Astronaut A person who travels into space to carry out experiments and pilot a spacecraft. In Russia, astronauts are known as cosmonauts; in China they are known as taikonauts.

Booster rocket A rocket attached to a larger rocket to increase its thrust. When its fuel runs out, it detaches from the rocket and parachutes back to Earth, where it can be collected and reused.

Escape velocity The speed (about 40,000 km/h / 25,000 mph) a spacecraft must reach to overcome the pull of Earth’s gravity completely (if travelling to the Moon or other planets).

Gravity assist The use of the relative movement and gravity of a planet to alter the path or speed of a spacecraft—often to accelerate it. The "assist" is provided by the motion of the planet as it pulls on the spacecraft.

International Space Station (ISS) A space station orbiting about 400 kilometres (about 250 miles) above Earth. It is made up of separate modules, inside which are laboratories and living spaces. The first part of the ISS was launched in 1998. Other components have been added on later missions. Solar panels provide the ISS with electricity.

Jettison The deliberate release of an item into space.

Kármán line An imaginary line marking an altitude of 100 kilometres (62 miles) above the Earth’s surface, which is the height required by the international organization Fédération Aéronautique Internationale to count as a space flight.

Lander A spacecraft that descends towards and comes to rest on the surface of another world in the Solar System. To slow its descent and achieve a soft landing, it may use parachutes and/or small landing rockets, which are fired just before impact. Some missions used inflatable airbags to cushion the lander's impact.

Launch vehicle A rocket-propelled vehicle used to carry a payload—for example, a satellite, a space probe or a crew of astronauts aboard a spacecraft—from Earth into space. The launch vehicle delivers the payload either into orbit around Earth, or to another destination in outer space, such as the Moon or the planets. 

Lift-off The moment when a rocket or other spacecraft leaves the ground.

Orbital Manoeuvring System (OMS) Two small engines that were attached to a Space Shuttle orbiter. They were fired in short blasts to steer the orbiter into its correct orbit. When the orbiter returned to Earth, the OMS slowed it down for a safe landing.

Orbiter The winged part of a Space Shuttle where the astronauts travelled. When it returned to Earth, it put down wheels and landed on a runway like an airliner.

Payload bay The area in a spacecraft where cargo, such as satellites, are carried.

Rocket engine An engine that burns fuel, creating a stream of gases that drives the engine in the opposite direction. Spacecraft are normally carried into space by rockets, which function without air.

Rover A vehicle used for exploration on the surface of a moon or planet. Rovers are robotic devices, fitted with cameras and sensors, and operated from Earth.

Satellite An artificial object that orbits the Earth. Satellites are used for many purposes. Common types include Earth observation satellites, communications satellites, navigation satellites, weather satellites and space telescopes. The International Space Station is also a satellite.

Service module A compartment within a spacecraft that contains life-support systems, such as oxygen and heating.

Solar panel A device that converts heat and light from the Sun into electricity.

Space probe An unmanned spacecraft, guided from Earth and used to take photographs and collect data. Some probes have passed close to or landed on the surface of other planets and moons.

Space Shuttle A reusable spacecraft that, from 1981 to 2011, flew into space like a rocket, then glided back to Earth like an aeroplane. At launch, it was attached to a large fuel tank and two boosters. These were cast off once their fuel was used up. Space Shuttles carried satellites into orbit. They also took people up to retrieve or repair satellites or carry out experiments.

Space station An orbiting laboratory launched into space as a satellite. Inside a space station, astronauts carry out experiments to see how people react to staying in space for long periods, and how plants and animals cope with very low gravity.

Spacecraft A vehicle or machine designed to fly in space. Satellites, space stations, rocket-powered launch vehicles and space probes are all types of spacecraft. They are used for a variety of purposes, including planetary and lunar exploration, scientific research, transportation of humans and cargo, communications, observing the Earth, forecasting the weather and navigation.

Spaceflight A flight that goes further than 100 kilometres (62 miles) above the Earth’s surface, the official border with space, is called a spaceflight. Aeroplanes cannot fly in space because their jet engines stop working through lack of oxygen. Spacecraft use rocket engines, which do not rely on oxygen in the air. To completely escape the pull of the Earth’s gravity (as when travelling to the Moon or another planet), they must reach a minimum speed of about 40,000 km/h (25,000 mph). Once beyond the pull of Earth's gravity, the craft’s engines can be turned off. It maintains its speed because there is no air to slow it down.

Spaceplane A vehicle that can fly like both an aeroplane in Earth's atmosphere and a spacecraft in space. Powered by rocket engines, after it is launched into orbit, a spaceplane re-enters the atmosphere and lands as an unpowered glider. It can be re-used many times, rather than just once like many spacecraft. Examples of spaceplanes are the now-retired Space Shuttle and the Boeing X-37.

Spacesuit An outfit that protects an astronaut from the intense heat and cold of space, from radiation and from small, fast-moving meteorites.

Consultant: Chris Oxlade