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  • We are prisoners on Earth. The Universe taunts us, by showing all the places we can't ever visit.


  • However, if our species wants to have a long term future, we have to escape our prison.


  • But what is keeping us here in the first place?

    然而 如果人類這種物種想要有長久的未來

  • Turns out, we owe the universe a debt that is 4.5 billion years old.


  • *Intro*


  • Everything with mass in the universe attracts every other thing with mass.


  • We call this phenomenon 'gravity'.


  • The closer you are to a big chunk of mass, the stronger the attraction or the more you're pulled


  • in.


  • This effect traps us on earth.


  • We can imagine this as being prisoners in a gravity prison, or a gravity well.

    當你越靠近一個具有巨大質量的物體 就會有越強的引力

  • It's not a literal well, but a handy concept to understand how this works.


  • Being in a gravity prison means that you owe gravity energy.


  • But how can you owe energy?


  • Because in our universe, things don't want to change their speed or direction.

    被囚禁在監獄 也就是所謂重力穴

  • To convince them to move, you have to expend energy.


  • Billions of years ago, the gravitational attraction of trillions of trillions of dust particles


  • orbiting our sun caught them together until they formed a planet.

    被困在引力的監獄中 意指你欠引力能量

  • This process used energy and created the gravity well we're now a part of.


  • The deeper you are inside the gravity well, the more energy you owe gravity.


  • If you don't find a way to get enough energy, then you aren't able to leave no matter what you do.


  • Because your atoms were once part of the dust that the universe expended energy on to get to this place.


  • Ok. Hmm...Let's summarise all of that again.


  • Objects in the universe don't like to move. You have to convince them to do so with energy.

    數十億年前 引力吸引了無數的塵埃粒子圍繞在太陽的軌道上

  • Gravity used energy to convince the parts of our planet to move together.

    將他們吸引在一起 直到行星的行成

  • This created a gravity prison in the process, trapping us .


  • To escape, it we need to repay it with energy.


  • Ok. How do we do that?

    當你陷在越深處的重力穴 也就代表你欠引力越多能量

  • To get into space, we need to go through a complicated process of exchanging energy.


  • For this purpose, we build a negative potential energy repaying machine.


  • Known By their more boring name 'rockets'


  • Rockets work by using some of the most energetic chemical reactions humans know about


  • to basically explode fuel in a controlled way.

    好的 讓我們來統整一下

  • This converts chemical energy into kinetic energy.


  • The exhaust of the reaction is directed outwards,


  • and pushes the rocket away from Earth.


  • By expanding a lot of energy, we are increasing our gravitational potential energy.


  • Which is a complicated way to say that we are paying back our energy debt to gravity.

    為了要逃脫 我們需要用能量回饋他

  • But it's actually a lot trickier than that.

    但是 我們要如何做到?

  • When you burn fuel to get into orbit, you lose lots of energy to heat, exhaust and atmospheric drag


  • ,so you actually need much more.

    為了要進入宇宙 我們必須透過複雜的能量交換程序

  • And you can't just pile a huge amount of radioactive, really explosive, dangerous fuel close to your

    因此 我們發明了一種反能量回饋裝置

  • payload and detonate it.


  • You need a controlled burn which is complicated and makes your rocket very heavy


  • ...which means it has more mass.


  • The more mass something has, the more energy you need to convince it to move,


  • so you need more fuel to lift up your rocket.

    將燃燒的產物排出火箭 使火箭脫離地球的重力

  • But,if you need more fuel, that means you need more rocket to carry that fuel!

    當我們消耗大量能量的同時 也增加了自身引力的能量

  • But, this makes your rocket heavier thus requiring more fuel which requires more rocket to carry that

    簡單來說 就是我們正在償還我們欠重力的能量

  • new fuel and so on.


  • At the end of this madness, you need closer to a 100x the weight of your payload to launch


  • Ariane 6, for example (the european rocket) will weigh 800 tons and should be able to

    你會失去大量的能量轉換成熱量 廢氣以及空氣阻力

  • transport 10 tons into geostationary transfer orbit or, 20 tons into medium earth orbit.


  • But a rocket can only produce so much thrust, so there is a maximum weight, after which it just won't

    而且你不能只是在你身邊堆一大堆具有輻射 高爆性又危險的燃料

  • take off.


  • If you add too much weight, it won't lift off. So, you can't just build bigger and bigger fuel tanks


  • This is the tyranny of the rocket equation and it means space flight will never become easy.


  • But wait, it gets worse.


  • Getting to space is still not good enough- you're still inside the gravity prison at the edge of space and

    物體的質量越重 你就需要越多能量以說服其移動

  • will crash back to Earth.


  • Staying in space is much harder than getting there.

    但是當你需要越多燃料 也就表示你需要更多火箭來裝這些燃料

  • To get to a stable position, where it can stay for a while, a rocket has to reach low Earth orbit.

    但這讓你整個火箭更重 因此也就需要更多燃料也就需要更多火箭來裝那些新的燃料

  • To do this, you need a lot of kinetic energy which means going extremely fast


  • at an altitude of about 100 km, this is 8 km/s

    在這惱人的過程的結果 你需要將近一百倍的重量以推動欲載的東西

  • 28,000 km/h is fast enough to travel around Earth in 90 minutes.

    以亞利安6號運載火箭(歐洲火箭)為例 將會重達800噸重

  • Here, we can use a trick.


  • Instead of flying straight up, we can go sideways!


  • Earth is a sphere.

    但是火箭的推力有限 也就是說他有重量的上限 超過了就無法起飛

  • So, if you're going sideways, fast enough (even though you're falling towards Earth) the ground will curve

    如果火箭太重 他就無法起飛 所以我們不能單單製造更重的燃料槽

  • away beneath you.

    這個問題對於火箭工程而言十分嚴苛 因此太空旅行會如此困難

  • So, as long as you're above the atmosphere (about 100 km up) you'll be able to stay up there in orbit.

    但等等 有件事情讓這變得更糟糕

  • This is what the ISS does (falling around Earth, expending energy form time to time) to stay

    不是進入宇宙就已經夠了 你還是會被困在宇宙邊緣的重力監獄

  • fast enough.


  • If we look at orbits in scale, we see that near Earth orbit is laughably close to Earth.


  • To deploy, for eg Satellites, on leave for other planets, requires another round of energy debt repayment.

    要達到穩定並且可以待一段時間的狀態 火箭必須要達到低地球軌道

  • Getting to orbit is the most difficult part of space flight for us right now.

    為了進入軌道 你需要大量的動能 也就是要非常的快

  • For example: If we want to send a rocket to Mars, half the energy is necessary just to get into orbit

    為了達到100公里的高度 必須要有每秒8公里的初速度

  • and the other half for the 55 million km to Mars.


  • Therefore, to be as effective as possible, rockets aren't built in one giant piece.

    在此 我們可以用一些小技巧

  • Instead, we use multistage rockets. We don't need to carry an empty fuel tank, so rockets drop it.

    比起直接往上飛 我們可以往旁邊飛

  • Rockets today, shed their boosters and main stage as they ascend with each successive stage being it's own


  • fully contained rocket, complete with its own engine and fuel.

    所以如果我們往旁邊飛 如果速度快到就算你正在往下墜落 地面還是會對你有利

  • Ok. So this is why getting to space is hard.

    所以 當你在大氣層外(約100公里) 你就可以維持在地球的軌道上

  • If you feel all of this seems really complicated, don't worry. It's literally rocket science!

    國際太空站(ISS)就是這樣運作的 不斷的墜落並且不斷的花費能量以維持速度

  • This video was made possible in part by a sponsorship by Airbus Safran Launchers


  • and Arianespace.

    為了部屬像是衛星的人造天體到其他星球上 需要更多能量的償還

  • Who are getting their new Ariane 6 rocket ready to launch into space in 2020.


  • You can learn more about the rocket here.

    舉例來說 如果我們要去火星 一半的能量會被消耗掉為了要進入軌道

  • And as always, if you like what we do please consider supporting us on


  • It really helps us out a lot!

    因此 考量到效率 火箭並不會是一體成形的巨大物件

  • If you're craving more space stuff now: here's a playlist for you.

    取而代之的是 我們會打造一個多個結構的火箭

We are prisoners on Earth. The Universe taunts us, by showing all the places we can't ever visit.



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