liftoff

[Zipporah Schumaker]

the initial ascent of a rocket from its launching pad

[Britney]

The point in the launch of a rocket where it leaves contact with the ground.

[argey]

Liftoff is the moment in which an aircraft, spacecraft or rocket begins its flight by leaving the ground or launch pad. It is the point at which all supporting structures are released and the vehicle starts ascending under its own power.