宇宙（2007）

The Universe S05E05

Part 3 April 22, 2021, 1:49 p.m.

But there is a more distant
但还有一个更远大
and difficult goal,
更艰巨的目标
One whose extremes are even more destructive than Venus:
还有一种星的极端环境比金星更具破坏力
the Outer Planets.
带外行星
And getting there requires more than just a big rocket.
仅有大型火箭不足以还到达那里
One of the biggest problems with space probes
空间探测器的最大问题之一
is having enough fuel to get where you're going.
是拥有足以飞抵目的地的的燃料
If you do a rocket burn, you burn a lot of fuel.
你发射火箭花费很多燃料
And if you keep doing a bunch of rocket burns,
保持一组火箭发射器运转
you're gonna run out of fuel,
会使你用尽燃料
and then your probe is dead.
你的探测器就无用了
But there is a solution
但存在一个解决方法
built into the fabric of the cosmos: gravity.
利用宇宙结构万有引力
In the early '60s, it was discovered
六十年代早期研究发现
that we can use the gravity of the planets
人们可以利用行星的引力
to assist a spacecraft,
来辅助航♥天♥器
to speed it up to fling it
使其加速
further out into the solar system.
将其送入外太阳系
That opened up the outer solar system to exploration.
这开辟了对于外太阳系的探索
The technique is called gravity assist,
这项技术被称为重力助推
a virtual engine that harnesses
是一个运用行星体的
the immense gravity of planetary bodies
巨大万有引力的虚拟引擎
to assist a spacecraft on a planned trajectory.
在预定轨道上对航♥天♥器进行助推
Hitting a baseball is a lot like a gravitational assist.
打棒球与借助重力的过程颇似
The space probe comes into a planet,
空间探测器到达一颗行星附近
it gets caught by the gravity
被其引力捕获
and redirected in another direction,
改变自己的方向
just like hitting a baseball with a bat
就像用球棒击打棒球
and it directs the baseball in another direction.
引导球转向其他方向
When the bat collides with the baseball,
当球棒撞击棒球
it changes the baseball's direction of motion
它就改变了棒球的运动方向
and it can propel that baseball
并且推动棒球
with a much greater speed than what it originally had.
达到比撞击前更快的速度
By harnessing the gravitational pull of planets,
通过利用行星的引力
NASA has been able to hit probes out of the park
美国宇航局可以将探测器送出驻留轨道
and to the Outer Planets.
送至外行星
Cassini's home-run journey
卡西尼号♥太空船的本垒打
covered 170 million miles
飞跃了一亿七千万英里
to the methane lakes of Saturn's moon, Titan.
到达土卫泰坦的甲烷湖泊
Without those gravity assists, this spacecraft,
离开了重力助推这艘在地球上
which weighs 12 tons in earth's gravity,
重十二吨♥的航♥天♥器
never would have made it to the outer solar system.
是不可能到达外太阳系的
We don't have a booster big enough
我们没有足以直接
to send it to Saturn directly.
发送将它到土星的助推器
We would not have explored Saturn
如果没有内行星的引力
were it not for the gravity of the inner planets.
我们不能探索土星
Now, 21st century space exploration
现在二十一世纪的空间探索
is poised to send probes
准备派遣探测器
beyond the outer planets to distant stars.
到外行星以外的遥远恒星
But gravity assist
但重力助推
doesn't have the power to get us there.
不足以令我们到达那里
Traveling into deep space requires propulsion
进入深空探测看起来
that seems to come straight out of science fiction:
显然需要科幻小说中的动力
the ion drive.
离子推进器
Ion engines are like a mini linear accelerator.
离子引擎就像一个小型直线加速器
You accelerate ions out the back,
你向后加速离子
the spacecraft goes the opposite direction.
航♥天♥器飞向相反的方向
That ion engine has very, very low thrust,
离子引擎的推力非常非常小
but it operates for months at a time, and eventually,
但它一次可以运转数月并且最终
gets the spacecraft up to faster and faster speeds.
使航♥天♥器的速度越行越快
The ion engine replaces the chemical fuel
离子引擎通过诸如氙气的惰性气体
with an inert gas like xenon.
取代了化学燃料
The xenon is given an electrical charge, or ionized.
氙气提供了电荷或称电离
An electric field then accelerates the ions
之后电子场加速离子
out the back of the spacecraft,
离子从航♥天♥器后端飞出
propelling it forward.
推动航♥天♥器前进
Ion propulsion is not like most rocket engines.
离子推进器和大多数火箭引擎不同
A standard chemical rocket engine propels itself
一个普通化学火箭引擎推动自己的方式
like a double-barreled 12-gauge shotgun.
像一把双管十二毫米口径猎枪
This shotgun is actually a chemical rocket engine,
猎枪实际上就是一个化学推力引擎
just like the space shuttle main engines.
和航♥天♥飞机的主发动机很像
I'm sitting on earth on a dolly track.
我坐在地球上的一辆小车上
So the question is, is there enough thrust
问题是猎枪能否提供
from the shotgun to overcome
足以克服轮子和轨道间
the friction between the wheels and the track?
的摩擦力的推力呢
A single blast moves the dolly about six inches.
单枪射击可以使小车移♥动♥六英尺
A second blast keeps the momentum going.
第二枪使运动状态持续
But now, replace the big double-barrel shotgun
现在用一个较小的武器
with a smaller weapon.
替换大型双管猎枪
Now, I have a .22 rifle.
现在我拿着雷帽弹步♥枪♥
It's a little different than the shotgun.
这和猎枪有些许区别
The shotgun shot many pellets out
猎枪以一个相当温和的速度
at a fairly moderate velocity.
射出许多子弹
The rifle shoots a small pellet out
步♥枪♥高速射击出
at very high velocity.
一颗很小的子弹
Now, the difference is that
区别就是
this is more like an ion engine.
这把更像离子引擎
The .22 recoil moves the dolly less than an inch.
雷帽弹的反冲使小车移♥动♥了不到一英寸
Multiple shots move it slightly more.
连发射击使他移♥动♥了稍多一点
But if we were in space,
但如果我们身处太空中
the .22 would be just like the ion engine.
雷帽弹就会像离子引擎
It would start pushing us slowly
它会开始慢慢推动我们
and eventually build up,
最终使我们
till we reached a really high velocity.
达到一个很高的速度
By compounding tiny thrusts through the vast,
通过微小推力不断汇集变大
frictionless depths of space,
在无摩擦力的太空深处
the ion engine can propel a probe for years.
离子引擎可以推动探测器数年
The technology could mean the end
这项技术意味着
for massive rocket boosters in space probe travel.
大型火箭推进器在空间探测上应用的终结
Chemical fuels are a problem
化学燃料存在问题
because they're pretty inefficient.
因为它们很低效
They weigh a lot. They have a lot of mass.
它们很重体积很大
And you have to transport all that stuff out there,
并且你需要把它们运到太空
and that means the rockets that launch the spacecraft
这意味着发射宇宙飞船的火箭
have to be even more powerful, even more expensive.
需要更多能量也更昂贵
Lightweight ion engines
轻量级离子引擎
have already passed the test in outer space.
已经通过了外太空试验
They powered the deep space 1 probe
他们在九十年代末
in the late 1990s,
推助了深空一号♥探测器
and recently propelled the probe, Hayabusa,
并在最近推动了日本宇宙航♥空♥研究开♥发♥机构
of the Japanese aerospace exploration agency
研制的隼鸟号♥号♥探测器
and helped it land on an asteroid.
帮助它着陆到一个小行星
Ion engines will completely
离子引擎会彻底
change deep-space exploration
改变深空探索
because we can go a lot more places
因为我们不需要很多燃料
without having to carry a lot of fuel.
就可以到达更多的地方
And we can get there, in the end, faster,
并且最终我们可能以更快的速度达到那里
depending on where it is we're going.
这取决于我们要去哪儿
One of the places we may be going
我们可能会去的地方之一
is our planetary neighbor.
是我们的邻近行星
Currently, the European space agency's mars express probe
目前欧洲航♥天♥局的火星快车探测器
holds the Earth-to-Mars speed title at six months,
保持了六个月从地球到达火星的速度冠军
but one advanced ion engine
但一个先进的离子引擎
is expected to shatter that record.
有望打破这个纪录
An ion engine could cut the travel time to Mars
离子引擎可以使到火星的时间
down to just a mere few weeks.
缩短至数周
Five weeks to Mars is only the beginning.
五周到达火星仅仅是一个开始
The next step in ion drives will amp up its speed as much as 100 times faster.
离子驱动器下一步将加快它的速度一百倍
It's called Vasimr,
这被称为Vasimr
an acronym for variable specific impulse magneto-plasma rocket.
可变比脉冲等离子体火箭的缩写