Alright, so most of us have been on an elevator many times in our lives. It’s pretty useful, bringing people or supplies efficiently up and down a building. But what if I told you that we can build an elevator specifically for getting to outer space? You might either laugh and think that I have been reading too much sci-fi lately, or you might continue to ask me a bunch of questions on how this would work. Well, for the latter half of people, you’re in luck! It’s time to talk about space elevators.
A space elevator is a form of transportation that gets something from the surface of a celestial body to outer space. The idea was pioneered in 1895 by Russian rocket scientist Konstantin Tsiolkovsky, also known as the father of rocket science. If you’ve ever taken an aerospace engineering course, he is the guy who came up with the good ol’ rocket equation that we all know and love. The idea was published in “Speculations about Earth and Sky and on Vesta”, which consisted of the multiple thought experiments he wrote about at this time. Tsiolkovsky had been inspired by the Eiffel Tower, and thought of a larger and longer structure that could reach space.
On Earth, a space elevator would be “grounded” at the equator, and would reach well beyond geostationary orbit (GEO). GEO is around 22,000 miles or 35,000 km above the surface, and an object orbiting here would have the same orbital period as Earth. This is where many commercial satellites reside.
Tsiolkovsky proposed a space elevator that relied on a compression structure, like a physical tower. The issue with this is that there exists no material that can support the weight of a structure so large. This is what led to the modern implementation of a space elevator that instead relied on tensile strength. How would this work?
There are four major components of a modern space elevator, which is the tether, anchor station, climber, and counterweight. Let’s start with the tether.
I would say this is probably the most important part of the space elevator because it holds every other component together. With the tensile design, the most tension would be at the tether’s center of mass, which is above where GEO is located. The tether needs to be strong enough to support its weight from the GEO point to its surface, be able to withstand numerous conditions, including space debris, micrometeorites, etc., and also have the ability to change in thickness throughout the tether to effectively meet the needs of all environments. The material used for the tether will be crucial then, and it wasn’t until the 1990s that scientists developed a material that would possibly be strong enough.
Carbon nanotubes (CNTs) are so far our best candidate for tether material. These are literally just tubes of rolled up carbon, or graphene, with its diameter ranging in nanometers. CNTs are so strong because they’re just long strands of very strong carbon bonds. The strength of CNTs is about 100 times stronger than a piece of steel of the same size. So yeah, definitely a great option. Scientists have also considered using diamond nanothreads.
The next component of the space elevator is the anchor station. A space elevator needs a base to even exist, and without it there would be nothing to hold down the structure. On Earth, it is favorable to situate the foundation on a mobile station in the ocean. This leads to flexibility between needing to move the station in case of natural processes, aka storms, wind, and waves. An early NIAC Phase II report from 2003 proposed that the best spot would be in the east Pacific based on weather and ocean patterns that they observed. They also stated that this anchor station would be the workplace of many scientists and engineers, with around 100 people on it, and also be in constant motion.
Up next is the climber, or what one would think of as the elevator cart. After all, in order for this to be a space elevator, we’re going to need a container to carry payloads and passengers from the anchor station to above. It is important to time the travel of these climbers so that not too much stress is put onto the cable. This could mean either one giant, heavy climber at one time, or multiple light climbers at once. As the climber rose up the tether, it would actually be gaining speed in the horizontal direction due to the continuous rotation of the Earth. The climber could be powered through numerous sources of energy including solar and even wireless energy.
Lastly, the counterweight. This is the object at the top of the tether that contributes to the tensile strength structure. To provide more detail, with the counterweight in place, at the center of mass, centrifugal force causes an upward pull, and below the center of mass, gravity causes a downward pull. This is how equilibrium is reached.
There are a couple of ideas of what could act as the counterweight, the two most popular options being either an asteroid or some sort of space station or docking station. I honestly think that having a space station would make more sense if we were to build here on Earth, and it allows for many more opportunities than just a plain asteroid (but this is just my own opinion).
This sounds cool and all, but what is the actual practical use of a space elevator?
So these structures provide a better alternative method of launching into space. As I previously mentioned, as the climber accelerates up the tether, it gains horizontal velocity. By the time it has reached the top, it will have reached escape velocity, or the speed needed to reach orbit and escape the downward gravitational pull of a celestial body. For example, lunar orbit can easily be achieved with a generalized space elevator (different designs lead to different spots in the solar system that can be reached).
One of the most beneficial aspects of the space elevator is that it will also rapidly reduce the cost of putting payloads into space by a large fraction. Currently, rocket launch company SpaceX is able to put a 1 kg into space for about $2700. A space elevator is proposed to be able to put 1 kg into space for around $200. That is a lot more economical, and allows for many possibilities, like manufacturing things in space and creating much larger structures.
Also, a space elevator can serve many commercial space tourism purposes. With a space elevator and the reduced cost of bringing items into outer space, it would elevate the commercial space industry by a ton, and allows for a new way of people experiencing space and microgravity instead of through suborbital commercial flights.
People have also looked into what space elevators would look like on other celestial bodies, including on Mars and the Moon. On Mars, a space elevator would be much easier to construct. Because it has a third of the gravity we have here on Earth, engineers would be able to build a much shorter tether since stationary orbit is much closer to the Martian surface, and also not have to be as strong. This means we could technically build a Martian space elevator with present day materials. There are issues that do come with this though, mainly the Martian moons getting in the way because of their low orbit, though people have looked into using one of the moons as a counterweight. Construction of a space elevator on the Moon would be much more feasible for similar reasons.
There are of course disadvantages and concerns that come with all of this. First, economics. A space elevator, if built, would be the biggest structure ever created by humanity. It will cost a ton of money. The NIAC Phase II proposal I mentioned earlier estimated a cost of around $6.5 billion dollars, though others have proposed costs even higher, being around $90 billion dollars.
The existence of the space elevator itself could cause many issues to the surrounding environment, and the people using it. Obviously radiation poses health risks for riders. Also, it would disrupt a good amount of things orbiting in the orbits lower than GEO, including Low Earth Orbit (LEO) and Medium Earth Orbit (MEO), and also for aircraft near the Earth’s surface. If the elevator were to ever break, it could cause catastrophic damage to Earth and an unimaginable amount of debris.
There is and has been efforts regarding the research of these space elevators, and organizations that support the development of them. There have been numerous competitions revolving around space elevator design, one of the most notable ones being Elevator:2010, which was a competition created in 2005 by a partnership between NASA’s Centennial Challenges and SpaceWard Foundation. The competition at some point even offered a prize of $500,000, though no one won that specific one. There is actually a Wikipedia page dedicated to the numerous space elevator competitions that have happened in the past, so if you’re interested, definitely check it out!
There are a couple of countries and organizations that to this day promote the development of space elevators. The International Space Elevator Consortium (ISEC) supports global efforts on space elevator development and does research and produces publications. They also host an annual conference in Seattle every year.
Japan is the country that does the most research on the space elevator front. There’s the Japanese Space Elevator Association (JSEA), and Japan also launched an experiment to the International Space Station in 2018 to test out the technology. The STARS-Me space elevator experiment consisted of two cubesats connected by a tether and had a mini climber attached. Japanese company Obayashi has also committed to having a space elevator constructed by 2050. So yeah, Japan is definitely the space elevator’s #1 fan.
These structures are something we could possibly see in our own lifetime. Wouldn’t it be amazing to be such a huge structure be built and allow for so many possibilities? I definitely think so. Space elevators...not so sci-fi after all!