Application of Kalman filtering techniques to strapdown system inertial alignment
Digital methods for determining initial alignment of strapdown inertial navigation system from vibration and sway corrupted data on launch pad
Earle B. Crocker↗
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Excitation of Na D-line radiation in collisions of sodium atoms with internally excited H2, D2, and N2
Excitation of D-line radiation in collisions of Na atoms with vibrationally excited N2, H2 and D2 was studied in two modulated crossed beam experiments. In both experiments, the vibrational excitation of the molecules was provided by heating the molecular beam source to temperatures in the range of 2000 to 3000 K, which was assumed to give populations according to the Boltzmann expression. In the first experiment, a total rate coefficient was measured as a function of molecular beam temperature, with absolute calibration of the photon detector being made using the black body radiation from the heated molecular beam source. Since heating affects both the internal energy and the collisional kinetic energy, the first experiment could not determine the relative contributions of internal energy transfer versus collisional excitation. The second experiment achieved partial separation of internal versus kinetic energy transfer effects by using a velocity-selected molecular beam. Using two simple models for the kinetic energy dependence of the transfer cross section for a given change in vibrational quantum number, the data from both experiments were used to determine parameters in the models.
Krause, H. F.↗
Concepts for a theoretical and experimental study of lifting rotor random loads and vibrations (identification of lifting rotor system parameters from transient response data), Phase 7-B
System identification methods have been applied to rotorcraft to estimate stability derivatives from transient flight control response data. While these applications assumed a linear constant coefficient representation of the rotorcraft, the computer experiments used transient responses in flap-bending and torsion of a rotor blade at high advance ratio which is a rapidly time varying periodic system. It was found that a simple system identification method applying a linear sequential estimator also called least square estimator or equation of motion estimator, is suitable for this periodic system and can be used directly if only the acceleration data are noise polluted. In the case of noise being present also in the state variable data the direct application of the estimator gave poor results.
Hohenemser, K. H.↗
FLUT - A program for aeroelastic stability analysis
A computer program (FLUT) that can be used to evaluate the aeroelastic stability of aircraft structures in subsonic flow is described. The algorithm synthesizes data from a structural vibration analysis with an unsteady aerodynamics analysis and then performs a complex eigenvalue analysis to assess the system stability. The theoretical basis of the program is discussed with special emphasis placed on some innovative techniques which improve the efficiency of the analysis. User information needed to efficiently and successfully utilize the program is provided. In addition to identifying the required input, the flow of the program execution and some possible sources of difficulty are included. The use of the program is demonstrated with a listing of the input and output for a simple example.
Johnson, E. H.↗
User's Guide for a Modular Flutter Analysis Software System (Fast Version 1.0)
The use and operation of a group of computer programs to perform a flutter analysis of a single planar wing are described. This system of programs is called FAST for Flutter Analysis System, and consists of five programs. Each program performs certain portions of a flutter analysis and can be run sequentially as a job step or individually. FAST uses natural vibration modes as input data and performs a conventional V-g type of solution. The unsteady aerodynamics programs in FAST are based on the subsonic kernel function lifting-surface theory although other aerodynamic programs can be used. Application of the programs is illustrated by a sample case of a complete flutter calculation that exercises each program.
Desmarais, R. N.↗
Planar-Wing Flutter Analysis
Flutter Analysis System, FAST, is group of five programs that perform flutter analysis of single planar wing. Each program performs certain portions of flutter analysis and may be run sequentially or individually. Modular approach is very versatile and flexible. FAST uses natural vibration modes as input data and performs conventional V-g solution.
Desmarais, R. N.↗
Acoustic and vibration environments for laboratory experiments in space
The basic parameters of random noise and vibration are described, and typical environments for the launch phase and orbital operations are presented. For the latter, both acoustically induced and structure-borne, thruster-included vibration are addressed, using data obtained during the Skylab and Titan programs.
Rader, W. P.↗
Integrated controls/structures study of advanced space systems
A cost tradeoff is postulated for a stiff structure utilizing minimal controls (and control expense) to point and stabilize the vehicle. Extra costs for a stiff structure are caused by weight, packaging size, etc. Likewise, a more flexible vehicle should result in reduced structural costs but increased costs associated with additional control hardware and data processing required for vibration control of the structure. This tradeoff occurs as the ratio of the control bandwidth required for the mission to the lowest (significant) bending mode of the vehicle. The cost of controlling a spacecraft for a specific mission and the same basic configuration but varying the flexibility is established.
Greene, C. S.↗
Multishaker Modal Testing
Report prepared for Marshall Space Flight Center summarizes recent advances in mathematical analysis of structural vibrations based on experimental data. Also includes summary of research by author as well as abstracts of technical reports and papers presented at meetings or otherwise published.
Graig, R. R., Jr.↗
Data presentation techniques for rotating machinery malfunction diagnosis
Baseline steady state data is excellent for documentation of vibration signals at normal operating conditions. Assuming that a set of initial data was acquired with the machinery in a good state of repair, any future changes or deterioration in mechanical condition can be easily compared to the baseline information. Often this type of comparison will yield sufficient information for evaluation of the problem. However, many malfunctions require the analysis of transient data in order to identify the malfunction. Steady-state data formats consist of: Time Base Waveform, Orbit, Spectrum. Transient data formats consist of: Polar, Bode, Cascade. Our objective is to demonstrate the use of the above formats to diagnose a machine malfunction. A turbine-driven compressor train is chosen as an example. The machine train outline drawing is shown.
Spettel, T.↗
The EUV dayglow at high spectral resolution
Rocket observations and spectra of the dayglow spectrum of the terrestrial atmosphere between 840 and 1860 A are studied. Three bands of the N2 c-prime 4 system are seen clearly resolved in the dayglow. Analysis of high-resolution N2 Lyman-Birge-Hopfield data shows no anomalous vibrational distribution as has been reported from other observations. Altitude profiles of the observed O and N2 emissions demonstrate that the MSIS-83 model O and N2 densities are appropriate for the conditions of the rocket flights.
Morrison, M. D.↗
System dynamic simulation of precision segmented reflector
A joint effort was undertaken on a Precision Segmented Reflector (PSR) Project. The missions in which the PSR is to be used will use large (up to 20 m in diameter) telescopes. The essential requirement for the telescopes is that the reflector surface of the primary mirror must be made extremely precise to allow no more than a few microns of errors and, additionally, this high surface precision must be maintained when the telescope is subjected to on-orbital mechanical and thermal disturbances. Based on the mass, size, and stability considerations, reflector surface formed by segmented, probably actively or passively controlled, composite panels are regarded as most suitable for future space based astronomical telescope applications. In addition to the design and fabrication of composite panels with a surface error of less than 3 microns RMS, PSR also develops related reflector structures, materials, control, and sensing technologies. As part of the planning effort for PSR Technology Demonstration, a system model which couples the reflector, consisting of panels, support truss and actuators, and the optical bench was assembled for dynamic simulations. Random vibration analyses using seismic data obtained from actual measurements at the test site designated for PSR Technology Demonstration are described.
Shih, Choon-Foo↗
Optical distributed sensing and computation for a proposed flexible beam experiment
A new technology is being developed that supports distributed sensing and computation wherein crystal mediums are used with real-time holography to gather images that contain vibration and instantaneous geometry data for a spacecraft. Optical computation techniques are employed to process the image data and to compute commands to actuators located on the spacecraft. This paper presents an integrated sensor/processor design for an experiment to demonstrate this technology. A performance estimate for the design is presented in terms of the optical spatial bandwidth of the imaging system, as opposed to the temporal bandwidth. The advantages of an integrated optical sensor/processor relative to control of large spacecraft are addressed.
Welch, S. S.↗
High-resolution spectra of the 6300-A region of Comet P/Halley
Echelle/reticon high resolution spectra have been obtained for the 6300-A region of P/Halley which show a clear separation in the relative contributions of the various rotational lines of the (0,8,0) band of NH2 and of the cometary and airglow contributions of O(1D). An analysis of these data indicates that the vibrational structure of the band could be useful as a diagnostic for coma temperatures and/or outflow kinematics. The inner radial brightness distribution for O(1D) is found to be in keeping with production by H2O parent-molecule dissociation; O(1D) also exhibited a detectable deviation from circular symmetry.
Combi, Michael R.↗
Cosmic Background Explorer
The COBE spacecraft is briefly described. The use of flight data to determine sinusoidal vibration levels to simulate Pogo events is discussed.
Coladonato, Robert↗
Structural design and analysis for an ultra low CTE optical bench for the Hubble Space Telescope corrective optics
The stringent stability requirements of the Corrective Optics Space Telescope Axial Replacement (COSTAR) necessitates a Deployable Optical Bench (DOB) with both a low CTE and high resonant frequency. The DOB design consists of a monocoque thin shell structure which marries metallic machined parts with graphite epoxy formed structure. Structural analysis of the DOB has been integrated into the laminate design and optimization process. Also, the structural analytical results are compared with vibration and thermal test data to assess the reliability of the analysis.
Neam, Douglas C.↗
Improvement of Space Shuttle Main Engine Low Frequency Acceleration Measurements
The noise floor of low frequency acceleration data acquired on the Space Shuttle Main Engines is higher than desirable. Difficulties of acquiring high quality acceleration data on this engine are discussed. The approach presented in this paper for reducing the acceleration noise floor focuses on a search for an accelerometer more capable of measuring low frequency accelerations. An overview is given of the current measurement system used to acquire engine vibratory data. The severity of vibration, temperature, and moisture environments are considered. Vibratory measurements from both laboratory and rocket engine tests are presented.
Stec, Robert C.↗
Current Progress of a Finite Element Computational Fluid Dynamics Prediction of Flutter for the AeroStructures Test Wing
This progress report focuses on the use of the STructural Analysis RoutineS suite program, SOLIDS, input for the AeroStructures Test Wing. The AeroStructures Test Wing project as a whole is described. The use of the SOLIDS code to find the mode shapes of a structure is discussed. The frequencies, and the structural dynamics to which they relate are examined. The results of the CFD predictions are compared to experimental data from a Ground Vibration Test.
Arena, Andrew S., Jr.↗