EFFECT OF FLIGHT AND MOTOR OPERATING CONDITIONS ON INFRARED SIGNATURE PREDICTIONS OF ROCKET EXHAUST PLUMES

A computationally efficient methodology based on computational fluid dynamics (CFD) has been developed to predict the flow field and infrared signatures of rocket motor plumes. Because of the extreme environment in the plume and the difficulties in taking measurements of motors in flight, it has been partially validated with temporally- and spatially resolved imaging spectrometer data from the static firings of small flight-weight motors using a non-aluminized composite propellant. Axisymmetric simulations were carried out for a variety of motor burn time, flight velocity, altitude, and modeling parameters to establish their effects on the results. By extrapolating the axisymmetric CFD output into three dimensions, images of the rocket plume as seen by an infrared sensor outside the computational domain were also created. The CFD methodology correctly predicted the afterburning zone downstream of the nozzle, and good agreement for its location was obtained with the imaging spectrometer data. It also showed that flight velocity and altitude have substantial effects on the size, shape, and infrared emissions of the plume. Smaller effects on plume properties were predicted for different motor burn times, but indicated that more experimental data of greater temporal and spatial resolution of single static firings are required to better validate the CFD plume prediction methodology.