Structural Identification Tests of the Ariane 5 EPS Stage.

Abstract

The EPS stage, the second upper stage of the Ariane 5 launcher, was tested in the launcher test stand in Lampoldshausen, Germany during the second half of 1994. The precalculations of its structural dynamic behaviour revealed the possibility of the occurrence of severe so-called POGO vibrations. In order to monitor and control the occurrence of these unstable variations, a so-called "red-line" system was developed based on modal data. Structural identification tests were performed by DLR to acquire a reliable data basis for POGO risk control. The tests comprised frequency response functions and free decay measurements. This report describes the test performance, data evaluation, and test results.