Drag Coefficient Mach Divergence

[SanderB]

I know that drag generally is something like [Drag Coefficient * Density * Velocity ^ 2]. However, with the new aerodynamics things are looking a little different and there is this debug menu that shows graphs concerning drag profiles. What do all the numbers mean? What is on the x and y axis' of both graphs? What does everything mean? How do I calculate exactly or at least roughly what forces KSP applies at any given altitude/speed/craftorientation?

My craft, going at 303.3m/s at 2000m altitude experiences 2Gs of drag, a few moments later at the same altitude it experiences 1G at 253m/s. At both points the craft had no fuel and its mass was constant nor were any engines producing any thrust. The velocity ^ 2 proportion seems not to be everything there is to KSP drag anymore and I'd like to understand it.

[cybersol]

Some more systematic observations from a reddit poster:

I was a little surprised that the higher drag region is actually wider than it "feels" with rapiers. Their increasing thrust curve hides some of the drag effects as you speed up.

For how its implemented, you likely don't want to know, but check out Overhaul's for 1.0 sticky if you want to know more.

Edited May 21, 2015 by cybersol

[Tank Buddy]

IRL and in KSP now, drag increases until you go trans-sonic. There you hit a drag "barrier" that jets IRL usually have to use afterburner to get through. (There is a dramatic increase in drag when approaching the sound barrier) After passing through the trans-sonic zone, drag tapers off.

Edited May 21, 2015 by Tank Buddy

[cybersol]

drag tapers off but never returns to pre-Mach 1 levels.

You might want to look at the chart I posted above...

[SanderB]

I've been experimenting with it using the RMB aero display option and made this scatter plot of velocity vs the displayed drag coefficient of my nose fairing:

The dots that don't neatly follow the apparant curve are similar speeds at very different altitudes. the Cd is what the game displays on the frontal fairing of the same vessel displayed in my original post. It will seem that Cd spikes at around Mach 1, then tapers off to where it used to be.

Edited May 22, 2015 by SanderB

[NathanKell]

Speed of sound changes with altitude, that's why it doesn't fit.