[dramatic percussion music]
- HEY, WELCOME TO "NASA LAUNCHPAD."
I'M YOUR HOST, VINCE WHITFIELD.
NOW, WHEN YOU THINK OF AN ENGINE,
WHAT COMES TO MIND?
PROBABLY A CAR WITH ITS RECIPROCATING GAS ENGINE
OR MAYBE EVEN A JET ENGINE.
OR LET'S GO OLD-SCHOOL.
HOW ABOUT A STEAM ENGINE?
NOW, ALL OF THESE PRODUCE ROTATIONAL ENERGY,
OR THE KINETIC ENERGY CREATED BY THE ROTATION OF AN OBJECT.
AND OF COURSE, YOU REMEMBER THAT ENERGY
IS SIMPLY THE CAPACITY OR ABILITY TO DO WORK.
BUT IF I TELL YOU TO THINK OF A NASA ENGINE,
WHAT COMES TO MIND?
YEAH, PROBABLY A ROCKET, RIGHT?
AND THE ENERGY IS WHAT'S NEEDED
TO GET THAT MASSIVE ROCKET OFF THE LAUNCHPAD
AND INTO ORBIT.
BUT GET THIS.
A ROCKET ENGINE IS FUNDAMENTALLY DIFFERENT
THAN OTHER TYPES OF ENGINES,
AND IT CAN BE BOTH SIMPLER AND MORE COMPLEX
AT THE SAME TIME.
ON THE ONE HAND, A ROCKET ENGINE IS VERY SIMPLE.
IN FACT, YOU CAN BUILD AND FLY MODEL ROCKETS FOR YOURSELF.
TO FIND OUT WHY ROCKETS WORK,
LET'S LOOK AT NEWTON'S THIRD LAW:
FOR EVERY ACTION,
THERE IS AN EQUAL AND OPPOSITE REACTION.
AND THAT'S BASICALLY IT.
THE ROCKET'S EXHAUST CREATES FORCE,
AND THE ROCKET MOVES IN THE OPPOSITE DIRECTION.
BUT ON THE OTHER HAND,
THE PRACTICAL APPLICATION OF ROCKETS IS VERY COMPLICATED.
I MEAN, COME ON, THEY CALL IT "ROCKET SCIENCE."
SURE, THE CONCEPT IS SIMPLE,
BUT AS YOU CAN SEE BY THIS PICTURE
OF THE SPACE SHUTTLE'S SOLID ROCKET BOOSTERS, OR SRBs,
THESE ROCKETS ARE PRETTY COMPLEX.
LET'S TALK FUEL.
WHAT KIND OF FUEL DOES A CAR TAKE?
YEAH, OF COURSE, GASOLINE.
BUT THE SRBs DON'T USE GASOLINE.
THEY USE SOMETHING WITH A LITTLE BIT MORE KICK.
LIKE THEIR NAME SUGGESTS,
THEY ACTUALLY USE SOLID FUEL AS A PROPELLANT
RATHER THAN A LIQUID LIKE GASOLINE.
EACH SOLID ROCKET MOTOR CONTAINS MORE THAN 450,000 KILOGRAMS,
OR 1 MILLION POUNDS, OF PROPELLANT,
WHICH, WHEN IT'S CURED,
LOOKS AND FEELS LIKE A HARD RUBBER ERASER.
THE FUEL IS ACTUALLY MADE UP OF POWDERED ALUMINUM.
YEAH, ALUMINUM, KIND OF LIKE THE FOIL
YOU MIGHT FIND IN YOUR KITCHEN.
BUT IN ITS POWDERED FORM, IT IS EXTREMELY FLAMMABLE
AND IS EXPLOSIVE WHEN MIXED WITH AIR.
SO STICK IN A CATALYST OR SOME CHEMICAL SUBSTANCE
THAT CAN ACTUALLY START OR SPEED UP A REACTION
WITHOUT INTERFERING WITH THE REACTION ITSELF,
A CURING AGENT,
AND A BINDER THAT HOLDS THE MIXTURE TOGETHER,
THEN ADD AN OXIDIZER--
IN THIS CASE, AMMONIUM PERCHLORATE--
AND YOU GET THE REST OF THE PROPELLANT MIXTURE.
BUT HOW DOES IT WORK?
WELL, TO GET THE PICTURE, WE NEED TO FOCUS ON TWO THINGS:
THE FUEL AND THE OXIDIZER.
HERE'S DR. RICHARD BYLES
OF THE VIRGINIA AIR AND SPACE CENTER
WITH A SMALL-SCALE DEMONSTRATION OF HOW SOLID-FUEL ROCKETS WORK.
- NOW, THIS IS THE BASIC OF ALL ROCKET MOTORS THAT ARE SOLID,
FIREWORKS AND EVERYTHING ELSE, IS,
YOU HAVE TO HAVE AN OXIDIZER, WHICH THIS STUFF IS.
THIS IS A POWERFUL OXIDANT.
AND YOU HAVE TO HAVE SOME FUEL SOURCE.
AND WHAT HAPPENS WITH THE FUEL SOURCE IS,
IN SOLID ROCKET BOOSTERS
ON THE SPACE SHUTTLE, FOR EXAMPLE,
THEY USE A FUEL SOURCE THAT IS SOLID
AND HAS THE OXIDIZER MIXED WITH IT.
AND IT'S NOT UNTIL THEY IGNITE IT FIRST
THAT IT GOES OFF.
IT'S STABLE AT ITS TEMPERATURE.
AS SOON AS IT HEATS UP,
THEN IT STARTS BURNING AND FLAMING,
AND THAT'S WHAT TAKES THE SPACE SHUTTLE UP
FOR THE FIRST TWO MINUTES, ALONG WITH THE MAIN ENGINE.
- SO BASICALLY, WHAT WE'VE GOT HERE IS SODIUM CHLORATE
AS OUR OXIDIZER
AND A GUMMY BEAR AS OUR FUEL.
NOW, WE PUT THE OXIDIZER INTO THE TEST TUBE
AND THEN THE FUEL,
JUST LIKE TEST TUBE IS A SOLID ROCKET BOOSTER.
NEXT, WE APPLY HEAT AND WAIT FOR THE REACTION.
AND WE HAVE IGNITION.
THAT FLAME COMING FROM THE BURNING GUMMY BEAR
IS A PRETTY GOOD APPROXIMATION OF WHAT YOU SEE
WHEN THE SHUTTLE TAKES OFF, RIGHT?
AND THE GUMMY BEAR DOES THAT
BECAUSE IT'S MADE UP PRIMARILY OF SUGAR,
AND SUGAR OXIDIZES VERY WELL.
NOW, THE SHUTTLE'S SOLID ROCKET BOOSTERS
ARE RELATIVELY INEXPENSIVE
COMPARED TO OTHER FORMS OF PROPULSION,
AND THEY'RE REUSABLE.
BUT THEY'RE NOT PERFECT.
FOR ONE THING,
ONCE YOU START THE REACTION AND THE SRBs HAVE IGNITED,
YOU CANNOT STOP THEM.
AND IT'S ALSO NOT EASY TO ADJUST THE AMOUNT OF FUEL USED
THROUGHOUT THE BURN ON THE FLY.
THAT'S ALL DETERMINED
IN THE MIXING AND PACKING OF THE PROPELLANT.
DIFFERENT CONCENTRATIONS OF FUEL, OXIDIZER, ET CETERA,
DETERMINE HOW MUCH ENERGY WILL BE USED
THROUGHOUT THE FLIGHT.
IN OTHER WORDS, IT'S NOT LIKE DRIVING A CAR,
WHERE YOU CAN STOMP ON THE GAS PEDAL
OR SLAM ON THE BRAKE TO SPEED UP OR SLOW DOWN THE CAR AT WILL.
BUT HEY, THAT'S OKAY.
REMEMBER, LIKE RICHARD SAID,
THE SRBs ONLY ADD BOOST
TO THE MAIN ENGINES OF THE SHUTTLE
FOR THE FIRST TWO MINUTES OF FLIGHT.
AND THOSE FIRST TWO MINUTES ARE ALL ABOUT GETTING LIFT
AND PROPELLING THE SHUTTLE UPWARD.
AFTER THAT, THE SRBs ARE JETTISONED
AND RETRIEVED TO BE REPACKED FOR OTHER FLIGHTS.
EVEN THE NEXT-GENERATION ARES SYSTEMS
IN NASA'S CONSTELLATION PROGRAM WILL USE SOLID ROCKET BOOSTERS
DERIVED FROM THE SPACE SHUTTLE PROGRAM FOR ITS LAUNCHES.
ARES 1 WILL USE AN SRB
ONLY FOR THE ROCKET'S FIRST STAGE.
ARES V, WHICH WILL BE HAULING THE CARGO AND EQUIPMENT,
MAY NEED A BIT MORE ENERGY.
SO ITS FIRST STAGE WILL BE A COMBINATION OF THE TWO--
COUNT THEM, TWO-- SOLID ROCKET BOOSTERS
AND A CRYOGENIC ENGINE.
NOW, WAIT A MINUTE.
WE'VE ONLY TALKED ABOUT
THE FIRST TWO MINUTES OF THE SPACE SHUTTLE'S FLIGHT.
WHAT HAPPENS AFTER THAT?
I DID SAY ROCKET SCIENCE WAS COMPLEX.
STAY TUNED TO FIND OUT.
THAT'S IT FOR NOW.
I'M VINCE WHITFIELD,
AND THANKS FOR WATCHING "NASA LAUNCHPAD."
I'LL CATCH YOU NEXT TIME.