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  • When you picture a spaceship, you probably think of something like this,

  • or this, or maybe this.

  • What do they all have in common?

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

  • and all sorts of supplies, scientific instruments,

  • and, in rare cases, planet-killing lasers.

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

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

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

  • They could explore distant stars and planets

  • by carrying sophisticated electronic sensors

  • that would measure everything from temperature to cosmic rays.

  • You could deploy thousands of them

  • for the cost of a single space shuttle mission,

  • exponentially increasing the amount of data

  • we could collect about the universe.

  • And they're individually expendable,

  • meaning that we could send them into environments

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

  • Several hundred small spacecraft are already orbiting the Earth,

  • taking pictures of outer space,

  • and collecting data on things,

  • like the behavior of bacteria in the Earth's atmosphere

  • and magnetic signals that could help predict earthquakes.

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

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

  • send microspacecraft to scout habitable planets

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

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

  • so how would such a vessel propel itself?

  • For microspacecraft, it turns out, you need micropropulsion.

  • On really small scales,

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

  • in particular, everyday Newtonian mechanics break down,

  • and forces that are normally negligible become powerful.

  • Those forces include surface tension and capillary action,

  • the phenomena that govern other small things.

  • Micropropulsion systems can harness these forces to power spacecraft.

  • One example of how this might work

  • is called microfluidic electrospray propulsion.

  • It's a type of ion thruster,

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

  • One model being developed at NASA's jet propulsion laboratory

  • is only a couple centimeters on each side.

  • Here's how it works.

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

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

  • A metal grid sits above the needles,

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

  • When the plate is heated, the indium melts

  • and capillary action draws the liquid metal up the needles.

  • The electric field tugs the molten metal upwards,

  • while surface tension pulls it back,

  • causing the indium to deform into a cone.

  • The small radius of the tips of the needles

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

  • and when that happens,

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

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

  • thanks to Newton's third law.

  • And while each ion is an extremely small particle,

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

  • is enough to generate significant acceleration.

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

  • this stream is much smaller and far more fuel efficient,

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

  • These micropropulsion systems haven't been fully tested yet,

  • but some scientists think that they will provide enough thrust

  • to break small craft out of Earth's orbit.

  • In fact, they're predicting that thousands of microspacecraft

  • will be launched in the next ten years

  • to gather data that today we can only dream about.

  • And that is micro-rocket science.

When you picture a spaceship, you probably think of something like this,

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【TED-Ed】Will future spacecraft fit in our pockets? - Dhonam Pemba

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    稲葉白兎   に公開 2015 年 06 月 28 日
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