Living in orbit
In orbit objects appear to have no weight. They do not fall if you let
them go. The Earth's gravity seems to have disappeared. But it is still
there. The spacecraft (and everything it contains) is actually falling
towards the Earth under gravity. But it is travelling so fast (28,000 km/h)
that the Earth beneath curves away at the same rate as it is falling. In
other words it stays at the same height - in orbit. This state is properly
called free fall, but is popularly termed weightlessness.
Weightlessness
dominates everything you do in orbit - moving, eating, drinking, sleeping
and going to the lavatory. For example, you cannot walk in orbit, because
there is nothing to hold your feet down. You cannot pour liquid from a
bottle - it just stays where it is. But you can it through a straw,
because that depends on air pressure. To sleep, you have to zip yourself
into a sleeping bag and fix it to something, otherwise you will just float
away. Space lavatories are fitted with an air-flushing system to draw wastes
away from your body once they have been excreted.
(above) Sleeping aboard the Shuttle orbiter. The sleeping quarters are
on the mid-deck, and comprise a number of bunks, to which the astronauts
attach their sleeping bags. When they are asleep, their arms tend to float
upwards in the weightless conditions. If the bunks are full, astronauts
fix their sleeping bags to the walls or anything suitable. Because the
orbiter is quite noisy, they usually wear ear plugs.
Mealtimes
can be fun on the Space Shuttle. Mike lounge chases a spherical globule
of raspberry drink during a dinner break on Shuttle mission STS-26. Astronauts
Fred Hauck and Dave Hilmers look on.
The
body itself is affected by the weightless state in a number of ways, some
of them serious. The study of these effects and their treatment is known
as space medicine. For the first few days in orbit you will probably feel
sick because the balance organs in your ears cannot make sense of the new
sensations. Without gravity to pump against, your heart will begin to lose
muscle tissue; so will your legs. Unless you take regular exercise, the
muscles will waste away, making you feel weak when you return to Earth
and gravity once again. Regular exercise is essential on long space missions.
(above) Guion Bluford gets in some exercise on a treadmill during an
early Shuttle flight. On Shuttle missions taking exercise is not really
necessary because they seldom last longer than a week. It is on long-stay
missions in space stations that it becomes vital to take regular exercise
to prevent the body muscles wasting away.
Even
more serious is a progressive loss calcium from the body, which reduces
the mass and strength of the bones. However, a careful diet and a strict
exercise regime helps to combat these effects, allowing astronauts to remain
in space for a year or more without suffering permanent body damage.
(left) European Space Agency astronaut Wubbo Ockels fitted out for an
experiment on a "space sled" during a Spacelab mission. He will later be
accelerated on the sled-like device along a track and stopped suddenly.
At the same time his eyes will be subjected to different sensations and
his reactions will be monitored. This experiment is designed to investigate
space sickness, or space adaptation syndrome, which affects the majority
of astronauts for the first few days in space.
The
days when astronauts have to wear cumbersome spacesuits in orbit are long
gone. For most of the time they live in "shirt-sleeve", air-conditioned
comfort. Occasionally they sport some really way-out gear, as the crew
did here on the STS-26 Shuttle mission in 1988.
This page is updated on
.