AJAX Concept‎ > ‎

Plasma control of aerodynamics

For realization of the aerocruise by hypersonic vehicle it is necessary to ensure the value of the aerodynamic quality (lift/drag ratio) K > 5. There is a need for practical implementation of the ideas that could help to optimize the flow-over hypersonic vehicle in order to enhance aerodynamic efficiency. Energy impact on the flow is to be used as the basis for creation of streamlining control systems (SCS). The functions of SCS should include:

  • drag reduction of aerodynamic elements of the vehicle; 
  • aerodynamic quality augmentation 
  • thermal loads reduction and aerodynamic characteristics of hypersonic vehicle control

To reduce or destroy a shock-wave front, the energy methods of streamlining control can use thermal effects arising from energy deposition into the air flow. It is also possible to create artificial plasma formations near the surface in order to change aerodynamic performance of hypersonic vehicle using plasma effects associated with non-linearity of characteristics of shock-waves propagation in plasma.

Artificially created spatial non-uniformities (in this case the irregularity during flow passage in the space near aerodynamic component is formed under the influence of specially created plasma sheath) have significant impact on the propagation and structure of the shock-waves. Preliminary assessments and experiments on the small wind tunnels bring us to the conclusion that impact of such irregularities has no significant dependence on the spatial dimensions of the impact domain, making it safe to assume that the proposed mechanism would be functional in a wide enough (in relation to low temperature plasma) range of pressures – from a few to hundreds of Torr. At the same time an important role in the shock wave passage through artificial plasma formation play the dispersive properties of low temperature gas-discharge plasma. Some useful for us results were obtained by the Russian and American researchers. Estimates show that at certain critical values of plasma parameters the shock wave changes its shape and its shock front begins to “blur” causing drag decrease of the aerodynamic component (or hypersonic vehicle as a whole) creating this shock wave.

Development of a system of controlling the aerodynamic characteristics is based on the following results:

  1. A physical model of the method has been developed of decreasing the drag of a hypersonic vehicle at the expense of the thermodynamic heating of the gas in front of the shock wave.
  2. The mechanism of such heating was proposed at the expense of direct-current discharge created in front of the streamlined body.
  3. Research of such a discharge have been undertaken which showed that it possesses a number of features that distinguish it from a dc discharge with dielectric walls. These features should be taken into consideration when designing real devices for flow ionization in front of hypersonic vehicle.
  4. The model of ionizer of hypersonic air flow has been developed that can be used when creating real device of flow ionization.
  5. Using this model we have measured the impact of the plasma presence upon the drag of the model object. The experimental results for static pressures corresponding to heights of about 40 km have shown the correctness of the main provisions of the developed technique. 22 ± 1 % of the drag reduction has been obtained at the power input ≈ 4 – 5 W/cm3 to the discharge.