Taking mass to low earth orbit (LEO) is the gating item to increased space travel and exploration; Skylon, SpaceX, Blue Origin, and Orbital Sciences are all focused on reducing this cost. It is quite well understood that outside of plans like Mars Direct and Semi-direct, interplanetary and interstellar travel will require other technologies such as novel electric and nuclear drives, but we are simply not at a point where that is an issue yet.[1][2]

[1] https://en.wikipedia.org/wiki/Ion_thruster

[2] https://en.wikipedia.org/wiki/Nuclear_thermal_rocket