Ares I-X Launch Vehicle Modal Test Overview

Buehrle, Ralph D.; Templeton, Justin D.; Reaves, Mercedes C.; Horta, Lucas G.; Gaspar, James L.; Bartolotta, Paul A.; Parks, Russell A.; Lazor, Daniel R.

doi:10.1007/978-1-4419-9834-7_88

Cited by 7 publications

(8 citation statements)

References 1 publication

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“…2, consisted of 44 capacitive accelerometers placed at 40 locations in both the tangential and radial directions (see Buehrle [18] for details). In addition, strain gage data at each of the four hold down posts were collected for load measurements.…”

Section: Brief Description Of the Ares I-x Modal Testmentioning

confidence: 99%

“…If the probability is not zero, a reconciling solution is obtained by minimizing a quadratic function of the prediction error using the nonlinear optimization approach described by Lewis [17]. Although some of the Ares I-X initial results are reported in Buehrle [18] and Horta [19], this document includes additional full vehicle calibration results.…”

Section: Introductionmentioning

confidence: 99%

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Finite Element Model Calibration for Ares I-X Flight Vehicle

et al. 2011

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Ares I-X is a flight test vehicle developed by NASA to demonstrate a new class of crew launch vehicle. For this first flight test, the first stage was a four segment solid rocket booster with mass simulators used to represent the other sections of the Ares I vehicle. Although this vehicle is significantly simpler than the Ares I, model calibration was required for the finite element model used in loads analysis and flight control evaluations before its maiden flight. The process of calibrating models involves updating parameters and reconciling predictions with test data. This work presents a probabilistic approach to the calibration process. The approach uses Analysis of Variance (ANOVA) for parameter sensitivity, nonlinear optimization to minimize the error between test and analysis, and multiple FEM models to bound the system response and to assess the probability of finding a reconciling solution. To reduce the computational burden associated with ANOVA, response surface models are used in lieu of computationally intensive finite element solutions. Uncertainty in the parameters and their effect on the frequency response function is studied in terms of Principal Values of the frequency response functions. Uncertainty bounds of the principal values are established across multiple models to allow one to determine the probability of finding a solution that reconciles analysis with test results. Results from applying this model calibration process to the Ares I-X project are described. Findings presented in the paper confirmed that the baseline model used for pre-flight assessments was within the acceptable range established for guidance and control.

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Section: Brief Description Of the Ares I-x Modal Testmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Finite Element Model Calibration for Ares I-X Flight Vehicle

et al. 2011

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“…14 Although the Ares I-X modal test were performed on the Mobile Launch Platform (MLP) in a fixed-free boundary condition, there is a strong similarity between the free-free bending modes in-flight and the second through fourth bending modes on the MLP. 3 Ares I-X in-flight mode shapes were also extracted from the ERA. Since the modal identification was performed on a series of linearized models using a sliding-time window, mode shapes were obtained at various, discrete times during the ascent period.…”

Section: In-flight Modal Identificationmentioning

confidence: 99%

Ares I-X In-Flight Modal Identification

Bartkowicz

James

2011

52nd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference

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Operational modal analysis is a procedure that allows the extraction of modal parameters of a structure in its operating environment. It is based on the idealized premise that input to the structure is white noise. In some cases, when free decay responses are corrupted by unmeasured random disturbances, the response data can be processed into cross-correlation functions that approximate free decay responses. Modal parameters can be computed from these functions by time domain identification methods such as the Eigenvalue Realization Algorithm (ERA). The extracted modal parameters have the same characteristics as impulse response functions of the original system. Operational modal analysis is performed on Ares I-X in-flight data. Since the dynamic system is not stationary due to propellant mass loss, modal identification is only possible by analyzing the system as a series of linearized models over short periods of time via a sliding time-window of short time intervals. A time-domain zooming technique was also employed to enhance the modal parameter extraction. Results of this study demonstrate that free-decay time domain modal identification methods can be successfully employed for in-flight launch vehicle modal extraction. Nomenclature C= damping matrix K = stiffness matrix M = mass matrix x = vector of x f = force vector ф A = mode shape A T = period

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“…The ability to observe the modes of interest of any modal test depends heavily on proper pre-test analysis, adequate sensor count, and sensor/shaker placement. Readers are referred to Buehrle [18] for details on the pre-test analysis and test configuration. Finally, the calibration process followed during test is shown in figure 3.…”

Section: Problem Formulationmentioning

confidence: 99%

Finite Element Model Calibration Approach for Ares I-X

Horta

Reaves

Buehrle

et al. 2011

Structural Dynamics, Volume 3

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Ares I-X is a pathfinder vehicle concept under development by NASA to demonstrate a new class of launch vehicles. Although this vehicle is essentially a shell of what the Ares I vehicle will be, efforts are underway to model and calibrate the analytical models before its maiden flight. Work reported in this document will summarize the model calibration approach used including uncertainty quantification of vehicle responses and the use of nonconventional boundary conditions during component testing. Since finite element modeling is the primary modeling tool, the calibration process uses these models, often developed by different groups, to assess model deficiencies and to update parameters to reconcile test with predictions. Data for two major component tests and the flight vehicle are presented along with the calibration results. For calibration, sensitivity analysis is conducted using Analysis of Variance (ANOVA). To reduce the computational burden associated with ANOVA calculations, response surface models are used in lieu of computationally intensive finite element solutions. From the sensitivity studies, parameter importance is assessed as a function of frequency. In addition, the work presents an approach to evaluate the probability that a parameter set exists to reconcile test with analysis. Comparisons of pre-test predictions of frequency response uncertainty bounds with measured data, results from the variancebased sensitivity analysis, and results from component test models with calibrated boundary stiffness models are all presented.

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Ares I-X Launch Vehicle Modal Test Overview

Cited by 7 publications

References 1 publication

Finite Element Model Calibration for Ares I-X Flight Vehicle

Finite Element Model Calibration for Ares I-X Flight Vehicle

Ares I-X In-Flight Modal Identification

Finite Element Model Calibration Approach for Ares I-X

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