Answered by Zoe Baily of the National Space Centre
The g-force of a rocket launch is limited by the cargo it is carrying. In the case of a manned mission, it is limited by what a human is able to endure.High levels of g-force can damage the body and at around 9gs most humans black out as blood struggles to reach the brain. Astronauts normally experience a maximum g-force of around 3gs during a rocket launch. This is equivalent to three times the force of gravity humans are normally exposed to when on Earth but is survivable for the passengers. Astronauts are trained in high g-force, wear g-suits and must be correctly prepared.