WEBVTT

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[dramatic percussion music]

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- HI THERE,
AND WELCOME TO "NASA LAUNCHPAD."

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I'M YOUR HOST, MOLLY.

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WE USE ELECTRICITY EVERY DAY.

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IT'S IN OUR HOMES.
IT'S IN OUR SCHOOLS.

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IT'S EVEN IN OUR CARS.

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SO LET'S THINK OF SOME WAYS
OF GENERATING ELECTRICAL POWER.

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WELL, TO START,
THERE'S SOLAR POWER,

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WHICH MAKES ENERGY
FROM SUNLIGHT.

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THERE'S ALSO WIND POWER,
WHICH USES THE FORCE OF WIND

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TO TURN A TURBINE
AND MAKE ELECTRICITY.

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THERE'S HYDROELECTRIC POWER
OR WATER POWER,

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WHICH USES THE FORCE
OF FLOWING WATER

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TO DO THE SAME THING.

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AND THEN THERE'S SOMETHING
CALLED RADIOISOTOPE POWER.

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NOT FAMILIAR WITH THAT LAST ONE?

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DON'T FEEL BAD.
MOST PEOPLE AREN'T.

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AND IT'S BECAUSE
IT'S NOT SOMETHING

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WE USE IN OUR EVERYDAY LIVES.

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RADIOISOTOPE POWER SYSTEMS

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ARE A SPECIAL TYPE OF TECHNOLOGY
THAT NASA USES

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TO PROVIDE ENERGY TO RUN
SOME OF ITS SPACE MISSIONS

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THAT EXPLORE THE SOLAR SYSTEM.

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OKAY, SO IT'S
AN ELECTRICAL POWER SYSTEM.

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YOU GET THAT.

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AND IT'S A TYPE
OF NUCLEAR POWER.

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BUT PROBABLY NOT
WHAT YOU'RE THINKING.

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THERE'S NO NUCLEAR FISSION,
CONTROL RODS,

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OR COOLING TOWERS INVOLVED.

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SO HOW DOES IT WORK?

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- A RADIOISOTOPE
IS A VARIATION ON AN ATOM.

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WE HAVE BASIC ATOMS LIKE CARBON,

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AND IT HAS AN ATOMIC NUMBER
OF SIX.

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AND THAT MEANS THERE ARE
SIX PROTONS IN THE CENTER OF IT.

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BUT IT ALSO HAS NEUTRONS.

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AND YOU CAN HAVE
A DIFFERENT NUMBER OF NEUTRONS.

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SO CARBON-12 HAS SIX PROTONS
AND SIX NEUTRONS.

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BUT CARBON-13 HAS SIX
AND SEVEN NEUTRONS.

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PLUTONIUM-238, WHICH IS
THE ISOTOPE WE'RE INTERESTED IN,

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IS AN UNSTABLE ATOM.

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- IF YOU HAVE AN ATOM THAT'S NOT
AT A STABLE ENERGY STATE,

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IT WANTS TO GIVE OFF THAT ENERGY
AND BECOME A NEW ELEMENT.

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AND THAT'S WHAT HAPPENS
WITH PLUTONIUM-238, IN OUR CASE.

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- THE WHOLE PROCESS
IS PRETTY SIMPLE:

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AS THE RADIOISOTOPE
PLUTONIUM-238 DECAYS,

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IT PRODUCES HEAT.

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AND THAT HEAT CAN BE PUT TO WORK
TO PRODUCE ELECTRICITY.

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SO A RADIOISOTOPE POWER SYSTEM

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IS BASICALLY A DEVICE
THAT USES HEAT

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TO PRODUCE ELECTRICITY

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AND NASA USES THESE
FOR SPACE MISSIONS.

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THE GREAT THING ABOUT
RADIOISOTOPE POWER SYSTEMS

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IS THAT THEY PRODUCE
ELECTRICAL POWER CONTINUOUSLY

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IN A PREDICTABLE WAY

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FOR A LONG TIME.

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THEY PRODUCE THIS POWER
WHETHER IT'S SUNNY OR DARK,

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REALLY HOT OR SUPER COLD,

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OR WHETHER THE SPACECRAFT'S
IN A PLACE THAT'S DUSTY

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OR FILLED WITH RADIATION
FROM CHARGED PARTICLES,

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LIKE THE SPACE
AROUND THE PLANET JUPITER.

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SO THAT MEANS
THE USE OF RADIOISOTOPE POWER

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ENABLES LONG MISSIONS

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TO SOME OF
THE MOST EXTREME ENVIRONMENTS

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WE CAN IMAGINE.

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SO AS WE SAID,
THE HEAT FROM RADIOACTIVE DECAY

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IS CONVERTED INTO ELECTRICITY.

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BUT HOW EXACTLY DOES THAT WORK?

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- THERMOCOUPLES
ARE VERY INTERESTING

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BECAUSE THEY'RE DEVICES
THAT YOU FIND

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ALL OVER YOUR HOUSE--

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EVERYTHING FROM YOUR OVENS
TO YOUR HOT WATER HEATERS.

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IF YOU APPLY HEAT ON ONE SIDE
OF A THERMAL ELECTRIC

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AND COLD TO THE OTHER SIDE,

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YOU CAN GET ELECTRICITY OUT.

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AND FOR SPACE APPLICATIONS,

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MOSTLY WE USE THEM
TO GENERATE ELECTRICITY

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TO POWER OUR SPACECRAFT.

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WE HAVE
RADIOISOTOPE HEAT SOURCES

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THAT PROVIDE THE HOT SIDE
FOR OUR THERMOCOUPLES

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AND THEN WE HAVE DEEP SPACE
PROVIDING THE COLD SIDE.

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- OKAY, CHECK THIS OUT.

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THERMOCOUPLES TAKE ADVANTAGE
OF AN ELECTRICAL EFFECT

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CALLED THE SEEBECK EFFECT.

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AND THAT OCCURS AT JUNCTIONS
BETWEEN DIFFERENT METALS

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WHEN THEY'RE EXPOSED TO

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A SIGNIFICANT DIFFERENCE
IN TEMPERATURE.

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FOR EXAMPLE, TAKE ONE IRON WIRE
AND ONE COPPER WIRE.

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TWIST ONE END OF THE COPPER WIRE

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AND ONE END
OF THE IRON WIRES TOGETHER.

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DO THE SAME WITH THE OTHER END
OF THE COPPER WIRE

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AND THE OTHER IRON WIRE.

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NOW, IF YOU HEAT
ONE OF THE TWISTED JUNCTIONS

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AND ATTACH THE WIRES
TO A VOLT METER,

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YOU WILL BE ABLE TO MEASURE
A VOLTAGE.

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THAT MEANS
ELECTRICITY'S FLOWING.

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AND THAT'S BASICALLY HOW
THE RADIOISOTOPE POWER SYSTEMS,

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THE ONES USED BY NASA SO FAR,
WORK.

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THE HEAT FROM
THE DECAY OF PLUTONIUM-238

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IS LIKE THE FLAME'S ENERGY
GIVEN OFF BY THAT MATCH

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IF IT COULD BURN STEADILY
FOR YEARS AND YEARS.

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OF COURSE,
IT'S NOT QUITE AS SIMPLE

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AS STRIKING A MATCH
AND HEATING SOME WIRES.

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LET'S LEARN MORE
ABOUT THE ENGINEERING INVOLVED

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IN THIS REMARKABLE TECHNOLOGY.

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- WHAT'S REALLY EXCITING
ABOUT R.P.S. TECHNOLOGY

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IS THAT YOU'RE ABLE
TO GET SO MUCH ENERGY

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OUT OF SUCH A SMALL PACKAGE.

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- WELL, THE FIRST TECHNOLOGY
YOU NEED, OF COURSE,

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IS TO MAKE THE PLUTONIUM-238

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AND TO REFINE IT AND GET IT
INTO THE FORM THAT YOU NEED.

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SO THERE ARE A LOT OF
NUCLEAR TECHNOLOGIES

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AND A LOT OF
CHEMICAL TECHNOLOGIES

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THAT YOU NEED TO DO THAT.

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AND THEN THERE'S
ALL THE MATERIALS TECHNOLOGIES,

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THE ELECTRICAL TECHNOLOGIES,

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AND ALL OF THAT
HAS TO GO TOGETHER

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IN A WAY THAT IS STABLE
AND THAT IS COMPACT.

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- WE'RE LITERALLY
FLYING SPACECRAFT

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THAT HAVE BEEN UP IN SPACE
LONGER THAN THREE DECADES

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USING THESE SAME
RADIOISOTOPE POWER SYSTEMS.

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AND THEY'RE STILL SENDING DATA
BACK TO US.

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- SO WHAT'S NEXT FOR R.P.S.?

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- A.S.R.G. OR ADVANCED STIRLING
RADIOISOTOPE GENERATOR

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IS THE NEXT GENERATION OF
RADIOISOTOPE POWER SYSTEMS

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THAT NASA'S WORKING ON.

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THE BIG DIFFERENCE BETWEEN
AN A.S.R.G. AND AN R.T.G. SYSTEM

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IS THAT IT HAS MOVING PARTS.

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AND IN THAT GENERATOR,
THERE IS A STIRLING ENGINE.

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- WELL,
THE STIRLING POWER SYSTEM

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IS ACTUALLY FOUR TIMES
MORE EFFICIENT

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THAN THE MATERIALS TYPE SYSTEMS
USING THERMO ELECTRICS.

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IT'S A MUCH MORE
EFFICIENT SYSTEM

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USING A MOVING MASS ALTERNATOR

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THAN IT IS USING THE PHYSICS
OF THE MATERIALS' PROPERTIES

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WHEN YOU ADD HEAT ON ONE END

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AND HAVE A COLD SIDE
ON THE OTHER.

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ONE OF THE THINGS
THE A.S.R.G. ALLOWS US TO DO

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IS, FIRST AND FOREMOST,

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USE A LOT LESS OF A PRECIOUS
RESOURCE, THE PLUTONIUM-238.

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BUT SECONDLY,
IT ALLOWS US TO BE MORE COMPACT

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IN THE POWER SYSTEM.

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- OKAY, A QUICK REVIEW.

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RADIOISOTOPE POWER SYSTEMS
LAST FOR A LONG TIME--

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LIKE DECADES.

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THEY'RE RUGGED, COMPACT,
HIGHLY RELIABLE,

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AND NOT EASILY AFFECTED
BY THE ENVIRONMENT

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WHERE A MISSION HAS TO OPERATE.

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THEY'RE IDEALLY SUITED

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FOR CERTAIN
LONG-DURATION MISSIONS

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IN THE INTENSE
ENVIRONMENTS OF SPACE

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AND ON ALIEN WORLDS
IN OUR OWN COSMIC BACKYARD.

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WELL, THAT'S IT FOR THIS TIME.

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THANKS FOR WATCHING.

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I'M MOLLY,

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AND I'LL CATCH YOU NEXT TIME
ON "NASA LAUNCHPAD."