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Peters, W. H.

Publications and source records attributed to Peters, W. H..

9 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Attitude control and stability of a Space Station

Certain problems arise in connection with the design and construction of a Space Station. These problems are partly related to the impossibility to predict in advance the ultimate form and size which the Space Station will assume. Due to the abatement of volume and strength constraints it will be desirable (for maximum utility of mass) to permit very low structural resonance frequencies, and due to complexity of the configuration there will be an extremely high density of modal frequencies. The basic approaches available to an attitude control system designer for coping with the dynamics of a plant with the considered characteristics are examined. In order to overcome difficulties related to a use of currently widely considered approaches, a technique is proposed whereby the degrees of freedom requiring active control are isolated mechanically from other superfluous vibratory modes.

Peters, W. H.↗
NASA NTRS1982

Digital imaging techniques in experimental stress analysis

Digital imaging techniques are utilized as a measure of surface displacement components in laser speckle metrology. An image scanner which is interfaced to a computer records and stores in memory the laser speckle patterns of an object in a reference and deformed configuration. Subsets of the deformed images are numerically correlated with the references as a measure of surface displacements. Discrete values are determined around a closed contour for plane problems which then become input into a boundary integral equation method in order to calculate surface traction in the contour. Stresses are then calculated within this boundary. The solution procedure is illustrated by a numerical example of a case of uniform tension.

Peters, W. H.↗
NASA NTRS1982

Experimental boundary integral equation applications in speckle interferometry

A complete data analysis system utilizing laser speckle interferometry and Experimental Integral Equation Method (EBIE) is described. A host computer provides the optical data analysis and serves as an input device to a PDP11/VAX computer for numerical analysis. The basic theory of pointwise filtering and digital correlation is described as experimental data input to the BIE method.

Fraley, J. E.↗
NASA NTRS1979

Influence of flaw geometries on hole-crack stress intensities

The paper deals with a frozen-stress photoelastic study of a class of flaw shapes where the ratio of the hole diameter to plate thickness is approximately unity. The study was carried out by a technique developed for estimating stress intensity factor variations along the border of flaws in three-dimensional problems. The results show that for deep flaws, the flaw shapes are not simple and the flow growth is not self-similar. The implications of this effect are discussed.

Smith, C. W.↗
NASA NTRS1977

Stress intensities for cracks emanating from pin-loaded holes

A series of stress freezing photoelastic experiments were conducted on large plates containing central holes with cracks emanating from the edge formed by the intersection of the hole with the plate surface. Loads were applied through rigid pins with neat fits in the holes. Stress-intensity factors (SIF) were estimated by a computer assisted least squares analysis of the photoelastic data taken from slices near the points of intersection of the flaw border with the hole boundary and the plate surface. Results indicate that the local mode of loading changes from Mode 1 near the hole boundary to mixed mode near the plate surface. The analysis is extended to include mixed mode loading, and results are compared with an existing approximate theory.

Smith, C. W.↗
NASA NTRS1975

Space Shuttle flight control system

The Space Shuttle is a control stabilized vehicle with control provided by an all digital, fly-by-wire flight control system. This paper gives a description of the several modes of flight control which correspond to the Shuttle mission phases. These modes are ascent flight control (including open loop first stage steering, the use of four computers operating in parallel and inertial guidance sensors), on-orbit flight control (with a discussion of reaction control, phase plane switching logic, jet selection logic, state estimator logic and OMS thrust vector control), entry flight control and TAEM (terminal area energy management to landing). Also discussed are redundancy management and backup flight control.

Klinar, W. J.↗
NASA NTRS1973

Apollo experience report: Guidance and control systems - Digital autopilot design development

The development of the Apollo digital autopilots (the primary attitude control systems that were used for all phases of the lunar landing mission) is summarized. This report includes design requirements, design constraints, and design philosophy. The development-process functions and the essential information flow paths are identified. Specific problem areas that existed during the development are included. A discussion is also presented on the benefits inherent in mechanizing attitude-controller logic and dynamic compensation in a digital computer.

Peters, W. H.↗
NASA NTRS1972

Inflight dynamics testing of the Apollo spacecraft

Response of the Apollo command module, service and lunar module airframe while in a docked configuration in the flight environment was measured in a frequency band encompassing the first two bending modes. Transfer characteristics from thrust-application point to control-system sensor were examined. The frequency and the stability margins of the first two predominant structural resonances were verified by the test. This report describes the flight test that was performed and the postflight data analysis.

Peters, W. H.↗