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  • 1
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    Dual control vibration tests of flight hardware (1991)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: A vibration retest of a spacecraft flight instrument, the Mars Observer Camera (MOC), was conducted using extremal dual control to automatically limit the shaker force and notch the shaker acceleration at resonances. This was the first application of extremal dual control with flight hardware at JPL. The retest was successful in that the environment was representative of flight plus some margin, the instrument survived without any structural or performance degradation, and the force limiting worked very well. The test set-up, force limiting procedure, and test results are described herein. It is concluded that dual control should be utilized when there is a concern about overtesting in hard-base-drive tests and the instrumentation for force measurement and control is available. Recommendations for improving the implementation of dual control are provided as a result of this first experience.
    Keywords: QUALITY ASSURANCE AND RELIABILITY
    Type: In: Institute of Environmental Sciences, Annual Technical Meeting, 37th, San Diego, CA, May 6-10, 1991, Proceedings (A93-27778 09-38); p. 68-77.
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  • 2
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    An assessment of the microgravity and acoustic environments in Space Station Freedom using VAPEPS (1992)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The Vibroacoustic Payload Environment Prediction System (VAPEPS) was used to predict the stationary on-orbit environments in one of the Space Station Freedom modules. The model of the module included the outer structure, equipment and payload racks, avionics, and cabin air and duct systems. Acoustic and vibratory outputs of various source classes were derived and input to the model. Initial results of analyses, performed in one-third octave frequency bands from 10 to 10,000 Hz, show that both the microgravity and acoustic environments will be exceeded in some one-third octave bands with the current SSF design. Further analyses indicate that interior acoustic level requirements will be exceeded even if the microgravity requirements are met.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: In: International Congress on Recent Developments in Air- and Structure-Borne Sound and Vibration, 2nd, Auburn Univ., AL, Mar. 4-6, 1992, Proceedings. Vol. 1 (A93-55851 24-31); p. 543-550.
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  • 3
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    Verification of force and acceleration specifications for random vibration tests of Cassini spacecraft equipment (1996)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The use of force limiting in the random vibration testing of the Cassini spacecraft's subsystems is reported on. A verification of the Cassini equipment random vibration test acceleration and force specifications is provided by interface acceleration and force data measured in acoustic tests of the Cassini spacecraft development test model (DTM). Acoustic tests were performed on the DTM structure with different structural and equipment configurations. The acceleration and force spectra at the interface between the equipment items and the spacecraft DTM structure were measured in the acoustic tests and compared with the equipment random vibration test specifications. The spacecraft's apparent masses were measured at the equipment mounting points and used in force limit predictions.
    Keywords: Spacecraft Design, Testing and Performance
    Type: Proceedings of International Conference on Spacecraft Structures, Materials and Mechanical Testing; Volume 2; 911-919; ESA-SP-382-Vol-2
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  • 4
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    Force limited vibration testing of Cassini spacecraft cosmic dust analyser (1996)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The testing of the cosmic dust analyzer for the Cassini mission using the force limited method in order to avoid overtesting and to verify the ability of the specimen design to withstand the loads during launch and cruise, is reported on. In order to implement the method, force gages, fixtures and a test controller are required and the test specimen is subjected to sine vibration, random vibration and half sine shock. The practical aspects of the use of the force limited method are described. Due to the high loads and the weak design of the structural element, a notching method is used which provides the possibility of limiting the excitation to flight expected levels.
    Keywords: Spacecraft Design, Testing and Performance
    Type: Proceedings of an International Conference on Spacecraft Structures, Materials and Mechanical Testing; Volume 3; 1039-1045; ESA-SP-386-Vol-3
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  • 5
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    Force limited vibration testing (1991)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: A new method of conducting lab vibration tests of spacecraft equipment was developed to more closely simulate the vibration environment experienced when the spacecraft is launched on a rocket. The improved tests are tailored to identify equipment design and workmanship problems without inducing artificial failures that would not have occurred at launch. These new, less destructive types of vibration tests are essential to JPL's protoflight test approach in which lab testing is conducted using the flight equipment, often one of a kind, to save time and money. In conventional vibration tests, only the input vibratory motion is specified; the feedback, or reaction force, between the test item and the vibration machine is ignored. Most test failures occur when the test item goes into resonance, and the reaction force becomes very large. It has long been recognized that the large reaction force is a test artifact which does not occur with the lightweight, flexible mounting structures characteristic of spacecraft and space vehicles. In new vibration tests, both the motion and the force provided to the test item by the vibration machine are controlled, so that the vibration ride experienced by the test item is as in flight.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA, Washington, Technology 2001: The Second National Technology Transfer Conference and Exposition, Volume 2; p 105-115
    Format: application/pdf
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  • 6
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    Vibration and acoustic testing of TOPEX/Poseidon satellite (1992)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The satellite was subjected to a 1.5G swept sine vibration test and a 146 dB overall level acoustic test, in accordance with Ariane launch vehicle requirements, at the NASA Goddard Space Flight Center. Extensive pretest analysis of the sine test was conducted to plan the input notching and to justify vibration testing the satellite only in the longitudinal axis. A unique measurement system was utilized to determine the six components of interface force between the shaker and the satellite in the sine vibration test. The satellite was heavily instrumented in both the sine vibration and acoustic test in order to insure that the launch loads were enveloped with appropriate margin and that satellite responses did not exceed the compatibilities of the structure and equipment. The test specification, objectives, instrumentation, and test results are described herein.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: The Seventeenth Space Simulation Conference. Terrestrial Test for Space Success; p 75-84
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  • 7
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    Derivation and Application of Force Limits for Vibration Tests (1994)
    In:  Other Sources
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    Publication Date: 2018-06-08
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  • 8
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    Research Problems Associated with Limiting the Applied Force in Vibration Tests and Conducting Base-Drive Modal Vibration Tests (1995)
    In:  Other Sources
    Details
    Publication Date: 2018-06-08
    Description: The intent of this paper is to make a case for developing and conducting vibration tests which are both realistic and practical (a question of tailoring versus standards). Tests are essential for finding things overlooked in the analyses. The best test is often the most realistic test which can be conducted within the cost and budget constraints. Some standards are essential, but the author believes more in the individual's ingenuity to solve a specific problem than in the application of standards which reduce problems (and technology) to their lowest common denominator. Force limited vibration tests and base-drive modal tests are two examples of realistic, but practical testing approaches. Since both of these approaches are relatively new, a number of interesting research problems exist, and these are emphasized herein.
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  • 9
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    Force Measurments in Vibration and Acoustic Tests (1996)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: The advent of trixial, piezoelectric force gauges and the associated signal processing has opened the door to several dynamics testing innovations.
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  • 10
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    Force Limited Vibration Testing of Cassini Spacecraft Cosmic Dust Analyzer (1996)
    In:  Other Sources
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    Publication Date: 2018-06-08
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