INTERACTION OF SOLID-ROCKET EXHAUST WITH THE ATMOSPHERE

Photometrically calibrated, ground-based, wide-band images were recent ly obtained for the exhaust trail of an aluminized solid-rocket motor of 10,000-kgf thrust operating and smoldering near 110 km. These obser vations were made in the visible and near infrared using an intensifie d video camera mounted on the acquisition telescope of the 1.6-m teles cope at the U.S. Air Force Maul Optical Site. The burn-associated lumi nous volume expands within a few frames to about 1 km transverse to th e trajectory, with most of the emission occurring near its stationary edges. Its initial lifetime, determined from individual as well as seq uential images, is 13 +/- 3 s. This spatial distribution and persisten ce show that the emission is not due to thermal radiation from or cata lyzed by micrometer-scale Al2O3 exhaust particles. Assuming that the c hemiluminescence is due to the reaction of ambient atomic oxygen with the combustion products of the exhaust, the data lead to a depletion-r ate coefficient of about 10(-12) cm(3) molecule(-1) s(-1). We suggest that a key step in producing the emission is due to Al-containing comp lexes reacting exothermally with O atoms in the upper atmosphere. The visible-light-emitting species is likely to be an electronically excit ed state of AlO2 or AlO. Analysis of the hydrodynamic development of t he radiating volumes leads to their scaling to other solid-rocket thru sts and altitudes.