Has anyone built the ram jet propulsion drive yet?

Answer 1

Yes, both American and Japanese scientists have flown prototype scramjets (I assume that's what you meant). If you really meant ramjets, those have been around for decades; the Boeing Bomarc missile used two ramjets as its primary propulsion source, after a boost on a rocket first stage. The Bomarc was deployed in the late 1950s.

Answer 2

Hi. Ram jets were used on the SR-71 many years ago. (Actually they were turbo ram jets so they could fly at lower speeds.) SCRAM jets (Super-sonic Combustion RAM) are being tested now.