Description: Drag reduction is a fundamental necessity in all aerodynamic designs, as it directly affects aircraft fuel efficiency which in turn affects endurance, range, and flight speed. Skin-friction drag reduction technology has a very significant impact in the future design of all aircraft, propellers, turbine blades, and wind-turbines, just to name few applications. Experimental and Direct Numerical Simulations results provide evidence that spanwise waves, of appropriate frequency and amplitude in the turbulent boundary layer, produce substantial skin-friction drag reduction. The generation and control of the spanwise waves however has been a significant practical barrier to the implementation of this technology, due to the requirement for complex moving parts that are too heavy and expensive to be added to an aircraft wing. In fact their additional weight and complex installation would essentially reduce or negate the benefits of the drag reduction. Lynntech proposes to use a proprietary technology based on Pulsed Plasma actuators, which are light-weight, simple to build, and easy to control, to generate turbulent boundary layer perturbations that induce significant skin-friction drag reduction. The proposed technology can be embedded in the wing, or propeller blade, to be flush with the wall and be electrically powered, thus avoiding additional ducting and other adverse characteristics that make competing skin-friction drag reduction approaches impractical for aeronautical applications. Lynntech's approach could also be exploited for dual use: the plasma actuators, in a different flight regime, could also be used to delay flow separation and thus delay stall onset, without the need to install an additional system. The proposed technology has a very wide outreach because it addresses a fundamental issue in aerodynamics and could be applied equally well to increase efficiency of aircraft within NASA programs, civilian transport aircraft, and military vehicles.

Benefits: NASA conducts a very significant amount of research for atmospheric vehicles: thus technologies that directly address aerodynamic drag reduction are well aligned with the agency needs and goals. Skin-friction drag reduction through plasma actuators allows dramatic increase in fuel efficiency, which translates directly in the ability to fly longer, farther, faster and with reduced carbon emissions. Areas of research in which NASA is particularly active are alternative fuels and Unmanned Aerial Systems (UAS) research. Alternative fuels are being researched primarily to reduce carbon emissions in the atmosphere; improved aerodynamic efficiency would significantly increase the chance of making these alternative fuels viable alternatives, as it would lower the requirements on the engine and fuel systems. Small UAS are typically even more constrained, with respect to payload, due to their limited flight endurance. Reducing skin-friction drag would allow all UAS to fly longer or at reduced cost: long endurance UAS is an active area of research within NASA (e.g. Global Hawk). Improved aerodynamic efficiency does not affect terrestrial vehicles only: future planetary exploration missions could exploit efficient aerial vehicles to explore wider surface areas, faster.

Fuel efficiency for civilian transport aircraft is always of great interest to aircraft manufacturers and operators. Airline profitability depends, to no small extent, on the cost of fuel per mile flown. Reducing aerodynamic drag, through the use of better designs and new materials, is a well established trend. The proposed technology would introduce a revolutionary change in the way transport aircraft wings and bodies are designed, which would result in dramatic reduction in costs for operators. Savings could then be passed on to the general public. The environmental aspect of better fuel economy for transport aircraft is also of increasing importance to both operators and the public. Wind turbine blades are also affected by skin-friction drag; efficiency of the whole wind-power system greatly depends on the aerodynamic efficiency of the blade: wind turbines are halted by the control system every time the efficiency falls below a certain threshold, because the overall economic viability of the turbine is very sensitive to changing wind conditions. The proposed system is well suited for utilization in wind turbine-blades to increase their efficiency, thus increasing clean energy production. Similarly, automotive designs could be improved to realize increased fuel efficiency by using the proposed technology.