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Advanced Method to Estimate Fuel Slosh Simulation ParametersThe nutation (wobble) of a spinning spacecraft in the presence of energy dissipation is a well-known problem in dynamics and is of particular concern for space missions. The nutation of a spacecraft spinning about its minor axis typically grows exponentially and the rate of growth is characterized by the Nutation Time Constant (NTC). For launch vehicles using spin-stabilized upper stages, fuel slosh in the spacecraft propellant tanks is usually the primary source of energy dissipation. For analytical prediction of the NTC this fuel slosh is commonly modeled using simple mechanical analogies such as pendulums or rigid rotors coupled to the spacecraft. Identifying model parameter values which adequately represent the sloshing dynamics is the most important step in obtaining an accurate NTC estimate. Analytic determination of the slosh model parameters has met with mixed success and is made even more difficult by the introduction of propellant management devices and elastomeric diaphragms. By subjecting full-sized fuel tanks with actual flight fuel loads to motion similar to that experienced in flight and measuring the forces experienced by the tanks these parameters can be determined experimentally. Currently, the identification of the model parameters is a laborious trial-and-error process in which the equations of motion for the mechanical analog are hand-derived, evaluated, and their results are compared with the experimental results. The proposed research is an effort to automate the process of identifying the parameters of the slosh model using a MATLAB/SimMechanics-based computer simulation of the experimental setup. Different parameter estimation and optimization approaches are evaluated and compared in order to arrive at a reliable and effective parameter identification process. To evaluate each parameter identification approach, a simple one-degree-of-freedom pendulum experiment is constructed and motion is induced using an electric motor. By applying the estimation approach to a simple, accurately modeled system, its effectiveness and accuracy can be evaluated. The same experimental setup can then be used with fluid-filled tanks to further evaluate the effectiveness of the process. Ultimately, the proven process can be applied to the full-sized spinning experimental setup to quickly and accurately determine the slosh model parameters for a particular spacecraft mission. Automating the parameter identification process will save time, allow more changes to be made to proposed designs, and lower the cost in the initial design stages.
Document ID
20130010437
Acquisition Source
Kennedy Space Center
Document Type
Conference Paper
Authors
Schlee, Keith
(Embry-Riddle Aeronautical Univ. Daytona Beach, FL, United States)
Gangadharan, Sathya
(Embry-Riddle Aeronautical Univ. Daytona Beach, FL, United States)
Ristow, James
(Embry-Riddle Aeronautical Univ. Daytona Beach, FL, United States)
Sudermann, James
(NASA Kennedy Space Center Cocoa Beach, FL, United States)
Walker, Charles
(NASA Kennedy Space Center Cocoa Beach, FL, United States)
Hubert, Carl
(Hubert Astronautics, Inc. Purcellville, VA, United States)
Date Acquired
August 27, 2013
Publication Date
July 10, 2005
Subject Category
Spacecraft Design, Testing And Performance
Report/Patent Number
KSC-2005-072
AIAA-2005-3596
Report Number: KSC-2005-072
Report Number: AIAA-2005-3596
Meeting Information
Meeting: 41st AIAA/ASME/SAE/ASEE Joint Propulsion Conference
Location: Tucson, AZ
Country: United States
Start Date: July 10, 2005
End Date: July 13, 2005
Sponsors: Society of Automotive Engineers, Inc., American Inst. of Aeronautics and Astronautics, American Society for Electrical Engineers, American Society of Mechanical Engineers
Distribution Limits
Public
Copyright
Public Use Permitted.
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