[rocket rumbling]
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- HEY, THERE.
WELCOME TO "NASA LAUNCHPAD."
I'M YOUR HOST, AMBER WHALEN.
OKAY, SO YOU KNOW THAT MASS
IS THE AMOUNT OF MATTER IN AN OBJECT.
KIND OF A SIMPLE CONCEPT, RIGHT?
AN OBJECT'S MASS DOESN'T CHANGE DUE TO GRAVITATIONAL PULL.
THAT'S WEIGHT.
BUT THE MASS OF AN OBJECT DOES HAVE RELEVANCE
TO SEVERAL OTHER PROPERTIES.
AND THOSE PROPERTIES ARE CALLED--
WAIT FOR IT-- MASS PROPERTIES.
NOW, WHAT ARE THESE PROPERTIES, AND WHAT DO THEY MEAN?
WELL, TO ANSWER THAT QUESTION,
WHO BETTER TO TURN TO THAN AMANDA CUTRIGHT?
SHE IS THE MASS PROPERTIES WORKING GROUP LEAD
SUPPORTING THE ORION FLIGHT TEST OFFICE
THROUGH THE ABORT FLIGHT TEST FLIGHT-TEST ARTICLES PROJECT.
THAT WON'T FIT IN THE LOWER-THIRD TITLE,
SO WE'RE GOING TO CALL HER A MECHANICAL ENGINEER,
WHICH SHE IS ALSO.
- WHEN I MENTION MASS PROPERTIES,
THERE ARE A LOT OF DIFFERENT PROPERTIES CONTAINED IN THERE.
THE ONES MOST COMMONLY KNOWN ARE THE MASS.
AND THERE'S ALSO THE CENTER OF GRAVITY,
SO THAT'S KIND OF THE POINT WHERE
THAT MASS COULD BE REFLECTED IN ONE POINT,
SO IF YOU'RE BALANCING IT ON A KNIFE,
THAT CENTER OF GRAVITY IS WHAT YOU NEED
TO PUT OVER THAT KNIFE TO MAKE IT BALANCED.
AND THERE'S ALSO AN INERTIA COMPONENT,
WHICH IS A FUNCTION OF THE MASS AND HOW FAR AWAY THAT MASS IS
FROM THE CENTER OF GRAVITY,
OR THE POINT THAT YOU WANT THE INERTIAS ABOUT.
- SO LET'S RECAP REAL QUICK.
THE TWO BIG PROPERTIES THAT AMANDA MENTIONED BESIDES MASS
ARE INERTIA AND THE CENTER OF GRAVITY.
GO BACK TO NEWTON'S FIRST LAW.
AN OBJECT AT REST STAYS AT REST
AND AN OBJECT IN MOTION STAYS IN MOTION
AT THE SAME SPEED AND DIRECTION
UNLESS SOME NEW FORCE COMES ON THE SCENE.
LET'S FACE IT; THE ONLY WAY YOU'RE GONNA GET OFF THAT COUCH
IS WHEN SOME OUTSIDE FORCE DRIVES YOU TO DO SO,
LIKE HUNGER, YOUR MOTHER YELLING AT YOU,
OR NATURE CALLING.
THAT'S BECAUSE ALL OBJECTS
REALLY HATE TO CHANGE WHAT THEY'RE DOING
WITHOUT A GOOD REASON.
AND THAT SOMETHING SCIENTISTS CALL INERTIA
OR THE RESISTANCE OF AN OBJECT
TO MAKE CHANGE IN THE STATE OF MOTION.
BUT THE HIGHER THE INERTIAL MASS OF AN OBJECT,
THE LARGER THE RESISTANCE TO CHANGING ITS STATE OF MOTION.
SO IF YOU HAD TWO OBJECTS WITH DIFFERENT MASSES,
THE OBJECT WITH THE LARGER MASS
WILL EXPERIENCE A SMALLER ACCELERATION,
AND THE OBJECT WITH THE SMALLER MASS
WILL EXPERIENCE A BIGGER ACCELERATION.
THE CENTER OF GRAVITY IS ANOTHER IMPORTANT PROPERTY.
REMEMBER THAT GRAVITY IS PULLING EQUALLY
AT ALL PARTS OF AN OBJECT.
SO AN OBJECT'S CENTER OF GRAVITY
IS THE POINT IN WHICH THE SYSTEM'S WEIGHT IS BALANCED.
BUT KEEP IN MIND,
THE CENTER OF GRAVITY DOESN'T ALWAYS CORRESPOND
WITH THE GEOMETRIC CENTER OF AN OBJECT.
FOR EXAMPLE, THE CENTER OF GRAVITY IN SPORTS CARS
WOULD BE DESIGNED LOW TO THE GROUND
TO MAKE FOR EASIER HANDLING ON SHARP TURNS
WHILE THE CENTER OF GRAVITY IN A BIG TRUCK IS MUCH HIGHER,
MAKING SUDDEN TURNS A PROBLEM.
WHERE DO YOU THINK THE CENTER OF GRAVITY IS
IN SOME OF THESE THINGS?
BUT HOW DO THOSE PROPERTIES AFFECT HOW SOMETHING FLIES?
HERE'S AMANDA AGAIN TO EXPLAIN.
- THOSE SPECIFIC PROPERTIES AFFECT FLIGHT
FROM A LOT OF DIFFERENT PERSPECTIVES.
PROBABLY THE MAIN ONES ARE THE AERODYNAMICS
AND THE FLIGHT DYNAMICS,
SO THE PATH, OR TRAJECTORY, THE OBJECT IS GOING TO TAKE,
WHICH ALSO THEN GOES INTO THE AVIONICS,
OR FLIGHT CONTROL SYSTEMS, THAT GO INTO THE ARTICLE,
AND IT ALSO GETS INVOLVED
FROM A STRUCTURE AND LOAD STANDPOINT,
SO THAT MASS AND THAT CENTER OF GRAVITY
AFFECTS HOW MUCH LOAD IS GOING TO BE APPLIED
TO CERTAIN COMPONENTS OF THE SYSTEM.
- BUT ARE THOSE PROPERTIES GOING TO BE THE SAME
IN A FLIGHT-TEST ARTICLE?
FOR EXAMPLE, IN THE ARES I-X FLIGHT-TEST ARTICLE,
CERTAIN COMPONENTS AREN'T GOING TO HAVE
ALL THE SAME INTERNAL SYSTEMS AND STRUCTURES
THAT WILL GO INTO THE FINAL ARES I VEHICLE.
AND OF COURSE, THERE WON'T BE ANY ASTRONAUTS
GOING UP IN THE ARES I-X.
THIS SEEMS TO BE A CHALLENGE FOR ENGINEERS.
SO HOW DO YOU HANDLE THAT? AMANDA?
- SO AS A MASS PROPERTIES ENGINEER,
A QUESTION THAT COMES UP A LOT IS,
ARE WE ACCURATELY REPRESENTING IN OUR FLIGHT-TEST ARTICLES
WHERE THE ASTRONAUTS ARE SITTING AND WHERE THEIR BEDS ARE
AND ALL THE DIFFERENT COMPONENTS?
SO THE ANSWER TO THAT QUESTION IS THAT
THE OPERATIONAL VEHICLE WILL HAVE ALL THOSE SYSTEMS IN THERE,
THE ASTRONAUTS IN THERE, AND THEREFORE,
IT HAS A RESULTING MASS AND CENTER OF GRAVITY POINT.
FOR OUR FLIGHT-TEST ARTICLES,
WE HAVE TO END UP WITH THE SAME MASS AND CENTER OF GRAVITY POINT,
BUT WE HAVE A DIFFERENT STRUCTURE
AND DIFFERENT SUBSYSTEMS IN THERE.
SO IN OUR PARTICULAR CASE FOR THE PAD-ABORT 1 FLIGHT TEST
AS WELL AS THE NEXT FLIGHT TEST, WHICH WILL BE ASCENT-ABORT 1,
WE HAVE THOUSANDS OF POUNDS OF BALLAST THAT WE USE
TO GET TO THAT MASS AND CG REQUIREMENT.
- SO IF THEY'RE PUTTING BALLAST IN,
OR SOME RANDOM HEAVY MATERIAL
ADDED TO HELP STABILIZE THE OBJECT,
THAT'S GOT ME WONDERING HOW THESE FLIGHT-TEST ARTICLES
COMPARE TO THEIR FINAL COUNTERPARTS.
WELL, IT DEPENDS.
DIFFERENT FLIGHT TESTS
HAVE DIFFERENT GOALS AND OBJECTIVES,
SO NOT ALL PARTS OF THE FLIGHT-TEST ARTICLE
NEED TO BE IDENTICAL.
AND IN SOME CASES,
THE MATERIALS USED MAY NOT EVEN BE THE SAME.
LET'S LET AMANDA EXPLAIN.
- SO WHAT YOU SEE BEHIND ME IS THE HEAT SHIELD
FOR THE ASCENT-ABORT 1 FLIGHT TEST,
AND I'LL USE THAT AS AN EXAMPLE FOR SOMETHING THAT WE DO
ON ALL THE COMPONENTS THAT GO INTO THE FLIGHT TESTS.
WE HAVE A CAD MODEL THAT REPRESENTS--
COMPUTER AIDED DESIGN MODEL--
THAT REPRESENTS THE IDEAL HEAT SHIELD,
SO THE DENSITY AND THE SHAPE
OF THAT PARTICULAR PART,
BUT WE ACTUALLY TAKE A MEASUREMENT
OF WHAT THAT ACTUALLY WEIGHS,
AND WE COMPARE IT TO THE ANALYTICAL MODEL.
SO FOR MASS PROPERTIES, WE HAVE BOTH ESTIMATES
THAT COME FROM A VARIETY OF AREAS
AS WELL AS THE ACTUALS FOR EACH COMPONENT.
- THANKS, AMANDA, FOR ALL THE INFORMATION.
TESTING AND RETESTING,
LOOKING FOR THE BEST ANSWERS.
AND YOU THOUGHT DRAFT VERSIONS ENDED WITH FRESHMAN ENGLISH.
WELL, THAT'S IT FOR THIS EPISODE.
I'M AMBER WHALEN, AND WE'LL CATCH YOU NEXT TIME
ON "NASA LAUNCHPAD."