In recent years, NASA has increased the frequency of extravehicular
activity to prepare for the assembly of the International Space
Station beginning in the late 1990s. Two recent extraordinary Shuttle
missions have demonstrated the potential for EVA on the Space Station.
These were the STS-61 and STS-82 missions in 1993 and 1997 in which
astronauts conducted multiple spacewalks to service the Hubble Space
Telescope. During each flight, crew members donned their spacesuits
and conducted EVAs in which they replaced instruments and installed
new solar panels. Their servicing activities required extreme precision
and dexterity during EVAs lasting more than seven hours.
Similar efforts will be needed for the assembly of the International
Space Station. During the nearly 40 American and Russian space flights
to the station, astronauts and cosmonauts will log over 1,200 hours
of EVAs. More hours of spacewalks are expected to be conducted during
just the years 1999 and 2000 than were conducted during all previous
US space flights.
Spacewalkers will assist in the assembly of the Space Station by
making all the connections that require greater dexterity than can
be accomplished with station robots. These operations include joining
electrical cables and fluid transfer lines and installing and deploying
communication antennas. To do this, spacewalkers will have to remove
locking bolts that secured components during launch to orbit.
As the Space Station evolves, astronauts will move components,
such as antennas, to the most advantageous locations. For example,
a communications antenna may become blocked when additional station
modules are joined to the structure. Spacewalkers will have to traverse
the outside of the modules and reposition the antenna where it will
be unblocked by modules, solar panels, and other structures.
(1997) STS-82 astronauts Mark C. Lee (top) and Steven L. Smith (bottom)
repair a worn area in the insulation of the Hubble Space Telescope.
Detailed work like this will be a frequent occurrence during the assembly
and opertion of the International Space Station.