Rocket staging

Rocket staging is the planned sequence in which a launch vehicle ignites, separates, and discards its stages. It sheds empty tanks and engines so later stages accelerate a smaller mass.

Multistage rocket: A launch vehicle made of two or more rocket stages that operate in sequence. Rocket staging is the sequence of events that makes a multistage vehicle work.
Tsiolkovsky rocket equation: An equation relating a rocket’s change in velocity to exhaust velocity and the ratio of initial to final mass. It shows why discarding empty stages improves the mass ratio for later flight.
Saturn V: The three-stage American launch vehicle that sent Apollo astronauts toward the Moon. Its three powered stages illustrate a classic sequential ascent design.
Single-stage-to-orbit: A vehicle architecture intended to reach orbit without dropping propulsion stages during ascent. It avoids stage disposal but must overcome demanding mass and performance constraints.
Stage separation: The release of one rocket stage from another during flight. Separation removes spent hardware before the next stage must accelerate the vehicle.
Mass ratio: The ratio of a vehicle’s initial mass to its final mass after propellant is consumed. A spent stage increases the mass that later stages would otherwise have to carry.
Falcon 9: A two-stage orbital launch vehicle developed and operated by SpaceX. Its stage separation is followed by first-stage recovery attempts on many flights.
Reusable launch system: A launch system designed to recover and use some or all of its hardware again. Recovery changes the purpose of separation: hardware is discarded from the upper vehicle but not necessarily lost.
Ignition sequence: The ordered start-up of engines and systems during a launch or flight. Staging coordinates engine shutdown and restart so thrust continues across stage transitions.
Specific impulse: A measure of rocket-engine efficiency based on thrust produced per unit weight flow of propellant. Engine efficiency affects how much velocity each stage can provide with its propellant.

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