Author: James M. Cubbage

Publisher:

Published: 1965

Total Pages: 66

ISBN-13:

A limited experimental investigation has been conducted to confirm the existence of exhaust backflow from a cluster of three widely spaced nozzles operating in a near-space environment and to determine pressure and heat- transfer coefficients in the region washed by the backflow. Experiments were conducted in a 61-foot-diameter vacuum sphere using a sine solid-propellant rocket motor and a reflection plate. The reflection plate was used to simulate the interference planes that would normally exist for a cluster of three nozzles. Data were obtained for nozzle spacings of 8.02 and 17.05 nozzle exit diameters for pressures which simulated a nominal altitude range of 3.2 x 109(exp 5) to 1.8 x 10(exp 5) feet. The pressure data indicated that the backflow was super- sonic for several nozzle exit diameters ahead (upstream) of the nozzle exit plane and that the flow over small-diameter thermocouples in this region was in the free-molecule region. Average heat-transfer coefficients obtained for small-diameter cylinders (thermocouples) in this region were on the order of 1 x 10(exp -4) Btu/sq ft-sec-degrees R.