The first space elevator

 

The idea of a space elevator had been around as early as 1895, when Russian scientist Konstantin Tsiolkovsky first explored the concept. Inspired by the newly-built Eiffel Tower, he described a free-standing structure reaching from ground level into geostationary orbit. Rising some 36,000 km (22,000 mi) above the equator and following the direction of Earth's rotation, it would have an orbital period of exactly one day and thus be maintained in a fixed position.

A number of more detailed proposals emerged in the mid-late 20th century, as the Space Race got underway and manned trips to Earth orbit became increasingly routine. It was hoped that a space elevator could drastically reduce the cost of getting into orbit – revolutionising access to near-Earth space, the Moon, Mars and beyond. However, the upfront investment and level of technology required meant that such a project was rendered impractical for now, confining it to the realm of science fiction.

By the early decades of the 21st century, the concept was being taken more seriously, due to progress being made with carbon nanotubes. These cylindrical molecules offered ways of synthesising an ultra-strong material with sufficiently high tensile strength and sufficiently low density for the elevator cable. However, they could only be produced at extremely small scales. In 2004, the record length for a single-wall nanotube was just 4 cm. Although highly promising, further research would be needed to refine the manufacturing process.

It was not until the 2040s that material for a practical, full-length cable became technically feasible, with the required tensile strength of 130 gigapascals (GPa). Even then, design challenges persisted – such as how to nullify dangerous vibrations in the cable, triggered by gravitational tugs from the Moon and Sun, along with pressure from gusts of solar wind.

Major legal and financial hurdles also needed to be overcome – requiring international agreements on safety, security and compensation in the event of an accident or terrorist incident. The insurance arrangements were of particular concern, given the potential for large-scale catastrophe if something went wrong. In the interim, smaller experimental structures were built, demonstrating the basic concept at lower altitudes. These would eventually pave the way to a larger and more advanced design.

By the late 2070s,*** following 15 years of construction,* a space elevator reaching from the Earth's surface into geostationary orbit has become fully operational. The construction process involves placing a spacecraft at a fixed position – 35,786 km (22,236 mi) above the equator – then gradually extending a tether down to "grow" the cable towards Earth. It also extends upwards from this point – to over 47,000 km (29,204 mi) – a height at which objects can escape the pull of gravity altogether. A large counterweight is placed at this outer end to keep it taut. Locations that are most suitable as ground stations include French Guiana, Central Africa, Sir Lanka and Indonesia.

As with most forms of transport and infrastructure in the late 21st century, the space elevator is controlled by artificial intelligence, which constantly monitors and maintains the structure throughout. If necessary, robots can be dispatched to fix problems in the cable or other components, from ground level to the cold vacuum of space. This is rarely required, however, due to the efficiency and safety mechanisms in the design.

A major space boom is now underway, as people and cargo can be delivered to orbit at vastly reduced costs, compared with traditional launches. Over 1,000 tons of material can be lifted in a single day, greater than the weight of the International Space Station, which took over a decade to build at the start of the century.

Although relatively slow – taking many hours to ascend – the ride is much smoother than conventional rockets, with no high-G forces or explosives. Upon leaving the atmosphere and reaching Low Earth Orbit, between 160 km (99 mi) and 2,000 km (1,200 mi), cargo or passengers can be transferred to enter their own orbit around Earth. Alternatively, they can be jettisoned beyond geosynchronous orbit, in craft moving at sufficient speed to escape the planet's gravity, travelling onward to more remote destinations such as the Moon or Mars.

In the decades ahead, additional space elevators become operational above Earth, the Moon, Mars and elsewhere in the Solar System,* with a considerable reduction in costs and technical risks. Construction is also made easier by lower gravity: 0.16 g for the Moon and 0.38 g on Mars. Further into the future, space elevators are rendered obsolete by teleportation and similar technologies.