Spacecraft Definition – What is a Spacecraft?

Spacecraft are vehicles designed to travel beyond Earth’s atmosphere and explore space, such as other planets or orbits, before returning home again. Spacecraft may be either manned or unmanned. Propulsion usually comes in the form of rocket engines which use hot gases ejected out in opposite directions to change their trajectory.


Spacecraft refers to any vehicle designed for travel beyond Earth’s atmosphere, such as satellites in orbit or robots sent out to other planets – as well as vehicles carrying human astronauts into space.

Spacecraft are comprised of several engineering subsystems that need to operate together: structure, attitude determination and control, onboard data handling, communications, power supply, thermal control and propulsion. Their designs must withstand forces imparted during launch as well as any potential planetary landing operations.

Spacecraft may be either unmanned or crewed and carry any number of payloads ranging from scientific instruments (cameras, telescopes and particle detectors) to cargo or people. Unmanned spacecraft do not need life support systems while crewed ones must provide pressurized environments and protection from radiation.


There is a variety of spacecraft, each one classified according to its function and characteristics. For instance, they could be powered by nuclear engines or solar panel arrays and must also collect information from different environments and transmit it back home.

Space telescopes are an important subclass of spacecraft. By employing satellites for observation purposes, space telescopes allow astronomers to gain a clearer perspective without suffering through filtering and distortion associated with terrestrial observatories.

All spacecraft require a power subsystem to produce and distribute energy to all other systems, as well as an attitude control subsystem that enables them to orient themselves in space, respond to external forces and torques and respond appropriately. Furthermore, navigation subsystems calculate commands for their control systems.


Spacecraft are equipped with various functions such as attitude determination and control, onboard data handling, communication, power supply, thermal management and propulsion that work together to produce their desired performance. Each function can be broken down into subsystems that work in concert to achieve that end goal.

Attitude determination and control subsystems ensure a spacecraft remains properly oriented in space for science pointing, sun tracking for solar array operation, communications aiming, as well as controlling any moving parts on board the spacecraft. In addition, this system controls its articulation mechanisms.

Earth observation satellites equipped with various types of sensors collect detailed, multifaceted information about our planet’s oceans and ice, land, biosphere, atmosphere, weather and climate. Micrometeorroid protection uses ablative shields to slow free-fall during atmospheric entry while communications spacecraft use transmitters and receivers to relay messages sent from Earth back out into space again.


Materials used on spacecraft must be both durable and lightweight for use on launch and reentry missions, to help ease launch forces as well as reduce fuel use or propellant requirements. Aluminum composite materials tend to be lightweight yet strong.

Orbiting satellites require propulsion systems and communication equipment, in addition to onboard control systems and propulsion mechanisms for movement, to alter their position within space. Each component must be tested individually and together before being placed into orbit – and its materials must also withstand the pressures and hazards of space such as impacts and corrosion.


As spaceflight costs have reduced, more missions to explore and broaden our knowledge of space have come forth. However, these endeavors require substantial amounts of money in order to launch successfully.

Since NASA retired its space shuttle fleet in 2011, they have relied heavily on Russia’s reliable Soyuz rockets – at approximately $1.5 billion each launch for low Earth orbit, this amounts to over $8000 per kilogram of payload heading toward space station destination.

Boeing and other large aerospace contractors are trying to reduce these costs with the use of reusable rockets, but this takes time and commitment from governments. Meanwhile, companies like SpaceX offer launches at significantly reduced prices: for example the partially reusable Falcon 9 costs less than $73 million per flight.

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