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Sky Walking

HarperCollins Publishers, Inc.

Obstacles cannot crush me. Every obstacle yields to stern resolve. He who is fixed to a star does not change his mind.
Leonardo DaVinci (1452-1519), Notebooks

November 28, 1996--Thanksgiving evening. The space-suit fan whirred quietly behind my head, pumping the weightless oxygen from backpack to helmet as I drifted in the airlock. The shuttle Columbia had completed 144 orbits of Earth. By this tenth day of our mission, we had recaptured the Wake Shield Facility, our space-based computer chip factory, and berthed it safely into the shuttle's payload bay, its mission complete. The other satellite we had deployed on this science mission, an ultraviolet astronomical telescope called ORFEUS-SPAS, trailed us in orbit by about thirty miles, busily surveying the heavens. In the four days before we chased down the telescope, we had an exciting new task to perform. It was time to prove that the National Aeronautics and Space Administration's (NASA's) plans for building a space station were practical and workable in the weightless environment of orbit. For our five-person crew on the eightieth mission of the Space TransportationSystem, or STS-80, this traditional American holiday was no day off. I had trained hard for six years for this moment.

Sealed inside the cramped canister-shaped compartment at the rear of Columbia's crew cabin, Tammy Jernigan and I were still connected to the orbiter's power and oxygen supplies by a pair of life-support umbilicals. Tammy, our crew's lead space walker, pushed aside a tangle of drifting tools and grasped the chamber's depressurization valve with a weightless glove. Cleared by Mission Control, she rotated the black knob to its open position: the life-giving air surrounding us roared through the valve directly into the vacuum of space. The only thing between us and space was the thin metal of the airlock's rear hatch. It was hard to imagine that there were no more practice sessions in NASA's Weightless Environment Training Facility (WETF) standing between us and our two planned space walks. But here we were, suited up and ready, not submerged in a big swimming pool but immersed in the real thing at last. Hovering above Tammy's backpack, I glanced down at the digital readout on my own suit and saw something never seen in our space-walk training under water: the airlock pressure was creeping toward zero.

The countdown to this first extravehicular activity (EVA) had gone perfectly so far. Story Musgrave, our veteran crewmate and in-cabin partner, had marched us through the preparation checklist, and as usual, his practiced eye had missed nothing. He had double-checked every detail of suit-up, and about thirty minutes earlier he had closed the hatch leading from Columbia's middeck, isolating Tammy and me from the crew cabin. Now, as my fingertips tingled with anticipation, we were executing the "Airlock Depress" checklist, with hatch opening just ahead.

Racing through my mind were the details of the six hours of work awaiting us outside. In our 130 hours of underwater drills and endless tabletop rehearsals, Tammy and I had burned into our memories every key task of our upcoming weightless ballet. Only by sticking with our tightly scripted timeline could we make it through the space walk's long list of Space Station assembly tests. All the WETF (pronounced Wet-F) rehearsals, the hours spent working out the orbital choreography, the space-suited vacuum chamber tests, and our final checklist review in the cabin last night lay behind us now. Outside, the new Space Station cargo crane waited for us in its payload bay cradle. Opposite the crane on the orbiter sidewall was a station solar array battery swathed in white thermal insulation, and the new station tools were nestled in their storage lockers down on the cargo bay floor. There was no time to methodically go over the whole plan again. Instead, I focused on the first few steps that would get me out the door; once there, I would rely on slipping into the comfortable groove that repetition had worn into our memories.

When the airlock pressure dropped down from the sea-level value of 14.7 pounds per square inch (psi) to 5, Tammy halted the depressurization for a planned space-suit leak check. Her suit pressure was running slightly high, but her breathing would soon consume enough oxygen to bring the reading within operational limits. My gauge reading was perfect at 4.3 psi, the pressure at which the suit's pure oxygen atmosphere would fully charge our blood with the life-giving gas. Satisfied, Tammy twisted the depressurization valve wide open, and the remaining air molecules fled into the void outside. Under the dim fluorescent lights of the airlock, we drifted in the hard vacuum conditions of space, where the pressure was less than one ten-billionth of that at sea level.

Still connected to the orbiter by our suit umbilicals, we got the critical "Go" from Story to open the airlock hatch. In a moment we would be out the door, "on stage" at last. The butterflies in my stomach were in full zero-g flight; feeling something akin to stage fright, I was more fearful of making a mistake in front of my colleagues than of the EVA hazards of micrometeoroids, searing temperatures, radiation, and hard vacuum.

With her gloved left hand gripping the yellow handrail rimming the outer hatch, Tammy reached out, grabbed the hatch handle with her other hand, and spun the crank clockwise. About 30 degrees through its single revolution the handle stopped unexpectedly. When she tried again, this time with more muscle, the force of her effort swung her weightless body back up toward me. I could hear her determined breathing over the intercom, but the handle resisted her efforts to advance it further. After straining through a half-dozen attempts with no success, she called for reinforcements. "Tom, it won't budge. Swap places and you have a go at it."

Continues...

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Excerpted from Sky Walking by Thomas Jones Copyright © 2006 by Thomas Jones. Excerpted by permission.
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