Being able to bring mass from the surface of the Earth into orbit in zero gravity has always been a gigantic achievement: it takes enormous amounts of energy, fuel and money to bring even just a few kilos of something into space. We have launched gigantic rockets with tiny payloads, and we are trying to launch them with a “centrifugal slingshot“. Maybe. What if we built a space elevator?
What is a space elevator?
Of course it's not about lifts in the conventional sense of the term. While a space elevator can indeed move objects up and down, it's more useful to think of such a craft as a railroad.
In essence, a space elevator would be a giant connecting cable extending from the ground at a point between 35.000 and 100.000 kilometers (22.000-62.000 miles) above the Earth, to an orbiting space station that would serve as a counterweight.
And what would keep this very long space elevator cable taut to allow the “cars” to go up and down? The power of the earth's rotation, thanks to centrifugal force.
What would be the benefits?
The advantages of using a space elevator over traditional rocketry would be multiple. The price of sending mass into space would drop from about $10.000 per kilo to just $100.
A space elevator would offer governments and businesses a vastly faster means of getting people and goods into space.
It would make building space stations and settlements for the Moon and Mars much easier and faster.
It would provide a safer and more reliable route for a tourism industry profitable space.
It would help bring more energy to Earth, reducing costs for launching and testing solar mirrors and stations to send energy from space.
Finally, security. Few unknowns: the journey would be slower, but without stresses like the current ones. And with much greater load capacities.
How did the idea of the space elevator come about?
The origins of the idea originate in Russia: the Soviet scientist Konstantin Tsiolkovsky (one of the godfathers of rocket science together with Goddard and Oberth) spoke of it for the first time as early as 1895. His proposal was essentially a tower built so high as to reach outer space.
Over 60 years later, still in Russia, the modern idea of a space elevator was born. It was another scientist, Yuri Artsutanov, to conceive in 1959 a "tensile structure" held in position thanks to centrifugal force.
How come we don't already have one, 130 years after the first idea? Aside from the costs of building such a structure, the main obstacle is the materials with which to build an incredibly long cable. Carbon nanotubes, often considered the best option, are not the only candidates: carbide, nitride and silicon nanowires are also in the running.
What would a space elevator look like?
The current plans all revolve around 6 sections: the ground station, the cable, the counterweight, the space station, the “cars” and the power source for the entire system. The counterweight must be placed at the far end of the cable, while the station itself must be at a point where the mass above it is equal to that below.
The energy sources imagined as a guide for the wagons? A mix of lasers and solar cells, but some also speculate fusion reactors.
With a space elevator, the cars could carry people and goods to an orbiting space station, or help satellites and probes get into orbit, or go to far more distant destinations, such as the Moon, Mars, the asteroid belt and beyond.
Are there already official plans?
The Marshall Space Flight Center's Advanced Projects Office of NASA has come up with an official plan.
NASA's concept space elevator is a structure that extends from the surface of the Earth to Earth's geostationary orbit (GEO), at an altitude of 35.786 km. The tower would be about 50km tall with a cable tied to the top. Its center of mass would be in orbit, so as to make the entire structure rotate in sync with the Earth's rotation. Along the cable, electromagnetic vehicles would carry people, payloads and energy between space and Earth.
Using carbon nanotubes, a cable just 7cm thick would be able to move 1.000 tons of cargo in just one day. It took us more than 10 years to assemble the ISS, which weighs the same.
According to an analysis by the Spaceward Foundation, that I link to you here, the specific force (a measure of stress/density known as Pascal) needed for a cable would be between 30-40milliYuris, or 30-40 million Pascals: about 75 times the specific force of steel wire.
A future… Space
Our future in space depends on three crucial factors. First, the economic one: (divestment in weapons and increase funds for mission research and development would not be bad). Second, the creative one: We need new and more effective ways to reach orbit and travel. Third, the cultural one: we need to train new space and rocket scientists, and educate new generations to abandon the archaic subculture of "going into space doesn't solve any problems on Earth".
The space elevator is the next big “leap” we need. And perhaps, with suitable funding and scientific efforts, it could become a reality sooner than expected.
