How fast does a NASA rocket launch?

A rocket doesn't shoot off instantly. On the pad, engine thrust barely exceeds the weight of the loaded vehicle, so initial acceleration is small. The Saturn V, weighing about 2,900 t at ignition, took about 12 seconds to clear the height of its umbilical tower, at a speed comparable to a car in city traffic. This apparent slowness is deliberate: accelerating faster would require larger engines and a heavier structure, and the dense atmosphere of the first few kilometers punishes any excess speed.

As it burns propellant, the rocket gets lighter and accelerates more and more. Between 60 and 90 seconds after liftoff, NASA's launch vehicles exceed the speed of sound and pass through the point of maximum dynamic pressure, called max Q, where the combination of speed and air density subjects the structure to its greatest aerodynamic load. Many vehicles briefly reduce thrust during this phase to protect the airframe; the space shuttle did so routinely.

Once outside the dense atmosphere, the growth in speed is dizzying. The Saturn V's first stage separated at about 2.7 km/s, and the following stages carried the spacecraft to the 7.8 km/s of low Earth orbit, about 28,000 km/h. Artemis's SLS follows a similar profile: the solid boosters release at two minutes and the core stage shuts down at eight, with the Orion spacecraft already at orbital velocity. Escaping Earth toward the Moon requires an additional burn that raises the figure to about 39,000 km/h.