The results of an evaluation of the fracture tolerance of three components of the thrust vector control servo-actuator for the solid rocket booster of the space shuttle are described. These components were considered as being potentially fracture critical and therefore having the potential to fall short of a desired service life of 80 missions (that is, a service life factor of 4.0 on a basic service life of 20 missions). Detailed stress analysis of the rod end, cylinder, and feedback link components was accomplished by three-dimensional finite-element stress analysis methods. A dynamic structural model of the feedback system was used to determine the dynamic inertia loads and reactions to apply to the finite-element model of the feedback link. Twenty mission stress spectra consisting of lift-off, boost, re-entry, and water impact mission segments were developed for each component based on dynamic loadings. Experimental fracture response data da/dN, K_Ic, and K_c were used for the structural alloys of the actuator components. These alloys were Inconel 718, 17-4 PH (H1025), 6061-T651, 2024-T851 (T351), and A286. Linear fatigue crack growth life and residual strength analyses were performed on the component critical locations using the Forman da/dN equation and CRACKS III computer code. Most components were determined to have the potential of reaching a service life of 80 missions or service life factor of 4.0.