Missions in Space
Spaceflight is the use of space technology to achieve the flight of spacecraft into and through outer space. Spaceflight is used in space exploration, and also in commercial activities like space tourism and satellite telecommunications. Additional non-commercial uses of spaceflight include space observatories, reconnaissance satellites and other earth observation satellites.
Some spacecraft remain in space indefinitely, some disintegrate during atmospheric reentry, and others reach a planetary or lunar surface for landing or impact. Physical exploration of space is conducted both by human spaceflights and by robotic spacecraft.
A spaceflight usually starts from a spaceport (cosmodrome), which may be equipped with launch complexes and launch pads for vertical rocket launches, and runways for takeoff and landing of carrier airplanes and winged spacecraft. Spaceports are situated well away from human habitation for noise and safety reasons. A launch is often restricted to certain launch windows. These windows depend upon the position of celestial bodies and orbits relative to the launch site. The biggest influence is often the rotation of the Earth itself. Once launched, orbits are normally located within relatively constant flat planes at a fixed angle to the axis of the Earth, and the Earth rotates within this orbit. A launch pad is a fixed structure designed to dispatch airborne vehicles. It generally consists of a launch tower and flame trench. It is surrounded by equipment used to erect, fuel, and maintain launch vehicles.
All current spaceflight except NASA's Space Shuttle and the SpaceX Falcon 1 use multi-stage expendable launch systems to reach space. An expendable launch system is a launch system that uses an expendable launch vehicle (ELV) to carry a payload into space. The vehicles used in expendable launch systems are designed to be used only once, and their components are not recovered after launch. The vehicle typically consists of several rocket stages, discarded one by one as the vehicle gains altitude and speed.
The first partially reusable orbital spacecraft, the Space Shuttle, was launched by the USA on April 12, 1981. During the Shuttle era, six orbiters were built, all of which have flown in the atmosphere and five of which have flown in space. The Enterprise was used only for approach and landing tests. The first Space Shuttle to fly into space was the Columbia, followed by the Challenger, Discovery, Atlantis, and Endeavour. The Endeavour was built to replace the Challenger when it was lost in January 1986. The Columbia broke up during reentry in February 2003. The Space Shuttle is due to be retired in 2011 due mainly to its old age and high cost of the program reaching over a billion dollars per flight.The Shuttle's human transport role is to be replaced by the partially reusable Crew Exploration Vehicle (CEV) no later than 2014. The Shuttle's heavy cargo transport role is to be replaced by expendable rockets such as the Evolved Expendable Launch Vehicle (EELV) or a Shuttle Derived Launch Vehicle.
Spacecraft are vehicles designed for spaceflight and capable of controlling their trajectory through space. On a sub-orbital spaceflight, a spacecraft enters space then returns to the Earth. For an orbital spaceflight, a spacecraft enters a closed orbit around the planetary body. Spacecraft used for human spaceflight carry people on board as crew or passengers. Spacecraft used for robotic space missions operate either autonomously or telerobotically. Robotic spacecraft that leave the vicinity of the planetary body are space probes. Robotic spacecraft that remain in orbit around the planetary body are artificial satellites. Spacecraft are used for a variety of purposes, including communications, earth observation, meteorology, navigation, planetary exploration and space tourism. The first true spacecraft is sometimes said to be Apollo Lunar Module, since this was the only manned vehicle to have been designed for, and operated only in space; and is notable for its non aerodynamic shape.
A human spaceflight is a spaceflight with a human crew, and possibly passengers. This makes it unlike robotic space probes or remotely-controlled satellites. Human spaceflight is sometimes called manned spaceflight, a term now deprecated by major space agencies in favor of its gender-neutral alternative. At times, astronauts must go outside the spacecraft to perform certain tasks. Working outside a vehicle in space is called extravehicular activity (EVA). As of 2009, human spaceflights are being actively launched by the Soyuz programme conducted by the Russian Federal Space Agency, the Space Shuttle program conducted by NASA, and the Shenzhou program conducted by the China National Space Administration.
A robotic spacecraft is a spacecraft with no humans on board, that is usually under telerobotic control. A robotic spacecraft designed to make scientific research measurements is often called a space probe. Many space missions are more suited to telerobotic rather than crewed operation, due to lower cost and lower risk factors. In addition, some planetary destinations such as Venus or the vicinity of Jupiter are too hostile for human survival, given current technology. Outer planets such as Saturn, Uranus, and Neptune are too distant to reach with current crewed spaceflight technology, so telerobotic probes are the only way to explore them. Many artificial satellites are robotic spacecraft, as are many landers and rovers.