[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:07.40,0:00:10.91,Default,,0000,0000,0000,,When you picture a spaceship,\Nyou probably think of something like this,
Dialogue: 0,0:00:10.91,0:00:13.41,Default,,0000,0000,0000,,or this, or maybe this.
Dialogue: 0,0:00:13.41,0:00:15.02,Default,,0000,0000,0000,,What do they all have in common?
Dialogue: 0,0:00:15.02,0:00:19.46,Default,,0000,0000,0000,,Among other things, they're huge\Nbecause they have to carry people, fuel,
Dialogue: 0,0:00:19.46,0:00:22.76,Default,,0000,0000,0000,,and all sorts of supplies, \Nscientific instruments,
Dialogue: 0,0:00:22.76,0:00:26.41,Default,,0000,0000,0000,,and, in rare cases, planet-killing lasers.
Dialogue: 0,0:00:26.41,0:00:31.23,Default,,0000,0000,0000,,But the next real-world generation \Nof spacecraft may be much, much smaller.
Dialogue: 0,0:00:31.23,0:00:35.40,Default,,0000,0000,0000,,We're talking fit-inside-your-pocket tiny.
Dialogue: 0,0:00:35.40,0:00:40.71,Default,,0000,0000,0000,,Imagine sending a swarm of these\Nmicrospacecraft out into the galaxy.
Dialogue: 0,0:00:40.71,0:00:43.22,Default,,0000,0000,0000,,They could explore \Ndistant stars and planets
Dialogue: 0,0:00:43.22,0:00:46.33,Default,,0000,0000,0000,,by carrying sophisticated \Nelectronic sensors
Dialogue: 0,0:00:46.33,0:00:50.03,Default,,0000,0000,0000,,that would measure everything\Nfrom temperature to cosmic rays.
Dialogue: 0,0:00:50.03,0:00:51.79,Default,,0000,0000,0000,,You could deploy thousands of them
Dialogue: 0,0:00:51.79,0:00:54.89,Default,,0000,0000,0000,,for the cost of a single \Nspace shuttle mission,
Dialogue: 0,0:00:54.89,0:00:57.23,Default,,0000,0000,0000,,exponentially increasing \Nthe amount of data
Dialogue: 0,0:00:57.23,0:01:00.06,Default,,0000,0000,0000,,we could collect about the universe.
Dialogue: 0,0:01:00.06,0:01:02.36,Default,,0000,0000,0000,,And they're individually expendable,
Dialogue: 0,0:01:02.36,0:01:04.72,Default,,0000,0000,0000,,meaning that we could send them \Ninto environments
Dialogue: 0,0:01:04.72,0:01:08.47,Default,,0000,0000,0000,,that are too risky \Nfor a billion dollar rocket or probe.
Dialogue: 0,0:01:08.47,0:01:13.42,Default,,0000,0000,0000,,Several hundred small spacecraft\Nare already orbiting the Earth,
Dialogue: 0,0:01:13.42,0:01:14.96,Default,,0000,0000,0000,,taking pictures of outer space,
Dialogue: 0,0:01:14.96,0:01:16.44,Default,,0000,0000,0000,,and collecting data on things,
Dialogue: 0,0:01:16.44,0:01:19.87,Default,,0000,0000,0000,,like the behavior of bacteria \Nin the Earth's atmosphere
Dialogue: 0,0:01:19.87,0:01:23.18,Default,,0000,0000,0000,,and magnetic signals that could help\Npredict earthquakes.
Dialogue: 0,0:01:23.18,0:01:28.48,Default,,0000,0000,0000,,But imagine how much more we could learn\Nif they could fly beyond Earth's orbit.
Dialogue: 0,0:01:28.48,0:01:32.39,Default,,0000,0000,0000,,That's exactly what organizations,\Nlike NASA, want to do:
Dialogue: 0,0:01:32.39,0:01:36.33,Default,,0000,0000,0000,,send microspacecraft \Nto scout habitable planets
Dialogue: 0,0:01:36.33,0:01:41.16,Default,,0000,0000,0000,,and describe astronomical phenomena\Nwe can't study from Earth.
Dialogue: 0,0:01:41.16,0:01:45.92,Default,,0000,0000,0000,,But something so small can't carry \Na large engine or tons of fuel,
Dialogue: 0,0:01:45.92,0:01:48.84,Default,,0000,0000,0000,,so how would such a vessel propel itself?
Dialogue: 0,0:01:48.84,0:01:53.74,Default,,0000,0000,0000,,For microspacecraft, it turns out, \Nyou need micropropulsion.
Dialogue: 0,0:01:53.74,0:01:55.60,Default,,0000,0000,0000,,On really small scales,
Dialogue: 0,0:01:55.60,0:01:58.60,Default,,0000,0000,0000,,some of the familiar \Nrules of physics don't apply,
Dialogue: 0,0:01:58.60,0:02:02.93,Default,,0000,0000,0000,,in particular, everyday \NNewtonian mechanics break down,
Dialogue: 0,0:02:02.93,0:02:06.98,Default,,0000,0000,0000,,and forces that are normally negligible\Nbecome powerful.
Dialogue: 0,0:02:06.98,0:02:11.09,Default,,0000,0000,0000,,Those forces include surface tension\Nand capillary action,
Dialogue: 0,0:02:11.09,0:02:13.70,Default,,0000,0000,0000,,the phenomena \Nthat govern other small things.
Dialogue: 0,0:02:13.70,0:02:19.41,Default,,0000,0000,0000,,Micropropulsion systems can harness\Nthese forces to power spacecraft.
Dialogue: 0,0:02:19.41,0:02:21.64,Default,,0000,0000,0000,,One example of how this might work
Dialogue: 0,0:02:21.64,0:02:26.25,Default,,0000,0000,0000,,is called microfluidic \Nelectrospray propulsion.
Dialogue: 0,0:02:26.25,0:02:28.21,Default,,0000,0000,0000,,It's a type of ion thruster,
Dialogue: 0,0:02:28.21,0:02:32.69,Default,,0000,0000,0000,,which means that it shoots out\Ncharged particles to generate momentum.
Dialogue: 0,0:02:32.69,0:02:36.34,Default,,0000,0000,0000,,One model being developed at NASA's\Njet propulsion laboratory
Dialogue: 0,0:02:36.34,0:02:39.48,Default,,0000,0000,0000,,is only a couple centimeters \Non each side.
Dialogue: 0,0:02:39.48,0:02:40.81,Default,,0000,0000,0000,,Here's how it works.
Dialogue: 0,0:02:40.81,0:02:46.20,Default,,0000,0000,0000,,That postage-stamp sized metal plate\Nis studded with a hundred skinny needles
Dialogue: 0,0:02:46.20,0:02:50.63,Default,,0000,0000,0000,,and coated with a metal \Nthat has a low melting point, like indium.
Dialogue: 0,0:02:50.63,0:02:53.59,Default,,0000,0000,0000,,A metal grid sits above the needles,
Dialogue: 0,0:02:53.59,0:02:57.58,Default,,0000,0000,0000,,and an electric field is set up\Nbetween the grid and the plate.
Dialogue: 0,0:02:57.58,0:03:00.75,Default,,0000,0000,0000,,When the plate is heated,\Nthe indium melts
Dialogue: 0,0:03:00.75,0:03:04.97,Default,,0000,0000,0000,,and capillary action draws \Nthe liquid metal up the needles.
Dialogue: 0,0:03:04.97,0:03:08.12,Default,,0000,0000,0000,,The electric field tugs \Nthe molten metal upwards,
Dialogue: 0,0:03:08.12,0:03:10.91,Default,,0000,0000,0000,,while surface tension pulls it back,
Dialogue: 0,0:03:10.91,0:03:14.21,Default,,0000,0000,0000,,causing the indium to deform into a cone.
Dialogue: 0,0:03:14.21,0:03:16.43,Default,,0000,0000,0000,,The small radius of the tips \Nof the needles
Dialogue: 0,0:03:16.43,0:03:21.18,Default,,0000,0000,0000,,makes it possible for the electric field\Nto overcome the surface tension,
Dialogue: 0,0:03:21.18,0:03:22.59,Default,,0000,0000,0000,,and when that happens,
Dialogue: 0,0:03:22.59,0:03:28.79,Default,,0000,0000,0000,,positively charged ions shoot off at\Nspeeds of tens of kilometers per second.
Dialogue: 0,0:03:28.79,0:03:33.83,Default,,0000,0000,0000,,That stream of ions propels the spacecraft\Nin the opposite direction,
Dialogue: 0,0:03:33.83,0:03:35.94,Default,,0000,0000,0000,,thanks to Newton's third law.
Dialogue: 0,0:03:35.94,0:03:38.93,Default,,0000,0000,0000,,And while each ion \Nis an extremely small particle,
Dialogue: 0,0:03:38.93,0:03:42.73,Default,,0000,0000,0000,,the combined force of so many of them\Npushing away from the craft
Dialogue: 0,0:03:42.73,0:03:46.34,Default,,0000,0000,0000,,is enough to generate \Nsignificant acceleration.
Dialogue: 0,0:03:46.34,0:03:49.36,Default,,0000,0000,0000,,And unlike the exhaust \Nthat pours out of a rocket engine,
Dialogue: 0,0:03:49.36,0:03:53.37,Default,,0000,0000,0000,,this stream is much smaller\Nand far more fuel efficient,
Dialogue: 0,0:03:53.37,0:03:57.74,Default,,0000,0000,0000,,which makes it better suited\Nfor long deep-space missions.
Dialogue: 0,0:03:57.74,0:04:01.37,Default,,0000,0000,0000,,These micropropulsion systems\Nhaven't been fully tested yet,
Dialogue: 0,0:04:01.37,0:04:04.51,Default,,0000,0000,0000,,but some scientists think that they\Nwill provide enough thrust
Dialogue: 0,0:04:04.51,0:04:07.69,Default,,0000,0000,0000,,to break small craft out of Earth's orbit.
Dialogue: 0,0:04:07.69,0:04:11.71,Default,,0000,0000,0000,,In fact, they're predicting that thousands\Nof microspacecraft
Dialogue: 0,0:04:11.71,0:04:14.01,Default,,0000,0000,0000,,will be launched in the next ten years
Dialogue: 0,0:04:14.01,0:04:18.06,Default,,0000,0000,0000,,to gather data that today \Nwe can only dream about.
Dialogue: 0,0:04:18.06,0:04:21.40,Default,,0000,0000,0000,,And that is micro-rocket science.