Keith, Thanks for your reply
My guess at the energy content in an expansion wave was based on the idea that some of the heat energy generated in the shockwave would be given back as pressure energy in the expansion wave, so dynamic plus static should go up slightly. It was only a guess.
I am absolutely sure you can have normal shocks in airflow over M1.0, if the object in the flow is blunt. In fact, turning to energy loss, a pitot intake at supersonic freestream speeds has a huge normal shock across the front of it, hence the rapid change from the P1 to the Lightning, to a pitot with a conical shock body to generate oblique shocks to recover the ram pressure in a more efficient way. The final shock, the air having decelerated a lot, was usually given as a normal shock just at the end of the conical body. Likewise the 2-dimensional wedge shock bodies on, eg, Concorde.
My throwaway line was that you couldn't have oblique shocks at M1.0, which is true exactly at M1.0, and unlikely at just above M1.0 unless you have a very small deflection angle.
I think we are agreed, if no speed is given, the lowest energy loss is at just above M1.0, and the shock is a small normal one. For deceleration from any given supersonic speed to subsonic speed, then a series of oblique shocks is better than one big normal shock.
What is truth, said jesting Pilate, and would not stay for an answer. I had hoped some ace aerodynamicist would have helped out here.
Regards, Dick