What is the Space Elevator?

Roads and bridges have been around for quite some time now. Their contribution to the modern world can hardly be overemphasized. Romans built the first road. This invention led them to a series of conquests allowing them to establish highway networks throughout the city. Historians agree that roads are what allowed them to rule the world of ago.

So, what’s the next big step after connecting all the major land masses? Take these highways to space. It sounds implausible but bear with me.

You construct a tether and secure its one end to the earth and the other one reaches into space. This tether should, in theory, haul tons of cargo from Earth’s surface into deep space. Essentially, creating a highway from earth to space or how it’s more aptly described a space elevator. Theoretically, it should provide transportation just as highways and bridges provide mass transportation all across the earth. It would also be much cheaper and cost-effective than huge rockets we use today for transportation of cargo to outer space.

History of the space elevator

This concept of extending a structure from earth to the heavens been around for centuries. Manuscripts well over two thousand years old speak of a civilization that tried to build a tower of brick and mortar from the earth which reached into heavens. This tower is more commonly known as the Tower of Babel, thought to have been an attempt by ancient Mesopotamians. The same manuscripts, written by Moses, further mention a dream that Jacob supposedly had of climbing a ladder to heavens. It is known as Jacob’s ladder.

A more recent theory about constructing a tower extending into earth’s orbit was put forth by a Russian rocket scientist, Konstantin Tsiolkovsky, in 1895. He proposed that hypothetically, a tower could be built so high that it reached earth’s geostationary orbit. Such a tower would have its center of the mass closer to earth’s surface because it would support its weight from the bottom. In other words, under compression.  It has been proved that a compression structure is not viable because there is no known material with enough compressive strength to support its own weight.

Later on, in 1966, John Isaacs published an article about a pair of hair-thin wires suspended from a geostationary satellite. In 1975, another paper was published titled Acta Astronautica, which detailed the modern concept of a space elevator. According to the theory, the cable will be held up by the competing forces of gravity and upward centrifugal force. The cable will be under tension and stationary in a single position on the planet. Once the cable is deployed, an elevator-like structure can be used to repeatedly to ascend from the surface of the planet to the orbit and back.

As opposed to compression, another idea is to suspend the tether from a counterweight past the earth’s geostationary orbit which would be kept in place by harnessing the centrifugal force from earth’s rotation. Russian scientist Yuri Artsutanov came up with this more feasible concept that utilizes a geostationary satellite as the base to deploy a structure going down to the Earth’s surface. The cable is lowered from the orbit to the surface with the use of a counterweight. The tension in the line should keep the structure intact. This structure would be called a tensile structure.

While the compression structure is not viable in practice, a tensile structure might just be feasible.

Potential materials for building a space elevator

The material used for tether would require an immense amount of strength-to-weight ratio. In simpler words, it should be extremely light yet extremely strong. There are a few potential candidates at different stages of development.

Carbon nanotubes (CNT) offer the strength-to-weight ratio a space elevator demands. They are tubes of carbon which are only one-atom-thick.

Structurally similar to carbon nanotubes, boron nitride tubes have also been considered. A relatively recent development, diamond nanothreads are another potential material. They are created by subjecting liquid benzene to immense pressure.

The strongest material to ever have been developed, Graphene, also meets the strength-to-ratio requirements of a space tether.

Proposed designs

Several designs have been suggested and they all invariably, make use of four basic components. A counterweight is used to deploy the cable, and provide the centrifugal force to keep that tether drawn and taut. A platform to secure the whole structure to the earth and climbers that can move up and down the cable with cargo.

A space station, a hypothetical space dock or spaceport could act as counterweights to the cable. One of the proposed solutions is to extend the cable wider which would supply the same centrifugal (upward pull) as a physical counterweight. This affords simplicity to the design but it would require more quantity of the material to be manufactured.

The cable would have to support its own weight as well as the weight of the climbers. The cable would start off thinner at the platform and grow thicker as it approached the geosynchronous orbit of the earth – the orbit where the satellite takes the same time to orbit the earth as the earth takes while rotating about its own axis. A cable built with any of the materials available today would collapse under its own weight, well before it reached the orbit in question. As mentioned above, there are many potential candidates available for the material but unfortunately, they fall a bit short of the strength-to-weight ratio needed. There are some ways around that problem. An as new materials are discovered or developed, we might have the material required that meets that requirement.

Ideally, the base station should be built as close to the equator as possible. The climate at the equator is mild and tornadoes and hurricanes cannot form at the equator. Several stationary designs have been proposed in the past, such as a tower or peak of a mountain.

But a mobile base station floating on the ocean might be our best bet since it offers maneuverability and stability.

Climbers vary in designs. A most common one being a pair of rollers held between the cable with friction. Thanks to the orbital rotation of the earth, the speed of the climber would go on increasing with height. Once the climber has reached the top, it would stay there suspended because it would start moving with the cable along the geosynchronous orbit. This is when the counterweight comes into play, for descending the climber.

What would it be like?

A geosynchronous elevator would take five days to travel from the surface to the orbit. The structure will often face collisions with debris such as meteorites, meteorites, and artificial orbiting debris, in space and would require regular maintenance, the same as any highway or bridge. In case the elevator is carrying people, it would need to shield them from radiation as well.

Space elevators on other planets

Theoretically, it is possible to build space elevators on other planets or asteroids. These space elevators would demand much less strength and will allow for more weight. We already have materials, that could be used to build space elevators in such conditions.

Modern Space Elevator Developments

Researchers are trying to develop a feasible space elevator. According to a study, an elevator to space is possible through a major international effort. Advances in technology can reduce the risks. It can be used to send people to space via electric vehicles that go up and down the tether. The Earth’s rotation will make the tether tense and able to support the electric vehicles.

There are several companies that are developing their versions of the space elevator. The LiftPort Group announced in 2005 that they will utilize carbon nanotubes to construct their elevator. They even launched a Kickstarter campaign to help fund their research.

Even Google got into the action when it considered designing one but the tech giant scraped the plan because they found it to be not feasible. In 2012, the Obayashi Corporation announced that a space elevator can be constructed in 38 years with the use of carbon nanotube technology.