A fully interactive, gas-flow-grain structural analysis was developed
and applied to reconstruct the failure mode of the first prequalificat
ion motor and to evaluate the redesigned grain configuration for the T
itan IV solid-rocket-motor upgrade. The gas-flow analysis was based on
an adaptive, unstructured, finite-element method for the solution of
full Navier-Stokes flows inside solid-rocket-motors. The grain structu
ral analysis was conducted using a general-purpose, finite-element pro
gram with the consideration of viscoelastic properties of the propella
nt and orthotropic properties of the graphite-epoxy motor case. The ex
act deformed grain geometry was considered in the fully interactive, g
as-flow-grain structural analysis. Results of the analyses for the fir
st prequalification motor and for the redesign motor agreed well with
the data obtained from the static firing tests, The study provided con
firmation and confidence required for the implementation of the grain
modification. The qualification program for the Titan IV solid-rocket-
motor upgrade was completed with five successful tests of the motors w
ith the redesigned grain configuration.