Spacecraft

A spacecraft is a vehicle specifically designed to fly and operate in the environment of outer space. These machines serve many vital purposes for humanity. They enable global communications, Earth observation, and meteorology. They also assist with navigation, planetary exploration, and the transportation of humans and cargo. Because most spacecraft lack the power to reach space alone, they require a launch vehicle, also known as a carrier rocket.

Spaceflights are categorized by the path the vehicle takes. In a sub-orbital flight, the vehicle enters space but lacks the energy or velocity to stay there. It eventually returns to the surface. In an orbital spaceflight, the spacecraft enters a closed orbit around the Earth or another celestial body. Spacecraft are also divided by whether they carry living beings. Crewed spacecraft carry people as crew or passengers. Robotic spacecraft operate without humans, using either autonomous systems or telerobotics, which is remote control from Earth.

Robotic spacecraft serve several distinct roles in science. Space probes are robotic craft sent to explore deep space or astronomical bodies. Unlike landers, probes work in open space rather than on planetary surfaces. Artificial satellites are robotic spacecraft that remain in orbit around a planetary body. A special class of these are space telescopes, such as the Hubble Space Telescope. These telescopes observe astronomical objects from space to avoid light pollution and the distortion of radiation caused by Earth's atmosphere.

History shows how quickly our reach into space has grown. The first spacecraft was a German V-2 rocket. It reached an altitude of 189 km in June 1944. On 4 October 1957, the Soviet Union launched Sputnik 1, the first artificial satellite. This launch marked the beginning of the Space Age. Sputnik 1 orbited the Earth every 96.2 minutes and helped scientists measure the density of the upper atmosphere. While Sputnik 1 was the first to orbit, other objects had already reached the Kármán line. This is the 100 km altitude required to be officially counted as a spaceflight.

Human spaceflight reached a major milestone in 1961. The Soviet Union's Vostok 1 carried Yuri Gagarin, the first person to complete a full Earth orbit. Later that year, the United States launched Freedom 7. This was a sub-orbital flight carrying American astronaut Alan Shepard. Since then, many different spacecraft have been developed. The Soviet Union used the Soyuz, which has flown more than 140 crewed missions since 1967. The United States utilized the Apollo, Gemini, and Space Shuttle programs. China's Shenzhou has also been used for crewed missions since 2003.

Modern spacecraft are often categorized by how they return to Earth. Most spacecraft are not recoverable and are lost after their mission. Recoverable spacecraft can be non-winged space capsules or winged spaceplanes. They are also classified as either expendable or reusable. Expendable spacecraft, like the Soyuz, are used only once. Reusable spacecraft, such as the Space Shuttle orbiters or the SpaceX Dragon, can be launched several times. Today, more space agencies are moving toward using reusable technology to save resources.

Spacecraft also play a critical role in maintaining life in orbit. Cargo spacecraft are robotic vehicles designed to carry supplies like food and propellant. These vehicles support space stations such as the International Space Station, Mir, and Tiangong. Automated cargo ships like the Russian Progress and the American SpaceX Dragon 2 provide these essential services. Additionally, communications satellites relay radio signals around the curve of the Earth. By using transponders, they allow for television, telephone, and internet services across vast distances.

Finally, deep space exploration relies on highly specialized robotic probes. The Voyager program provides a famous example of this technology. In 1977, the Voyager 1 and 2 probes were launched to visit the outer planets. They used a rare alignment of Jupiter, Saturn, Uranus, and Neptune to perform gravity assists. This allowed them to move faster using the planets' own gravity. Voyager 1 and 2 have even left the heliosphere, which is the region of space influenced by our Sun. Other probes, like New Horizons, continue to explore the furthest reaches of our Solar System.