spacecraft

A spacecraft is a vehicle designed for travel or operation beyond Earth's atmosphere. It can carry crew, instruments, or both, and may perform autonomous tasks. Spacecraft encompass crewed systems such as capsules and space stations, as well as unmanned vehicles including orbiters, landers, rovers, flyby probes, and sample-return craft. Some spacecraft serve as platforms for experiments or observations, such as space telescopes or remote sensing instruments mounted on orbiting bodies.

Core subsystems common to most spacecraft include a structural framework, propulsion and power systems, avionics and software, attitude determination and control, thermal management, life support for crewed missions, and communications. Payloads vary by mission and may consist of scientific instruments, cameras, communication relays, or hyperspectral sensors. The design emphasis balances safety, reliability, mass, and power efficiency, with redundancy for critical functions.

Propulsion and power are central considerations. Chemical rockets provide high thrust for launches and major trajectory maneuvers, while electric propulsion technologies offer higher specific impulse for in-space propulsion. Alternative concepts such as solar sails and, in development, nuclear propulsion explore different trade-offs between thrust, efficiency, and mission duration. Power typically derives from solar panels or, for some missions, radioisotope power sources.

Operations usually begin with launch aboard a rocket, followed by orbital insertion or translunar/transmart approach. Mission phases include ascent, cruise, operational activities, and end-of-life disposal or reentry. Ground control monitors performance and commands, with autonomous onboard systems handling routine tasks.

Spacecraft enable scientific discovery, telecommunications, weather monitoring, and global navigation. Advances in miniaturization, reliability, and, increasingly, reusability have broadened access to space and expanded mission capabilities.