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Sending rockets into space requires sacrificing expensive equipment, burning massive amounts of fuel, and risking potential catastrophe.
将火箭发射到太空中，需要非常昂贵的设备、燃烧巨量的燃料，还必须冒着灾害发生的风险。
So in the space race of the 21st century, some engineers are abandoning rockets for something much more exciting: elevators.
所以在这场21世纪的太空竞赛中，有些工程师已经弃火箭于不顾，转向更令人兴奋的这个东西：电梯。
Okay, so maybe riding an elevator to the stars isn't the most thrilling mode of transportation.
好吧，搭电梯到其他星球去，可能真的不是最刺激的交通方式。
But using a fixed structure to send smaller payloads of astronauts and equipment into orbit would be safer, easier, and cheaper than conventional rockets.
但使用固定的建筑将较小的负载量--包含航天员和设备--送上轨道，比传统火箭更安全、更简单也更便宜。
On a SpaceX Falcon 9 rocket, every kilogram of cargo costs roughly $7,500 to carry into orbit.
以猎鹰9号运载火箭而言，要将每一公斤的货物送上轨道，就必须花上7500美元。
Space elevators are projected to reduce that cost by 95%.
太空电梯预计可减少95%的成本。
Researchers have been investigating this idea since 1895,
从1895年开始，研究者就开始调查这个方案，
when a visit to what was then the world's tallest structure inspired Russian scientist Konstantin Tsiolkovsky.
这是俄罗斯的科学家康斯坦丁·齐奥尔科夫斯基拜访当时世界上最高的建筑物后受到的启发。
Tsiolkovsky imagined a structure thousands of kilometers tall, but even a century later, no known material is strong enough to support such a building.
他想象出一个高数千公里的结构，但就算在一个世纪后，也尚未发现能支撑这种建物的物质。
Fortunately, the laws of physics offer a promising alternative design.
幸运的是，物理定律提供了一个充满希望的替代设计方案。
Imagine hopping on a fast-spinning carousel while holding a rope attached to a rock.
想象你跳上一座快速运转的旋转木马，手上抓着一条末端绑着石头的绳子。
As long as the carousel keeps spinning, the rock and rope will remain horizontal, kept aloft by centrifugal force.
只要旋转木马持续旋转，石头和绳子就会维持水平，因为离心力而在空中飘浮。
If you're holding the rope, you'll feel this apparent, inertial acceleration pulling the rock away from the center of the rotating carousel.
如果你抓住绳子，就能感受到明显的惯性加速，正在将石头带离这个不停旋转的木马。
Now, if we replace the carousel with Earth, the rope with a long tether, and the rock with a counterweight,
现在，如果我们用地球取代旋转木马，用长拴练取代绳子，用配重取代石头，
we have just envisioned the modern space elevator -- a cable pulled into space by the physics of our spinning planet.
我们刚刚看见的就是现代太空电梯的理想模样：一条靠着地球旋转的物理力学被甩入太空中的电缆。
For this to work, the counterweight would need to be far enough away
要达到这个目标，这个配重必须离地球够远，
that the centrifugal force generated by the Earth's spin is greater than the planet's gravitational pull.
直到抵达因地球转动产生的离心力大于地球重力拉扯的地方。
These forces balance out at roughly 36,000 kilometers above the surface, so the counterweight should be beyond this height.
这两股力量大概会在距离地球表面36000公里的地方失去平衡，所以衡重必须在比它更远的地方。
Objects at this specific distance are in geostationary orbit,
处在这个特定距离下的物体，同时也处在地球同步轨道上，
meaning they revolve around Earth at the same rate the planet spins, thus appearing motionless in the sky.
意味着它们绕行地球的速率和地球自转相同，因此它们在天空中的位置看起来静止不动。
The counterweight itself could be anything, even a captured asteroid.
衡重可以是任何事物，就算是被捕获的小行星也可以。
From here, the tether could be released down through the atmosphere and connected to a base station on the planet's surface.
系链会从衡重被放下来，穿过大气层和星球表面的基地连接。
To maximize centrifugal acceleration, this anchor point should be close to the Equator.
为了使离心加速度最大化，这个锚点应该要和赤道很接近。
And by making the loading station a mobile ocean base, the entire system could be moved at will,
而只要将装运站建成移动式的海洋基地，整个系统都能照需要移动，
allowing it to maneuver around extreme weather, and dodge debris and satellites in space.
让它在极端气候中仍可被使用，并闪避太空中的残骸与人造卫星。
Once established, cargo could be loaded onto devices called climbers, which would pull packages along the cable and into orbit.
一旦建造完成，货舱就能被放上“攀升器”，这个设备能沿着货舱拉起包裹，并将它丢上轨道。
These mechanisms would require huge amounts of electricity, which could be provided by solar panels or potentially even nuclear systems.
这些机械装置需要巨额电力，可以由太阳能板供给，甚至也能用核电供应。
Current designs estimate that it would take about 8 days to elevate an object into geostationary orbit.
依照现在的设计，预估大约需要八天才能将一个物体抛上地球同步轨道。
And with proper radiation shielding, humans could theoretically take the ride too.
而如果有适当的辐射护盾，理论上人类也能搭一次太空电梯。
So, what's stopping us from building this massive structure?
所以，我们为什么还不盖这个超巨大的建筑物？
For one thing, a construction accident could be catastrophic. But the main problem lies in the cable itself.
首先，一场建筑意外就会带来毁灭性的灾害。但主要的问题是缆线。
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.
为了支撑这么庞大的重量，缆线的材质必须够坚固，才能承受衡重的拉力。
And because this tension and the force of gravity would vary at different points, its strength and thickness would need to vary as well.
而因为缆线各点所受的拉力和重力都不同，它的强壮程度和粗细也必须随之改变。
Engineered materials like carbon nanotubes and diamond nano-threads seem like our best hope for producing materials strong and light enough for the job.
工程材料如纳米碳管或纳米钻石线最有希望，让我们能制造出够坚固又够轻盈、能胜任这个工作的材料。
But so far, we've only been able to manufacture very small nanotube chains.
但到目前为止，我们能做出的纳米管线非常小。
Another option would be to build one somewhere with weaker gravity.
另一个选择是把电梯盖在重力较小的星球上。
Space elevators based on Mars or the Moon are already possible with existing materials.
建造于火星或月亮上的太空电梯，已可能可用现存的材料制造。
But the huge economic advantage of owning an Earth-based space elevator has inspired numerous countries to try and crack this conundrum.
但是拥有一座地球上太空电梯带来的巨大经济效益，已经激发无数国家试着完成这个难题。
In fact, some companies in China and Japan are already planning to complete construction by 2050.
事实上，中国和日本的一些公司已经开始计划在2050年前完成建造了。
