Doing my undergrad thesis on a ramjet and am confused about scramjets. A ramjet's diffuser slows down supersonic inlet flow to low subsonic to allow combustion. But a scramjet's diffuser first slows the flow down, then speeds it back up in the "diverging" section for supersonic combustion. Why would you slow the flow down only to speed it back up? Wouldn't this result in more total pressure loss (thus efficiency) than if you just slowed the flow down slightly?