A method has been developed by which an estimate of the launch vehicle/payload interface response is derived from the interface responses obtained from missions with the identical launch vehicle but different payloads. This method requires the knowledge of the launch vehicle eigenvalues, interface modal displacements, and the dynamic characteristics of the payloads. No other launch vehicle information is required. The organization responsible for the payload is able to perform loads and responses analysis resulting from a payload change without interfacing with the launch vehicle organization. SPACE mission often utilizes an existing launch vehicle for a new payload designed for a specific mission; such will be the case for future Shuttle missions. The dynamic design loads for the payload are obtained by performing a transient analysis of the analytical dynamic model of the coupled payload and launch vehicle. Each analysis iteration for a specific payload configuration is expensive and time consuming. The combined dynamic model of the payload/launch vehicle is not only large and complex, but the time duration of one iteration is extensive because of the number of different organizations involved. The proposed methodology allows the payload organization to estimate the dynamic loads for a design iteration independent of other organizations. It should be noted that the proposed method can also be applied to the general class of subsystems coupled to relatively large vehicles such as the guidance system on a missile and the auxiliary power unit on an aircraft. This method will make a significant contribution to the time- critical development of subsystems constrained by complex technical and project interfaces. The procedure assumes that the acceleration time history at the payload/launch vehicle is available from past flight measurements or analyses, the dynamic characteristics of the launch vehicle do not change, the forcing function on the launch vehicle can be approximated by a delta function, and the mass of the payload is small compared to the mass of the launch vehicle. These assumptions are realistic for most projects for design/analysis iterations. Historically, during the payload design phase, the payload/launch vehicle interface accelerations have been defined as a sine wave input or a shock spectrum.1'2 Both methods essentially eliminate the time dependency of the interface response. In the past 10 years, estimates of spacecraft interface ac- celerations measured from flight data have been used as an input forcing function to the payload to obtain more realistic estimates of the dynamic loads. At the Jet Propulsion Laboratory similar procedures were used on the Ranger, Surveyor, Mariner, and Viking Projects. In 1971, Caughey3 investigated the potential error in this procedure by assuming that the interface acceleration is invariant as the payload is modified. The study indicates that the error can be very large and is dependent on the dynamic characteristics of the system.