But by designing suitable transport and living accommodation, human beings have shown that they can live quite happily in space. They find that their bodies can tolerate the strange state of weightlessness for at least a year. And, protected in pressurized spacesuits, they can venture outside their spacecraft to "walk" and work in space: carrying out experiments and mending satellites.
At the beginning of the Space Age no one had the remotest idea whether flesh-and-blood human beings would be able to survive the hazards of space flight. First they had to withstand the high g-forces during launch - the forces on their bodies caused by the fierce acceleration of the launch rockets. This would make their bodies up to eight times heavier than normal.
When, however, they entered orbit, the pull on their bodies would cease abruptly. They would become weightless. What effect would this have on their blood, their heart and on the other body organs? Would these organs fail?
To help them find out, space scientists subjected astronauts to high g-forces in giant centrifuges. They sent chimpanzees and dogs into space, first for brief suborbital trips and then into orbit and back. The results were encouraging. Human beings could survive high g-forces for a short time; animals could survive short periods of weightlessness.
But no one really knew what would happen to the first humans to brave the space frontier until 12 April 1961. On that day the Russian Yuri Gagarin soared into space, circled the Earth once, and returned safely to a hero's welcome. In 108 minutes this first cosmonaut travelled a distance of 40,000 km. He appeared unharmed by the g-forces and one hour of weightlessness. This gave Russian space scientists the confidence to launch a second cosmonaut. In August Gherman Titov, aged only 25, remained in space for more than a day without coming to any harm. The breakthrough had been made. Space no longer appeared to be such a barrier. Humankind had begun its journey to the stars.
The Russian cosmonauts who pioneered space travel in 1961. Yuri Gagarin (right) made a one-orbit flight on 12 April; Gherman Titov made 17 orbits on 6 August.
Glenn enters the Mercury capsule Friendship 7 on 20 February 1962. Within
hours he will be speeding around the Earth in orbit at 28,000 km/h. He
was the first US astronaut to confront and overcome the hazards of space
In space, astronauts experience weightlessness, or zero gravity. This
is not an easy thing to simulate on the Earth. The closest
approximation is to train astronauts underwater to move and operate machinery.
Even then the effect of resistance in water gives a false