Advances in Space Elevator Concepts and Materials
Introduction
A space elevator is a theoretical type of planet-to-space transportation system. The main component would be a cable (also called a tether) anchored to the surface and extending into space. The design would permit vehicles to travel along the cable from a planetary surface, such as the Earth's, directly into space or orbit, without the use of large rockets. An Earth-based space elevator would consist of a cable with one end attached to the surface near the equator and the other end in space beyond geostationary orbit (35,786 km altitude). The competing forces of gravity, which is weaker at the higher end, and the outward/upward centrifugal force, which is stronger at the higher end, would result in the cable being held up, under tension, and stationary over a single position on Earth. Once deployed, the tether would be ascended repeatedly by mechanical means to orbit, and descended to return to the surface from orbit.
History of Space Elevator Concepts
The concept of a space elevator dates back to 1895 when Russian scientist Konstantin Tsiolkovsky considered a tower that reached all the way into space. Tsiolkovsky's conceptual tower was a compression structure, while modern concepts call for a tensile structure (or "tether").
Advances in Space Elevator Concepts
Over the years, there have been numerous advances in space elevator concepts. One of the most significant is the introduction of the idea of using carbon nanotubes to construct the tether. Carbon nanotubes are a form of carbon with a cylindrical nanostructure. These cylindrical carbon molecules have unusual properties, which are valuable for nanotechnology, electronics, optics and other fields of materials science and technology.
Another significant advance in space elevator concepts is the idea of using a counterweight at the end of the tether. The counterweight would be swung outward and kept there, creating enough upward force on the tether to keep it taut. This would allow the tether to remain stationary over a single position on Earth, making it easier for vehicles to ascend and descend.
Advances in Space Elevator Materials
The materials used in the construction of a space elevator are of critical importance. The tether, in particular, must be made of a material with an extremely high tensile strength and light weight. Carbon nanotubes have been identified as a suitable material due to their exceptional strength and lightness. However, as of now, we are unable to manufacture carbon nanotubes in the lengths required for a space elevator tether.
In recent years, there have been advances in the production of carbon nanotubes, including methods to spin them into a thread. There have also been advances in the production of other potential tether materials, such as boron nitride nanotubes (BNNTs). BNNTs have many of the same properties as carbon nanotubes but are more resistant to high-energy cosmic rays that could potentially damage the tether.
Challenges and Potential Solutions
There are numerous challenges to building a space elevator, including the current inability to manufacture a suitable tether material in sufficient quantities and lengths, the need for extremely precise engineering and construction, and the need for significant advances in robotics to handle the construction and operation of the elevator.
Potential solutions to these challenges are being researched. For example, advances in nanotechnology may eventually allow for the production of carbon nanotubes or BNNTs in sufficient quantities and lengths. Advances in robotics and automation could address the engineering and operational challenges.
Future Prospects
While the concept of a space elevator is still largely theoretical, advances in materials science and engineering are bringing us closer to the possibility of constructing one. If built, a space elevator could revolutionize space travel, drastically reducing the cost and increasing the accessibility of reaching space.