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, researchers have been investigating the idea of a space elevator since 1895:
“In 1895 in the book Dreams of Earth and Sky, Russian space pioneer Konstantin Tsiolkovsky wrote of an imaginary tower extending 36,000 kilometers high, where weightlessness would be achieved. But he fell short of inventing the concept of a space elevator and did not calculate the stresses involved.”
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?
Owning an Earth-based space elevator has great economic advantages. There also have been proposals construction of a ‘lunar space elevator’ – a cable extending from the Moon to Earth’s geostationary orbit. Researchers claim that Carbon-based polymers (including ultra-strong Zylon) can constitute the cable for the lunar space elevator. According to a report in The Business Standard, the lunar space elevator can help us towards our mission of ‘permanent space habitation’:
” The elevator would also provide reliable access to the Earth-Moon Lagrange point – a gravitational sweet spot where objects remain stable. Unlike low Earth orbit, where equipment drifts unpredictably, the Lagrange point allows tools, satellites, and infrastructure to stay put. Scientists envision it as a future ‘space hub’, ideal for telescopes, orbital laboratories, and as a launchpad for interplanetary missions. Its relative calm and low debris environment make it a safe and strategic outpost for space exploration.”
Students at the University of Colorado at Colorado Springs analyzed the case of building a space elevator on Ceres, the largest object in the asteroid belt. They found that one can construct a space elevator here and the costs would equal $5.2 billion. Universe Today reported that half an hour of delay in communication between Ceres and the Earth makes the prospect challenging, there are benefits to be reaped:
” SE, if made of currently manufacturable carbon nanotubes, can carry payloads of approximately 6,534 kg up to the station at the top of the elevator. From there, they can be flung into space using the space granted by the station which rotates in line with Cere’s rotation of once every nine hours. At that speed, it would decrease the amount of energy needed to get a payload back to Earth by approximately 60%, and a fuel savings of 15%.”
Spending billions of dollars on a project whose practical efficacy hasn’t been measured as of yet might cause space agencies to look elsewhere. But space science enthusiasts hope that the tune of a space elevator comes to us at last when:
“..all are one, and one is allTo be a rock and not to rollAnd she’s buying a stairway to Heaven”