Anything built to operate in space is a spacecraft. That covers satellites, probes, crewed capsules, space stations, and landers. Some stay in orbit for decades. Others operate for hours before burning up or landing.

Every spacecraft balances the same trade-offs. Mass limits what can be carried. Power determines what instruments can run. Thermal control keeps components within operating temperatures as the vehicle moves between sunlight and shadow.

Common subsystems

• Structure and thermal protection
• Power generation and storage
• Guidance, navigation, and control
• Communication and data handling
• Propulsion for manoeuvres

Redundancy runs through every design. A spacecraft cannot be repaired by a technician on site, so critical systems are duplicated and often triplicated. Engineers assume something will fail and build around that expectation.