A shock spectra and impedance method to determine a bound for spacecraft structural loads

This paper proposes a method for the determination of design loads of a spacecraft mounted on a launch vehicle when the significant frequency ranges of the two structures overlap. The derived loads are realistic upper bounds of the flight loads. The method utilizes shock spectra of the spacecraft/launch vehicle interface directional accelerations for each event separately and introduces a reduction factor for the shock spectra which is based on the relative impedance of the spacecraft and launch vehicle. The main advantages of the method are low cost of analysis and timeliness in the design. These advantages are attained with only a slight expense of structural weight compared to the more exact transient analysis method.