Spaceflight
The human race has come a long
way from dreams of a trip to the Moon in the novels of Jules Verne to the astronauts of the
latter part of the twentieth century to space tourists of the early part of the twenty first
century.
Apart from anything else space flight involves travelling enormous
distances. As I write this people have orbited the Earth in spacecraft and space stations and
men have walked on the Moon but these involve relatively small distances compared with
exploring the edges of the Solar System or going to the stars.
It took the
Apollo astronauts a few days to get to the Moon in the 1960s and 1970s but how long it
would take to get to Pluto in a spaceship that was moving at 25000 mph?
The
closest that Pluto gets to the Earth is about four thousand five hundred million kilometers and
so travelling at 2500 mph (40 000 km/hr) it would take us almost thirteen years to get
there!
It's when we come to think about travel to the stars that things get really
staggering.
The nearest star (Proxima Centauri) is just over four light-years away. This
means that it takes a beam of light moving at 300 000 km/s takes about 4.3 years to travel that
distance. Our spacecraft moving at a pathetic 40 000 km/hr (11 km/s) would make the
journey in a hundred and eighteen thousand years! You can see that unless we find another
way of powering our spacecraft so that can move much faster trips to the stars are virtually
impossible. Certainly the astronauts who set out from Earth would only make a fraction of the
journey in their lifetimes.
Problems for the human body during long space
flights
There are many problems with manned space flights, especially long ones.
All manned space flights have difficulties because
of:
(a) a high acceleration at take off (high g forces)
(b) weightlessness in orbit and in
'deep' space
(c) very high and very low temperatures outside the spacecraft
(d)
'radio silence' at re-entry
(e) the need for a breathable air supply
(f) eating and
drinking in weightless conditions
(g) problems with waste products from the body
(h)
breathing out carbon dioxide when you are asleep
Astronauts on long space flights
also suffer from:
(a) boredom
(b) getting on with the rest of the crew
(c)
deterioration of their bones and heart
(d) muscle deterioration
(e) radiation
effects
Some of these problems can be solved – others just need
training.
Spacecraft have layers of insulation to protect the crew against the very
high temperatures at take off and the very low temperature in space.
The
astronauts on long flights are encouraged to exercise regularly using an exercise bike. This
helps to keep their muscles and heart in good condition.
Space stations can be
made to spin slowly – this produces artificial gravity.
If you want to know more about this
see:
16-19/Mechanics/Circular motion/Text/Space stations and artificial gravityThe
British astronaut Helen Sharman tells that it was noisy in the Russian spacecraft in which she
flew because of the fans. When you are asleep in weightless conditions the carbon dioxide
that you breathe out does not 'fall to the floor' – its stays in a sort of globe around your head
and eventually you suffocate from breathing it back in. The fans helped to blow this around
the spacecraft and prevent a build up around the astronauts' heads.
The space
capsules have thick walls and space walks are limited in time to reduce the dangers of
cosmic radiation.
Technological spin-off from the space
programme
Space flight has produced a number technological advances that were
developed purely for the space programme and are now used in everyday
life.
Space travel disasters
In spite of the enormous care taken with
manned space flight there have sadly been some disasters. When you think of the millions of
components in the American space shuttle or he Apollo moon rockets this is probably only to
be expected.
These range from the crash landing of a Russian space capsule to the fire
on in an Apollo capsule while still on the launch pad, the ill fated Apollo 13 and the two space
shuttle disasters.
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