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Hamilton, D. A.

Publications and source records attributed to Hamilton, D. A..

Spectral representation of high-frequency Space Shuttle data

High frequency Space Shuttle liftoff data are treated by autoregressive (AR) and autoregressive-moving-average (ARMA) digital algorithms. These algorithms provide useful information on the spectral densities of the data. Further, they yield spectral models, which lend themeselves to incorporation into the concept of the random response spectrum. This concept yields a reasonably smooth power spectrum for the design of structural and mechanical systems when the available data bank is limited. Due to the nonstationary of the liftoff event, the pertinent data are split into three slices. Each of the slices is associated with a rather distinguished phase of the liftoff event, in which stationarity can be expected. The presented results are preliminary in nature; they aim to call attention to the availability of the discussed concepts and to the need to augment the Space Shuttle data bank as more flights are completed.

Spanos, P. D.

Efficient loads analyses of Shuttle-payloads using dynamic models with linear or nonlinear interfaces

An efficient method for the load analysis of Shuttle-payload systems with linear or nonlinear attachment interfaces is presented which allows the kinematics of the interface degrees of freedom at a given time to be evaluated without calculating the combined system modal representation of the Space Shuttle and its payload. For the case of a nonlinear dynamic model, an iterative procedure is employed to converge the nonlinear terms of the equations of motion to reliable values. Results are presented for a Shuttle abort landing event.

Spanos, P. D.

Digital spectral estimation and modeling of Space Shuttle flight data

Application of the digital signal processing technique of autoregressive-moving-average (ARMA) modeling to the estimation of power spectra and shock spectra from Space Shuttle lift-off flight accelerograms is described in this paper. The background for application to ARMA of lift-off accelerograms which are non-stationary in nature is exemplified through a step-by-step discussion of actual numerical results. Included is a discussion of pertinent mathematical background for the ARMA approximations. Potential areas for application of ARMA modeling in payload integration activities are suggested.

Spanos, P. D.

Decoupled dynamic analysis of combined systems by iterative determination of interface accelerations

A dynamic analysis technique is presented that can be used to determine the response of a discrete model of a large linear structural system composed of multiple substructures. The technique circumvents the costly computation of the modal characteristics of the combined system. This is accomplished by relying on a predictor-corrector scheme to converge iteratively to the interface accelerations of the combined system, while the equations of motions of the individual structures are integrated separately. In this regard, the temporal slopes of the interface accelerations (jerks) are computed at each time point of integration to predict the interface accelerations at the next time point. The proposed technique is exemplified by conducting a Space Shuttle landing loads analysis; the obtained numerical data demonstrate its reliability and efficiency.

Spanos, P. D.

Loads environment for payload/cargo integration

Space Shuttle users are required to design their payload to the Shuttle loads environment. This loads environment covers mission phases from prelaunch to landing. Transient response loads analyses are required for lift-off and landing events. Other mission events are analyzed statically because they result in payload loads that either change slowly or are lower than lift-off and landing loads. Response data from flight instrumentation located on the orbiter and payloads have been compared to preflight design conditions and to nominal predictions. The results have verified that the design loads envelop flight responses.

Frederick, D. H.

A review of Shuttle payload bay low-frequency response for STS-1 through STS-5

Flight data from the Space Shuttle missions STS-1 through STS-5 have been evaluated to assess the Orbiter payload bay low-frequency loads and dynamics. An overview of external loading environments for lift-off is presented and a summary of landing impact conditions is given. Accelerometer data at various Orbiter locations are presented and comparisons are made with analytical predictions. The measured accelerations at lift-off for the STS-2 through STS-5 missions were very repeatable and much lower than those of STS-1 because of the reduction of solid rocket booster overpressure loading on the Shuttle. The environments for the quasi-static conditions were below design requirements for all flights. The landing conditions and responses for STS-3 were near limit but nominal on the other flights. Comparisons are made with frequency content of analytical and test data. The primary emphasis of this assessment was to verify the adequacy of Space Transportation System design load environments to envelop flight responses.

Hamilton, D. A.

Orbiter Landing Loads Math Model Description and Correlation with ALT Flight Data

Results of the space shuttle approach and landing test are examined in order to assess landing gear characteristics and performance and verify landing dynamic analyses. The landing gears were instrumented with load-calibrated strain gages, a wheel-speed sensor, and strut stroke measurement devices. The mathematical procedure used in predicting the shuttle touchdown loads and dynamics is presented together with the comparisons between measured flight data and the analytical predictions. Conclusions from these data are also presented.

Hamilton, D. A.

The staging dynamics of a proposed space shuttle configuration

A mathematical model was developed to simulate the staging dynamics of a proposed space shuttle configuration. Included in the mathematical model is the kinematics and dynamics of the staging mechanism, thrust forces and thrust vector control, rigid-body dynamics, and structural dynamics of both the booster and orbiter stages of the configuration. The mathematical model was incorporated into a computer program so that the staging maneuver could be simulated. Results of the simulations are presented.

Hamilton, D. A.