翻译 时轴 lawyerlulu
我们是地球的“囚犯” 宇宙嘲笑我们 展示那些我们遥不可及的地方 We are prisoners on Earth. The Universe taunts us, by showing all the places we can't ever visit.
然而 如果人类想有一个长久的未来 我们必须逃离这里 However, if our species wants to have a long term future, we have to escape our prison.
但首先应该了解 到底是什么力量将我们滞留此地 But what is keeping us here in the first place?
结果是 我们欠了宇宙一大笔“债”数额为45亿年 Turns out, we owe the universe a debt that is 4.5 billion years old.
能量产生的监狱 A PRISON MADE FROM ENERGY
宇宙中有质量的物体会吸引另一个有质量的物体 Everything with mass in the universe attracts every other thing with mass.
此种现象称为“引力” We call this phenomenon 'gravity'.
距离某大型质量体越近 引力越大或者越容易被拉入重力圈 The closer you are to a big chunk of mass, the stronger the attraction or the more you're pulled in
这种影响力使我们深陷狱中 This effect traps us on earth.
我们可以想象 我们是引力场或引力井中的囚犯 We can imagine this as being prisoners in a gravity prison, or a gravity well.
其并非一口真正的井 却是理解何为引力较为实用的概念 It's not a literal well, but a handy concept to understand how this works.
身陷引力监狱意味着 你欠着引力能量 Being in a gravity prison means that you owe gravity energy.
那我们是如何欠了一屁股债的？ But how can you owe energy?
因为宇宙中 物体一般维持速度和方向 Because in our universe, things don't want to change their speed or direction.
为使其发生改变 需要消耗能量 To convince them to move, you have to expend energy.
几十亿年前 围绕太阳公转的无数尘埃颗粒在引力作用下 Billions of years ago, the gravitational attraction of trillions of trillions of dust particles
凝聚在一起 形成一颗行星 orbiting our sun caught them together until they formed a planet.
此过程需消耗能量 同时产生引力井 目前我们是其组成部分 This process used energy and created the gravity well we're now a part of.
在引力井中越深 你欠引力的能量越多 The deeper you are inside the gravity well, the more energy you owe gravity.
如果你不能获得足够的能量 无论如何 只能乖乖地待在监狱 If you don't find a way to get enough energy, then you aren't able to leave no matter what you do.
因为你的原子曾经是宇宙尘埃的一部分 Because your atoms were once part of the dust
宇宙曾消耗能量将这些尘埃聚集在一起 以达到目前的状态 that the universe expended energy on to get to this place
好的 让我们再次总结一下 Ok. Hmm...Let's summarise all of that again
宇宙中的物体不会轻易移动 消耗能量才能使物体移动 Objects in the universe don't like to move. You have to convince them to do so with energy.
引力利用能量 使得组成地球的部分聚集在一起 Gravity used energy to convince the parts of our planet to move together.
此过程中产生一个引力监狱 限制住人类 This created a gravity prison in the process, trapping us .
为逃脱此监狱 我们需要偿还能量 To escape, it we need to repay it with energy.
好的 那我们如何做呢？ Ok. How do we do that?
要到达宇宙中 我们需要经过复杂的能量交换过程 To get into space, we need to go through a complicated process of exchanging energy.
为达此目的 我们建造一个负电位的能量偿还机 For this purpose, we build a negative potential energy repaying machine.
众所周知 俗称“火箭” Known By their more boring name 'rockets'
火箭利用一些人类所知反应最剧烈的化学反应 Rockets work by using some of the most energetic chemical reactions humans know about
以可控的方式 点燃燃料 to basically explode fuel in a controlled way.
将化学能量转为动能 This converts chemical energy into kinetic energy.
反应产生的废物向外排出 The exhaust of the reaction is directed outwards,
将火箭推离地球 and pushes the rocket away from Earth.
我们增加引力潜在的能量 By expending a lot of energy, we are increasing our gravitational potential energy.
复杂地讲 人类向引力偿还“能量”债 Which is a complicated way to say that we are paying back our energy debt to gravity.
但实际上 此系统更加繁杂 But it's actually a lot trickier than that.
消耗燃料到达预定轨道过程中 你付出了许多能量用来加热 排气 摆脱地球牵引力 When you burn fuel to get into orbit, you lose lots of energy to heat, exhaust and atmospheric drag
因此你实际需要更多的能量 ,so you actually need much more.
你不能只是将大量危险爆炸性燃料堆积在卫星装置下 And you can't just pile a huge amount of radioactive, really explosive, dangerous fuel close to your
然后引爆 payload and detonate it.
你需要以可控制的形式进行点燃 设计很复杂 重量巨大 You need a controlled burn which is complicated and makes your rocket very heavy
这意味着质量更大 ...which means it has more mass.
质量越大 需要更多的能量使其移动 The more mass something has, the more energy you need to convince it to move,
因此火箭升空 需要越多的燃料 so you need more fuel to lift up your rocket.
但如果你需要越多的燃料 意味着你需要更多火箭携带燃料 But,if you need more fuel, that means you need more rocket to carry that fuel!
然而这么做 火箭重量则越大 需要的燃料越多 需要的越多火箭携带燃料 But, this makes your rocket heavier thus requiring more fuel which requires more rocket to carry that
以此类推 new fuel and so on.
最终你需要重于卫星质量100倍的燃料 使其发射升空 At the end of this madness, you need closer to a 100x the weight of your payload to launch
阿丽亚娜6号火箭为例 此颗欧洲火箭重达800吨 可以将 Ariane 6, for example (the european rocket) will weigh 800 tons and should be able to
10吨重量运送至同步传输轨道或将20吨重量运送至地球中轨道 transport 10 tons into geostationary transfer orbit or, 20 tons into medium earth orbit.
但火箭带来推进力只有这么多 因此有一个重量的极限值 But a rocket can only produce so much thrust, so there is a maximum weight
超过此值 火箭将不会升空 after which it just won't take off
如果再增加重量 火箭将不会起飞升空 因此你不能只是建造更大的燃料舱 If you add too much weight, it won't lift off. So, you can't just build bigger and bigger fuel tanks
发射技术一直受限于火箭方程式 这意味着太空旅行永远不会是易事 This is the tyranny of the rocket equation and it means space flight will never become easy.
但等一下 情况可能更糟糕 But wait, it gets worse.
到达太空还远远不够 你目前依旧身处引力监狱 太空的边缘处 Getting to space is still not good enough- you're still inside the gravity prison at the edge of space and
还是会被拉回地球 will crash back to Earth.
维持在太空中比到达太空更加困难 Staying in space is much harder than getting there.
到达一个稳定的位置 并且停留一会 火箭需要到达近地轨道 To get to a stable position, where it can stay for a while, a rocket has to reach low Earth orbit.
达成此目的需要更多的动能 意味着速度需要飞快 To do this, you need a lot of kinetic energy which means going extremely fast
海拔在100公里 速度在每秒8公里 at an altitude of about 100 km, this is 8 km/s
时速在28000公里 这个速度环绕地球一圈仅需90分钟 28,000 km/h is fast enough to travel around Earth in 90 minutes.
这里我们可以用点小技巧 Here, we can use a trick.
相比直飞冲天 我们可以另辟蹊径 Instead of flying straight up, we can go sideways!
地球是圆形的 Earth is a sphere.
如果走小路速度够快 即便你在坠落中 So, if you're going sideways, fast enough (even though you're falling towards Earth)
地表仍在你的下方 the ground will cover way beneath you.
只要到达大气上层 海拔100公里处 你就能维持在轨道 So, as long as you're above the atmosphere (about 100 km up) you'll be able to stay up there in orbit.
国际空间站就是用此法保持在轨道上 This is what the ISS does
其绕着地球转 不时消耗能量 以维持速度 (falling around Earth, expending energy form time to time) to stay fast enough.
如果在此范围内观察轨道 我们会发现近地轨道与地球表面如此之近 If we look at orbits in scale, we see that near Earth orbit is laughably close to Earth.
例如 卫星前往其他星球 需要偿还另一笔能量债 To deploy, for eg Satellites, on leave for other planets, requires another round of energy debt repayment.
到达轨道目前对于人来说 是空间域光场最困难的部分 Getting to orbit is the most difficult part of space light for us right now.
比如 如果火箭飞往火星 到达轨道就消耗一半的能量 For eg: If we want to send a rocket to Mars, half the energy is necessary just to get into orbit
另一半则提供前往火星5500万公里的动力 and the other half for the 55 million km to Mars.
因此 为尽可能高效 火箭不应只有一个组成体 Therefore, to be as effective as possible, rockets aren't built in one giant piece.
相反 我们应用多级火箭 Instead, we use multistage rockets
我们不必携带耗尽的燃料舱 而是耗尽后脱落 We don't need to carry an empty fuel tank, so rockets drop it.
如今火箭可以分级脱落推进器 在连续的多个阶段脱落火箭 不断升空 Rockets today, shed their boosters and main stage as they ascend with each successive stage
每个阶段有自己满载的火箭 有自己的引擎和燃料 being it's own fully contained rocket, complete with its own engine and fuel.
所以 这就是为何到达太空是如此困难 Ok. So this is why getting to space is hard.
如果你感觉有点复杂 别慌 这是火箭科学！ If you feel all of this seems really complicated, don't worry. It's literally rocket science!
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