A series of modal tests on Nasa's Ares I-X flight test vehicle were performed using M+P International's SO Analyzer and VXI hardware for data acquisition.
The modal tests were performed with the 327ft-tall launch vehicle fully assembled on a mobile launcher platform in the vehicle assembly building at Nasa's Kennedy Space Centre.
The SO Analyzer software allowed 104 channels of data to be collected while exciting the vehicle with up to four hydraulic shakers.
SO Analyzer's throughput option was used to store time history data from all channels directly to disk during test runs so that it could be reprocessed as desired using the post-processing feature.
Excitation techniques utilised during testing included multi-shaker random and single-shaker force-controlled sine sweep.
Tap tests were also performed in order to investigate local modes inside the vehicle.
Many of these tap tests utilised the company's eight-channel Vibpilot system for data acquisition.
The modal test data was used to identify and investigate the first four bending mode pairs of the launch vehicle on the mobile launcher platform.
These experimental modal parameters were used to calibrate the finite-element model.
Additional analysis predicted in-flight modal parameters, which were used to ensure the robustness of the flight control system design.
The modal test was a multi-centre effort including the Nasa Langley Research Centre, the Glenn Research Centre, the Marshall Space Flight Centre, the Kennedy Space Centre and the Aerospace Corporation.
