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Don Pettit
IMAGE: NASA ISS Science Officer Don Pettit, background, with Expedition Six Commander Ken Bowersox
NASA ISS Science Officer Don Pettit, background, and Expedition Six Commander Ken Bowersox review a checklist as they wrap up a U.S. spacesuit demonstration inside the Quest Airlock.
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Don Pettit Space Chronicles

Expedition Six
Space Chronicles #14

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By: ISS Science Officer Don Pettit

Space Walk Prep

In the sci-fi movies, astronauts can quickly don their spacesuits and in short order, be out the door in the vacuum of space. They seem to always be in a hurry to chase bad guys, alien monsters, or look for holes in the hull spewing out precious atmosphere. In the reality of our current technology, it does not happen this way. Perhaps with future invention it will be more like in the movies, but for the present, we have less advanced technology.

Nothing happens fast during the preparations for a space walk. Thelarge amount of time needed to prepare is partly due to the sheer magnitude of the technical chores and partly due to human physiology. And you must pay attention to the techno-details as if your life depended on them. Making a mistake here is no longer minus ten points on a midterm exam. It takes several days over about a week to prepare for a space walk.

First you do some house cleaning. The airlock tends to be used as a storage place for other bulky items so it must be cleaned up and organized. You do not want anything in the airlock that is not related to your pending activity lest it interferes in some obtuse way.

Your spacesuit must be assembled from a suitcase full of parts, where you pay special attention to the rubber ring seals and corresponding mating surfaces. You do not want a leak.

There are batteries to tend, where they are first discharged and then recharged to ensure the best possible performance. And there are three different kinds of batteries, a large one that operates your spacesuit, smaller ones for running your helmet lights, and another for the glove heaters and helmet video camera. You do not want to be outside and have your batteries die from the same neglect that so often happens when you unplug a laptop computer.

It is important to regenerate the carbon dioxide scrubbers. They are like a small chemical factory built into the spacesuit using reversible chemical reactions with silver oxide as the absorption substrate. They are placed in a special oven and baked out over a 14-hour cycle.

You check the cooling system that includes a pump and many feet of clear thin-walled plastic tubing sewn into your long underwear. You check the connections for leaks and observe the flow for excess bubbles. The pump shaft rotates at 20,000 revolutions per minute. Cavitation at this speed is not desirable. If bubbles are present, you bleed them out.

You top off the water tanks. Water sublimating from an icepack in the vacuum of space transports away your metabolic heat from the latent heat of sublimation.

Small details are important. You clean your visor 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. You install a valsalva device on the inside of the helmet. Shaped like two small side-by-side mounds, this block of soft rubber is used to plug your nose without a helping hand so you can clear your ears during the pressure changes. It has the habit of snagging your headset cord if it is not installed at the correct angle.

You should not forget to check coated membranes in your headset. They keep onerous water vapors out of the headphones. Condensing water vapor from sweat shorts out the headset and results in a loss of communications. That alone could prematurely end a space walk.

You install your drink bag and place the straw so it will not tangle in the headset cord. If there is air in your drink bag, it will expand and burp out a few ounces creating fluid spheres inside of your helmet. Like irksome bug spots on your windshield, they invariably find their way onto the visor right where you need to see the most. Or they ricochet off obstacles as if playing three-dimensional pinball until they settle into your eye. You score five thousand points for that one. You make sure to burp all the air out of your drink bag.

You dress up in your spacesuit in a dry-run to check the fit, the sizing, and to check the operations of all the systems. You do a leak check to verify the pressure integrity. You check out your SAFER, a compressed nitrogen thruster backpack used to fly back to structure if by some mistake you were to drift off. When we do a space walk without the presence of a docked Space Shuttle, drifting away from structure would be a fatal mistake. You would literally become Earth's newest satellite. The most anyone on the ground could do is wish upon a falling star. If it were to happen, the SAFER backpack gives you one brief chance to correct this situation and you make certain the equipment is in good form.

You set up your tools. Some have batteries to recharge. Some have protruding handles that always seem to get in the way. Like solving a puzzle cube, you juggle the tools on your workstation until they all fit in the right place. You load film and change batteries in the space camera.

All the tools have strings attached -- retractable strings we call tethers. You check all the tethers for cuts and frays and smooth retraction. A tether that won't retract is as responsive as a tangled spool of fishing line on a spin-cast reel.

You review your script. Like part actor in a Broadway play and part Olympic athlete, you think, you plan, you rehearse your part and your actions until you know them by heart. 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. You know to expect a forward lurch and a clunk after 10 turns of a stanchion bolt and then 17 more before the running torque begins to increase. If it does not happen this way, something is wrong and you must stop and investigate.

The Universe is a tough critic, and the reviews will not be good if you have slacked in your preparations. Preparing oneself to go out the hatch on space walk day involves a carefully crafted ritual. The bends, a condition where nitrogen bubbles are squeezed out from solution in your blood stream causing all sorts of circulation havoc, are well known in the field of deep sea diving. You would not expect such problems associated with diving to the bottom of the oceans to also occur in the orbital environment of space, but it does. The space station is pressurized to one atmosphere pressure at 20percent oxygen and 80percent nitrogen, just what is found on Earth at sea level. A spacesuit operates with a 100percent oxygen atmosphere at about 1/4th of an atmosphere pressure. If one were to quickly go from space station into the spacesuit, a case of the bends could develop, rendering one incapacitated.

On space walk day, you start off with an exercise period on a stationary bicycle while breathing 100percent oxygen through a facemask attached to 120 feet of snaking hose. An exercise prescription, carefully crafted by flight surgeons, is followed where you exercise at known wattage rates for set periods of time. The increased cardiovascular circulation while breathing 100percent oxygen rapidly purges your blood stream of excess nitrogen. A rather short period of this exercise replaces many hours of the standard oxygen pre-breath. While still breathing from a now sweat-fogged facemask, you towel off and take care of any toilet duties. Wrestling 120 feet of stiff snaking hose is a pain in weightlessness until you find yourself in need of a toilet which is located it seems, about 122 feet away. You find your way back to the airlock and isolate the compartment from the rest of space station where the pressure is lowered to the equivalent of being on a mountain at 9,200 feet. Only then can you remove the oxygen masks.

Now the task of suiting up begins. You rely on the help from an extra crew member, referred to in space vernacular as the "IV." He tugs on the sleeves of your synthetic-fiber long underwear to straighten out wrinkles, locks connectors forged from aluminum alloy located in places that are hard to reach, buttons down flaps, and installs your composite helmet with a gold-plated polycarbonate visor.

Spacesuit gloves make a nice click when they are installed. Eight little doggies make a sound with the quality of the finest Swiss-made mechanism. You have a vested interest in listening for this sound.

This help struck me as the space age equivalent of squires helping knights of the middle ages suit up for battle. I can imagine their squires smoothing wrinkles in chain mail, fastening heavy buckles with leather straps, tugging hearth-forged metal plates into their proper overlap, and installing the metal helmet with a forged slit visor.

Our IV helps us dismount from the wall, assists with the SAFER backpack, and stuffs us in the now much smaller part of the airlock that will be vented into space. This part of the airlock, which seemed so roomy without your spacesuit, now seems cramped. A thousand years earlier, a squire would attach the scabbard that sheaths the broad-blade sword and mount the knight on his steed. It amuses me to ponder how far we have advanced, yet how similar the human actions remain.

It takes about six hours from the time you start in the morning to the time you are ready to open the hatch. After having gone through all of this preparation, you will not take lightly to a hatch that does not want to open. For us the crank would rotate almost to the open position and then hang up. It was not a hard metallic type of jam but more like a piece of rubber that was blocking the mechanism. No amount of torque would make it budge. I thought we were going to break the handle off. We wanted to go outside, real bad.

The hatch dogs were partly released and allowed the hatch to crack open perhaps 3/8th of an inch. A shaft of brilliant sunlight came through the crack as if teasing us to come out and play when it knew we could not. 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.


Curator: Kim Dismukes | Responsible NASA Official: John Ira Petty | Updated: 05/13/2003
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