AbstractMany rocky exoplanets are heavier and larger than the Earth and have higher surface gravity. This makes space-flight on these worlds very challenging because the required fuel mass for a given payload is an exponential function of planetary surface gravity, exp(g₀). We find that chemical rockets still allow for escape velocities on Super-Earths up to 10× Earth mass. More massive rocky worlds, if they exist, would require other means to leave the planet, such as nuclear propulsion. This is relevant for space colonization and the search for extraterrestrial intelligence.