Quote Originally Posted by AgentPaper View Post
To stay efficient, make sure you throttle down your main engine after you're off the launchpad, aiming for 100 m/s speed and low but still positive acceleration.
I usually set my limit at 200 m/s, not 100...if you're going too slowly you burn a lot of fuel just maintaining speed through the lower atmosphere, if you go too fast then air drag losses become significant; I find 200 is a nice sweet spot between the two.