AFRL’s Mach 5 plasma channel is a low-density flow channel designed for the study of plasma dynamics and magnetoaerodynamic phenomena (see Figure 2). It consists of a two-dimensional conical nozzle operating at a stagnation temperature of about 280 K, and it relies upon a vacuum system to generate low-density airflows. The research team performed these plasma studies at a stagnation pressure of 370 torr. The engineers fabricated the entire plasma channel from acrylic plastic and assembled it with nylon screws in order to avoid unintentional grounding. The facility includes a test cabin to house a model support and instrumentation probes. The model for this test consisted of a 660 mm long ceramic plate with two copper electrodes embedded in the surface 317 mm apart and three pressure taps mounted on the centerline between the electrodes.¹

Figure 2. Schematic of AFRL’s Mach 5 plasma channel

Figure 3. Model during a test, with a high-voltage

The Boundary Layers and Hypersonics program is focused on developing the knowledge of fluid physics needed to facilitate future revolutionary aerospace vehicle designs. The program strives to characterize, predict, and control high-speed fluid dynamics events, including boundary layer transition; shock/boundary layer and shock/shock interactions; and other airframe propulsion integration phenomena, such as real-gas effects, plasma aerodynamics, magnetohydrodynamics, and high-speed flow heat transfer. This test demonstrated that air diverted by plasma heating could successfully exert force on an aerodynamic surface in a hypersonic environment and, therefore, that the plasma actuator concept is a viable area for further study and development.

Ms. Melissa Withrow (Azimuth Corporation), formerly of the Air Force Research Laboratory’s Air Vehicles Directorate, wrote this article. For more information, visit http://www.afrl.af.mil/techconn_index.asp. Reference document VA-H-06-05.

Reference

¹ Kimmel, R. L., et al. “Effect of Surface Plasma Discharges on Boundary Layers at Mach 5.” AIAA 2004-509, 42nd AIAA Aerospace Sciences Meeting and Exhibit, Jan 04.