Pugno of the Polytechnic of Turin (Turin (Türìn in Piedmontese – Torino in Italian) is a city, capital of …) points out, however, that the carbon nanotube assemblies on which all hope rested would not be strong enough. In an article from Journal of Physics : Condensed Matter, he adds that even in the event that the space elevator could be deployed, micrometeorites and oxygen erosion would be sure to weaken it.
Initially at stade (A stadium (from the ancient Greek στ? Διον stadion, from the verb …) science fiction fantasy, recent studies on nanotubes as well as the NASA feasibility study make the long-term realization of such a system more and more credible. Indeed, the manufacturing processes of nanotubes in large amount (Quantity is a generic term in metrology (count, amount); a scalar, …) start to see the day (The day or the day is the interval between sunrise and sunset; it is the …), and the strength of materials (The resistance of materials, also called RDM, is a particular discipline …) made up of nanotubes becomes larger and larger.
However, the problem of collisions with satellites currently in orbit, as well as that of resonance (Resonance is a phenomenon whereby certain physical systems …) inevitable on a structure having such a ratio between length and size. In particular, the combination (A combination can be 🙂 of the’tilt (In celestial mechanics, tilt is an orbital element of a body orbiting a …) the axis of the Earth and the presence of moon (The Moon is Earth’s only natural satellite and the fifth largest satellite in …) can create an imbalance dynamic (The word dynamic is often used to designate or qualify what is relative to movement. It …) weakening the structure.