Uncrewed spacecraft

Uncrewed spacecraft, also called robotic spacecraft, are vehicles that travel through space without any people on board. They can be controlled from far away, follow pre-programmed instructions, or make decisions on their own. These spacecraft are used for many missions that are too dangerous, far away, or expensive for humans to handle directly.

Some places in space, like the planet Venus or faraway worlds such as Saturn, Uranus, and Neptune, are too harsh or distant for humans to reach with today’s technology. Uncrewed spacecraft let scientists study these places safely and without putting people at risk.

The very first uncrewed mission was Sputnik, launched on October 4, 1957, which became the first human-made object to orbit Earth. Most satellites, landers, and rovers we use today are robotic. Even though many spacecraft meant for humans have robotic parts, true uncrewed spacecraft carry no people at all—though sometimes they might carry other animals on research missions.

History

The first robotic spacecraft was launched by the Soviet Union on 22 July 1951, carrying two dogs on a suborbital flight. The first artificial satellite, Sputnik 1, was launched by the USSR on 4 October 1957, followed by Sputnik 2 which carried the dog Laika.

The United States launched its first satellite, Explorer 1, on 31 January 1958. This began a competition between the US and the USSR to send increasingly advanced probes. Missions studied planets like Venus and Mars, and gathered important information about the Moon. The first interstellar probe, Voyager 1, was launched in 1977 and entered interstellar space in 2012, followed by Voyager 2 in 2018.

Design

In spacecraft design, the United States Air Force considers a vehicle to consist of the mission payload and the bus (or platform). The bus provides the structure, power, and control systems needed for the spacecraft to operate.

Key parts of a spacecraft include its structure, which supports all components, and systems for handling data, controlling its orientation, and communicating with Earth. Spacecraft also need ways to land safely, generate power—often using solar cells or special generators—and protect themselves from extreme temperatures and small space particles. Propulsion systems, like rocket engines, help the spacecraft move through space. Some systems use special fuels, while others use electric fields to push the spacecraft forward, though these can be very slow.

Robotic vs. uncrewed spacecraft

Robotic spacecraft are built for specific harsh environments, and their complexity and abilities can vary a lot. An uncrewed spacecraft, on the other hand, is any spacecraft that operates without people on board, either by itself or by remote control from Earth. Not all uncrewed spacecraft are robotic.

Robotic spacecraft send data and status updates back to Earth using telemetry. Early spacecraft like Sputnik 1 and Explorer 1 did not receive commands from Earth. Later, systems were added to allow remote control. As probes travel farther from Earth, they need more autonomy to make decisions on their own, especially when the time it takes for signals to travel is too long. Spacecraft like Cassini–Huygens and the Mars Exploration Rovers can operate independently for long periods using their own computers.

Space probes

Main article: Space probe

Further information: List of Solar System probes

A space probe is a robotic spacecraft that explores space beyond Earth. These probes carry scientific instruments to study the Moon, planets, and even areas far from our solar system. They send the information they collect back to Earth for scientists to study. Some probes can also collect samples from other worlds and bring them back to Earth for further analysis. To travel to other planets, probes often use paths around the Sun, with some using tricks like flying by planets to save fuel and travel faster.

Space telescopes

Main article: Space telescope

Further information: List of space telescopes

A space telescope or space observatory is a telescope that orbits Earth to study stars, planets, and other objects in space. Unlike telescopes on Earth, space telescopes are not affected by Earth’s atmosphere or light pollution, giving them clearer and more detailed views. There are two main types of space telescopes: those that scan large areas of the sky and those that focus on specific objects or areas for closer study.

Cargo spacecraft

Further information: Comparison of space station cargo vehicles

Cargo or resupply spacecraft are robotic vehicles that carry supplies like food, fuel, and equipment to space stations where people live. They are different from space probes, which are mainly used for scientific exploration.

Automated cargo spacecraft have been helping space stations since 1978. They have supported missions to stations like Salyut 6, Salyut 7, Mir, the International Space Station (ISS), and the Tiangong space station. Today, the ISS uses several types of cargo spacecraft, including the Japanese HTV-X, the Russian Progress, the American Cargo Dragon 2, and Cygnus. The European Automated Transfer Vehicle was used from 2008 to 2015. China’s Tiangong space station is supplied only by the Tianzhou.