[dramatic percussion music]
- HEY, WELCOME TO "NASA LAUNCHPAD."
I'M YOUR HOST, AMBER WHALEN.
DO YOU REMEMBER WHEN WE TALKED ABOUT THE SOLID ROCKET BOOSTERS,
OR SRBs, ON THE SPACE SHUTTLE
AND WE LEFT YOU ON A CLIFF-HANGER
JUST TWO MINUTES INTO FLIGHT?
WELL, YOU DON'T HAVE TO WAIT ANY LONGER,
BECAUSE WE'RE GOING TO DIVE INTO THE SSMEs
AND EXTERNAL TANK RIGHT HERE, RIGHT NOW ON "NASA LAUNCHPAD."
OKAY, FIRST THING FIRST.
WHAT IS AN SSME?
WELL, SSME STANDS FOR SPACE SHUTTLE MAIN ENGINE.
SO IF YOU'RE LOOKING AT THE BACK OF THE SPACE SHUTTLE ORBITER,
THOSE THREE ENGINE NOZZLES YOU SEE THERE ARE ATTACHED TO
OR ACTUALLY A PART OF THE MAIN ENGINES, THE SSMEs.
NOW, LET'S DO A LITTLE COMPARING AND CONTRASTING
WITH THE SRBs, SHALL WE?
THE SRBs ARE SEPARATE ROCKETS
THAT ARE ATTACHED TO THE SHUTTLE SYSTEM
AND ARE JETTISONED DURING THE FLIGHT,
WHILE THE SSMEs ARE BUILT INTO THE SHUTTLE ORBITER.
THE SRBs ARE MUCH MORE POWERFUL THAN THE SSMEs.
THEY PROVIDE 71% OF THE THRUST FROM LIFTOFF
TO SRB SEPARATION,
UP TO 3.1 MILLION POUNDS OF THRUST.
EACH SHUTTLE MAIN ENGINE
HAS ONLY 400,000 POUNDS OF THRUST.
SO THE SOLID FUEL IN THE SRB IS GENERALLY MORE POWERFUL,
BUT IT DOES HAVE ITS DISADVANTAGES.
FOR ONE THING, IT'S VIRTUALLY IMPOSSIBLE
TO ADJUST THE AMOUNT OF ENERGY GIVEN OFF BY THE SOLID FUEL
ONCE IT'S IGNITED.
BUT WITH LIQUID PROPELLANT, LIKE IN A CAR,
IT'S EASIER TO CONTROL HOW MUCH FUEL IS GOING INTO THE ENGINE,
WHICH IN TURN LETS YOU CONTROL HOW FAST THE VEHICLE GOES.
BUT UNLIKE A CAR,
THE SSMEs DON'T USE REGULAR UNLEADED
OR EVEN DIESEL FUEL.
THEY ACTUALLY BURN
LIQUID HYDROGEN AND LIQUID OXYGEN,
WHICH ARE SUPPLIED
BY THE SPACE SHUTTLE'S EXTERNAL TANK.
THAT'S THE BIG ORANGE PART
OF THE SHUTTLE TRANSPORTATION SYSTEM,
AND I DO MEAN BIG.
THE SPACE SHUTTLE ENGINES COLLECTIVELY BURN
3,917 LITERS OF LIQUID PROPELLANT PER SECOND.
JUST TO PUT THAT INTO PERSPECTIVE,
IF THE SHUTTLE ENGINES BURNED WATER
INSTEAD OF LIQUID HYDROGEN AND LIQUID OXYGEN,
THE AMOUNT OF FUEL THAT COULD FILL
AN AVERAGE-SIZED SWIMMING POOL
WOULD BE DRAINED IN ONLY 25 SECONDS.
THE SPACE SHUTTLE ENGINES
ARE DESIGNED TO PERFORM IN EXTREME TEMPERATURES.
WHEN ICY COLD LIQUID HYDROGEN IS BURNED WITH LIQUID OXYGEN,
THE TEMPERATURE INSIDE THE COMBUSTION CHAMBER
REACHES AN INCREDIBLE 3,300 DEGREES CELSIUS.
THAT'S HIGHER THAN THE BOILING POINT OF IRON.
NO WONDER THE 3.2-TON ENGINES
ARE TAKEN TO THE SPACE SHUTTLE MAIN ENGINE PROCESSING FACILITY
AFTER EVERY FLIGHT
AND INSPECTED TO SEE IF ANY PARTS NEED TO BE REPLACED
BEFORE THE NEXT MISSION.
AND JUST HOW POWERFUL ARE HYDROGEN AND OXYGEN
AS FUEL SOURCES?
WELL, HERE WITH A DEMONSTRATION IS DR. RICHARD BYLES
OF THE VIRGINIA AIR AND SPACE CENTER.
AND DO I REALLY HAVE TO SAY IT?
DON'T TRY THIS AT HOME.
- SO NOW WE HAVE A HYDROGEN BALLOON.
THAT'S THE BALLOON WE FILLED UP
WITH A LITTLE BIT OF OXYGEN AND THE REST HYDROGEN.
AND HYDROGEN IS A LIGHTER-THAN-AIR GAS
AND IS ONE OF THE GASES THAT MAKES THE SHUTTLE GO.
AND ITS MAIN TANK
IS FULL OF LIQUID HYDROGEN AND LIQUID OXYGEN,
AND THEY'RE REALLY COMPRESSED.
SO WHEN THEY MEET TOGETHER DOWN AT THE BOTTOM, THEY FIRE.
SO I JUST WANTED TO SHOW YOU
WHAT HYDROGEN DOES WHEN YOU LIGHT IT.
- BIG BOOM, RIGHT?
ACTUALLY, ROCKETS ARE JUST CONTROLLED EXPLOSIONS.
SO WHILE OUR LITTLE DEMONSTRATION
MAY NOT BE EXACTLY WHAT HAPPENS WITH THE SHUTTLE,
IT DOES SHOW YOU THE KIND OF ENERGY
THAT HYDROGEN IS CAPABLE OF GENERATING.
IF A LITTLE BALLOON FILLED WITH HYDROGEN
HAS THAT KIND OF ENERGY,
IMAGINE HOW MUCH POTENTIAL ENERGY IS STORED
IN THE MASSIVE 550,000-LITER,
OR 146,000-GALLON, EXTERNAL TANK.
BUT OBVIOUSLY, ALL THAT ENERGY ISN'T RELEASED AT ONE TIME.
IT'S GRADUALLY RELEASED THROUGH A SERIES OF VENTS AND VALVES,
ALLOWING FOR CONTROLLED EXPLOSIONS,
LETTING NASA CONTROL HOW FAST THE SHUTTLE TRAVELS.
NOW, YOU KNOW THAT THE SRBs, AFTER THEIR FUEL IS EXPENDED,
SEPARATE FROM THE SHUTTLE
AND FALL BACK DOWN INTO THE OCEAN,
WHERE THEY ARE RETRIEVED FOR REUSE.
BUT THE EXTERNAL TANK STAYS WITH THE SHUTTLE
UNTIL IT'S ALMOST IN ORBIT,
SO IT HAS TO COME BACK DOWN THROUGH THE ATMOSPHERE
AT A HIGH SPEED.
THIS CAUSES IT TO BREAK APART, SO IT'S UNABLE TO BE REUSED.
HOWEVER, THE EXTERNAL TANK TECHNOLOGY
IS BEING REUSED IN A DIFFERENT SENSE.
YOU KNOW THAT THE SPACE SHUTTLE PROGRAM
IS SCHEDULED TO END IN 2010.
AND THE SHUTTLES,
WHICH SERVED AS THE WORKHORSE FOR THE SPACE AGENCY,
WILL BE RETIRED.
AND WHAT'S COMING NEXT?
THAT'S RIGHT: THE CONSTELLATION PROGRAM.
IF YOU LOOK CLOSELY AT THE ARES V ROCKET,
YOU MIGHT NOTICE SOMETHING VERY FAMILIAR.
THAT BIG ORANGE SECTION RIGHT THERE IN THE MIDDLE?
YEAH, THAT'S THE CORE PROPULSION STAGE,
WHICH IS, AS YOU CAN PROBABLY GUESS,
DERIVED FROM THE SPACE SHUTTLE'S EXTERNAL TANK.
SURE, IT'S BEEN MODIFIED,
BUT ISN'T THAT WHAT IT'S ALL ABOUT,
LEARNING FROM EXPERIENCE OF THE PAST
AND PUTTING THAT KNOWLEDGE TO GOOD USE
IN THE PRESENT AND FUTURE?
SOUNDS LIKE A GOOD IDEA TO ME, ANYWAY.
ALL RIGHT, THAT'S ALL THE TIME WE'VE GOT FOR NOW.
UNTIL NEXT TIME, I'M AMBER WHALEN.
THANKS FOR WATCHING "NASA LAUNCHPAD."