Oxygen-Independent Pressure Sensitive Paint

Intelligent Optical Systems (IOS) proposes to develop a unique coating that uses fluorescence quenching in an entirely new way to provide high resolution images of the true pressure distribution on surfaces in hypersonic flow. IOS will use unique pigments whose fluorescence depends directly on absolute ambient pressure, not on the partial pressure of oxygen in the flow field, to develop coatings that will allow "legacy" (oxygen-based) visualization equipment to characterize flows in oxygen-free atmospheres. The new pigments will also be completely compatible with temperature indicating materials and binders currently used in temperature-compensated pressure sensitive paints. In Phase I IOS will create two different oxygen-insensitive pressure-sensitive pigment materials, combine them with a suitable binder, and apply the resulting paints to stainless steel test coupons. The fluorescence of these test samples will be measured under varying static pressures of pure nitrogen, and imaged in a low-speed flow environment at varying angles of attack. This will set the stage for Phase II development and delivery of a complete temperature-compensated true ambient pressure sensitive paint system that can be used to characterize flow around structures in hypersonic wind tunnels and other facilities where oxygen-independent pressure mapping is needed.

True ambient pressure sensitive (TAPS) paint will be immediately useful in wind-tunnel based studies of hypersonic flow, where working fluids other than oxygen are often used to achieve Reynolds numbers characteristic of air flow at higher speeds, particularly in the study of real gas aerodynamic effects. TAPS paint will be rapidly adopted by other aerodynamic test facilities where oxygen-independent pressure mapping is needed; for example in the study of combustion-related phenomena (where the partial pressure of oxygen clearly does not depend exclusively on the local ambient pressure). Once the advantages of oxygen-free pressure mapping are demonstrated in these applications, TAPS-based PSPs will rapidly displace the conventional oxygen-sensitive paints currently used in lower speed wind tunnels as well.

One very obvious advantage of TAPS-based PSPs is that they can be used in "water tunnels" for testing hydrodynamic structures. Thus ship designers (including both the U.S. Navy and commercial naval architects) will be able to use the whole-surface image-based pressure mapping techniques hitherto available only to aerospace engineers. A large class of industrial and commercial structures that emit oxygen-reactive species – from tailpipes to smokestacks – that has hitherto been unaddressable by PSPs can be studied using TAPS-based paints. Pressure mapping of other non-aerodynamic structures (e.g., automobiles, trains, buildings) can be accomplished with conventional PSPs, but the increased shelf-life and stability of TAPS-based paints will make them attractive for these applications as well. Finally, the true-pressure-sensitive pigments developed in this project will also be useful in a host of spinoff applications, from "point sensors" (e.g., on the tips of optical fibers) to optical pressure switches.

This is early/mid-stage (TRL 3) — the most realistic path in is NASA SBIR/STTR, which funds small businesses and research institutions to develop technology aligned with NASA's needs (equity-free, phased funding). Check whether a current SBIR/STTR solicitation topic overlaps with this project's technology area, or contact the project directly (above) to ask.

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