Theodore von Karman

Introduction to Compressible Flow

“We call the speed range just below and just above the sonic speed – Mach number nearly equal to one – the transonic range. Hugh Dryden and I invented the word transonic. We had found that a word was needed to denote the critical speed range of which we were talking. We could not agree whether it should be written with one s or two. Dryden was logical and wanted two s’s. I thought it wasn’t necessary and always to be logical in aeronautics, so I wrote it with one s. I introduced the term in this form in a report to the Air Force. I am not sure whether the general who read it knew what it meant, but his answer contained the word, so it seemed to be officially accepted. I well remember this period (1941) when designers were rather frantic because of the unexpected difficulties of transonic flight. They thought the troubles indicated a failure in aerodynamic theory.” Theodore von Karman at Cornell in lecture, 1953.