Sending rockets into space is expensive. The North American X-15, the hypersonic research program that was the first airplane to have touched space, cost $300 million in 1969 dollars, with each flight estimated to have cost $600,000. The cost of Ingenuity helicopter – the only chopper to have flown on a planet outside the Earth – was $80 million.
In addition to the exorbitant expenses of sending missiles and rockets into space, such spacefaring endeavors also release massive amounts of harmful emissions, so much so that the Bikanuar cosmodrome has “11 000 tons of space scrap metal, polluted by especially toxic UDMH is still laying on the falling grounds“. Therefore, some space engineers of the 21st century are abandoning rockets for something much more exciting: space elevators.
A space elevator might not come across as a novel mode of transportation if you were to think of it as an elevator in the normal sense of the word. But it does involve a fixed structure to send astronauts (and/or payload equipment) into orbit. It has been reported that the use of space elevators would reduce costs of carrying cargo to space by 95%. For instance, every kilogram of cargo on a SpaceX Falcon rocket costs $7,500 to carry into orbit. A space elevator would diminish this expense to $375. But before we get to the economics of it all, what does a space elevator look like?
Konstantin Tsiolkovsky and imagination of tower that would stretch to space
According to the International Space Elevator Consortium (ISEC), the origins of the space elevator concept can be traced back to 1895. Russian scientist Konstantin Tsiolkovsky envisioned a tower extending about 36,000 kilometers into space in his book Dreams of Earth and Sky, although his idea did not yet constitute a true space elevator and did not address the structural stresses such a system would face.
ISEC considers Tsiolkovsky’s proposal the first of several stages in the development of the space elevator concept. The modern idea of using a tensile cable extending from Earth into space emerged much later, with Yuri Artsutanov developing the concept further in 1960.
The stress involved in creating (imaginary) structures as tall as buildings that rise from the Earth to space is extraordinarily high. Mountains, for instance, don’t get much taller than Everest, because with all their muscle, they find it “too hard to do that work against gravity“. This is why despite Konstantin Tsiolkovsky’s musings no known material is strong enough to support such a building.
Yuri Artsutanov, is regarded to be the co-inventor of a space tower and was the first in conceptualizing the building a space tower as he envisaged “a geosynchronous satellite as the base from which to construct it“. His article titled “To the Cosmos by Electric Train.” was published on 31 July 1960 in the Russian tabloid Komsomolskaya Pravda. Ironically, the word “Pravda” refers to “truth” in the Russian language and was used by the Soviets for carrying out mass propaganda.
Nontheless, Artsutanov believed that a cable “lowered from the satellite to the surface of the Earth while a counterweight was extended from the satellite away from Earth” would act as a space elevator. And the fundamental premise of a modern space elevator hasn’t seen a lot of change even as NASA works on building one.
Theorizing and Conceptualizing a space elevator
To imagine how a space elevator would work, you can Imagine hopping on a fast-spinning carousel while holding a rope attached to a rock. The rock and rope will remain horizontal as long as the carousel keeps spinning and there’s an interplay of centrifugal forces. You’ll feel inertial acceleration pulling the rock away from the center of the rotating carousel [if you are holding on to the carousel that is].
All you now need to envision is the Earth as a carousel, a rope with a long tether (that is projected from the Earth), a counterweight (instead of the rock), and voila, you have the sketches of the modern space elevator. In other words, a cable pulled into space by the physics of our spinning planet would act as a space elevator.
Image:NASA
One of the essences of a space elevator is the placement of a counterweight far enough in space so that the centrifugal force generated by the Earth’s spin is greater than the planet’s gravitational pull. As these two forces balance out at roughly 36,000 kilometers (a figure that you can see in Konstantin Tsiolkovsky’s work quoted above) above the Earth’s surface, the counterweight should be beyond this height.
36,000 kilometers is exactly where the Earth’s geostationary orbit (also known as Clarke orbit as it was first popularised by science fiction author Sir Arthur C. Clarke in 1945). NASA points out that any object placed on a geostationary orbit “hangs seemingly motionless above a point on Earth“. An asteroid could also serve as the counterweight of our space elevator.
Complications in practicalizing the space elevator
The tether (to the asteroid or any other counterweight) could be released down through the atmosphere and connected to a base station on the planet’s surface. If we have hopes of maximizing centrifugal acceleration, the anchor point should be close to the Equator.
According to Italian astrophysicist, Fabio Pacucci, “by making the loading station a mobile ocean base, the entire system could be moved at will, allowing it to maneuver around extreme weather, and dodge debris and satellites in space” . He further explains the time it would take to climb up the space elevator and the potential constraints:
” Current designs estimate that it would take about 8 days to elevate an object into geostationary orbit. And with proper radiation shielding, humans could theoretically take the ride too. Once established, cargo could be loaded onto devices called climbers, which would pull packages along the cable and into orbit. These mechanisms would require huge amounts of electricity, which could be provided by solar panels or potentially even nuclear systems.”
Practical limitations in the construction of the elevator
While a construction accident of such a massive scale can be fatal (to say the least), an engineering problem lies in the construction of a cable that could withstand the pull of the counterweight. Other problems include:
- The thickness and strength of the cable need to vary as tension and the force of gravity would vary at different points (depending upon atmospheric constrains).
- While carbon nanotubes and diamond nano-threads can be a fit, only small nanotube chains of such materials have been actualized.
On the bright side, space elevators based on Mars or the Moon (given the low gravity of these astronomical objects) might be more feasible as we already have engineering capabilty of constructing cables that could withstand Moon or Mars’ gravity.
What is the latest on the construction of a space elevator?
An Earth-based space elevator could offer significant economic advantages, but researchers have also explored the possibility of constructing a lunar space elevator using a cable extending from the Moon toward Earth’s geostationary orbit. Studies suggest that carbon-based polymers, including ultra-strong materials such as Zylon, could potentially provide the strength needed for such a structure.
According to The Business Standard, a lunar space elevator could also support the long-term goal of permanent human habitation beyond Earth. It could provide reliable access to the Earth-Moon Lagrange point, a region where gravitational forces allow spacecraft and infrastructure to remain relatively stable. Such a location could eventually serve as a space hub for telescopes, orbital laboratories and staging interplanetary missions, while its relatively low debris environment could offer additional advantages.
Researchers have also examined the possibility of building a space elevator on Ceres, the largest object in the asteroid belt. Students at the University of Colorado Colorado Springs concluded that such a system could potentially be constructed for around $5.2 billion.
However, the concept faces major practical challenges, including the roughly 30-minute communication delay between Earth and Ceres. Universe Today reported that a space elevator made using currently manufacturable carbon nanotubes could transport payloads of approximately 6,534 kg to a station positioned above Ceres. From there, the station’s rotation could allow payloads to be launched into space, potentially reducing the energy required to send material toward Earth by about 60% and cutting fuel consumption by around 15%.
Despite these potential advantages, the enormous cost of developing space elevators and the lack of real-world demonstrations make their practical effectiveness difficult to assess. Space agencies may therefore remain cautious about investing billions of dollars in a technology whose long-term economic and operational benefits have yet to be proven.
