[dramatic percussion music]
- HEY, AND WELCOME TO "NASA LAUNCHPAD."
I'M YOUR HOST, CALEB.
PART OF GETTING A SPACECRAFT
TO LAND ON AND EXPLORE OTHER WORLDS
IS GETTING IT SAFELY THROUGH THE ATMOSPHERE,
AND THAT REQUIRES A HEAT SHIELD.
BUT THE ATMOSPHERE ALSO PLAYS A CRITICAL ROLE
IN HELPING TO SLOW A VEHICLE DOWN SO IT CAN LAND.
SO BIGGER HEAT SHIELDS MAKE SENSE.
IN AN ATMOSPHERE, BIGGER HEAT SHIELDS MEAN
WE CAN GET BIGGER SPACECRAFT DOING MORE SCIENCE
IN NEW PLACES,
BUT THAT MEANS A BRAND-NEW DESIGN.
AND NEW DESIGNS MEANS ENGINEERS HAVE TO SOLVE NEW CHALLENGES,
CHALLENGES INVOLVING CONTROLLABILITY
AND AERODYNAMICS.
BEFORE WE CAN CONTROL THE SPACECRAFT,
WE HAVE TO UNDERSTAND HOW IT FLIES,
AND THAT MEANS UNDERSTANDING A BIT ABOUT AERODYNAMICS.
- WELL, WHEN YOU'RE TALKING ABOUT THE ATMOSPHERE,
YOU'RE MOSTLY INTERESTED IN THE DENSITY OF THE ATMOSPHERE
AND ANY KIND OF WINDS THAT YOU MIGHT ENCOUNTER.
THE DENSITY IS REALLY DIRECTLY PROPORTIONAL
TO WHAT KIND OF DRAG FORCE YOU WILL GET ON THE VEHICLE
AS YOU DESCEND.
AND ANY WINDS MIGHT DIVERT YOUR VEHICLE
ONE WAY OR ANOTHER OFF COURSE.
SO WE ACCOUNT FOR ANY UNCERTAINTIES
IN BOTH DENSITY AND WINDS.
- WHEN YOU THINK ABOUT AN ATMOSPHERE--
I'M A MECHANICAL ENGINEER.
I HAVE TO THINK ABOUT THINGS REALLY SIMPLY.
SO WHEN I THINK ABOUT AN ATMOSPHERE,
I THINK ABOUT LITERALLY JUST LIKE A POOL.
AND I'M THROWING SOMETHING IN THERE,
AND WHERE IS IT GONNA LAND ON THE BOTTOM OF THE POOL?
AND THAT'S ANALOGOUS TO, YOU KNOW,
WE'RE HITTING THE TOP OF THE ATMOSPHERE,
AND WHERE ARE WE GONNA BE HITTING THE GROUND?
WHEN WE LAND ON MARS AND WE'RE SENDING CREW THERE,
IT'S NOT ACCEPTABLE TO LAND ON THE OTHER SIDE OF THE PLANET.
WE NEED TO LAND FAIRLY CLOSE TO THE TARGET DESTINATION,
BECAUSE THAT'S WHERE-- YOU'RE LANDING AT BASE CAMP.
YOU NEED TO BE NEAR BASE CAMP.
- BUT THERE'S NO STEERING WHEEL ON ANY OF THESE SPACECRAFT,
SO HOW DO WE CONTROL A SPACECRAFT'S DESCENT
THROUGH AN ATMOSPHERE,
ESPECIALLY WHEN IT'S TRAVELING AT HYPERSONIC SPEEDS?
THAT MEANS IT'S ZOOMING THROUGH THE ATMOSPHERE
AT OVER FIVE TIMES THE SPEED OF SOUND.
- ENTRY AND DESCENT KIND OF HAS HERITAGE
BACK TO COLD WAR ERA,
WHERE WE WOULD THROW SOMETHING UP IN THE SKY
AND LET IT FALL DOWN, HOPEFULLY ON AN ENEMY TARGET.
AND A LOT OF THE TECHNOLOGY SORT OF MOVED FROM, YOU KNOW,
DROPPING BOMBS INTO, WELL, PUTTING A PERSON IN A CAPSULE
AND HAVING THAT BODY REENTER.
THE STANDARD DESIGN IS BASED AROUND, YOU KNOW,
AN ENTRY BODY WITH A STATIC CENTER OF GRAVITY POSITION,
AND KIND OF WHAT THAT DOES IS, YOU CAN KIND OF IMAGINE,
YOU KNOW, THE LEAF FALLS OUT OF A TREE,
AND THE STEM IS HEAVIER,
AND SO IT KIND OF FALLS IN THE DIRECTION OF THE STEM.
- WHEN YOU'RE TALKING ABOUT THINGS THAT WE'VE SENT TO MARS,
WE REALLY HAVEN'T REALLY CONTROLLED THEM
VERY MUCH AT ALL.
WE USUALLY JUST POINT IT IN THE RIGHT DIRECTION,
AND THEN IT FALLS THROUGH THE ATMOSPHERE.
- THE OLD JUST ISN'T GOOD ENOUGH ANYMORE,
SO RESEARCHERS AT NASA ARE WORKING
ON A BRAND-NEW TYPE OF ENTRY AND DESCENT SYSTEM.
IT'S A HYPERSONIC INFLATABLE AERODYNAMIC DECELERATOR,
OR HIAD.
ESSENTIALLY, IT'S AN INFLATABLE HEAT SHIELD.
A HIAD COULD LAND LARGER PAYLOADS
IN PLACES THAT ARE CURRENTLY UNREACHABLE.
- THE BIG IDEA WITH HIADs IS THAT YOU CAN MAKE THEM BIGGER
FOR THE SAME MASS OR EVEN LESS MASS
THAN A RIGID VEHICLE.
SO THEY WILL ACTUALLY SLOW DOWN MORE QUICKLY
THAN A RIGID VEHICLE,
AND YOU CAN PUT MORE STUFF,
MORE POUNDS OF THINGS ON THE VEHICLE
THAT YOU WANT TO LAND ON THE SURFACE.
SO IT WILL GET HOT.
ACTUALLY, FOR THE HIADs,
SINCE THEY SLOW DOWN MORE QUICKLY,
THEY WON'T GET AS HOT AS A NORMAL CAPSULE.
- SINCE THE HIAD AEROSHELL
WILL HAVE UNIQUE AERODYNAMIC CHARACTERISTICS,
THE HIAD SYSTEM HAS AN ENTIRELY DIFFERENT METHOD OF CONTROL
FROM THE EARLIER EDL SYSTEMS,
SOMETHING NASA ENGINEERS CALL AN ACTIVE CONTROL SYSTEM.
BUT JUST HOW DIFFERENT IS IT?
- SO PASSIVE CONTROL
IS WHEN WE WILL BUILD THE SPACECRAFT
BEFORE WE LAUNCH IT,
AND WE'LL DESIGN IT AHEAD OF TIME,
AND WE'LL BASICALLY POINT IT IN THE RIGHT DIRECTION
AND LET IT FALL THROUGH THE ATMOSPHERE,
AND WE DON'T TRY TO CONTROL IT ACTIVELY.
THAT'S PASSIVE CONTROL.
SO FOR ACTIVE CONTROL, FOR INSTANCE,
IF WE HAD SOMETHING LIKE THIS THAT HAD A FLAP ON IT,
PERHAPS WE COULD PUT THIS ON A HINGE
SO WE COULD ACTUALLY DEFLECT IT MORE OR LESS
AS WE'RE DESCENDING,
AND THAT WILL GIVE US MORE OR LESS CONTROL,
AND THAT'S ACTIVE CONTROL
AS THE VEHICLE IS FLYING IN THE ATMOSPHERE.
- SO ANOTHER APPROACH TO ACTIVE CONTROL
IS WHERE WE'RE LOOKING
AT FALLING THROUGH THE ATMOSPHERE
AND ACTUALLY MOVING THE CENTER OF GRAVITY
OF THE VEHICLE.
SO BACK TO THE LEAF ANALOGY,
AS WE'RE FALLING FROM THE TREE, LET'S SAY WE HAVE A RIDER--
JUST PUT A LITTLE ANT OR A BEETLE
ON THE BACK OF THIS LEAF.
HE RUNS TO ONE SIDE, THE LEAF KIND OF TIPS,
AND THE LEAF FALLS IN THE DIRECTION THAT HE MOVED.
HE RUNS TO THE OTHER SIDE,
AND THE LEAF'S GONNA FALL IN THE OTHER DIRECTION.
SO YOU CAN KIND OF IMAGINE THIS NOTION
THAT WE'RE MOVING A CHUNK OF THE ENTRY VEHICLE,
AND AS WE'RE DOING THAT, WE'RE ADJUSTING AND MANIPULATING
THE DIRECTION THAT THE VEHICLE'S GOING TO FALL.
WHAT WE'RE DOING WITH IRVE 3--
THIS IS THE INFLATABLE REENTRY VEHICLE EXPERIMENT--
IS, WE'RE ACTUALLY TAKING THE BACK OF THE VEHICLE
AND MOVING IT BACK AND FORTH
AS WE'RE FALLING THROUGH THE ATMOSPHERE
TO DEMONSTRATE THIS EFFECT OF LIFTING BY CG MANIPULATION.
- TO SOLVE THESE CHALLENGES,
NASA HAS A WHOLE TEAM WORKING ON HIAD
AND OTHER GAME-CHANGING TECHNOLOGIES--
PROJECT MANAGERS AND TECHNICIANS,
MECHANICAL AND ELECTRICAL ENGINEERS,
MATERIALS SCIENTISTS AND DATA ANALYSTS--
ALL WORKING TOGETHER
TO MAKE OUR DREAM OF EXPLORATION A REALITY.
NOW, THAT'S WHAT I CALL A DREAM TEAM.
THAT'S IT FOR NOW.
I'M CALEB,
AND I'LL SEE YOU NEXT TIME ON "NASA LAUNCHPAD."