[dramatic percussion music]
- HI THERE, AND WELCOME TO "NASA LAUNCHPAD."
I'M YOUR HOST, MOLLY.
WE USE ELECTRICITY EVERY DAY.
IT'S IN OUR HOMES. IT'S IN OUR SCHOOLS.
IT'S EVEN IN OUR CARS.
SO LET'S THINK OF SOME WAYS OF GENERATING ELECTRICAL POWER.
WELL, TO START, THERE'S SOLAR POWER,
WHICH MAKES ENERGY FROM SUNLIGHT.
THERE'S ALSO WIND POWER, WHICH USES THE FORCE OF WIND
TO TURN A TURBINE AND MAKE ELECTRICITY.
THERE'S HYDROELECTRIC POWER OR WATER POWER,
WHICH USES THE FORCE OF FLOWING WATER
TO DO THE SAME THING.
AND THEN THERE'S SOMETHING CALLED RADIOISOTOPE POWER.
NOT FAMILIAR WITH THAT LAST ONE?
DON'T FEEL BAD. MOST PEOPLE AREN'T.
AND IT'S BECAUSE IT'S NOT SOMETHING
WE USE IN OUR EVERYDAY LIVES.
RADIOISOTOPE POWER SYSTEMS
ARE A SPECIAL TYPE OF TECHNOLOGY THAT NASA USES
TO PROVIDE ENERGY TO RUN SOME OF ITS SPACE MISSIONS
THAT EXPLORE THE SOLAR SYSTEM.
OKAY, SO IT'S AN ELECTRICAL POWER SYSTEM.
YOU GET THAT.
AND IT'S A TYPE OF NUCLEAR POWER.
BUT PROBABLY NOT WHAT YOU'RE THINKING.
THERE'S NO NUCLEAR FISSION, CONTROL RODS,
OR COOLING TOWERS INVOLVED.
SO HOW DOES IT WORK?
- A RADIOISOTOPE IS A VARIATION ON AN ATOM.
WE HAVE BASIC ATOMS LIKE CARBON,
AND IT HAS AN ATOMIC NUMBER OF SIX.
AND THAT MEANS THERE ARE SIX PROTONS IN THE CENTER OF IT.
BUT IT ALSO HAS NEUTRONS.
AND YOU CAN HAVE A DIFFERENT NUMBER OF NEUTRONS.
SO CARBON-12 HAS SIX PROTONS AND SIX NEUTRONS.
BUT CARBON-13 HAS SIX AND SEVEN NEUTRONS.
PLUTONIUM-238, WHICH IS THE ISOTOPE WE'RE INTERESTED IN,
IS AN UNSTABLE ATOM.
- IF YOU HAVE AN ATOM THAT'S NOT AT A STABLE ENERGY STATE,
IT WANTS TO GIVE OFF THAT ENERGY AND BECOME A NEW ELEMENT.
AND THAT'S WHAT HAPPENS WITH PLUTONIUM-238, IN OUR CASE.
- THE WHOLE PROCESS IS PRETTY SIMPLE:
AS THE RADIOISOTOPE PLUTONIUM-238 DECAYS,
IT PRODUCES HEAT.
AND THAT HEAT CAN BE PUT TO WORK TO PRODUCE ELECTRICITY.
SO A RADIOISOTOPE POWER SYSTEM
IS BASICALLY A DEVICE THAT USES HEAT
TO PRODUCE ELECTRICITY
AND NASA USES THESE FOR SPACE MISSIONS.
THE GREAT THING ABOUT RADIOISOTOPE POWER SYSTEMS
IS THAT THEY PRODUCE ELECTRICAL POWER CONTINUOUSLY
IN A PREDICTABLE WAY
FOR A LONG TIME.
THEY PRODUCE THIS POWER WHETHER IT'S SUNNY OR DARK,
REALLY HOT OR SUPER COLD,
OR WHETHER THE SPACECRAFT'S IN A PLACE THAT'S DUSTY
OR FILLED WITH RADIATION FROM CHARGED PARTICLES,
LIKE THE SPACE AROUND THE PLANET JUPITER.
SO THAT MEANS THE USE OF RADIOISOTOPE POWER
ENABLES LONG MISSIONS
TO SOME OF THE MOST EXTREME ENVIRONMENTS
WE CAN IMAGINE.
SO AS WE SAID, THE HEAT FROM RADIOACTIVE DECAY
IS CONVERTED INTO ELECTRICITY.
BUT HOW EXACTLY DOES THAT WORK?
- THERMOCOUPLES ARE VERY INTERESTING
BECAUSE THEY'RE DEVICES THAT YOU FIND
ALL OVER YOUR HOUSE--
EVERYTHING FROM YOUR OVENS TO YOUR HOT WATER HEATERS.
IF YOU APPLY HEAT ON ONE SIDE OF A THERMAL ELECTRIC
AND COLD TO THE OTHER SIDE,
YOU CAN GET ELECTRICITY OUT.
AND FOR SPACE APPLICATIONS,
MOSTLY WE USE THEM TO GENERATE ELECTRICITY
TO POWER OUR SPACECRAFT.
WE HAVE RADIOISOTOPE HEAT SOURCES
THAT PROVIDE THE HOT SIDE FOR OUR THERMOCOUPLES
AND THEN WE HAVE DEEP SPACE PROVIDING THE COLD SIDE.
- OKAY, CHECK THIS OUT.
THERMOCOUPLES TAKE ADVANTAGE OF AN ELECTRICAL EFFECT
CALLED THE SEEBECK EFFECT.
AND THAT OCCURS AT JUNCTIONS BETWEEN DIFFERENT METALS
WHEN THEY'RE EXPOSED TO
A SIGNIFICANT DIFFERENCE IN TEMPERATURE.
FOR EXAMPLE, TAKE ONE IRON WIRE AND ONE COPPER WIRE.
TWIST ONE END OF THE COPPER WIRE
AND ONE END OF THE IRON WIRES TOGETHER.
DO THE SAME WITH THE OTHER END OF THE COPPER WIRE
AND THE OTHER IRON WIRE.
NOW, IF YOU HEAT ONE OF THE TWISTED JUNCTIONS
AND ATTACH THE WIRES TO A VOLT METER,
YOU WILL BE ABLE TO MEASURE A VOLTAGE.
THAT MEANS ELECTRICITY'S FLOWING.
AND THAT'S BASICALLY HOW THE RADIOISOTOPE POWER SYSTEMS,
THE ONES USED BY NASA SO FAR, WORK.
THE HEAT FROM THE DECAY OF PLUTONIUM-238
IS LIKE THE FLAME'S ENERGY GIVEN OFF BY THAT MATCH
IF IT COULD BURN STEADILY FOR YEARS AND YEARS.
OF COURSE, IT'S NOT QUITE AS SIMPLE
AS STRIKING A MATCH AND HEATING SOME WIRES.
LET'S LEARN MORE ABOUT THE ENGINEERING INVOLVED
IN THIS REMARKABLE TECHNOLOGY.
- WHAT'S REALLY EXCITING ABOUT R.P.S. TECHNOLOGY
IS THAT YOU'RE ABLE TO GET SO MUCH ENERGY
OUT OF SUCH A SMALL PACKAGE.
- WELL, THE FIRST TECHNOLOGY YOU NEED, OF COURSE,
IS TO MAKE THE PLUTONIUM-238
AND TO REFINE IT AND GET IT INTO THE FORM THAT YOU NEED.
SO THERE ARE A LOT OF NUCLEAR TECHNOLOGIES
AND A LOT OF CHEMICAL TECHNOLOGIES
THAT YOU NEED TO DO THAT.
AND THEN THERE'S ALL THE MATERIALS TECHNOLOGIES,
THE ELECTRICAL TECHNOLOGIES,
AND ALL OF THAT HAS TO GO TOGETHER
IN A WAY THAT IS STABLE AND THAT IS COMPACT.
- WE'RE LITERALLY FLYING SPACECRAFT
THAT HAVE BEEN UP IN SPACE LONGER THAN THREE DECADES
USING THESE SAME RADIOISOTOPE POWER SYSTEMS.
AND THEY'RE STILL SENDING DATA BACK TO US.
- SO WHAT'S NEXT FOR R.P.S.?
- A.S.R.G. OR ADVANCED STIRLING RADIOISOTOPE GENERATOR
IS THE NEXT GENERATION OF RADIOISOTOPE POWER SYSTEMS
THAT NASA'S WORKING ON.
THE BIG DIFFERENCE BETWEEN AN A.S.R.G. AND AN R.T.G. SYSTEM
IS THAT IT HAS MOVING PARTS.
AND IN THAT GENERATOR, THERE IS A STIRLING ENGINE.
- WELL, THE STIRLING POWER SYSTEM
IS ACTUALLY FOUR TIMES MORE EFFICIENT
THAN THE MATERIALS TYPE SYSTEMS USING THERMO ELECTRICS.
IT'S A MUCH MORE EFFICIENT SYSTEM
USING A MOVING MASS ALTERNATOR
THAN IT IS USING THE PHYSICS OF THE MATERIALS' PROPERTIES
WHEN YOU ADD HEAT ON ONE END
AND HAVE A COLD SIDE ON THE OTHER.
ONE OF THE THINGS THE A.S.R.G. ALLOWS US TO DO
IS, FIRST AND FOREMOST,
USE A LOT LESS OF A PRECIOUS RESOURCE, THE PLUTONIUM-238.
BUT SECONDLY, IT ALLOWS US TO BE MORE COMPACT
IN THE POWER SYSTEM.
- OKAY, A QUICK REVIEW.
RADIOISOTOPE POWER SYSTEMS LAST FOR A LONG TIME--
LIKE DECADES.
THEY'RE RUGGED, COMPACT, HIGHLY RELIABLE,
AND NOT EASILY AFFECTED BY THE ENVIRONMENT
WHERE A MISSION HAS TO OPERATE.
THEY'RE IDEALLY SUITED
FOR CERTAIN LONG-DURATION MISSIONS
IN THE INTENSE ENVIRONMENTS OF SPACE
AND ON ALIEN WORLDS IN OUR OWN COSMIC BACKYARD.
WELL, THAT'S IT FOR THIS TIME.
THANKS FOR WATCHING.
I'M MOLLY,
AND I'LL CATCH YOU NEXT TIME ON "NASA LAUNCHPAD."