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Alexander Chin

Publications and source records attributed to Alexander Chin.

10 records
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

3rd Aeroelastic Prediction Workshop (AePW-3) Flight Test Working Group

- Introduction - Background - X-56 Body Freedom Flutter Mechanism - Challenges in X-56 Flutter Modeling - Flight Test Working Group Challenge - Individual Presentations - Steve Massey - Jos Aalbers - Jared Grauer - Jeffrey Ouellette - Combined Results - Discussion

Jeffrey Ouellette↗
NASA NTRSDate not supplied

Finite Element Based Model of Fiber-optic Strain Sensor Mounted on a Semi-monocoque Structure

Fiber-optic strain sensing (FOSS) provides an opportunity for additional awareness and can enable other mitigations such as flutter suppression or gust load alleviation but requires an accurate computational model as part of a design process that integrates structures and controls. A modeling approach for fiber-optic strain sensors has been developed using a shell element formulation in a detailed finite element model. The new FOSS modeling approach is designed to better scale to more complex realistic structures and fiber layouts than previous approaches. The modeling method was applied to the X-56A vehicle and results were compared to experimental static ground-test data. Additionally, the experimental sensor noise of these fiber optic sensors was assessed for the correlations in time and correlations along the fiber. The noise does show significant correlations both in time and along the fibers. These correlations of the noise should also be considered in modeling and assessing algorithms that will use FOSS.

Jeffrey Ouellette↗
NASA NTRSDate not supplied

Summary of Results from the Third Aeroelastic Prediction Workshop Flight Test Working Group

This paper summarizes results of the Flight Test Working Group presented at the third Aeroelastic Prediction Workshop held in January 2023. The Flight Test Working Group was looking at the application of flutter prediction tools of a complete aircraft and comparing those predictions to flight-test data. The teams generated a total of six different predictions of the body freedom flutter exhibited by the X-56A experimental aircraft with flexible wings. The computational predictions of frequency and damping are compared with the flight-test data. All of the methods gave similar predictions of the flutter speed, but were all about 10 to 20 knots higher than the measured flutter speed. Additionally, the different generalized aerodynamic forces and the aerodynamic work from the computational tools are compared to illustrate the differences in the methods. Looking at the aerodynamic work done by the flutter mode, suggests that the pitch motion is dissipating less energy and the plunge motion is adding more in the methods which better predict the flutter. However, with only six different predictions it was not possible to develop more definitive conclusions.

Jeffrey Ouellette↗
NASA NTRSDate not supplied

Finite Element Based Model of Fiber-optic Strain Sensor Mounted on a Semi-monocoque Structure

Fiber-optic strain sensing (FOSS) provides an opportunity for additional awareness and can enable other mitigations such as flutter suppression or gust load alleviation but requires an accurate computational model as part of a design process that integrates structures and controls. A modeling approach for fiber-optic strain sensors has been developed using a shell element formulation in a detailed finite element model. The new FOSS modeling approach is designed to better scale to more complex realistic structures and fiber layouts than previous approaches. The modeling method was applied to the X-56A vehicle and results were compared to experimental static ground-test data. Additionally, the experimental sensor noise of these fiber optic sensors was assessed for the correlations in time and correlations along the fiber. The noise does show significant correlations both in time and along the fibers. These correlations of the noise should also be considered in modeling and assessing algorithms that will use FOSS.

Jeffrey Ouellette↗
NASA NTRSDate not supplied

Summary of Results from the Third Aeroelastic Prediction Workshop Flight Test Working Group

This paper summarizes results of the Flight Test Working Group presented at the third Aeroelastic Prediction Workshop held in January 2023. The Flight Test Working Group was looking at the application of flutter prediction tools of a complete aircraft and comparing those predictions to flight-test data. The teams generated a total of six different predictions of the body freedom flutter exhibited by the X-56A experimental aircraft with flexible wings. The computational predictions of frequency and damping are compared with the flight-test data. All of the methods gave similar predictions of the flutter speed, but were all about 10 to 20 knots higher than the measured flutter speed. Additionally, the different generalized aerodynamic forces and the aerodynamic work from the computational tools are compared to illustrate the differences in the methods. Looking at the aerodynamic work done by the flutter mode, suggests that the pitch motion is dissipating less energy and the plunge motion is adding more in the methods which better predict the flutter. However, with only six different predictions it was not possible to develop more definitive conclusions.

Jeffrey Ouellette↗
NASA NTRSDate not supplied

Operational Modal Analysis of the Artemis I Dynamic Rollout Test and Wet Dress Rehearsal

NASA has developed an expendable heavy lift launch vehicle capability, the Space Launch System (SLS), to support lunar and deep space exploration. The uncrewed Artemis I was the first flight of this new launch vehicle and tested critical systems for the upcoming crewed Artemis II flight to the moon. Accelerations were recorded at a multitude of locations on Artemis, the Mobile Launcher (ML), and the Crawler Transporter (CT)during the rollout of Artemis I from the Vehicle Assembly Building (VAB) to Launch Pad 39B March 2022 and is referred to as the Artemis I Dynamic Rollout Test (DRT). While Artemis I was at Launch Pad 39B, the Wet Dress Rehearsal (WDR) was performed to demonstrate launch readiness and acceleration measurements were also recorded. Finally, Artemis I rolled back from Launch Pad 39B to the VAB in April 2022, where acceleration measurements were also recorded and is referred to as the rollback portion of DRT. Because the forces during rollout and at the launch pad acting on Artemis I, the ML, and the CT are not directly measurable, Operational Modal Analysis (OMA) techniques, instead of traditional Experimental Modal Analysis (EMA) techniques, were used to identify modal characteristics. The OMA analysis of DRT and WDR directly builds upon the lessons learned from the OMA analysis of an earlier rollout of the ML from the VAB. DRT and WDR dynamic characteristics will be used to support SLS Integrated Modal Test finite element model correlation efforts and Exploration Ground System ML and CT finite element model verification and validation, which are part of the Building Block approach the Space Launch System program has implemented. The dynamic characteristics extracted from DRT as well as the rollout acceleration time histories themselves will be used in the development of generic rollout forcing functions that will provide refined estimates of the Artemis IV rollout forces, which will have the heavier and larger SLS Block 1B launch vehicle and Mobile Launcher 2 (ML-2). This paper briefly describes Artemis I, the ML, and the CT physical characteristics, DRT rollout/rollback and WDR data collection, the challenges in implementing OMA techniques due in part to the CT harmonics, and how these challenges were overcome to obtain the Artemis I DRT configuration and WDR configuration modal characteristics.

Apollo↗