Acceleration at liftoff is lower than maximum acceleration during the rest of the launch. Most of the mass in a rocket is fuel. As the fuel is burned off, the

Acceleration at liftoff is lower than maximum acceleration during the rest of the launch. Most of the mass in a rocket is fuel. As the fuel is burned off, the same amount of thrust gets divided over a progressively lower remaining mass. The Shuttle stack has a mass of 2.03 million kg at launch, and delivers 30.45 MN of thrust. That's 15.0 m/s² of acceleration, or 1.53 g's. (Because it's thrusting vertically, though, it only accelerates upward at 0.53 g's.) This is much lower than the maximum acceleration attained later in flight.