Since the 1930s when rockets were developed that could overcome Earth’s gravity and reach orbital velocities, human space exploration has been an important goal for many nations. These space programs have served a broad range of national interests including increasing knowledge, providing prestige and national pride, serving as indicators of military and technological strength and generating jobs.
The exploration of outer space has involved a variety of vehicles including satellites, probes, and crewed missions. These have led to a string of discoveries about the Moon, Mars and the other planets in our Solar System. They have also revealed the rings of Saturn, the asteroid belt, the comets, Jupiter’s moons, the Sun’s atmosphere, and the farthest active spacecraft, Voyager 1 and 2, have even left our solar system’s heliosphere.
For a long time only national governments could afford the very high costs of sending people and machines into space, so national programs focused on science and national prestige. In the latter half of the 20th century, however, private companies have begun to offer suborbital and orbital flights using their own privately funded rockets, and commercial space activities have become increasingly popular.
Space exploration requires a wide variety of equipment, facilities and supplies. For example, space stations and colonies need to be able to supply their inhabitants with food and other necessary resources. They will also need water recycling and purification systems to recapture the moisture from daily washing and urine, a source of oxygen for breathing, a way to heat the space station and capsules and to cool electronic equipment.