Abstract:
For free-stream Mach numbers between 10 and 4, a study is made of the profiles assumed and isentropic waves produced in non-viscous flows by two-dimensional sails, under pure tension and of finite weight. At the higher free-stream Mach numbers, large parts of the compression flow are virtually centred, and even for long sails (e.g. 100 ft chord) at a high Mach number (e.g. 10) and low stress (e.g. 5 tons/in2), the weight of such a membrane need not exceed 1 lb/ft². The analysis is modified to include the effects of skin friction and is then extended to singly-curved 'caret' sails, which allow leading edges to be swept but can still produce two-dimensional waves; while their curvature imparts to such sails a stiffness-due-to-shape, it is shown that equilibrium can alternatively be maintained by appropriately applied tensile forces. Rectangular and/or caret sails may find applications as wings, intakes, cowls and nozzles for hypersonic vehicles.
