FIRSTstage

First stage is the initial segment of a multi-stage system, occupying the lowest position in a vehicle or process. It is designed to perform early tasks and to provide the necessary initial energy or momentum, after which subsequent stages take over.

In rocketry, the first stage is the launch propulsion unit that supplies most thrust during ascent. It typically carries a large portion of the vehicle’s mass, burns propellant, and is jettisoned after burnout to allow the upper stage to continue. In reusable designs, the first stage may separate and return to a landing zone for refurbishment and reuse.

In other contexts, the term denotes the initial phase of a process. Examples include manufacturing pipelines (planning and setup), software deployment pipelines (prebuild and build stages), or onboarding phases in product lifecycles. The concept emphasizes establishing the foundation for later stages and handling early risks or requirements.

Notable uses include Saturn V’s first stage, the S-IC, which relied on multiple large engines to provide the initial velocity, and SpaceX’s Falcon 9 first stage, designed for controlled descent and reuse. These cases illustrate how the first stage balances thrust, mass, and the transition to subsequent stages to enable successful missions.

See also: stage, multistage rocket, stage separation, booster.