[sarex] STS-112 An Extraordinary Movie

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Submitted by Arthur - N1ORC

                 An Extraordinary Movie
On October 2nd, NASA TV plans to broadcast the first live video from a
space shuttle's fuel tank as it soars into Earth orbit on the belly of
Atlantis and falls back again. 
 .

Sept. 26, 2002: I love the movie Apollo 13. I've seen Jim Lovell pilot
that balky lunar module with Earth lurching back and forth through the
windshield about a dozen times--and it's still thrilling. From the
exploding oxygen tanks ("Houston, we have a problem...") to the CO2
crisis to the breathless re-entry ... the tension never stops.

But the best part of Apollo 13, the most thrilling scene, has nothing at
all to do with the accident. The best part, in my opinion, was the
launch.

When Lovell's Saturn V rocket blasted off the pad in Florida--seven
million pounds of pure power soaring toward space with angelic voices
singing in the background--it gave me goosebumps. The footage revealed
what I had never "got" from books: The Saturn V was terrifyingly
powerful. No one who saw it lift off could imagine spaceflight was
routine.
 
I remember wondering when I watched that scene whether a "routine"
shuttle launch might seem equally thrilling--if only we could see it from
the right point of view.

On October 2nd we get to find out.

That's when the space shuttle Atlantis (STS-112) is slated to blast off
from Cape Canaveral on a mission to visit the International Space
Station. For the first time ever, a camera attached to the shuttle will
record the ascent and transmit images live to NASA TV. The point of view
will be similar to the launch scene in Apollo 13.

The camera--called the "ET camera" around NASA--will be mounted near the
top of the shuttle's burnt-orange external fuel tank (ET). It will look
down toward Atlantis's nose, the 40 degree field of view encompassing
most of the fuel tank, one of the white solid rocket boosters (SRBs), and
the shuttle itself.

The camera will "go live" about 15 minutes before liftoff. Nothing much
will happen during that time--consider it a dramatic pause. Then, at T-7
("tee-minus-7") seconds, ground controllers will ignite the shuttle's
main engines (first) and the solid rocket boosters (second). SRBs always
start second because, once they're lit, they can't be turned off again.


Eight giant bolts hold down the SRB's. As soon as the boosters are
ignited (T=0 on the countdown clock) the bolts will be released and
Atlantis will rise off the pad. At that moment, the shuttle's two solid
rocket boosters and three main engines produce 7.8 million pounds of
thrust--more than Lovell's Saturn V moon rocket. (The shuttle's engines
contribute 29% of that thrust, the SRBs 71%.)

During those early moments, the camera will see bright flames and a lot
of smoke. The grayish-brown clouds are exhaust from the SRBs. The white
stuff is water vapor. Water is sprayed across the launch pad, in part to
prevent fires and also to mute the thunderous noise. The spray is
vaporized by heat from the SRBs and the engines. The engines themselves
spew water as a result of oxygen-hydrogen combustion, thus adding to the
steam.

It takes about seven seconds for the shuttle to clear the 247-ft tower
and its 100-ft lightning rod. In that short time the shuttle's engines
and rocket boosters consume more than 150,000 pounds of fuel. Hard to
believe? Just think about all that fire and smoke....

Right: A short animated artist's concept of the roll maneuver. You can
also view a 500 kb Quicktime animation of the roll or a 2.5 MB movie of
the entire ascent.

At first Cape Canaveral will recede smoothly beneath the shuttle; then,
around T+20 ("tee-plus-20") seconds, the ground will suddenly spin.
That's the roll maneuver. The entire shuttle "stack" turns so the orbiter
lies underneath the fuel tank. This is done for many reasons, e.g., it
reduces stress on the shuttle's delicate wings. It also lets astronauts
see the horizon, giving them a reference point should the mission have to
be aborted and the shuttle forced to land

Pay close attention during the first minute of ascent, you might spot
clouds swishing by the shuttle. There won't be any warning because the
camera points down, not up. These flybys will stop as soon as the shuttle
climbs above the tropospheric cloud layer, 3 to 6 miles high.

One of the most interesting parts of the movie comes two minutes after
launch when the shuttle is about 28 miles above Earth and the SRBs run
out of fuel. Explosive bolts separate the empty boosters from the
external tank, and motors (with their own little exhaust) push the
boosters away from the shuttle. SRBs fall back to Earth, but they don't
crash. Parachutes lower them gently to the Atlantic Ocean, where they are
retrieved for use in future missions.

Above: A short animated artist's concept of the SRB separation. You can
also view a 400 kb Quicktime animation of the SRB separation or a 2.5 MB
movie of the entire ascent.

With the SRBs gone, the shuttle relies solely on its three main engines
for propulsion. During the next six minutes, they will accelerate the
spaceship to 17,500 mph. The engines drain the fuel tank at a rate of
60,000 gallons per minute--fast enough to empty a family swimming pool in
10 seconds flat.

When the shuttle first eaves the launch pad, it flies vertically, but the
spacecraft gradually levels during the ascent. Sometime around T+4
minutes, the shuttle become horizontal enough for the camera to see the
distant curved horizon of Earth. The sky will appear space-black--a
lovely view. NASA insiders would say the shuttle is almost "on orbit" ...
which means it's time for the grand finale.



At T+8 minutes, with the shuttle 52 miles above Earth, the ET finally
runs out of fuel. There's no reason to carry a huge empty tank in orbit,
so ground controllers jettison it. The tank will fall back to Earth, with
the camera attached, slowly tumbling as it goes. Eventually it will burn
up over some deserted stretch of ocean, although the camera won't last
that long. NASA expects the live feed to stop about six minutes after ET
separation or until the tank moves out of range, whichever comes first.

Like any good movie, the ending of this one is a mystery. What's the last
thing the camera will record? No one knows. Will it give you goosebumps
like Apollo 13? Will you ever watch NASA TV again? There's only one way
to find out: tune in on Oct. 2nd and see for yourself.


Editor's note: This movie, unlike ordinary films at the theater, might be
delayed by weather or other factors. If you have a copy of Apollo 13,
keep it handy. You might need a backup plan.
 

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