staged rocket

Launch vehicle driven by several rocket systems mounted in vertical sequence.

The lowest, or first, stage ignites and lifts the vehicle (sometimes assisted by attached booster rockets) at increasing speed until its propellants have been used up. The first stage then drops off, which makes the vehicle lighter, and the second stage ignites and accelerates the vehicle further. The use of additional stages generally follows the same pattern until the payload

the spacecraft

has reached the velocity needed to achieve orbit or leave the vicinity of Earth. The number of stages required depends on the details of the mission, the launch vehicle's characteristics, and other factors. Some early vehicles needed five stages to reach orbit; most current launch vehicles need only two.

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▪ space vehicle

      vehicle driven by several rocket systems mounted in vertical sequence. The lowest, or first stage, ignites and then lifts the vehicle at increasing velocity until exhaustion of its propellants. At that point the first stage drops off, lightening the vehicle, and the second stage ignites and accelerates the vehicle further. Most space launch vehicles (launch vehicle) have three stages. See also launch vehicle.

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