So I went to the link in a recent question and discovered SpaceX turns its first stage around while it is going, what, several km/s in the upper atmosphere, restarts 3 of the engines and fires retrograde to slow the stage down and get it heading back towards the launchpad. Aside from suddenly realizing I had absolutely failed to appreciate the distances involved in this maneuver, I had a real 'Wait, what?' moment when thinking about turning around a mostly hollow tube at those speeds in even a thin atmosphere, aiming it precisely retrograde, and keeping it aimed that way as it slows down without losing control.
That sounds stupendously difficult. Is it? How do they manage it? (The link is to a good article in Aviation Week about the data NASA collected from the September CRS-4 launch during the retrograde burn, which the hope to use for design of propulsive deceleration on Mars.)