The rocket equation states that the amount of fuel that you need (to send a given payload into orbit) increases exponentially with the escape velocity of the pl

The rocket equation states that the amount of fuel that you need (to send a given payload into orbit) increases exponentially with the escape velocity of the planet: mass of the rocket with fuel = mass of the payload * exp(escape velocity / engine exaust velocity) That is because the faster you need to go, the more fuel you need to use, but now, you also need even more fuel to accelerate the fuel that you just added. So, it becomes exponential. So, if the earth was bigger, its escape velocity would increase, and the amount of fuel needed to power a space rocket would increase (exponentially) so much that it would become unpractical. Vice versa, with a smaller planet it would require exponentially less fuel to reach orbit. The only solution would be to have an engine with a higher exaust velocity. With the current technology, ion engines have very high exaust velocity but low thrust are very energy hungry. The thermal nuclear engines have both high exaust velocity and high thrust, working prototypes have been built, but all projects were boxed 60 years ago because of the fear of an accident.