Prandtl and Meyer

It would be difficult to create the right mood under the present circumstances, but perhaps by accident another beautiful differential equation will come along again, as it once did when I worked with you. Letter from Meyer to Prandtl, May 5, 1918. Ref. no. GOAR:2647, DLR-Gottingen Archives

On the On-Set of Hypersonics

Almost everyone has their own definition of the term hypersonic. If we were to conduct something like a public opinion poll among those present, and asked everyone to name a Mach number above which the flow of a gas should properly be described as hypersonic there would be a majority of answers round about 5 …