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08 April 2003

Space Station Science
Picture of the Day

Getting Ready for a Space Walk
Photo Credit: Nikolai Budarin, ISS Expedition 6 Flight Engineer

Explanation: "In the sci-fi movies, astronauts can quickly don their
spacesuits and in short order, be out the door into the vacuum of
space. They're always in a hurry to chase bad guys, alien monsters,
or look for holes in the hull spewing out precious atmosphere," says
ISS science officer Don Pettit. 

In real life it doesn't work that way.

"Nothing happens fast," says Pettit. "It takes several days to
prepare for a space walk." The airlock has to be cleaned out. The
suits must be assembled--with exquisite care--from a suitcase full of
parts. The checklist is long: charging batteries, regenerating the
carbon dioxide scrubbers, topping off the water tanks, checking for
leaks. "Small details are important," he says. For example: "We clean
our visors and spread a thin layer of anti-fog on the inside surface.
If there is too much anti-fog it can make your eyes sting and water;
too little and it will fog up. It has to be just right if you want to
see anything." 

"You also check out your SAFER, a compressed nitrogen thruster
backpack that we can use to fly back to the ISS. When we do a space
walk without the presence of a docked Space Shuttle, drifting away
would be a fatal mistake." 

"You review your script. It's like being an actor on a Broadway play.
You think, you plan, you rehearse. In your sleep, you dream about
your part. You know where every bolt and pin is located, what
direction it is oriented, and how much torque is required to turn it.
The Universe is a tough critic, and the reviews will not be good if
you have slacked in your preparations." 

"On space walk day, you start off with an exercise period on a
stationary bicycle while breathing 100% oxygen through a facemask.
After that, the task of suiting up begins. You rely on help from an
extra crew member who tugs on sleeves, straightens out wrinkles,
locks connectors.... It reminds me of a squire in the Middle Ages
helping his knight suit up for battle." 

"It takes about six hours from the time you start in the morning
until you are ready to open the hatch. After all of this preparation,
you will not take lightly to a hatch that does not want to open.
That's what happened to us before our spacewalk earlier this year.
The hatch dogs were partly released and allowed the hatch to crack
open only 3/8th of an inch. A shaft of brilliant sunlight came
through the crack, as if teasing us to come out and play."

"Fortunately, experience gained by owning an old pickup truck with
cantankerous doors came in handy. With a little jockeying on the
handle and some soft-spoken words, the hatch came open and we started
our day." 

"If we were chasing bad guys, I am afraid they would be well into
hyperspace by now." 

Editor's Note: This story is based on Don Pettit's Space Chronicles
#14, where you can read a fuller account of his preparations for the
January 15, 2003 spacewalk. Pettit is conducting his 2nd spacewalk
today.

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