Space
Station Extravehicular Activity
 | | 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.
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. |
