Friction-Sensing Retroreflector Array Patches (FRAP)

Research Support Instruments, Inc. (RSI) proposes to develop the Friction-Sensing Retroreflector Array Patches (FRAP), a technology that will measure the shear stress distribution on aerodynamic surfaces in ground test facilities with high resolution, sensitivity, and bandwidth. Unlike the oil-film interference method, FRAP patches will not be thinned as a function of time during a test. No knowledge of the streamlines of the flow will be needed in order to calculate the local stress distribution; this will avoid the tracers needed with the oil-film interference approach. Flexible patches of FRAP arrays, inexpensive due to simple, mass-production-compatible microfabrication techniques, will be interrogated using a light source and camera. FRAP will be independent of the flow species and applied as a very thin, flexible, adhesive material. The Phase I goals will be to design sensors, develop a microfabrication technique and use it to fabricate prototype units, demonstrate feasibility, and select the most promising design for Phase II development. In Phase II, the prototype units will be field-demonstrated at NASA facilities, with manufacturing issues and realistic operating conditions addressed. The result will be a product that will address a critical NASA instrumentation need.