DAISY: At NASA, safety is job one.
Engineers go to extreme lengths to ensure safe
travels for astronauts...
We’ll show you how they do it, next on Real World.
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FLIGHT ATTENDANT: An oxygen mask will automatically drop
from a compartment above your seat. To start the...
DAISY: When you fly commercial, you know there
are lots of safety measures in place...
But if you go for a ride in the Space Shuttle, multiply
that to the 10th power and you’ll get an idea of how
much safety goes into every Space Shuttle mission.
NASA engineers divide shuttle safety into three areas:
Pre-flight, flight, and post-flight.
Pre-flight safety includes planning the mission,
testing Shuttle components and procedures,
and spacecraft design.
In fact, the Shuttle recently underwent some upgrades to
make missions safer than ever including a
Cockpit Avionics Upgrade.
It’s kind of like getting a whole new set of gages
for your car’s dashboard.
The Cockpit Avionics Upgrade brings news hardware and
software, providing the crew with better informational
displays and warning functions.
This upgrade helps the crew get data on the
Shuttle’s performance more quickly.
During flight, one of the coolest safety features is a
monitoring system for the shuttle’s
Thermal Protection System.
It uses the Remote Manipulator Arm along with an
Orbiter Boom Sensor System. The Orbiter Boom extends the
Manipulator Arm and has a camera at its end.
While the Shuttle is orbiting, astronauts take
hundreds of images of the Shuttle’s exterior.
These images are beamed back to earth and the Mission
Evaluation Room where engineers examine them
looking for any damage that might have occurred
during the mission.
Of course, while in flight, NASA ground control is
constantly monitoring and checking every aspect
of the mission and the Shuttle.
MIKE MOSES: You get most of your data by flying...
DAISY: Mike Moses is Launch Integration Manager for the
Space Shuttle Program, and he eats, sleeps,
and breaths safety.
MIKE: The real art of making sure we stay safe every time
is to look at that data.
DAISY: Safety issues are again addressed during post-
flight, when NASA engineers focus on how all the systems
performed during the mission.
They gain a little more knowledge each time up.
MIKE: On the last flight we saw a signature as we were
going uphill for ascent, one of the pressures just didn’t
respond the way it was supposed to.
DAISY: It didn’t cause any problems during the mission,
STS-126, but after landing, engineers rolled up their
sleeves to take a closer look at the issue.
MIKE: When we started looking at it we found
the valve itself was cracked. DAISY: The pressure that Mike
is talking about inside the Shuttle’s external fuel tank
is measured in pascal units.
For example, the pressure of the air all around us at sea
level... called standard atmospheric pressure...
is 101,325 pascal.
Pascal units measure force per unit area, such as 1
newton per square meter. A Newton is a unit of force.
It was the release of pressure that caused the
valve to crack. MIKE: This is the inside of
the valve so there’s a sleeve outside of this and it goes
up and down. And what it’s for is, the big external tank
has hydrogen and oxygen in it, and we need to keep them
pressurized to feed the engines at the right rate.
So we kind of boot strap, we siphon off a little bit of
that hydrogen, burn it through the engine, and make
it into hot gas, and then we send it back up into the tank
to pressurize it. So this valve controls the rate at
which we keep that tank pressurized. So this little
tiny lip, here, it was fluttering up in down in...
we call it the wind, basically... as the hydrogen
rushed past, it made this thing flap and eventually it
stressed it and broke it off. And we never expected that
there would be that type of flow past this little valve.
When this valve was designed, now, probably 30 year ago,
it was state of the art. It’s exactly what it should
do. Now that we have all these advanced computational
fluid dynamic modeling, you can, in a computer, model
exactly how this flow works and know the exact velocities
and speeds. It’s absolutely amazing.
DAISY: Thanks to computer modeling and math, engineers
are able to visualize how the flow of hydrogen and nitrogen
caused the valve to fail.
From there, they can calculate the likelihood
that the component will fail again.
MIKE: We did a whole bunch of math to show basically that
when this thing cracks we know how the little stresses
will propagate around and we can say it probably won’t be
more than a 90 degree piece that breaks off. And then you
want to look at what that little piece does as it goes
downstream. Is it going to hit a line and make a hole?
Is it going to let too much hydrogen through so the tank
gets over pressurized? So we boiled our way down through
all those options. And basically, at the end of the
day, we found that it was acceptable. The probability
of any one of those things happening was pretty small.
DAISY: The issue delayed the next flight, STS-119, by two
weeks, but all that math certified that that
mission would go off safely.
MIKE: Space flight is really hard and it’s really hard
because it’s so complicated... everything has
to play just right with each other.
DAISY: So as you can see, when it comes to safety, NASA
engineers really sweat the details...doing all they can
to make sure crews come back safely.
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