I was reading about wave drag and Concorde recently and found some contradictory information relating to drag. For example Wikipedia says:
Afterburner was added to Concorde for take-off to cope with weight increases that came after the initial design, and was used to push through the transonic drag barrier.
And they add the following image (it's sad that they don't mention what kind of aircraft it relates to):
But this image (from this article) suggest that aircraft with swept wings don't experience this sudden drag at transonic speeds, only later. Concorde has swept wings so it should experience max drag coefficient near mach 2 but it didn't have to use afterburners at this speed. How can it be? Were afterburners in Concorde necessary to break sound barrier, or only used for climbing?
Maybe someone knows some specific drag parameters at different speeds and would care to share, as I could't find anything specific...