WEBVTT

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[dramatic percussion music]

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- HEY, AND WELCOME
TO "NASA LAUNCHPAD."

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I'M YOUR HOST, CALEB.

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PART OF GETTING A SPACECRAFT

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TO LAND ON AND EXPLORE
OTHER WORLDS

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IS GETTING IT SAFELY
THROUGH THE ATMOSPHERE,

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AND THAT REQUIRES
A HEAT SHIELD.

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BUT THE ATMOSPHERE
ALSO PLAYS A CRITICAL ROLE

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IN HELPING TO SLOW
A VEHICLE DOWN SO IT CAN LAND.

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SO BIGGER HEAT SHIELDS
MAKE SENSE.

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IN AN ATMOSPHERE,
BIGGER HEAT SHIELDS MEAN

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WE CAN GET BIGGER SPACECRAFT
DOING MORE SCIENCE

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IN NEW PLACES,

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BUT THAT MEANS
A BRAND-NEW DESIGN.

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AND NEW DESIGNS MEANS ENGINEERS
HAVE TO SOLVE NEW CHALLENGES,

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CHALLENGES INVOLVING
CONTROLLABILITY

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AND AERODYNAMICS.

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BEFORE WE CAN CONTROL
THE SPACECRAFT,

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WE HAVE TO UNDERSTAND
HOW IT FLIES,

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AND THAT MEANS UNDERSTANDING
A BIT ABOUT AERODYNAMICS.

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- WELL, WHEN YOU'RE TALKING
ABOUT THE ATMOSPHERE,

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YOU'RE MOSTLY INTERESTED
IN THE DENSITY OF THE ATMOSPHERE

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AND ANY KIND OF WINDS
THAT YOU MIGHT ENCOUNTER.

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THE DENSITY IS REALLY
DIRECTLY PROPORTIONAL

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TO WHAT KIND OF DRAG FORCE
YOU WILL GET ON THE VEHICLE

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AS YOU DESCEND.

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AND ANY WINDS
MIGHT DIVERT YOUR VEHICLE

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ONE WAY OR ANOTHER OFF COURSE.

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SO WE ACCOUNT
FOR ANY UNCERTAINTIES

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IN BOTH DENSITY AND WINDS.

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- WHEN YOU THINK
ABOUT AN ATMOSPHERE--

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I'M A MECHANICAL ENGINEER.

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I HAVE TO THINK ABOUT THINGS
REALLY SIMPLY.

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SO WHEN I THINK
ABOUT AN ATMOSPHERE,

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I THINK ABOUT LITERALLY
JUST LIKE A POOL.

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AND I'M THROWING SOMETHING
IN THERE,

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AND WHERE IS IT GONNA LAND
ON THE BOTTOM OF THE POOL?

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AND THAT'S ANALOGOUS TO,
YOU KNOW,

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WE'RE HITTING THE TOP
OF THE ATMOSPHERE,

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AND WHERE ARE WE GONNA BE
HITTING THE GROUND?

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WHEN WE LAND ON MARS
AND WE'RE SENDING CREW THERE,

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IT'S NOT ACCEPTABLE TO LAND
ON THE OTHER SIDE OF THE PLANET.

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WE NEED TO LAND FAIRLY CLOSE
TO THE TARGET DESTINATION,

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BECAUSE THAT'S WHERE--
YOU'RE LANDING AT BASE CAMP.

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YOU NEED TO BE NEAR BASE CAMP.

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- BUT THERE'S NO STEERING WHEEL
ON ANY OF THESE SPACECRAFT,

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SO HOW DO WE CONTROL
A SPACECRAFT'S DESCENT

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THROUGH AN ATMOSPHERE,

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ESPECIALLY WHEN IT'S TRAVELING
AT HYPERSONIC SPEEDS?

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THAT MEANS IT'S ZOOMING
THROUGH THE ATMOSPHERE

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AT OVER FIVE TIMES
THE SPEED OF SOUND.

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- ENTRY AND DESCENT
KIND OF HAS HERITAGE

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BACK TO COLD WAR ERA,

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WHERE WE WOULD THROW SOMETHING
UP IN THE SKY

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AND LET IT FALL DOWN,
HOPEFULLY ON AN ENEMY TARGET.

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AND A LOT OF THE TECHNOLOGY
SORT OF MOVED FROM, YOU KNOW,

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DROPPING BOMBS INTO, WELL,
PUTTING A PERSON IN A CAPSULE

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AND HAVING THAT BODY REENTER.

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THE STANDARD DESIGN
IS BASED AROUND, YOU KNOW,

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AN ENTRY BODY WITH A STATIC
CENTER OF GRAVITY POSITION,

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AND KIND OF WHAT THAT DOES IS,
YOU CAN KIND OF IMAGINE,

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YOU KNOW, THE LEAF
FALLS OUT OF A TREE,

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AND THE STEM IS HEAVIER,

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AND SO IT KIND OF FALLS
IN THE DIRECTION OF THE STEM.

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- WHEN YOU'RE TALKING ABOUT
THINGS THAT WE'VE SENT TO MARS,

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WE REALLY HAVEN'T REALLY
CONTROLLED THEM

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VERY MUCH AT ALL.

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WE USUALLY JUST POINT IT
IN THE RIGHT DIRECTION,

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AND THEN IT FALLS
THROUGH THE ATMOSPHERE.

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- THE OLD JUST ISN'T
GOOD ENOUGH ANYMORE,

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SO RESEARCHERS AT NASA
ARE WORKING

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ON A BRAND-NEW TYPE
OF ENTRY AND DESCENT SYSTEM.

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IT'S A HYPERSONIC INFLATABLE
AERODYNAMIC DECELERATOR,

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OR HIAD.

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ESSENTIALLY,
IT'S AN INFLATABLE HEAT SHIELD.

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A HIAD COULD LAND
LARGER PAYLOADS

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IN PLACES
THAT ARE CURRENTLY UNREACHABLE.

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- THE BIG IDEA WITH HIADs
IS THAT YOU CAN MAKE THEM BIGGER

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FOR THE SAME MASS
OR EVEN LESS MASS

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THAN A RIGID VEHICLE.

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SO THEY WILL ACTUALLY
SLOW DOWN MORE QUICKLY

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THAN A RIGID VEHICLE,

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AND YOU CAN PUT MORE STUFF,

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MORE POUNDS OF THINGS
ON THE VEHICLE

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THAT YOU WANT TO LAND
ON THE SURFACE.

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SO IT WILL GET HOT.

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ACTUALLY, FOR THE HIADs,

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SINCE THEY SLOW DOWN
MORE QUICKLY,

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THEY WON'T GET AS HOT
AS A NORMAL CAPSULE.

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- SINCE THE HIAD AEROSHELL

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WILL HAVE UNIQUE
AERODYNAMIC CHARACTERISTICS,

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THE HIAD SYSTEM HAS AN ENTIRELY
DIFFERENT METHOD OF CONTROL

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FROM THE EARLIER EDL SYSTEMS,

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SOMETHING NASA ENGINEERS CALL
AN ACTIVE CONTROL SYSTEM.

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BUT JUST HOW DIFFERENT IS IT?

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- SO PASSIVE CONTROL

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IS WHEN WE WILL BUILD
THE SPACECRAFT

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BEFORE WE LAUNCH IT,

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AND WE'LL DESIGN IT
AHEAD OF TIME,

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AND WE'LL BASICALLY POINT IT
IN THE RIGHT DIRECTION

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AND LET IT FALL
THROUGH THE ATMOSPHERE,

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AND WE DON'T TRY
TO CONTROL IT ACTIVELY.

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THAT'S PASSIVE CONTROL.

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SO FOR ACTIVE CONTROL,
FOR INSTANCE,

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IF WE HAD SOMETHING LIKE THIS
THAT HAD A FLAP ON IT,

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PERHAPS WE COULD PUT THIS
ON A HINGE

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SO WE COULD ACTUALLY DEFLECT IT
MORE OR LESS

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AS WE'RE DESCENDING,

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AND THAT WILL GIVE US
MORE OR LESS CONTROL,

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AND THAT'S ACTIVE CONTROL

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AS THE VEHICLE IS FLYING
IN THE ATMOSPHERE.

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- SO ANOTHER APPROACH
TO ACTIVE CONTROL

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IS WHERE WE'RE LOOKING

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AT FALLING
THROUGH THE ATMOSPHERE

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AND ACTUALLY MOVING
THE CENTER OF GRAVITY

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OF THE VEHICLE.

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SO BACK TO THE LEAF ANALOGY,

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AS WE'RE FALLING FROM THE TREE,
LET'S SAY WE HAVE A RIDER--

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JUST PUT A LITTLE ANT
OR A BEETLE

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ON THE BACK OF THIS LEAF.

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HE RUNS TO ONE SIDE,
THE LEAF KIND OF TIPS,

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AND THE LEAF FALLS
IN THE DIRECTION THAT HE MOVED.

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HE RUNS TO THE OTHER SIDE,

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AND THE LEAF'S GONNA FALL
IN THE OTHER DIRECTION.

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SO YOU CAN KIND OF IMAGINE
THIS NOTION

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THAT WE'RE MOVING A CHUNK
OF THE ENTRY VEHICLE,

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AND AS WE'RE DOING THAT,
WE'RE ADJUSTING AND MANIPULATING

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THE DIRECTION THAT THE VEHICLE'S
GOING TO FALL.

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WHAT WE'RE DOING WITH IRVE 3--

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THIS IS THE INFLATABLE
REENTRY VEHICLE EXPERIMENT--

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IS, WE'RE ACTUALLY TAKING
THE BACK OF THE VEHICLE

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AND MOVING IT BACK AND FORTH

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AS WE'RE FALLING
THROUGH THE ATMOSPHERE

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TO DEMONSTRATE THIS EFFECT
OF LIFTING BY CG MANIPULATION.

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- TO SOLVE THESE CHALLENGES,

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NASA HAS A WHOLE TEAM
WORKING ON HIAD

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AND OTHER GAME-CHANGING
TECHNOLOGIES--

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PROJECT MANAGERS
AND TECHNICIANS,

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MECHANICAL
AND ELECTRICAL ENGINEERS,

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MATERIALS SCIENTISTS
AND DATA ANALYSTS--

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ALL WORKING TOGETHER

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TO MAKE OUR DREAM
OF EXPLORATION A REALITY.

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NOW, THAT'S WHAT I CALL
A DREAM TEAM.

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THAT'S IT FOR NOW.

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I'M CALEB,

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