A lucky discovery of a Kerbal engineer's writing gave this deep insight into the mechanics of climbing to orbit:
the best way to minimize d/v losses through the atmosphere is to always go at exactly the terminal velocity at any given altitude (because this is the point of intersection between the graphs of drag losses vs gravity losses).
I had always found the mathematics of the gravity turn to be daunting. This would really toss a lot of that detail away, allowing many quick and useful back-of-the-envelope calculations.
But why should I believe it? Maybe it's just a Kerbal old wives tale. Is there any real theoretical model that suggests something like this?
Furthermore, it's not clear what terminal velocity should be used anyway. The mass of the rocket is changing throughout the climb, and with mass, the terminal velocity changes. Would this rule use the dynamic mass value, or the final mass, or next mass before staging, or something else?