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What are the g-forces during launch?

A Soyuz launcher gives a maximum of 3.5g of acceleration (however, returning to Earth is more physically demanding, with 5.5g of deceleration). The launch does not gradually build up to 3.5g but it is lumpy and bumpy: as fuel is used up the rocket becomes lighter so acceleration increases; when the fairing or a rocket stage is jettisoned there is a bump and between stages there is a gap when the acceleration drops to less than 1g. The maximum acceleration comes with the third and final stage. As soon as this is jettisoned, acceleration immediately drops to zero and the astronauts feel weightless.