AN UNCOOLED, RAPID RESPONSE PROBE FOR MEASURING STAGNATION PRESSURES IN HIGH VELOCITY ARC PLASMA.
Interim technical rept. for Mar 63-Apr 64,
GENERAL ELECTRIC CO PHILADELPHIA PA MISSILE AND SPACE DIV
Pagination or Media Count:
A means for measuring stagnation pressures in high temperature, high current plasmas is described. The device employs a small .060 in. o.d. uncooled pitot tube designed for minimum response time .001 sec. which is rapidly swept through the plasma flow field .015 sec.. A simple technique for evaluating the transient response of the probe is described. Because the probe tip is inexpensive and expendable, a moderate amount of molten phase ablation is tolerable in the stagnation zone. Consequently, it appears possible to obtain meaningful results at heat flux rates exceeding 10,000 calsq. cm -sec., which is one to two orders of magnitude greater than have thus far been tolerable with water-cooled probes. In preliminary tests a single probe was successfully employed for eight successive measurements of total pressure in an atmospheric pressure, air-arc plasma at currents ranging from 200 to 1000 amperes at Mach numbers close to unity. Heat flux rates encountered are estimated to be in the vicinity of 2000-3000 cal sq.cm sec. The principle merits of the probe described are its small size, rapid response and its inexpensive, expendable probe tip.