A space elevator that takes us from Earth to outer space is typically the stuff of science fiction movies.
However, plans to test this structure are set to be implemented in the coming years.
The concept of a space elevator was first proposed in 1895, and possibly even earlier.
Today, due to modern technology, knowledge, and new materials, this futuristic idea is becoming increasingly tangible.
The most notable benefit of a space elevator is the significant reduction in the cost of sending supplies and crew to space stations or nearby planets.
Even with the advantage of reusable rockets from Elon Musk’s SpaceX, the cost of putting anything into orbit remains extraordinarily high.
The main reason for this high cost is that to free an object from Earth’s gravitational pull, it must reach a certain velocity.
In fact, each planet has a different gravitational force, so launch speeds will vary. For example, for Earth, a rocket must reach a minimum speed of 40,270 km/h to escape our planet, which requires a massive amount of fuel, not to mention the environmental impact that can threaten the climate.
This has led scientists to consider the idea of building a space elevator, consisting of a cable extending from Earth to a distant orbit powered by solar energy, eliminating the need for any fossil fuels.
The primary focus of research is to find a material that is strong enough, long enough, and light enough. The second challenge is to reduce the force requirements when carrying a specific payload. Although there are many challenges, this idea is entirely feasible in today’s world.
What is a space elevator?
The National Aeronautics and Space Administration (NASA) defines this concept as follows: “A space elevator is a physical connection between the surface of Earth and geostationary orbit (GEO) – located above Earth at an altitude of approximately 35,786 km. Its center of mass is at a geostationary point so that it has a 24-hour orbit and remains above the same point on the equator as Earth rotates on its axis.”
To clarify this concept, British scientist Arthur C. Clarke (1917-2008) provided another definition in his speech at the 30th International Astronautical Congress (1979): “A space elevator is a structure that connects a point on the equator with a satellite in geostationary orbit directly overhead. By providing a vertical route, it would significantly reduce the costs of space activities.”
The structural components of a space elevator include a base (or anchor), cables, climbing mechanisms, power systems, and counterweights in space.
To prevent the cable from breaking, it must be balanced on the other end by a mass in a similar orbit. The entire elevator would then be supported by centrifugal force due to our planet’s rotation.
However, at that time, no known materials were strong enough to withstand these forces. The technical challenges and costs associated with such a structure are immense.
Over the decades, each generation of scientists has conducted new research to overcome these obstacles.
Testing set for 2050
One of Japan’s leading construction companies, Obayashi Corporation, recently announced plans to begin testing carbon nanotubes, which theoretically could help construct a massive elevator reaching into space.
“This space elevator” will push humans beyond Earth’s atmosphere at record speeds. Based on estimates from several scientists, this idea could reduce travel time to Mars from 6-8 months to just 40 days. But will such an ambitious project really come to fruition? The Obayashi Corporation believes “Yes.”
What will this space elevator look like? According to conceptual images and plans outlined by Obayashi, it appears as a gigantic tube connecting Earth to a geostationary satellite outside the planet’s atmosphere. This carbon nanotube will be nearly 96,000 km long, utilizing a wheeled elevator called a “climber” to transport materials as well as people.
Obayashi Corporation states that construction of the space elevator will involve transporting materials via rockets in multiple stages throughout the spacecraft construction process in Low Earth Orbit (LEO).
Concept of the space elevator.
Afterward, the spacecraft will use electric engines to ascend while orbiting Earth until it reaches Geostationary Orbit (GEO), where it will begin to orbit at a speed similar to Earth’s rotation.
At a distance of approximately 35,000 km from Earth, the spacecraft will begin deploying the carbon nanotube with a booster attached to its end, moving further away from Earth.
Eight months later, Obayashi Corporation estimates the carbon nanotube will reach the Earth’s surface, and the spacecraft will achieve its final height of 96,000 km, where it will act as a counterweight for the tube. From there, a climber will ascend the tube, reinforcing it with cables before connecting it to the counterweight at the top.
Obayashi Corporation estimates that after being reinforced about 500 times, this tube will be able to support a wheeled elevator weighing 100 tons, used to transport materials to complete the GEO station.
Below, scientists plan to build Earth Port, a gateway to space with two sections, one on land at the equator and another at sea. Each section will be connected by an underwater tunnel.
From Earth Port, the climbers will ascend the carbon nanotube at a speed of about 150 km per hour, reaching the height of the International Space Station in about two and a half hours. Theoretically, the entire process will be powered by solar energy, with the GEO station acting as a massive solar panel.
Each launch, the corporation states, could cost a few thousand USD, which is relatively inexpensive compared to the current cost of sending spacecraft into orbit.
“Crazy” ideas
In 2019, researcher Zephyr Penoyre from the University of Cambridge and Emily Sandford from Columbia University in New York announced that the idea of a cable connecting Earth directly to space is feasible with today’s technology.
According to MIT Technology Review, the two scientists took a different approach. Instead of anchoring the cable to Earth, they proposed anchoring it to the Moon and hanging it down to Earth.
The significant difference comes from the centrifugal forces mentioned earlier.
A conventional space elevator would complete one rotation each day, in phase with Earth’s rotation. However, an elevator station set on the Moon would only orbit once a month, at a much slower speed due to the corresponding weaker forces.
The space elevator is facing several challenges, including finding a material that is strong enough and lightweight (Illustration: National Geographic).
Additionally, the supporting cable extending from the Moon to Earth would pass through a region of space where the gravitational forces of both Earth and the Moon cancel each other out, known as a Lagrange point.
In other words, below, gravity pulls the cable toward Earth; while above, gravity pulls the cable toward the Moon’s surface. The researchers propose that the risk of impact from space objects (like meteors) in this area is low, and the cable could be designed to withstand minor jolts.
For the second idea, initially, travelers would take a rocket to a station located at the base of the elevator, and then use the solar-powered space elevator system to travel to the Moon.
The two scientists added that “This would reduce the amount of fuel needed to reach the Moon’s surface to one-third of current travel requirements.”
They stated that their system could be constructed for a few billion dollars using existing technology and would lower the costs of traveling on the Moon by reducing reliance on rockets.
The authors believe that this could facilitate more frequent scientific explorations to the Moon and even industrial projects, such as mining for rare minerals abundant on the surface of this planet.
Penoyre explains in a press release: “Spaceline (the name of their concept) will become an infrastructure, much like an old railway, allowing people and materials to move easily in space.”
In addition to the ideas of Penoyre and Sandford, the basic concept of a space elevator involves launching a satellite into a geostationary orbit, to lower a cable down to the Earth’s surface, which can then be used to lift travelers up and down in space.
This requires a material strong and light enough to support its own weight plus the payload. The tether would be 100,000 km long and 1 meter wide.
Expensive Materials
Until recently, the only candidate material was carbon nanotubes, but producing this material at the aforementioned length and width is a significant challenge.
Notably, scientists from the International Space Elevator Consortium (ISEC) claim that a cost-effective manufacturing process could produce graphene ribbons (a new material that is 200 times stronger than steel yet very flexible) for this cable.
Their latest findings were detailed in a paper presented at the International Astronomical Union conference in September 2022, in Paris (France).
It is worth noting that in 2010, two scientists from the University of Manchester, UK, won the Nobel Prize in Physics for discovering and isolating a new material, namely graphene.
Graphene is a new form of carbon, 200 times stronger than steel, yet it remains flexible, transparent, and non-toxic. This makes graphene strong and light enough for a space elevator.
In 2021, the American company General Graphene provided ISEC with samples of polycrystalline graphene in thicknesses ranging from one atom to 30 atoms. It is estimated that the cable of the space elevator will be a maximum thickness of around 12,000 atoms.
Over the past three decades, there has been little progress in producing carbon nanotubes. The process is extremely slow, and the obtained tubes are never long enough. They can currently be produced at lengths of under one meter. Creating a one-meter-long nanotube would take 11 days!
It is estimated that producing this type of cable for the space elevator could consume about 15% of NASA’s 2022 budget (equivalent to $3.6 billion).
What if the Elevator Fails?
Scientists have also considered failure scenarios for the space elevator.
Scenario 1: If the elevator cable breaks at its anchor point on Earth, the outward force from the counterweight would cause the entire elevator to ascend to a higher orbit or completely escape Earth’s gravity.
Scenario 2: If the break occurs at a higher altitude, around 25,000 km, the lower part of the lift force will descend to Earth and hang vertically along the equator to the east of the anchor point, while the unbalanced upper part will fly high into space.
Finally, Scenario 3: If the break occurs at the counterweight side of the elevator, the lower part, including the “central station”, will begin to fall back to the atmosphere (where it will either burn up or crash to the ground).
This requires an immediate cable-cutting mechanism just below the station to prevent unwanted incidents and allow the elevator to continue into high orbit.
The idea of constructing a space elevator has actually existed since the 1980s and 1990s, and it will certainly require a considerable amount of time to realize. However, with the current advancements in science and technology, the possibility of humans traveling to space via an elevator is entirely feasible.
