Spaceflight (or space flight) is an application of astronautics to fly spacecraft into or through outer space, either with or without humans on board. Most spaceflight is uncrewed and conducted mainly with spacecraft such as satellites in orbit around Earth, but also includes space probes for flights beyond Earth orbit. Such spaceflight operates either by telerobotic or autonomous control. The more complex human spaceflight has been pursued soon after the first orbital satellites and has reached the Moon and permanent human presence in space around Earth, particularly with the use of space stations. Human spaceflight programs include the Soyuz, Shenzhou, the past Apollo Moon landing and the Space Shuttle programs, with currently the International Space Station as the main destination of human spaceflight missions while China's Tiangong Space Station is under construction.

Spaceflight is used for placing in Earth's orbit communications satellites, reconnaissance satellites, Earth observation satellites, but also for space exploration such as space observatories and space probes, or even for space tourism.

Spaceflight can be achieved with different types of launch systems, conventionally by rocket launching, which provide the initial thrust to overcome the force of gravity and propel a spacecraft from the surface of the Earth. Once in space, the motion of a spacecraft – both when unpropelled and when under propulsion – is covered by the area of study called astrodynamics.

Some spacecraft remain in space practically indefinitely, which has created the issue of space pollution in the form of light pollution and space junk, which is a hazard to spaceflight. Otherwise spacecraft are terminated by atmospheric reentry, in which they disintegrate, or if they do not, their reentry is mostly controlled to safely reach a surface by landing or impacting, often being dumped in the oceanic spacecraft cemetery. As such spacecraft have been the subject of some space traffic management.

 

Note:   The above text is excerpted from the Wikipedia article Spaceflight, which has been released under the GNU Free Documentation License.