# 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
(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

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.

16-19/Mechanics/Circular motion/Text/Space stations and artificial gravity

The 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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