An apparatus in {TAIL ~ accordance} 6 wherein said supply means comprises an annular chamber surrounding said evacuation chamber, means for supplying said drive medium to said annular chamber under pressure and a ring nozzle means for feeding the drive medium from said annular chamber to {HEAD ~ said evacuation chamber} at a supersonic speed 
An apparatus in { TAIL ~ accordance } 6 wherein said supply means comprises an annular chamber surrounding said evacuation chamber , means for supplying said drive medium to said annular chamber under pressure and a ring nozzle means for feeding the drive medium from said annular chamber to { HEAD ~ said evacuation chamber } at a supersonic speed
OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH