space walks

With precise grace, an overhead crane swings a 10-ton building block into position. Then, workers move in, climbing on to the structure and using hand and power tools to bolt the pieces together. It is a workaday scene that could be found on almost any city street corner, but this construction site is 250 miles up - in the airless reaches of space, where conditions alternate hourly between freezing and searing. The construction workers are astronauts, the cranes are a new generation of space robotics and the skyscraper taking shape is the International Space Station.

To assemble the 1-million pound International Space Station, Earth orbit will become a day-to-day construction site for the next five years. Humankind has begun a move off of the planet Earth on an unprecedented scale. Astronauts will perform more spacewalks in the next five years than have been conducted since space flight began, more than two and a half times as many. They will be assisted by an "inch-worming" robotic arm; a two-fingered "Canada hand;" and maybe even a free-flying robotic "eye" that may can circle and inspect the station. Before the station's assembly is completed, more than 100 different components launched on about 46 space flights - using three different types of rockets - will have been bolted, latched, wired, plumbed and fastened together.

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Because of the unprecedented complexity, NASA expects to encounter surprises during the orbital construction work. But to prepare for the challenges, engineers and astronauts have been methodically practicing procedures, preparing tools, testing equipment and building experience during more than a decade of spacewalking flight tests. A total of 37 Space Shuttle missions are scheduled to assemble, outfit and begin research use of the station from 1998 to 2004. Two of those have been completed. About 160 spacewalks - four already completed - totaling 960 clock hours, or 1,920 man-hours, will be performed during that time to assemble and maintain the station. Since astronaut Ed White stepped out of an orbiting U.S. Gemini spacecraft in 1964 to become the first American to walk in space, NASA has conducted only about 377 hours of spacewalks.

A cooperative effort by 16 nations, the International Space Station will provide living quarters and science labs for long-term stays by up to seven astronauts. In building, operating, and performing research on the station, humanity also gains experience needed for future travels beyond Earth orbit.

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*Click on images for captions
Photo credits for all images: NASA.
Additional materials in this section courtesy of NASA and Boeing.