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Space Station Extravehicular Activity

IMAGE: STS-96 Astronaut Tamara Jernigan performs EVA
Astronaut Tamara Jernigan delivers a Russian crane to the International Space Station on STS-96. Jernigan and fellow Astronaut Dan Barry spent more than seven hours during the spacewalk at an altitude of 320 kilometers (173 nautical miles.)

With precise grace, an overhead crane swings a 10-ton building block into position. Then, workers move in, climbing onto the structure and using hand and power tools to bolt the pieces together. It is a workday scene that could be found on almost any city street corner, but this construction site is 402 kilometers (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.

With the assembly of the 454,000-kilogram (million-pound) International Space Station, Earth orbit has become a day-to-day construction site. Humankind has begun a move off of the planet Earth on an unprecedented scale. Astronauts will perform more spacewalks in upcoming years than have been conducted since space flight began, more than 2.5 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 can circle and inspect the station. Before the station's assembly is completed, more than 100 different components launched on more than 40 space flights -- using three different types of rockets -- will have been bolted, latched, wired, plumbed and fastened together.

IMAGE: STS-88 Astronaut James Newman performs EVA
During STS-88, Astronaut James Newman performs final tasks to the just mated Russian Zarya Module and U.S. Unity Module.

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 2005. About 160 spacewalks totaling 960 clock hours, or 1,920 man-hours, will be performed during that time to assemble and maintain the station.

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.

EVA Details
Spacewalk History
IMAGE: First American spacewalk
Astronaut Edward White performs the first American spacewalk during Gemini 4 on June 3, 1965.
Related Links
ISS: The NASA Research Plan, an Overview (979Kb PDF)

Curator: Kim Dismukes | Responsible NASA Official: Amiko Kauderer | Updated: 04/06/2009
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