Quote:
Originally Posted by aerospacepilot 
As I am sure you could see, it is MUCH MUCH MUCH more efficient to escape the Earth's gravity by accelerating to escape velocity from a LEO, rather than firing your rockets to fight off the force from Earth/Sun gravity all the way to the planet.
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The idea you are brushing up against but not naming is termed gravity loss. To grasp what it is consider a hovering rocket that generates just enough thrust to cancel its weight. It's belching exhaust but not transferring energy from the fuel/oxidizer to its forward motion. The method to mitigate the loss is through minimizing the time spent firing the rocket in a direction aligned with the gravitational force vector. In an ideal world rockets would always be aligned perpendicular to the graviational field or they would behave like artillery shells, giving impulse instantaneously. There is a limit to the practial amount of thrust that can be developed by a rocket engine as well as the limitations that soft cargo (humans) bring, so the artillery shell approach cannot be used. You will see, however, in the shuttle's trajectory that it climbs vertically for a short bit and then tips over to continue its burn perpendicular to gravity. Launch trajectories are a balance between aerodynamic considerations such as maximum dynamic pressure allowable and gravity loss.