Launcher-Spacecraft Coupled Loads Analysis   Coupled dynamic analysis     An important step in the design and verification process of spacecraft structures is the coupled dynamic analysis with the launch vehicle, also referred to as coupled loads analysis (CLA). The objective of such analyses is the computation of the dynamic environment of the spacecraft (payload) in terms of interface accelerations, interface forces, center of gravity (CoG) accelerations as well as the internal state of stress typically for frequencies below 100 Hz. For Europe’s small launcher called VEGA, an efficient, fast and accurate CLA tool has been developed at the Structures Section.           FE-models of the stages of the launcher   The VEGA launcher model has been built from industrial specifications and drawings of all substructures and has been correlated dynamically with solid rocket motor firing tests and flight data. All FE-models of the stages of the launcher are condensed to superelements to reduce the computational cost of dynamic analyses. Special techniques have been developed to find the dominant modes in a response and to back-transform the corresponding system modeshapes. In addition new equivalent viscous damping techniques have been employed that accurately take into account the material structural damping of the stiff load carrying structure and flexible solid propellant.         VEGA CLA tool computes   The VEGA CLA tool computes the spacecraft mechanical environment in terms of quasi-static loads and base equivalent sine for the following load cases: Lift-off which encompasses first stage ignition and blastwaves Gust at Mach 1 and maximum dynamic pressure First stage pressure oscillations Second stage ignition Third stage ignition           Last update: 12 March 2013