I remember reading (a long time ago in a library far, far away...) that, if Earth's gravity were that much stronger, the rocket equation (?) would mean that it were impossible to actually reach orbit from the surface given contemporary (chemical) propulsion.
I cannot for the life of me remember where I read it, or the exact numbers.
This came up again recently in a discussion on worldbuilding.SE. Can anyone give me a rough estimate of how strong a gravitational field could no longer be "escaped" to orbit given chemical propellants, making space exploration effectively impossible for the theoretical inhabitants of such a stellar body?