Lv.3 Universe B_Space Elevator

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

Sending rockets into space requires sacrificing（犠牲的な）expensive equipment, burning massive amounts of fuel, and risking potential catastrophe（大惨事）. So, in the space race of the 21st century, some engineers are abandoning（捨てる）rockets for something much more exciting: elevators. 

Okay, so maybe riding an elevator to the stars isn’t the most thrilling mode of transportation. But using a fixed structure to send smaller payloads（積載器具） of astronauts and equipment into orbit（軌道）would be safer, easier, and cheaper than conventional rockets. 

On a SpaceX Falcon 9 rocket, every kilogram of cargo（積み荷）costs roughly $7,500 to carry into orbit. Space elevators are projected to reduce that cost by 95%. Researchers have been investigating this idea since 1895, when a visit to what was then the world’s tallest structure inspired Russian scientist Konstantin Tsiolkovsky. Tsiolkovsky imagined a structure thousands of kilometers tall, but even a century later, no known material is strong enough to support such a building. 

Fortunately, the laws of physics offer a promising alternative design. Imagine hopping on a fast-spinning carousel（メリーゴーランド）while holding a rope attached to a rock. As long as the carousel keeps spinning, the rock and rope will remain horizontal（水平の）, kept aloft（高く）by centrifugal force（遠心力）. If you’re holding the rope, you’ll feel this apparent, inertial（慣性による）acceleration pulling the rock away from the center of the rotating carousel. 

Now, if we replace（取り替える）the carousel with Earth, the rope with a long tether（ロープ）, and the rock with a counterweight（つり合いを取るための重り）, we have just envisioned（想像する） the modern space elevator– a cable pulled into space by the physics of our spinning planet. For this to work, the counterweight（対重）would need to be far enough away that the centrifugal force generated by the Earth’s spin is greater than the planet’s gravitational（重力による）pull. These forces balance out at roughly 36,000 kilometers above the surface, so the counterweight should be beyond this height. 

Objects at this specific distance are in geostationary orbit（静止軌道）, meaning they revolve around Earth at the same rate the planet spins, thus appearing motionless（静止した）in the sky. The counterweight itself could be anything, even a captured asteroid（小惑星）. From here, the tether could be released down through the atmosphere and connected to a base station on the planet’s surface. To maximize centrifugal acceleration, this anchor（固定するもの） point should be close to the Equator（赤道）. And by making the loading（荷積み）station a mobile（動かすことのできる）ocean base,  the entire system could be moved at will（好きなように）, allowing it to maneuver（巧みに動かす） around extreme weather, and dodg（かわす）debris（破片）and satellites in space. 

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. Current designs estimate that it would take about 8 days to elevate an object into geostationary orbit. And with proper radiation（放射線）shielding（保護） humans could theoretically（理論上では）take the ride too. 

So, what’s stopping us from building this massive structure? For one thing, a construction accident could be catastrophic（大惨事の）. But the main problem lies in the cable itself. In addition to supporting a massive amount of weight, the cable’s material would have to be strong enough to withstand the counterweight’s pull. And because this tension and the force of gravity would vary at different points, its strength and thickness would need to vary as well. 

Engineered materials like carbon nanotubes（カーボンナノチューブ） and diamond nano-threads（ナノスレッド）seem like our best hope for producing materials strong and light enough for the job. But so far, we’ve only been able to manufacture very small nanotube chains. 

Another option would be to build one somewhere with weaker gravity. Space elevators based on Mars or the Moon are already possible with existing materials. But the huge economic advantage of owning an Earth-based space elevator has inspired numerous countries to try and crack this conundrum（難問）. In fact, some companies in China and Japan are already planning to complete construction by 2050.