Space elevator

A space elevator is an exciting idea for a new way to travel between Earth and space. It is often called a space bridge, star ladder, or orbital lift, and it appears in many science fiction stories. The main part of a space elevator would be a very strong cable, also known as a tether. One end of this cable would be attached to the ground near the equator, and the other end would be attached to a special weight far out in space, beyond geostationary orbit, which is about 35,786 kilometers above Earth.

The space elevator would stay in one place because of two forces: gravity, which pulls more strongly on the lower part of the cable, and the upward push from the weight in space, called centrifugal pseudo-force. This balance would keep the cable stretched tight and still over one spot on Earth. Special vehicles called climbers could move up and down the cable. They would carry people and cargo between Earth and space.

One of the biggest advantages of a space elevator is that it could let vehicles travel between Earth and orbit without the use of large rockets. This could make space travel much easier and cheaper in the future. While we have not built a space elevator yet, the idea continues to inspire scientists and engineers to think about new ways to explore space.

History

The idea of a space elevator was first imagined by Russian scientists in the late 1800s. One of them, Konstantin Tsiolkovsky, wrote about a "sky ladder" to reach space. Later, scientists like Yuri Artsutanov and John D. Isaacs also had similar ideas.

In the 1970s, American scientist Jerome Pearson began studying space elevators. Since then, many people have worked on designs to make this dream real. Today, companies and researchers keep looking for new materials and methods to build a space elevator someday.

Materials

One of the biggest challenges for building a space elevator is finding materials strong enough to support it. The cable must be very strong to hold its own weight and any cargo it carries. Most ideas for space elevators use materials that can stretch and hold tension, like an upside-down plumb bob.

Building a space elevator on Earth is hard because we don’t yet have materials strong and light enough. But on places like the Moon or Mars, where gravity is weaker, materials we already have, such as Kevlar, might work. Scientists are studying new materials like carbon nanotubes, boron nitride nanotubes, diamond nanothreads, and graphene, which could make an Earth space elevator possible in the future.

Main article: Specific strength
Main articles: Space tether, Plumb bob
Further information: Carbon nanotubes, Boron nitride nanotubes, Diamond nanothreads, Graphene

In fiction

Space elevators are popular in science fiction books and stories. In 1979, famous author Arthur C. Clarke wrote about a space elevator in his book The Fountains of Paradise. Other well-known books, like Red Mars by Kim Stanley Robinson and Old Man’s War by John Scalzi, also include space elevators. These stories explore how space elevators might change space travel and life on other planets.

Physics

The space elevator would spin with Earth. Objects on the cable would feel two forces: Earth's gravity pulling down, and the spinning motion pushing up. Higher up, gravity gets weaker but the spinning push gets stronger. At a special height called geostationary orbit, these forces balance perfectly. Above this point, the spinning push is stronger than gravity, making things want to move upward.

The strength of the cable is very important. The biggest pull happens at geostationary orbit, about 35,786 km above Earth. The cable must be strong enough to hold its own weight from the ground all the way up to this height. Engineers design the cable to have the right thickness at each height to balance these forces. Special materials are needed to make sure the cable can handle the big forces involved.

Taper ratio for some materials
Material	Tensile strength (MPa)	Density (kg/m³)	Specific strength (MPa)/(kg/m³)	Taper ratio
Steel	2,000	7,900	0.25	1.6×10³³
Kevlar	3,600	1,440	2.5	2.5×10⁸
UHMWPE @23°C	3,600	0,980	3.7	5.4×10⁶
Single wall carbon nanotube	130,000	1,300	100	1.6

Structure

One concept for the space elevator has it tethered to a mobile seagoing platform.

A space elevator is an idea for a way to travel between Earth and space. It would have a long cable stretching from the ground up into space. A special weight at the top would keep the cable tight.

Climbers would move up and down the cable, carrying things and people. The base where the cable starts could be on land or at sea. The cable would need to be very strong and light, made from special materials like carbon nanotubes. The climbers would get power from methods like wireless energy transfer. The weight at the top would help keep the cable balanced and steady.

Applications

Space elevator Phobos

A space elevator could help send things into space far from Earth. If you let go of something from the elevator at about 53,100 km above Earth, it would move fast enough to leave Earth's pull. You could also send things to the Moon or even Jupiter this way.

Space elevators might also be built on other planets or moons. On Mars, the elevator could be shorter because the planet's gravity is weaker. The Moon could also have a space elevator, though it would need to be very long. Small, fast-spinning space rocks could also use similar ideas to move materials.

Construction

Building a space elevator would need new advances in engineering and technology. After the first one is built, making more would be easier and cheaper. Early ideas thought the cable would be made in space using materials from asteroids, but now most plans focus on simpler ways. These ideas suggest launching a long cable from a satellite in space and letting it stretch down toward Earth while balancing it with a weight moving away from Earth.

One plan suggests using rockets to put up a very small cable first. This tiny cable could support a small vehicle. More vehicles would add pieces to the cable, making it stronger and wider until it could carry much heavier loads.

International Space Elevator Consortium (ISEC)

The International Space Elevator Consortium (ISEC) is a US non-profit group that supports the idea of building a space elevator. It started after a conference in Redmond, Washington in July 2008. ISEC works closely with the National Space Society.

Each year, ISEC holds a conference at the Seattle Museum of Flight to talk about progress and new ideas.

ISEC also works with groups in Japan and Europe that have the same goal. It helps organize meetings and talks at big space science events around the world.

Related concepts

The idea of a space elevator has changed over time. It was first thought to be a very tall tower reaching into space. Now, it is usually seen as a strong cable fixed to the ground and stretching high above a special orbit level. This lets cargo climb up and then be let go into orbit.

There are many other ideas related to space elevators. Some use rotating cables, like one suggested by Hans Moravec, which could help move objects into orbit. Others imagine very tall towers that make it easier for rockets. One interesting idea is called the aerovator, a long ribbon that spins in the air, helping planes pull payloads into orbit. Additional concepts include orbital rings, space fountains, launch loops, skyhooks, space tethers, and even a buoyant "SpaceShaft".