Shuttle orbiter vibroacoustics
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Colonna, R. A.↗
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Application of a computerized vibroacoustic data bank for random vibration criteria development
A computerized data bank system was developed for utilization of large amounts of vibration and acoustic data to formulate component random vibration design and test criteria. This system consists of a computer, graphics tablets, and a dry silver hard copier which are all desk top type hardware and occupy minimal space. Currently, the data bank contains data from the Saturn 5 and Titan 3 flight and static test programs. The vibration and acoustic data are stored in the form of power spectral density and one third octave band plots over the frequency range from 20 to 2000 Hz. The data were stored by digitizing each spectral plot by tracing with the graphics tablet. The digitized data were statistically analyzed, and the resulting 97.5 percent confidence levels were stored on tape along with the appropriate structural parameters. Standard extrapolation procedures were programmed for prediction of component random vibration test criteria for new launch vehicle and payload configurations. A user's manual is included to guide potential users through the programs.
Ferebee, R. C.↗
Evaluation of a procedure for the analysis of nonstationary vibroacoustic data
Numerical techniques for the spectral analysis of vibration data from space-vehicle launches are described and demonstrated. A nonstationary product model described by Bendat and Piersol (1986) and its locally stationary version (Silverman, 1957) are applied to Space Shuttle flight data, and the results are presented in extensive graphs. It is shown that the nonstationary model can analyze data from longer sampling periods and thus significantly reduce random error; this in turn leads to vibration spectra lower than those obtained with short-duration models.
Himelblau, Harry↗
Prediction of vibroacoustic loads for the modular attitude control system
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Staley, J. A.↗
Vibroacoustic Response of Pad Structures to Space Shuttle Launch Acoustic Loads
This paper presents a deterministic theory for the random vibration problem for predicting the response of structures in the low-frequency range (0 to 20 hertz) of launch transients. Also presented are some innovative ways to characterize noise and highlights of ongoing test-analysis correlation efforts titled the Verification Test Article (VETA) project.
Margasahayam, R. N.↗
Validation of a Deterministic Vibroacoustic Response Prediction Model
This report documents the recently completed effort involving validation of a deterministic theory for the random vibration problem of predicting the response of launch pad structures in the low-frequency range (0 to 50 hertz). Use of the Statistical Energy Analysis (SEA) methods is not suitable in this range. Measurements of launch-induced acoustic loads and subsequent structural response were made on a cantilever beam structure placed in close proximity (200 feet) to the launch pad. Innovative ways of characterizing random, nonstationary, non-Gaussian acoustics are used for the development of a structure's excitation model. Extremely good correlation was obtained between analytically computed responses and those measured on the cantilever beam. Additional tests are recommended to bound the problem to account for variations in launch trajectory and inclination.
Caimi, Raoul E.↗
Nonstationary Transient Vibroacoustic Response of a Beam Structure
This study consists of an investigation into the nonstationary transient response of the Verification Test Article (VETA) when subjected to random acoustic excitation. The goal is to assess excitation models that can be used in the design of structures and equipment when knowledge of the structure and the excitation is limited. The VETA is an instrumented cantilever beam that was exposed to acoustic loading during five Space Shuttle launches. The VETA analytical structural model response is estimated using the direct averaged power spectral density and the normalized pressure spectra methods. The estimated responses are compared to the measured response of the VETA. These comparisons are discussed with a focus on prediction conservatism and current design practice.
Caimi, R. E.↗
Vibroacoustic Response of the NASA ACTS Spacecraft Antenna to Launch Acoustic Excitation
The Advanced Communications Technology Satellite was an experimental NASA satellite launched from the Space Shuttle Discovery. As part of the ground test program, the satellite s large, parabolic reflector antennas were exposed to a reverberant acoustic loading to simulate the launch acoustics in the Shuttle payload bay. This paper describes the modelling and analysis of the dynamic response of these large, composite spacecraft antenna structure subjected to a diffuse acoustic field excitation. Due to the broad frequency range of the excitation, different models were created to make predictions in the various frequency regimes of interest: a statistical energy analysis (SEA) model to capture the high frequency response and a hybrid finite element-statistical energy (hybrid FE-SEA) model for the low to mid-frequency responses. The strengths and limitations of each of the analytical techniques are discussed. The predictions are then compared to the measured acoustic test data and to a boundary element (BEM) model to evaluate the performance of the hybrid techniques.
Larko, Jeffrey M.↗
"Model Informed" Vibroacoustic Scaling for Space Launch System Booster Forward Skirt, DYN-CY14-082
No abstract available
Leavitt, Gerald↗
Reverberant Acoustic Test Facility (RATF) Structural Design for Vibroacoustic Loads
No abstract available
McNelis, Mark E.↗
Effect of Stagger on the Vibroacoustic Loads from Clustered Rockets
The effect of stagger startup on the vibro-acoustic loads that form during the end- effects-regime of clustered rockets is studied using both full-scale (hot-gas) and laboratory scale (cold gas) data. Both configurations comprise three nozzles with thrust optimized parabolic contours that undergo free shock separated flow and restricted shock separated flow as well as an end-effects regime prior to flowing full. Acoustic pressure waveforms recorded at the base of the nozzle clusters are analyzed using various statistical metrics as well as time-frequency analysis. The findings reveal a significant reduction in end- effects-regime loads when engine ignition is staggered. However, regardless of stagger, both the skewness and kurtosis of the acoustic pressure time derivative elevate to the same levels during the end-effects-regime event thereby demonstrating the intermittence and impulsiveness of the acoustic waveforms that form during engine startup.
Rojo, Raymundo↗
Attenuation of the Cassini Spacecraft Vibroacoustic Environment
Cassini is a robotic spacecraft currently under development at the Jet Propulsion Laboratory (JPL) whose interplanetary scientific mission is to explore Saturn, its rings, and its moons. Cassini is scheduled to launce on a Titan IV rocket with a Centaur upper stage booster, and will be protected during ascent through the atmosphere by a lightweight aluminum payload fairing (PLF).
robotic↗
VAPEPS user's reference manual, version 5.0
This is the reference manual for the VibroAcoustic Payload Environment Prediction System (VAPEPS). The system consists of a computer program and a vibroacoustic database. The purpose of the system is to collect measurements of vibroacoustic data taken from flight events and ground tests, and to retrieve this data and provide a means of using the data to predict future payload environments. This manual describes the operating language of the program. Topics covered include database commands, Statistical Energy Analysis (SEA) prediction commands, stress prediction command, and general computational commands.
Park, D. M.↗
Preliminary vibration design and test criteria considerations for the space shuttle
This paper presents some Marshall Space Flight Center preliminary vibration design and test criteria considerations for the space shuttle. The discussion is primarily concerned with the formulation of vibration criteria for the design and testing of the equipment installations on the shuttle. A recommended criteria format is presented with a discussion of when the vibration environment has to be considered in design and testing. A semiempirical method of predicting the vibration criteria for the shuttle from vibroacoustic structural data banks is presented. Some preliminary vibration criteria predictions are presented for the orbiter and booster equipment bays and for the main shuttle engine. A research testing program to determine the vibroacoustic transfer through a typical shuttle thermal protection system (TPS) panel configuration is described.
Harry J. Bandgren↗
Investigation of a vibration-damping unit for reduction in low-frequency vibrations of electric motors
The vibroacoustical characteristics of different types of electric motors are discussed. It is shown that the basic source of low frequency vibrations is rotor unbalance. A flexible damping support, with an antivibrator, is used to obtain the vibroacoustical effect of reduction in the basic harmonic of the electric motor. A model of the electric motor and the damping apparatus is presented. Mathematical models are developed to show the relationships of the parameters. The basic purpose in using a calculation model id the simultaneous replacement of the exciting force created by the rotor unbalance and its inertial rigidity characteristics by a limiting kinematic disturbance.
Grigoryey, N. V.↗
Comparative evaluation of test methods to simulate acoustic response of shroud-enclosed spacecraft structures
Test methods were evaluated to ascertain whether a spacecraft, properly tested within its shroud, could be vibroacoustic tested without the shroud, with adjustments made in the acoustic input spectra to simulate the acoustic response of the missing shroud. The evaluation was based on vibroacoustic test results obtained from a baseline model composed (1) of a spacecraft with adapter, lower support structure, and shroud; (2) of the spacecraft, adapter, and lower structure, but without the shroud; and (3) of the spacecraft and adapter only. Emphasis was placed on the magnitude of the acoustic input changes required to substitute for the shroud and the difficulty of making such input changes, and the degree of missimulation which can result from the performance of a particular, less-than optimum test. Conclusions are drawn on the advantages and disadvantages derived from the use of input spectra adjustment methods and lower support structure simulations. Test guidelines were also developed for planning and performing a launch acoustic-environmental test.
On, F. J.↗
The influence of various test plans on mission reliability
Methods have been developed for the evaluation of cost effective vibroacoustic test plans for Shuttle Spacelab payloads. The shock and vibration environments of components have been statistically represented, and statistical decision theory has been used to evaluate the cost effectiveness of five basic test plans with structural test options for two of the plans. Component, subassembly, and payload testing have been performed for each plan along with calculations of optimum test levels and expected costs. The tests have been ranked according to both minimizing expected project costs and vibroacoustic reliability. It was found that optimum costs may vary up to $6 million with the lowest plan eliminating component testing and maintaining flight vibration reliability via subassembly tests at high acoustic levels.
Stahle, C. V.↗