Thanks! It makes sense to me and I always used to follow the previous "rules" of aiming for specific speeds at specific altitudes on the way as seen here: http://wiki.kerbalspaceprogram.com/wiki/Atmosphere#Terminal_velocity Just as an experiment, I put a 3 part rocket together. Mk1 pod + big orange tank + mainsail. I launched it straight at full throttle with SAS on, no gravity turn and reached an AP of 16,400,000m with Mach effects, flames and everything. Basically, everything they say not to do. If I use the same rocket but throttle down when the mach effects start and then gradually throttle back up enough to keep mach effects at bay, I only reach an AP of 6,300,000m. Perhaps I'm missing the point entirely, but it seems the old "terminal velocity" rule with regards to speed no longer exists. It's full throttle all the way and the only logical reason to back off is to keep your lumpy rocket stable through the dense 5k-15k altitudes and permit early gravity turns. Right now it almost seems cheaper on fuel to just blast through to 20k as quickly as possible and then start turning than it does to gravity turning early (and have to slow down). This is just based on some pretty rudimentary tests but flames with regards to fuel economy appear to be a good thing. I don't quite understand.