Launch vehicle dynamic and control effects from solid rocket motor slag ejection

The effects of the ejection of slag from a Titan IV solid rocket motor upgr ade (SRMU) are analyzed at maximum dynamic pressure. It is assumed that the 2500 lb of slag onboard at that time is ejected, and the corresponding thr ust perturbation is determined using existing theory for the discharge of a n inert body. The event is a hypothetical, critical flight condition not ob served during any of the first three launches of the Titan IV with SRMUs. S lag ejection causes sharp thrust transients during blockage of the nozzle t hroat and blowdown of the motor Internal pressure. Control simulations indi cate a worst-case SRMU gimbal angle change of 0.51 deg during the event, an d small-amplitude limit cycles after the excitation. An aeroelastic analysi s yields yaw shear loads and bending moments as high as 13,600 lbf and 5.1 x 10(6) lbf in., respectively, at the aft end of the vehicle. It is shown t hat the degree of the nozzle throat blockage primarily defines the lateral load magnitudes. The Titan IV has adequate structural and control margins, and the ejection of slag is not a concern for its missions.