Showing papers in "Journal of Aerospace Engineering in 1988"
TL;DR: In this article, the relative importance of the three known sources of radiation in space environment (direct solar, Earth's albedo, and direct Earth) was studied simultaneously on the orbital motion, attitude motion, and axial deformation of a very large, axially flexible space structure describing a planar pitch motion around the earth.
Abstract: Radiation thermal effects are studied simultaneously on the orbital motion, attitude motion, and axial deformation of a very large, axially flexible space structure describing a planar pitch motion around the earth. The relative importance of the three known sources of radiation in space environment—direct solar, Earth's albedo, and direct Earth—are studied for low Earth orbit (LEO) and geosynchronous Earth orbit (GEO). Influences of the area‐to‐mass ratio of the structure on thermal effects have been investigated for elliptical orbit. Radiation thermal effects are found to be significant in causing structural deformation and in producing libration in the attitude angle of a large space structure. However, on the orbital parameters of the space structure, the thermal effects are negligible. In LEO, effects of the earth's albedo and its direct radiation on the structure are appreciable, whereas in higher altitude orbits such as GEO, these may be neglected. The area‐to‐mass ratio of the structure is realize...
19 citations
TL;DR: The design process required for a lunar base observatory is considered in this article, where critical issues to be resolved include those relating to communications, data handling, controls, structures, materials, soil mechanics, and foundation engineering, as well as the research and development sequences and logistical problems.
Abstract: The design process required for a lunar base observatory is considered. An observatory on the moon with significant capability could be operational by the year 2015. Astronomical observations from a lunar base will require one or more of a wide variety of instruments. Optical telescopes, optical interferometers, radio telescopes, and radio interferometers have often been suggested. Possibilities also exist for options such as high-energy photon detectors, cosmic ray detectors, and neutrino astronomy instruments on the lunar surface. Successful designs for any of these options will require a step-by-step process involving close collaboration of many disciplines. Critical issues to be resolved include those relating to communications, data handling, controls, structures, materials, soil mechanics, and foundation engineering, as well as the research and development sequences and logistical problems.
18 citations
TL;DR: In this paper, the sparsity and symmetry of the mass and stiffness matrices of the finite element models of structures is exploited to suppress the nonlinear vibrations of an impulsively loaded, highly flexible beam.
Abstract: The need to account for geometric and material nonlinearities in the active control of highly flexible, large, space structures is emphasized herein. The performance index of the control problem is minimized subject to equations of state and costate using a variable metric algorithm. Unlike the conventional techniques for active control, the present algorithm is able to exploit the sparsity and symmetry of the mass and stiffness matrices of the finite element models of structures. The algorithm thus has the potential of being able to control moderately large‐scale, finite element models of highly flexible, large, space structures in a cost‐effective manner. The proposed algorithm is validated in suppressing the nonlinear vibrations of an impulsively loaded, highly flexible beam, and the need for inclusion of nonlinearities is demonstrated.
12 citations
TL;DR: In this article, a rational methodology for the development of advanced joining concepts for structural systems capable of providing enhanced dissipation of vibrational energy without serious penalties in strength, stiffness, or weight characteristics is described.
Abstract: Passively damped joints, in which the conventional adhesives are replacedby high damping viscoelastic materials, have the potential of being effective practical means for passive vibration control of dynamically loaded civil and aerospace structures. However, this potential cannot be realized unless the associated structural penalties are reduced to acceptable limits. This paper describes a rational methodology for the development of advanced joining concepts for structural systems capable of providing enhanced dissipation of vibrational energy without serious penalties in strength, stiffness, or weight characteristics. One such configuration is that of a rhombic-type joint, which provides a beneficial deformation coupling between the direction of load transfer and less critical offset directions. A comprehensive parametric study has been carried out in order to establish design guidelines for favorable trade-offs between damping benefits and the associated stiffness, strength, and weight penalties in a rhombic joint. The results are compared with the corresponding trade-offs for a double-lap joint made of the same materials.
8 citations
TL;DR: In this article, a description of metal matrix composites is presented which includes fiber materials, matrix materials, fibermatrix combinations, and fabrication methods, including fiber-based and metal-based methods.
Abstract: A description of metal matrix composites is presented which includes fiber materials, matrix materials, fibermatrix combinations, and fabrication methods. Over the past 25 years there has been an i...
8 citations
TL;DR: The United States is committed to the exploration of and the expansion into space and a manned earth-orbiting space station is planned for the next decade and studies continue looking at manned lunar bases as discussed by the authors.
Abstract: The United States is committed to the exploration of and the expansion into space. A manned earth‐orbiting space station is planned for the next decade and studies continue looking at manned lunar bases. Appropriate planning should be initiated for such a mission now as a high national priority. Many systems must be examined and technologies developed as soon as possible. Some of these include types of power sources, life support systems, construction equipment and techniques, construction methods, lunar mapping, and logistical constraints.
6 citations
TL;DR: In this paper, a rule-based expert system methodology has been developed and the Terrain Analysis Expert (TAX) has been implemented for modeling interpretation logic involved in identifying landforms from aerial images.
Abstract: Terrain analysis is a time‐consuming, costly, and labor‐intensive process requiring special skills and training. Furthermore, an enormous amount of remotely sensed data is routinely generated by satellite and airborne sensors which can be used for terrain analysis. Thus, there is an urgent need for an automated approach to analyzing these data and model human reasoning. A rule‐based expert system methodology has been developed and the Terrain Analysis Expert (TAX) has been implemented for modeling interpretation logic involved in identifying landforms from aerial images. Knowledge about the geographic location of the image was used to arrive at hypotheses about the landform of the site manifested on the aerial image. These hypotheses were then established or rejected based on the degree of match between the hypothesized landform's pattern elements and those of the site. The site was declared to be the landform with which it had the best match. The pattern elements of the site were obtained interactively f...
6 citations
TL;DR: A post-disaster investigation revealed a wealth of information, such as the finding that the storm was a microburst, and not a tornado as it was originally classified, that the aircraft tiedown system was flawed, that a gravel road was the principal source of damage to cars parked at the airport terminal, and that the gust factor of this type of wind is much higher than normally assumed for structural design.
Abstract: High winds at a maximum speed of 96 mph (43 m/s) hit the Columbia Regional Airport in Missouri on June 17, 1985, causing heavy damage to parked aircraft, hangars, building glass windows, automobiles, and so on. A post‐disaster investigation reveals a wealth of information, such as the finding that the storm was a microburst, and not a tornado as it was originally classified, that the aircraft tiedown system was flawed, that a gravel road was the principal source of damage to cars parked at the airport terminal, that the gust factor of this type of wind is much higher than normally assumed for structural design, and so on. Additional findings are that the atmospheric pressure of the storm measured was greatly affected by the wind‐generated pressure of the building in which the barometer was housed, and that west is the predominant direction of high winds at this airport. Lessons learned from the investigation can be very helpful in reducing future wind damage at airports and in improving understanding of w...
5 citations
TL;DR: In this paper, a simple and generalized static residual' strength model was formulated on the basis of equivalent damage size concept and stress fracture criterion, which can be applied to any type of damage.
Abstract: A simple and generalized static residual' strength model was formulated on the basis of equivalent damage size concept and stress fracture criterion. The model is semiempirical in nature and requires two data points, i.e., one test for the undamaged case and another with a damaged specimen. Good correlations were obtained with either impact‐damaged or simulated delamination tests. Theoretically speaking, this model can be applied to any type of damage.
5 citations
TL;DR: In this paper, the feasibility of using low-altitude aerial photography to inventory submersed macrophytes in the connecting channels of the Great Lakes was demonstrated using aerial color transparencies and ground truth information.
Abstract: This study demonstrates the feasibility of using low‐altitude aerial photography to inventory submersed macrophytes in the connecting channels of the Great Lakes. For this purpose, we obtained aerial color transparencies and collateral ground truth information about submersed vegetation at 160 stations within four study sites in the St. Clair and Detroit rivers, September 17 to October 4, 1984. Photographs were interpreted by five test subjects to determine with what accuracy they could detect beds of submersed macrophytes, and the precision of delineating the extent of such vegetation beds. The interpreters correctly determined the presence or absence of vegetation 80% of the time (range 73–86%). Differences between individuals were statistically significant. Determination of the presence or absence of macrophytes depended partly on their relative abundance and water clarity. Analysis of one photograph from each of the four study sites revealed that photointerpreters delineated between 35 and 75 ha of ri...
3 citations
TL;DR: The importance of early involvement of the engineering test perspective and approach in the engineering analysis, design, and development of capabilities for this construction activity in space, especially construction that incorporates the use of extraterrestrial resources is discussed in this article.
Abstract: A number of engineers and constructors have been looking at the engineering analyses and syntheses associated with preparations for the establishment of a base on the Moon and human flight to Mars. This paper discusses the importance of early involvement of the engineering test perspective and approach in the engineering analysis, design, and development of capabilities for this construction activity in space, especially construction that incorporates the use of extraterrestrial resources. The effectiveness and suitability of mission equipment and proposed resource extraction processes must be shown by analysis, simulation, ground test, and flight test. Facilities and resources for test and evaluation (T&E) of extraterrestrial facilities must be acquired in a timely fashion, and time must be allowed for T&E.
TL;DR: The analysis of earthquake fault lineament patterns within the alluvial valley of west Tennessee, which is often made difficult by the presence of unconsolidated sediments, is presently undertaken through a synergistic use of Landsat satellite images in conjunction with gravity anomaly data, which were quantitatively analyzed and compared by means of two-dimensional histograms and rose diagrams.
Abstract: The analysis of earthquake fault lineament patterns within the alluvial valley of west Tennessee, which is often made difficult by the presence of unconsolidated sediments, is presently undertaken through a synergistic use of Landsat satellite images in conjunction with gravity anomaly data, which were quantitatively analyzed and compared by means of two-dimensional histograms and rose diagrams. The northeastern trend revealed for the lineaments corresponds to faults and is in keeping with reactivation of the Reelfoot rift near the Mississippi River; this suggests that deeper features, perhaps at earthquake focal depth, may extend to the land surface as Landsat-detectable lineaments.
TL;DR: In this paper, the least-weight problem of a truncated, hollow, hexagonal core and subjected to a given bending moment along each edge is analyzed in order to meet the practical manufacturing requirements and be within allowable stress limits, constraints are placed on the geometrical dimensions of the structural parts of the sandwich panel as well as on the physical strength.
Abstract: The least‐weight problem of a sandwich panel with a truncated, hollow, hexagonal core, and subjected to a given bending moment along each edge is analyzed in this paper. In order to meet the practical manufacturing requirements and be within allowable stress limits, constraints are placed on the geometrical dimensions of the structural parts of the sandwich panel as well as on the physical strength, such as the allowable stresses. Upper and lower limiting values are assigned for each of the design variables. Through the use of the penalty function, the minimization problem subjected to a set of twenty inequality constraints is changed to a sequence of unconstrained ones. The modified Fletcher‐Powell method is used by a proper choice of the penalty parameter and the reduction factor. The methodology presented here can be extended to include multiple loading conditions, bending rigidity, and shear rigidity requirements, which present no additional difficulties except to increase the number of constraints.
TL;DR: From the perspective of a 250 nautical mile orbit aboard the Space Shuttle, the author has had the opportunity to observe the effects of man on the earth, to reflect on his future in space, and to examine the role civil engineers may have in building our future.
Abstract: From the perspective of a 250 nautical mile orbit aboard the Space Shuttle, the author has had the opportunity to observe the effects of man on the earth, to reflect on his future in space, and to examine the role civil engineers may have in building our future. In the decades to come, civil engineers will require skills that are not currently provided by universities and which are not adequately represented in professional societies. All disciplines of the civil engineering profession will need to examine their strategies to enable them to establish a significant place on the team. From launch pads to remote sensing satellites, from space stations to lunar bases, civil engineers can and should play a significant role in design requirements, engineering, testing, assembly, and operation. The Aerospace Division of the ASCE should take the lead to insure that civil engineers are prepared to meet the challenge.
TL;DR: In this paper, a calibration approach is verified by evaluation of radar depths and actual depths of soil features in five cores taken on the same transect, away from the pits.
Abstract: In soils developed in loess over glacial till, the presence and depth to clay layers, or fragipans, and other features are identified with radar. Radar evaluation of depths to soil features compares well with the soil pit and core descriptions by traditional methods. Regressions of radar‐derived, actual depths of soil features are used to calibrate radar measurements. The calibration approach is verified by evaluation of radar depths and actual depths of soil features in five cores taken on the same transect, away from the pits. Radar measurements of depths to features in soils have several practical applications.
Abstract: The building of stationary facilities in space and on the lunar surface will bring humankind to the verge of a new era in its exploration of space. Many new and unprecedented construction problems have to be solved. Terrestrial construction technology, developed over centuries, had to overcome similar earthbound extremes. Viable examples include underwater construction and building on the frozen terrain of north and south poles. Many specialized techniques and kinds of equipment have emerged to meet those extreme conditions. This body of knowledge and technology may become a valuable resource for the design and construction of buildings in space. The objective of this paper is to demonstrate why experts from space technology and construction engineering should combine their specialized knowledge to benefit human advances into space.
TL;DR: In this article, the authors explore the idea of developing space-construction animation "tools" to facilitate extraterrestrial design and construction activities, which would integrate engineering operations in space, but in order to develop such tools, it is necessary to determine their functional requirements.
Abstract: This paper explores the idea of developing space‐construction animation “tools” to facilitate extraterrestrial design and construction activities. These tools would integrate engineering operations in space. However, in order to develop such tools, it is necessary to determine their functional requirements. This involves an assessment of existing technological trends as well as an understanding of the future needs of this technology. The need for improved forms of communication between parties involved in space design and construction suggests the need for a dynamic or animated representation of the construction processes. Computer animation offers a unified approach to modeling the spatial dynamics so crucial in the planning and controlling of construction activities, and evaluation of automation models. For remotely monitored processes, simply providing critical information in an easily—and quickly—understood format could aid the space‐construction manager in anticipating interference and other critical...
TL;DR: This paper seeks to provide a brief overview of the somewhat unfamiliar concept underlying system identification, especially as it applies to large flexible space structures.
Abstract: This paper seeks to provide a brief overview of the somewhat unfamiliar concept underlying system identification, especially as it applies to large flexible space structures. Having elaborated on t...