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Progress in Operational Analysis of Launch Vehicles in Nonstationary FlightThis paper presents recent results in an ongoing effort to understand and develop techniques to process launch vehicle data, which is extremely challenging for modal parameter identification. The primary source of difficulty is due to the nonstationary nature of the situation. The system is changing, the environment is not steady, and there is an active control system operating. Hence, the primary tool for producing clean operational results (significant data lengths and data averaging) is not available to the user. This work reported herein uses a correlation-based two step operational modal analysis approach to process the relevant data sets for understanding and development of processes. A significant drawback for such processing of short time histories is a series of beating phenomena due to the inability to average out random modal excitations. A recursive correlation process coupled to a new convergence metric (designed to mitigate the beating phenomena) is the object of this study. It has been found in limited studies that this process creates clean modal frequency estimates but numerically alters the damping.
Document ID
Document Type
Conference Paper
James, George (NASA Johnson Space Center Houston, TX, United States)
Kaouk, Mo (NASA Johnson Space Center Houston, TX, United States)
Cao, Timothy (NASA Johnson Space Center Houston, TX, United States)
Date Acquired
August 27, 2013
Publication Date
February 11, 2013
Subject Category
Launch Vehicles and Launch Operations
Report/Patent Number
Meeting Information
International Modal Analysis Conference 31st(Garden Grove, CA)
Distribution Limits
Work of the US Gov. Public Use Permitted.

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