Space beyond the Earth has been the center of interest for astronomers since the second millennium BC, when the Babylonians and later the ancient Greeks formulated systems of thought about the Sun, Earth, Moon, Mercury, Venus, Mars, Jupiter, and Saturn. .
The search for the sky has never stopped, it continues today. Between 1600-1650 several satellites of the planets Jupiter and Saturn were identified, in 1781 the planet Uranus was discovered, in 1846 Neptune, in 1870 the two satellites of Mars, in 1930 Pluto, in 2003 the dwarf planet Eris.
The understanding of celestial mechanics has changed over time, Nicolas Copernicus, Galileo Galilei, Johannes Kepler and Isaac Newton are the first to intuit, respectively confirm by calculations and demonstrations that the Earth moves around the Sun and not vice versa, being a planet like all others .
Outer space is defined by convention as being 100 km from the Earth's surface.
The imaginary line that surrounds the Earth at this altitude was called the Kármán Line, the name of the scientist, whose calculations show for the first time that at this altitude the air is too sparse to be able to sustain the flight.
During and immediately after the Second World War, the great powers began the development of ballistic missiles for military purposes. It is the spark that ignites the ambition to go further, beyond the atmosphere, into outer space.
Astronautics is the science and technique of space flight. Approach outer space with aircraft.
The beginnings of space exploration are missions, military actions, more or less secret. Even today, when the objectives of the flights are diverse, from the military to the commercial and tourist one, not all the details of the missions are made public.
The history of space flight has had many successes, some resounding: the first man in space, the first man out of the vehicle (EVA), the first docking of vehicles in space, the first exchange of cosmonauts between vehicles in orbit, the first landing of a spacecraft on another celestial body, the first man on the moon, the first vehicle to travel beyond the solar system.
The successes of the missions are popularized and known, except for the countless failures and fatal incidents. They are part of the effort to conquer outer space and can intervene at any time during the mission.
The most dangerous maneuvers are: launching, docking and re-entering the atmosphere or descending on another celestial body. The biggest risks for a space traveler are explosions, high gravitational forces (g), take-off vibrations due to the dense atmosphere of the Earth, re-entry high temperatures (16000C) that form with the compression of air in front of the ship, space radiation and collisions with meteoroids or cosmic debris.