Yes, scientists are actually building an elevator to space - Fabio Pacucci

804,470 views ・ 2021-12-07

TED-Ed


Please double-click on the English subtitles below to play the video.

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Sending rockets into space requires sacrificing expensive equipment,
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burning massive amounts of fuel, and risking potential catastrophe.
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So in the space race of the 21st century,
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some engineers are abandoning rockets for something much more exciting:
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elevators.
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Okay, so maybe riding an elevator to the stars
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isn't the most thrilling mode of transportation.
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But using a fixed structure to send smaller payloads
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of astronauts and equipment into orbit
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would be safer, easier, and cheaper than conventional rockets.
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On a SpaceX Falcon 9 rocket,
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every kilogram of cargo costs roughly $7,500 to carry into orbit.
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Space elevators are projected to reduce that cost by 95%.
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Researchers have been investigating this idea since 1895,
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when a visit to what was then the world's tallest structure
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inspired Russian scientist Konstantin Tsiolkovsky.
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Tsiolkovsky imagined a structure thousands of kilometers tall,
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but even a century later, no known material is strong enough
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to support such a building.
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Fortunately, the laws of physics offer a promising alternative design.
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Imagine hopping on a fast-spinning carousel
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while holding a rope attached to a rock.
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As long as the carousel keeps spinning, the rock and rope will remain horizontal,
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kept aloft by centrifugal force.
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If you're holding the rope, you'll feel this apparent, inertial acceleration
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pulling the rock away from the center of the rotating carousel.
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Now, if we replace the carousel with Earth,
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the rope with a long tether, and the rock with a counterweight,
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we have just envisioned the modern space elevator—
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a cable pulled into space by the physics of our spinning planet.
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For this to work, the counterweight would need to be far enough away
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that the centrifugal force generated by the Earth's spin
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is greater than the planet's gravitational pull.
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These forces balance out at roughly 36,000 kilometers above the surface,
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so the counterweight should be beyond this height.
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Objects at this specific distance are in geostationary orbit,
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meaning they revolve around Earth at the same rate the planet spins,
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thus appearing motionless in the sky.
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The counterweight itself could be anything,
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even a captured asteroid.
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From here, the tether could be released down through the atmosphere
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and connected to a base station on the planet's surface.
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To maximize centrifugal acceleration,
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this anchor point should be close to the Equator.
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And by making the loading station a mobile ocean base,
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the entire system could be moved at will,
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allowing it to maneuver around extreme weather,
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and dodge debris and satellites in space.
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Once established, cargo could be loaded onto devices called climbers,
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which would pull packages along the cable and into orbit.
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These mechanisms would require huge amounts of electricity,
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which could be provided by solar panels or potentially even nuclear systems.
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Current designs estimate that it would take about 8 days
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to elevate an object into geostationary orbit.
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And with proper radiation shielding,
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humans could theoretically take the ride too.
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So, what's stopping us from building this massive structure?
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For one thing, a construction accident could be catastrophic.
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But the main problem lies in the cable itself.
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In addition to supporting a massive amount of weight,
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the cable's material would have to be strong enough
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to withstand the counterweight's pull.
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And because this tension and the force of gravity would vary at different points,
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its strength and thickness would need to vary as well.
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Engineered materials like carbon nanotubes and diamond nano-threads
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seem like our best hope for producing materials
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strong and light enough for the job.
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But so far,
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we've only been able to manufacture very small nanotube chains.
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Another option would be to build one somewhere with weaker gravity.
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Space elevators based on Mars or the Moon
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are already possible with existing materials.
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But the huge economic advantage of owning an Earth-based space elevator
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has inspired numerous countries to try and crack this conundrum.
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In fact, some companies in China and Japan
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are already planning to complete construction by 2050.
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