Accession Number : AD0718976

Title :   Alleviation of the Plasma Boundary Layer by Chemical Injection,

Corporate Author : MASSACHUSETTS INST OF TECH CAMBRIDGE AEROPHYSICS LAB

Personal Author(s) : Haldeman,Charles W. ; McGuirk,James P.

Report Date : DEC 1970

Pagination or Media Count : 82

Abstract : Work performed on the transmission and radiation characteristics of antennas on the surface of a plasma-covered wind tunnel model is reported. The model used is a blunted cone-cylinder operated in a supersonic wind tunnel at M = 4, To = 80 to 100 F and P(o) = 1.2 to 3 psi. The plasma sheath was obtained by injecting nitrogen plasma from a DC arc jet located in the model nose. A new chemical injection system was used to inject a number of halogenated hydrocarbons into the plasma layer. It was found that nearly complete restoration of free space antenna impedance and transmitted power could be achieved from 25 mw S-Band signals at 50 percent or less additive mass fraction. Data from electrostatic probes is presented which indicates that the mechanism of alleviation is electron attachment to form heavy negative species. Teflon and carbon phenolic ablative plasmas were also studied and the effects of these ablative materials on the plasma sheath are presented. The effect of ultrasonic energy on small fluid jets was also studied, as was the penetration of these jets into the wind stream. (Author)

Descriptors :   (*BLACKOUT(PROPAGATION), INHIBITION), (*SLOT ANTENNAS, *PLASMA SHEATHS), REENTRY VEHICLES, INJECTION, HALOGENATED HYDROCARBONS, MICROWAVE COMMUNICATIONS, HALOGENS, ABLATION, ELECTRICAL IMPEDANCE, TEST METHODS, WIND TUNNELS

Subject Categories : Electrical and Electronic Equipment
      Radiofrequency Wave Propagation

Distribution Statement : APPROVED FOR PUBLIC RELEASE