I am aware of the operational difference between a ramjet and a scramjet my point was that I had understood that the term ram accelerator covered cannons that operated both in subsonic and supersonic combustion regimes among other things this is what that Discover article you mention described I had never heard the term scram accelerator and the description on the combustion modes page you link doesn t mention it either which makes me leery of considering it a technical term Google turns up a handful of hits for papers that used it but ram accelerator is far more common Please don t take this as an attack it just strikes me as a term that is not in common use among academics discussing this type of device