Hypersonic Wake Structure Observed with Electrostatic Probes
MASSACHUSETTS INST OF TECH LEXINGTON LINCOLN LAB
Pagination or Media Count:
Wakes of 9.5-mm diameter non-ablating spheres fired at speeds of about 5.5 kmsec into air and into N2 at a pressure of 40 Torr have been observed with electrostatic probes. Ionization is observed, immediately after passage of the pellet, over a region approximately 4 cm in diameter. After 0.1 msec 60 body diameters downstream, the ionized region grows at a rate in agreement with schlieren observations of turbulent wakes. Somewhat after 1 msec, the electron concentration in a 5-cm diameter core dips precipitously, followed by large subsequent fluctuations for N2 but staying very small for air. Regions of the wake at greater radial distances continue to contain electrons and to grow, and experience the precipitous dip further downstream. No corresponding sudden reduction in positive ion concentration is observed, implying that the electron loss is by attachment. The data are not yet sufficient to describe the structure of the electron-deficient core.
- Atmospheric Physics