or this, or maybe this.

或這樣，或者是這樣

What do they all have in common?

以上太空船的共通點是什麼?

Among other things, they're huge because they have to carry people, fuel,

綜合以上是其體型巨大，因為要搭載人員、燃料

and all sorts of supplies, scientific instruments,

各類物資、科學儀器

and, in rare cases, planet-killing lasers.

甚至罕見情況下，足以摧毀行星的雷射

But the next real-world generation of spacecraft may be much, much smaller.

但是，新一代真實世界的太空船實際上可能很小

We're talking fit-inside-your-pocket tiny.

這裏講的大約是可以放進你口袋的大小

Imagine sending a swarm of these microspacecraft out into the galaxy.

想像發射一群這麼小的微太空船進入銀河

They could explore distant stars and planets

它們可探索遙遠的恆星及行星

by carrying sophisticated electronic sensors

攜帶著複雜的電子感應器

that would measure everything from temperature to cosmic rays.

能從溫度、宇宙射線等測量各種資料

You could deploy thousands of them

你可部署上千台這樣的微太空船

for the cost of a single space shuttle mission,

其成本和一次太空梭任務相當

exponentially increasing the amount of data

卻可大量增加

we could collect about the universe.

我們從宇宙蒐集的資料量

And they're individually expendable,

個別而言，每台微太空船是消耗品

meaning that we could send them into environments

其意謂我們可將之送到高風險環境

that are too risky for a billion dollar rocket or probe.

這比發射數十億元的火箭或探測器還划算

Several hundred small spacecraft are already orbiting the Earth,

目前，已有數百個小太空船圍繞地球軌道

taking pictures of outer space,

拍攝外太空照片

and collecting data on things,

蒐集各種資料

like the behavior of bacteria in the Earth's atmosphere

例如，地球大氣層內細菌的行為

and magnetic signals that could help predict earthquakes.

和電磁信號，以幫助地震預測

But imagine how much more we could learn if they could fly beyond Earth's orbit.

想像微太空船若能飛越地球軌道 我們將可獲得更多

That's exactly what organizations, like NASA, want to do:

這正是許多機構，例如NASA，想作的事

send microspacecraft to scout habitable planets

送出微太空船偵察可居住的行星

and describe astronomical phenomena we can't study from Earth.

和觀察一些地球無法研究的天文現象

But something so small can't carry a large engine or tons of fuel,

但是，這麼小的太空船 無法攜帶大引撆或數噸燃料

so how would such a vessel propel itself?

所以太空船要如何推動自己?

For microspacecraft, it turns out, you need micropropulsion.

顯然，微太空船需要微推進器

On really small scales,

在很小尺度上

some of the familiar rules of physics don't apply,

一些熟悉的物理定律並不適用

in particular, everyday Newtonian mechanics break down,

尤其是日常的牛頓力學不再有效

and forces that are normally negligible become powerful.

平常可忽略的作用力變得強而有效

Those forces include surface tension and capillary action,

這些力包括表面張力和毛細管作用

the phenomena that govern other small things.

這些現象支配一些小物質的運作

Micropropulsion systems can harness these forces to power spacecraft.

微推進系統可駕馭上述作用力而驅動太空船

One example of how this might work

一種可能的運作方式

is called microfluidic electrospray propulsion.

稱為微流體電噴灑推進法

It's a type of ion thruster,

這是一種離子推進器

which means that it shoots out charged particles to generate momentum.

作法為噴出帶電粒子，以產生動能

One model being developed at NASA's jet propulsion laboratory

NASA的噴射推進實驗室開發出一種模型

is only a couple centimeters on each side.

每邊只有幾公分寬

Here's how it works.

其工作原理如下

That postage-stamp sized metal plate is studded with a hundred skinny needles

此郵票大小的金屬面板配有一百根細針

and coated with a metal that has a low melting point, like indium.

其表層塗有低鎔點金屬，例如銦

A metal grid sits above the needles,

一個金屬網格置於細針上方

and an electric field is set up between the grid and the plate.

再於網格及面板之間設立電場

When the plate is heated, the indium melts

當面板受熱，銦開始鎔解

and capillary action draws the liquid metal up the needles.

毛細管作用將把液態金屬吸上細針

The electric field tugs the molten metal upwards,

一方面電場牽引鎔化金屬上升

while surface tension pulls it back,

另一方面表面張力將其拉回

causing the indium to deform into a cone.

造成銦變形成圓錐狀

The small radius of the tips of the needles

針尖的小半徑

makes it possible for the electric field to overcome the surface tension,

可讓電場克服表面張力

and when that happens,

一旦實現

positively charged ions shoot off at speeds of tens of kilometers per second.

帶正電離子的噴離速度可達每秒數10公里

That stream of ions propels the spacecraft in the opposite direction,

此離子束可將太空船往相反方向推進

thanks to Newton's third law.

這是受牛頓第3定律影響之故

And while each ion is an extremely small particle,

雖然每個離子為一極小粒子

the combined force of so many of them pushing away from the craft

眾多離子推離太空船的總合力量

is enough to generate significant acceleration.

足以產生有效加速度

And unlike the exhaust that pours out of a rocket engine,

不像排出火箭引撆的廢氣

this stream is much smaller and far more fuel efficient,

此離子束比較小，而且燃料效率高

which makes it better suited for long deep-space missions.

更適合長途的深太空任務

These micropropulsion systems haven't been fully tested yet,

這類微推進系統尚未完整測試過

but some scientists think that they will provide enough thrust

但是，一些科學家認為可提供足夠動力

to break small craft out of Earth's orbit.

讓小太空船脫離地球軌道

In fact, they're predicting that thousands of microspacecraft

事實上，他們預估上千台微太空船

will be launched in the next ten years

將在10年內發射

to gather data that today we can only dream about.

蒐集眾多我們今日只能想像的資料

And that is micro-rocket science.

此稱為微火箭科學