As much as we all wish there were an easy,

それが簡単になれば

and affordable way to see our planet floating in the dark

どれほど楽しいだろう

Right now, the only way is to become an astronaut or a billionaire

今行けるのは宇宙飛行士か 金持ちだ

But there is a concept that might make it possible

でも宇宙旅行の夢を叶える

-while serving as the starting point for the exploration of the universe-

ある概念が考案されている

The space elevator

宇宙エレベーターだ

How exactly does it work?

どんなものだろう？

To understand how a space elevator will get us into space

宇宙エレベーターとは何か

We must first understand what an orbit is

まずは軌道から説明しよう

Being in orbit basically means falling towards something,

軌道に入るとは つまり

but moving fast enough to miss

落ち続けるということだ

If you throw a ball on earth it makes an arch through the air,

物を投げると 弧を描いて地面に付く

and then hits the ground

宇宙でも同じことが起きるが

In space, gravity makes you move much the same way,

横に速く進むことで 地面に付かず

but if you move sideways fast enough

地球を回り続けることができる

the curvature of the earth makes the ground fall away beneath you

軌道に入るには

as fast as gravity pulls you towards it

ロケットは速く飛ぶ必要がある

So, to enter Earth's orbit rockets have to go up

一方 高い位置から飛べば

and sideways fast

速度を稼ぐことができる

By contrast, a space elevator taps into energy from Earth's rotation

おもちゃを回す子どもと

to get the cargo going fast

アリを考えてほしい

Imagine a child spinning a toy on a rope with an ant on the child's hand

先の方にいるアリは

As the ant climbs out along the rope

それだけ速く飛べる

it starts to move faster and faster as it ascends

高い所からロケットを飛ばせば

Compared to rockets, with cargo launched on an elevator

燃料が少なくて済む

you only need to provide the energy to go up

地球の遠心力を利用できるのだ

Fast sideways movement comes free with the Earth's rotation

だが宇宙エレベーターは

But the space elevator would without a doubt

史上最も高価な建築物になりそうだ

be the single largest and most expensive structure ever built by humans

作る価値はあるのか？

So, is it worth it?

計算してみよう

It all comes down to costs

ロケットは少しの輸送でも

Rockets burn a huge amount of rocket fuel

大量の燃料を使う

just to get a small amount of cargo into space

今は１kg送るのに

At current prices, it costs about $20,000 to put one kilogram of payload into space

２万ドルの費用がかかる

that's $1.3 million dollars for the average human

人を送れば130万ドル

$40 million dollars for your car

車なら4000万ドル

billions for an international space station

宇宙ステーションは億単位だ

This immense cost is one of the major limitations of human spaceflight

これが宇宙進出の障壁になっている

Even with advancing technology,

技術が進んでも

this cost isn't likely to be comparable with the price of an airline ticket anytime soon

まだ飛行機程度にはなりそうにない

A space elevator would solve this problem

宇宙エレベーターなら大丈夫

After construction,

一度作れば 費用は大幅に減って

a space elevator is projected to reduce the cost one hundredfold to $200 per kilogram

１kg200ドルになる

If an inexpensive space elevator costs 20 billion dollars,

エレベーターが200億ドルなら

then we'll recoup our losses after launching only one million tons

100万トン分運ぶことで元が取れる

Close to the weight of two international space stations

宇宙ステーション２機分だ

So what would a space elevator look like in real life?

どうやって作るのだろうか

A space elevator has four major components:

主な構成要素が４つある

the tether, anchor, counterweight and climber

テザー 錨 おもり 上昇機だ

The elevator part of the space elevator is the tether and the climber

紐状のテザーが地球と終点を繋ぎ

It extends from the surface of the Earth to space

上昇機がそれを昇る

The climber is like a conventional elevator carriage

普通のエレベーターのように

A chamber that works its way up and down the tether

これで昇り降りをする

At the base would be an anchor

地下には錨を置き

pinning the tether to the Earth along with a port for climbers

これでテザーを地球に固定して

At the top is the counterweight which holds up the tether

上からはおもりが引っ張る

The tether is held tight like a rope

これによりテザーは

and supported from above by the tension from the counterweight

伸びた状態で安定する

Located higher than 36,000 kilometers above the Earth's surface

その長さは３万6000キロ以上になる

At the counterweight could be a space station,

おもりとして使えるなら

a launching point for all missions from the spaceport elevator

発射台などを置くことも可能だ

But can we actually build one?

しかし実際 作るのは難しい

It's hard to say

特にテザーは

The biggest challenge is the tether

軽くて 安くて

It needs to be light, affordable

今ある物質より強いものが必要だ

and more stable than any material we can produce right now

グラフェンやダイアモンドナノ糸は

There are promising materials like graphene and diamond nanothreads,

強さが不十分だ

but even they may not be strong enough

強さ以外にも

And aside from being incredibly strong,

雨による腐食や宇宙の放射線

the tether would also have to withstand atmospheric corrosion, radiation

デブリに耐える必要がある

and micrometeorite and debris impacts

さらに 上昇には数日かかるが

Additionally, it takes several days to climb the elevator

その動力は何なのか

How do we power the climber?

莫大なエネルギーだ

It requires a lot of energy to go up

原子炉でも乗せるのだろうか

Do we need a nuclear reactor on our elevator carriage?

レーザーで何とかできるのか

Or do we beam it power from the ground with a super powered laser?

テザー３万6000キロ分の材料は？

And where do we get the raw materials for a 36,000-kilometer-long tether?

地球から伸ばすのか

Do we make it on Earth and launch it into space?

宇宙から地球に伸ばすのか

Or do we make it in space and lower it down to the Earth?

小惑星から調達できるか

Could asteroid mining be the answer?

技術的障壁はまだ山のようにある

Put simply, there are still some major technological hurdles to overcome

事故の危険性もある

And a space elevator is not without risk

テザーが切れたら大惨事だ

Should the tether break, it would collapse in spectacular style

もし地表近くで切れたら

If it breaks near the anchor

上昇機が落ち テザーは宇宙に逃げる

the force exerted by the counterweight will cause the entire elevator to rise up

宇宙で切れたら

ascending into space

テザーが地球に落ちてくる

Should it break near the counterweight

デブリは将来 大問題になるだろう

the tether will fall,

もし作るのなら 失敗は許されない

wrapping around the world and whipping the end off

だからまずは月に作る

The resulting debris in orbit could pose serious problems to future spaceflight

という案もある

If we build a space elevator on Earth, we have to do it right the first time

重力が地球より弱いので

For these reasons some experts have proposed first building

ケブラー等の物質がテザーに使える

a space elevator on the Moon

困難な挑戦でも

The Moon's gravity is much weaker than the Earth's

宇宙エレベーターの価値は大きい

so a flimsier but existing material like kevlar

宇宙進出の真の一歩となるだろう

could serve as a tether

実現できなくても

Even with all these challenges,

その過程で多くを学べるはずだ

the payoff of having a working space elevator would be immense

宇宙の時代が来れば

It might be the first step to truly becoming a space-faring civilization

輝く未来は夢ではなくなる

Maybe we will never build a space elevator,

Subtitles by the Amara.org community

but in trying to do so we might learn an awful lot

And when it comes to the exploration of the universe,

there can't be too many dreams of a glorious future

Subtitles by the Amara.org community