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Propulsion

The systems a spacecraft or rocket uses to change its velocity - both the engines that reach orbit and the thrusters that manoeuvre once there.

Why it matters

In orbit, propulsion is a budget rather than a capability: every manoeuvre spends propellant that cannot be replaced, so a satellite's usable life is usually set by how much it carries, not by whether its electronics still work. That single fact drives station-keeping strategy, orbit-raising choices, end-of-life disposal, and the growing interest in refuelling. Chemical propulsion is powerful and fast; electric propulsion is far more efficient but takes months to do the same job.

In our data

Propulsion decides how our own manifest should be read. The 23 missions logged as geostationary transfer orbit do not end there - each satellite raises itself the rest of the way on its own propulsion, spending months of manoeuvring that never appears as a separate line in any launch schedule.

Where we use it

Not to be confused with

Thrust, which is a single quantity describing force, and power, which electric systems need in quantity but which produces no motion by itself.