Launch Vehicle Dynamic and Control Effects from Solid Rocket Motor Slag Ejection

Abstract

The effects of the ejection of slag from a Titan IV solid rocket motor upgrade (SRMU) are analyzed for the maximum dynamic pressure time. It is assumed that the 2500 Ibs of slag on board at that time is ejected, and the corresponding thrust perturbation is determined using existing theory for the discharge of an inert body. The slag ejection event causes sharp thrust transients during blockage of the nozzle throat and blow-down of the motor internal pressure. Control simulations indicate a worst-case SRMU gimbal angle change of 0.51 deg during the event, and small-amplitude limit cycles after the excitation. An aeroelastic analysis yields yaw shear loads and bending moments as high as 13600 Ibf and 5.1x 106 Ibf-in, respectively, at the aft end of the vehicle. It is shown that the degree of the nozzle throat blockage primarily defines the lateral load magnitudes. The Titan IV has adequate structural and control margins, and slag ejection does not pose a concern for its missions. Nomenclature A* =