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  • 1
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    Wavelet Applications for Flight Flutter Testing (1999)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Wavelets present a method for signal processing that may be useful for analyzing responses of dynamical systems. This paper describes several wavelet-based tools that have been developed to improve the efficiency of flight flutter testing. One of the tools uses correlation filtering to identify properties of several modes throughout a flight test for envelope expansion. Another tool uses features in time-frequency representations of responses to characterize nonlinearities in the system dynamics. A third tool uses modulus and phase information from a wavelet transform to estimate modal parameters that can be used to update a linear model and reduce conservatism in robust stability margins.
    Keywords: Aircraft Stability and Control
    Type: CEAS/AIAA/ICASE/NASA Langley International Forum on Aeroelasticity and Structural Dynamics 1999; Pt. 1; 393-402; NASA/CP-1999-209136/PT1
    Format: application/pdf
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  • 2
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    Impregnation of Catalytic Metals in Single-Walled Carbon Nanotubes for Toxic Gas Conversion in Life Support System (2004)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: Carbon nanotubes (CNTs) possess extraordinary properties such as high surface area, ordered chemical structure that allows functionalization, larger pore volume, and very narrow pore size distribution that have attracted considerable research attention from around the world since their discovery in 1991. The development and characterization of an original and innovative approach for the control and elimination of gaseous toxins using single walled carbon nanotubes (SWNTs) promise superior performance over conventional approaches due to the ability to direct the selective uptake of gaseous species based on their controlled pore size, increased adsorptive capacity due to their increased surface area and the effectiveness of carbon nanotubes as catalyst supports for gaseous conversion. We present our recent investigation of using SWNTs as catalytic supporting materials to impregnate metals, such as rhodium (Rh), palladium (Pd) and other catalysts. A protocol has been developed to oxidize the SWNTs first and then impregnate the Rh in aqueous rhodium chloride solution, according to unique surface properties of SWNTs. The Rh has been successfully impregnated in SWNTs. The Rh-SWNTs have been characterized by various techniques, such as TGA, XPS, TEM, and FTIR. The project is funded by a NASA Research Announcement Grant to find applications of single walled nanocarbons in eliminating toxic gas Contaminant in life support system. This knowledge will be utilized in the development of a prototype SWNT KO, gas purification system that would represent a significant step in the development of high efficiency systems capable of selectively removing specific gaseous for use in regenerative life support system for human exploration missions.
    Keywords: Mechanical Engineering
    Type: 34th International Conference on Environmental Systems; Jul 19, 2004 - Jul 22, 2004; Colorado Springs, CO; United States
    Format: text
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  • 3
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    SSME Bearing and Seal Tester Data Compilation, Analysis and Reporting; and Refinement of the Cryogenic Bearing Analysis Mathematical Model (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: SRS and NASA/MSFC have developed software with unique capabilities to couple bearing kinematic modeling with high fidelity thermal modeling. The core thermomechanical modeling software was developed by SRS and others in the late 1980's and early 1990's under various different contractual efforts. SRS originally developed software that enabled SHABERTH (Shaft Bearing Thermal Model) and SINDA (Systems Improved Numerical Differencing Analyzer) to exchange data and autonomously allowing bearing component temperature effects to propagate into the steady state bearing mechanical model. A separate contract was issued in 1990 to create a personal computer version of the software. At that time SRS performed major improvements to the code. Both SHABERTH and SINDA were independently ported to the PC and compiled. SRS them integrated the two programs into a single program that was named SINSHA. This was a major code improvement.
    Keywords: Mechanical Engineering
    Type: TR00-1017
    Format: application/pdf
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  • 4
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    Worst-Case Flutter Margins from F/A-18 Aircraft Aeroelastic Data (1997)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: An approach for computing worst-case flutter margins has been formulated in a robust stability framework. Uncertainty operators are included with a linear model to describe modeling errors and flight variations. The structured singular value, micron, computes a stability margin which directly accounts for these uncertainties. This approach introduces a new method of computing flutter margins and an associated new parameter for describing these margins. The micron margins are robust margins which indicate worst-case stability estimates with respect to the defined uncertainty. Worst-case flutter margins are computed for the F/A-18 SRA using uncertainty sets generated by flight data analysis. The robust margins demonstrate flight conditions for flutter may lie closer to the flight envelope than previously estimated by p-k analysis.
    Keywords: Aircraft Stability and Control
    Type: NASA/TM-97-207564 , NAS 1.15:207564 , AIAA Paper 97-1266 , Structures, Structural Dynamics and Materials Conference; Apr 01, 1997; Orlando, FL; United States
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  • 5
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    Wavelet Filtering to Reduce Conservatism in Aeroservoelastic Robust Stability Margins (1998)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Wavelet analysis for filtering and system identification was used to improve the estimation of aeroservoelastic stability margins. The conservatism of the robust stability margins was reduced with parametric and nonparametric time-frequency analysis of flight data in the model validation process. Nonparametric wavelet processing of data was used to reduce the effects of external desirableness and unmodeled dynamics. Parametric estimates of modal stability were also extracted using the wavelet transform. Computation of robust stability margins for stability boundary prediction depends on uncertainty descriptions derived from the data for model validation. F-18 high Alpha Research Vehicle aeroservoelastic flight test data demonstrated improved robust stability prediction by extension of the stability boundary beyond the flight regime.
    Keywords: Aircraft Stability and Control
    Type: NASA/TM-1998-206545 , NAS 1.15:206545 , H-2222 , AIAA Paper 98-1896 , Structures, Structural Dynamics and Materials Conference; Apr 20, 1998 - Apr 23, 1998; Long Beach, CA; United States
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  • 6
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    Estimation of Modal Parameters Using a Wavelet-Based Approach (1997)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Modal stability parameters are extracted directly from aeroservoelastic flight test data by decomposition of accelerometer response signals into time-frequency atoms. Logarithmic sweeps and sinusoidal pulses are used to generate DAST closed loop excitation data. Novel wavelets constructed to extract modal damping and frequency explicitly from the data are introduced. The so-called Haley and Laplace wavelets are used to track time-varying modal damping and frequency in a matching pursuit algorithm. Estimation of the trend to aeroservoelastic instability is demonstrated successfully from analysis of the DAST data.
    Keywords: Aircraft Stability and Control
    Type: NASA/TM-97-206300 , NAS 1.15:206300 , H-2214 , Atmospheric Flight Mechanics Conference; Aug 08, 1997 - Aug 11, 1997; New Orleans, LA; United States
    Format: application/pdf
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  • 7
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    Utilizing Flight Data to Update Aeroelastic Stability Estimates (1997)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Stability analysis of high performance aircraft must account for errors in the system model. A method for computing flutter margins that incorporates flight data has been developed using robust stability theory. This paper considers applying this method to update flutter margins during a post-flight or on-line analysis. Areas of modeling uncertainty that arise when using flight data with this method are investigated. The amount of conservatism in the resulting flutter margins depends on the flight data sets used to update the model. Post-flight updates of flutter margins for an F/A-18 are presented along with a simulation of on-line updates during a flight test.
    Keywords: Aircraft Stability and Control
    Type: Atmospheric Flight Mechanics Conference; Aug 01, 1997; New Orleans, LA; United States
    Format: text
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  • 8
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    SSME Bearing and Seal Tester Data Compilation, Analysis, and Reporting; and Refinement of the Cryogenic Bearing Analysis Mathematical Model (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: SRS and NASA/MSFC have developed software with unique capabilities to couple bearing kinematic modeling with high fidelity thermal modeling. The core thermomechanical modeling software was developed by SRS and others in the late 1980's and early 1990's under various different contractual efforts. SRS originally developed software that enabled SHABERTH (Shaft Bearing Thermal Model) and SINDA (Systems Improved Numerical Differencing Analyzer) to exchange data and autonomously allowing bearing component temperature effects to propagate into the steady state bearing mechanical model. A separate contract was issued in 1990 to create a personal computer version of the software. At that time SRS performed major improvements to the code. Both SHABERTH and SINDA were independently ported to the PC and compiled. SRS them integrated the two programs into a single program that was named SINSHA. This was a major code improvement.
    Keywords: Mechanical Engineering
    Type: NASA/CR-2000-210139 , NAS 1.26:210139 , TR00-1017
    Format: application/pdf
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  • 9
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    Wavelet Applications for Flight Flutter Testing (1999)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Wavelets present a method for signal processing that may be useful for analyzing responses of dynamical systems. This paper describes several wavelet-based tools that have been developed to improve the efficiency of flight flutter testing. One of the tools uses correlation filtering to identify properties of several modes throughout a flight test for envelope expansion. Another tool uses features in time-frequency representations of responses to characterize nonlinearities in the system dynamics. A third tool uses modulus and phase information from a wavelet transform to estimate modal parameters that can be used to update a linear model and reduce conservatism in robust stability margins.
    Keywords: Aircraft Stability and Control
    Type: H-2364 , International Forum on Aeroelasticity and Structural Dynamics; Jun 22, 1999 - Jun 25, 1999; Williamsburg, VA; United States
    Format: application/pdf
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