Astronauts
began leaving the comparative safety of their spacecraft and floating in
space in 1965. This extravehicular activity (EVA) has been popularly termed
spacewalking. EVAs are always risky because the astronauts have only a
few thin layers of fabric and plastic between them and the lethal space
environment. A small rip in their spacesuit would bring an agonizing death
in seconds.
The first spacewalk
On 18 March 1965 the Russian cosmonaut Alexei Leonov (left) opened the airlock of his spacecraft, Voshkod2, and "walked" out into space. No one had done this before. His spacewalk lasted nearly 10 minutes.
Surface EVAs took place on the Moon during the Apollo missions of the
late 1960s and early 1970s. The astronauts wore self-contained spacesuits
and roamed far and wide across the lava plains and rugged highlands of
the Moon. On the last three missions they had wheeled transport in the
shape of the lunar roving vehicle, or Moon buggy.
Useful EVA in orbit did not begin until the Skylab space station mission of 1973. Skylab was damaged during launch, losing a solar panel and some vital insulation. In orbit, exposed to the Sun, it began to overheat. But the first crew ferried up to the station carried out two daring EVAs and managed to erect a sunshade over the damaged area. The mission was saved and became spectacularly successful.
Over the years since then, the long-stay residents in Russia's space stations have carried out many in-orbit EVAs to effect essential repairs to their craft. Some of the EVAs have been vital. In July 1990, for example, cosmonauts Anatoli Solovyov and Alexsandr Balandin made two long EVAs on Mir to cheek and repair their Soyuz ferry craft and close a faulty airlock.
Since
the Space Shuttle was introduced, many scheduled and a few unscheduled
EVAs have taken place. EVAs have been scheduled, for example, to support
experiments taking place in the payload bay. Shuttle astronauts have also
made EVAs to repair satellites that have been captured from orbit and secured
in the payload bay. This happened with Solar Max in 1984 and Leasat 3 a
year later.
On Shuttle mission 51-A in November 1984 (left) astronauts Dale Garner and Joseph Alien helped capture two communications satellites.
While working in the payload bay, the astronauts are usually tethered
to a safety line or "ride" on the orbiter's robot arm. Often they are actively
involved in satellite capture, "flying" the jet-propelled backpack known
as the manned manoeuvring unit (MMU).
Bruce McCandless test-flies the jet-propelled manned manoeuvring unit (MMU) in February 1984 during the 41 -B Shuttle mission.
