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Modal Test of the NASA Mobile Launcher at Kennedy Space CenterThe NASA Mobile Launcher (ML), located at Kennedy Space Center (KSC), has recently been modified to support the launch of the new NASA Space Launch System (SLS). The ML is a massive structure—consisting of a 345-foot tall tower attached to a two-story base, weighing approximately 10.5 million pounds—that will secure the SLS vehicle as it rolls to the launch pad on a Crawler Transporter, as well as provide a launch platform at the pad. The ML will also provide the boundary condition for an upcoming SLS Integrated Modal Test (IMT). To help correlate the ML math models prior to this modal test, and allow focus to remain on updating SLS vehicle models during the IMT, a ML-only experimental modal test was performed in June 2019. Excitation of the tower and platform was provided by five uniquely-designed test fixtures, each enclosing a hydraulic shaker, capable of exerting thousands of pounds of force into the structure. For modes not that were not sufficiently excited by the test fixture shakers, a specially-designed mobile drop tower provided impact excitation at additional locations of interest. The response of the ML was measured with a total of 361 accelerometers. Following the random vibration, sine sweep vibration, and modal impact testing, frequency response functions were calculated and modes were extracted for three different configurations of the ML in 0 Hz to 12 Hz frequency range. This paper will provide a case study in performing modal tests on large structures by discussing the Mobile Launcher, the test strategy, an overview of the test results, and recommendations for meeting a tight test schedule for a large-scale modal test.
Document ID
Document Type
Conference Paper
Stasiunas, Eric C.
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Parks, Russel A.
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Sontag, Brendan D.
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Chandler, Dana E.
(Jacobs Engineering Group Huntsville, AL, United States)
Date Acquired
March 17, 2020
Publication Date
February 10, 2020
Subject Category
Ground Support Systems And Facilities (Space)
Report/Patent Number
Meeting Information
Meeting: IMAC
Location: Houston, TX
Country: United States
Start Date: February 10, 2020
End Date: February 13, 2020
Sponsors: Society for Experimental Mechanics, Inc.
Distribution Limits
Public Use Permitted.
Hydraulic shakers
Multi-sine sweep
Large structures
Impact drop tower
Experimental modal analysis
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