Guidelines for Dynamic Environmental Criteria: An Invitation to Participate in Their Development
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Dynamic design Mission quality↗
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Piersol, Allan G.
Publications and source records attributed to Piersol, Allan G..
Guidelines for dynamic data acquisition and analysis
The recommendations concerning pyroshock data presented in the final draft of a proposed military handbook on Guidelines for Dynamic Data Acquisition and Analysis are reviewed. The structural responses produced by pyroshocks are considered to be one of the most difficult types of dynamic data to accurately measure and analyze.
Piersol, Allan G.↗
Optimum data analysis procedures for Titan 4 and Space Shuttle payload acoustic measurements during lift-off
Analytical expressions have been derived to describe the mean square error in the estimation of the maximum rms value computed from a step-wise (or running) time average of a nonstationary random signal. These analytical expressions have been applied to the problem of selecting the optimum averaging times that will minimize the total mean square errors in estimates of the maximum sound pressure levels measured inside the Titan IV payload fairing (PLF) and the Space Shuttle payload bay (PLB) during lift-off. Based on evaluations of typical Titan IV and Space Shuttle launch data, it has been determined that the optimum averaging times for computing the maximum levels are (1) T (sub o) = 1.14 sec for the maximum overall level, and T(sub oi) = 4.88 f (sub i) (exp -0.2) sec for the maximum 1/3 octave band levels inside the Titan IV PLF, and (2) T (sub o) = 1.65 sec for the maximum overall level, and T (sub oi) = 7.10 f (sub i) (exp -0.2) sec for the maximum 1/3 octave band levels inside the Space Shuttle PLB, where f (sub i) is the 1/3 octave band center frequency. However, the results for both vehicles indicate that the total rms error in the maximum level estimates will be within 25 percent the minimum error for all averaging times within plus or minus 50 percent of the optimum averaging time, so a precise selection of the exact optimum averaging time is not critical. Based on these results, linear averaging times (T) are recommended for computing the maximum sound pressure level during lift-off.
Piersol, Allan G.↗
Pyroshock recommendations in proposed MIL-HDBK on 'Dynamic Data Acquisition and Analysis'
The pyroshock recommendations presented in a military handbook on Guidelines for Dynamic Data Acquisition and Analysis, which is being prepared by the Jet Propulsion Laboratory, are summarized. Numerous comments,including suggestions for modifications and additions to the handbook, are discussed. Particular attention is given to recommendations concerning measurement locations, transducers, signal conditioners, data recorders, data sampling, data editing, and data analysis.
Piersol, Allan G.↗
Proposed military handbook for dynamic data acquisition and analysis - An invitation to review
A draft Military Handbook prepared under the sponsorship of the USAF Space Division is presently being distributed throughout the U.S. for review by the aerospace community. This comprehensive document provides recommended guidelines for the acquisition and analysis of structural dynamics and aeroacoustic data, and is intended to reduce the errors and variability commonly found in flight, ground and laboratory dynamic test measurements. In addition to the usual variety of measurement problems encountered in the definition of dynamic loads, the development of design and test criteria, and the analysis of failures, special emphasis is given to certain state-of-the-art topics, such as pyroshock data acquisition and nonstationary random data analysis.
Himelblau, Harry↗
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↗
The analysis of nonstationary vibration data
The general methodology for the analysis of arbitrary nonstationary random data is reviewed. A specific parametric model, called the product model, that has applications to space vehicle launch vibration data analysis is discussed. Illustrations are given using the nonstationary launch vibration data measured on the Space Shuttle orbiter vehicle.
Piersol, Allan G.↗
Evaluation of LRC Spectral Analyses of Simulated Gust Velocity Data
The NASA Langley Research Center (LRC) has been computing power spectra of simulated atmospheric turbulence data by various techniques, in preparation for the B-57 gust velocity data analysis program. The results of these studies have confirmed earlier suspicions that conventional first-difference pre-whitening of gust velocity data can produce serious distortions in the spectral densities at very low frequencies (below the frequency of the gust velocity spectral "knee"). The results also indicate that the frequency averaging procedures have certain merits over ensemble averaging procedures in the computation of spectra by direct Fourier transform operations. Finally, the results do not reveal any significant difference in the spectral estimates obtained using Hann versus Parzen smoothing procedures.
Piersol, Allan G.↗