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At least 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Space Station truss structures and construction considerations

Although a specific configuration has not been selected for the Space Station, a gravity gradient stabilized station as a basis upon which to compare various structural and construction concepts is considered. The Space Station primary truss support structure is described in detail. Three approaches (see sketch A) which are believed to be representative of the major techniques for constructing large structures in space are also described in detail so that salient differences can be highlighted.

Mikulas, M. M., Jr.↗
NASA NTRS1985

System and structural dynamic observations of a slewed box truss antenna

A parametric analysis was performed in order to define the slewing capability of the Earth Observation Spacecraft (EOS) box-truss antenna. The input data for the analysis consisted of the slew rate, settling time, damping, maneuver frequencies, and attitude hold times of the antenna. The dynamic transient response of the antenna was evaluated, and the results are compared with NASA operational requirements. The results of the parametric analysis are summarized in a series of tables.

Bachtell, E. E.↗
NASA NTRS1985

Thermal design of the ACCESS erectable space truss

Thermal design requirements for the erectable truss beam to be assembled in-orbit during extra-vehicular activity as part of the ACCESS experiment to take place in 1985-1986 are formulated and assessed. The coatings, insulation, and materials chosen for the structural elements of the beam are detailed. A combined radiation and conduction thermal model reveals that worst-case thermal gradients within the ACCESS structure over plane-to-sun angles of 0 to 80 deg will be less than 29 F, which is within the allowable limit of 50 F. The individual strut insulation concept using aluminized Kapton is shown to offer significant advantages over white paint or a chromic acid anodized surface for controlling the thermal response.

Bradley, O. H., Jr.↗
NASA NTRS1986

Dynamic characteristics of power-tower space stations with 15-foot truss bays

A power tower space station concept which generates power with photovoltaic arrays and where the truss structure has a bay size of 15 ft is described. Rigid body and flexible body dynamic characteristics are presented for a 75-kW Initial Operating Capability (IOC) and 150-kW and 300-kW growth stations. The transient response of the IOC and 300-kW growth stations to shuttle dock, orbit reboost, and mobile remote manipulator system translation loads are studied. Displacements, accelerations, and bending moments at various locations on the IOC and 300-kW growth stations are presented.

Dorsey, J. T.↗
NASA NTRS1986

Deployable M-braced truss structure

A deployable M-braced truss structure, efficiently packaged into a compact stowed position and expandable to an operative position at the use site is described. The M-braced configuration effectively separates tension compression and shear in the structure and permits efficient structural design. Both diagonals and longerons telescope from an M-braced base unit and deploy either pneumatically, mechanically by springs or cables, or by powered reciprocating mechanisms. Upon full deployment, the diagonals and longerons lock into place with a simple latch mechanism.

Mikulas, M. M., Jr.↗
NASA NTRS1986

Integrated analysis system for box truss antenna mesh performance

An integrated analysis system has been developed to more efficiently design and analyze the mesh reflective surface and the mesh tie system of the box truss antenna. Six integrated computer programs using nonlinear finite-element, surface topography and interpolation, and RF aperture integration techniques, analyze the effects of manufacturing errors, mesh pillowing, and operating environment on antenna performance. The level of rigor of analysis can be varied, providing the possibility of a lower cost preliminary study on various designs using a minimum number of reduced box section models. By including the random and systematic errors with the aperture integration of minimum rms reflector surface roughness, the RF Performance Solver determines the far-field pattern, including the beam efficiency, and thus the antenna performance of the mesh reflector antenna.

Bachtell, E. E.↗
NASA NTRS1985

Thermal analysis of the ACCESS space truss

This paper introduces the Assembly Concept for the Construction of Erectable Space Structure (ACCESS) experiment and describes the thermal requirements in detail. The experiment, an erectable truss beam to be flown and assembled aboard the Space Shuttle, was thermally modeled using the TRASYS and SINDA computer codes. Results from the thermal analysis are presented. Development tests dictate the application of a metallized film insulation on the aluminum beam struts to control transient orbital temperature extremes.

Foss, R. A.↗
NASA NTRS1987

Wedge Joints for Trusses

Structure assembled rapidly with simple hand tools. Proposed locking wedge joints enable rapid assembly of lightweight beams, towers, scaffolds, and other truss-type structures. Lightweight structure assembled from tubular struts joined at nodes by wedge pins fitting into mating slots. Joint assembled rapidly by seating wedge pin in V-shaped slots and deforming end of strut until primary pawl engages it.

Wood, Kenneth E.↗
NASA NTRS1986

Near-field testing of the 5-meter model of the tetrahedral truss antenna

This report documents the technical results from near-field testing of the General Dynamics 5-meter model of the tetrahedral truss antenna at the Martin Marietta Denver Aerospace facility. A 5-meter square side of the tetrahedral served as the perimeter of the antenna, and a mesh surface and extensive surface contouring cord network was used to create a parabolic aperture shape to within an rms accuracy of 30 mils or better. Pattern measurements were made with offset feed systems radiating at frequencies of 7.73, 11.60, 2.27, and 4.26 (all in GHz). This report discusses the method of collecting the data, system measurement accuracy, the test data compiled, and diagostics and isolation of causes of pattern results. The technique of using near-field phase for measuring surface mechanical tolerances is included. Detailed far field antenna patterns and their implications are provided for all tests conducted.

Kefauver, Neill↗
NASA NTRS1986

Joint nonlinearity effects in the design of a flexible truss structure control system

Nonlinear effects are introduced in the dynamics of large space truss structures by the connecting joints which are designed with rather important tolerances to facilitate the assembly of the structures in space. The purpose was to develop means to investigate the nonlinear dynamics of the structures, particularly the limit cycles that might occur when active control is applied to the structures. An analytical method was sought and derived to predict the occurrence of limit cycles and to determine their stability. This method is mainly based on the quasi-linearization of every joint using describing functions. This approach was proven successful when simple dynamical systems were tested. Its applicability to larger systems depends on the amount of computations it requires, and estimates of the computational task tend to indicate that the number of individual sources of nonlinearity should be limited. Alternate analytical approaches, which do not account for every single nonlinearity, or the simulation of a simplified model of the dynamical system should, therefore, be investigated to determine a more effective way to predict limit cycles in large dynamical systems with an important number of distributed nonlinearities.

Mercadal, Mathieu↗
NASA NTRS1986

Vibration suppression of planar truss structures utilizing uniform damping control

A variety of methods has been devised for vibrational control of a structure using both passive and active controls. Presented in this paper is a relatively new method for vibration suppression, uniform damping control. This method consists of implementing a control law which tends to dampen each vibrational mode of the structure at the same desirable exponential rate. The unique aspects of this method are that the control law is not explicitly dependent on the structural stiffness, the control forces are directly proportional to the distribution of the structural mass, and the control law is natural and decentralized. The control law was applied to a flexible planar truss structure and the various aspects of implementation of the control law examined are: actuator/sensor number, placement, and the impact of the actuator/sensor number and placement on the necessary control 'power' requirements such as peak power loads, total power requirements, etc. Also examined are the effects of using a limited number of active members in terms of the vibrational performance when compared with the 'ideal' distributed control law.

Andersen, G. C.↗
NASA NTRS1986

Wind deflection compensated, zero-coma telescope truss geometries

Six telescope truss geometries are evaluated for both wind and gravity deflection stiffness. The existence of simultaneous solutions for gravity and wind deflections is demonstrated. A baseline design for the Texas 7.6-meter telescope with an F/1.4 Angel lightweight borosilicate primary mirror is shown.

Meinel, Aden B.↗
NASA NTRS1988

Truss-Core Corrugation

Strength-to-weight ratio exceeds beaded-web design by 60 percent. New corrugation design offers significant weight saving. Truss-core web replaces beaded web of previous corrugation designs.

Davis, Randall C.↗
NASA NTRS1988

Folding Truss Structure

Concept for foldable and deployable truss offers advantages of strength, rigidity, and mechanical simplicity. Structure consists of series of boxlike bays with 9-ft sides. Each box has panels on top and bottom and two sides. Two remaining sides open. Panels hinged at connecting edges. Adapted to terrestrial transportable structures, scaffolds, cranes, and rows of cubicles.

Warren, Aubrey D.↗
NASA NTRS1987

Telerobotic truss assembly

The ACCESS truss was telerobotically assembled in order to gain experience with robotic assembly of hardware designed for astronaut extravehicular (EVA) assembly. Tight alignment constraints of the ACCESS hardware made telerobotic assembly difficult. A wider alignment envelope and a compliant end effector would have reduced the problem. The manipulator had no linear motion capability, but many of the assembly operations required straight line motion. The manipulator was attached to a motion table in order to provide the X, Y, and Z translations needed. A programmable robot with linear translation capability would have eliminated the need for the motion table and streamlined the assembly. Poor depth perception was a major problem. Shaded paint schemes and alignment lines were helpful in reducing this problem. The four cameras used worked well for only some operations. It was not possible to identify camera locations that worked well for all assembly steps. More cameras or movable cameras would have simplified some operations. The audio feedback system was useful.

Sheridan, Philip L.↗
NASA NTRS1988

Extension and validation of a method for locating damaged members in large space trusses

The damage location approach employs the control system capabilities for the structure to test the structure and measure the dynamic response. The measurements are then used in a system identification algorithm to produce a model of the damaged structure. The model is compared to one for the undamaged structure to find regions of reduced stiffness which indicate the location of damage. Kabe's 3,4 stiffness matrix adjustment method was the central identification algorithm. The strength of his method is that, with minimal data, it preserves the representation of the physical connectivity of the structure in the resulting model of the damaged truss. However, extensive storage and computational effort were required as a result. Extension of the damage location method to overcome these problems is the first part of the current work. The central system identification algorithm is replaced with the MSMT method of stiffness matrix adjustment which was previously derived by generalizing an optimal-update secant method form quasi-Newton approaches for nonlinear optimization. Validation of the extended damage location method is the second goal.

Smith, Suzanne Weaver↗
NASA NTRS1988

Optimal location of actuators for correcting distortions due to manufacturing errors in large truss structures

A continuum approximation to the calculation of the statistical properties of the corrected shape of a beam truss is presented, and results of a comparison with the exact statistical analysis were found to be very good. In addition, the position of the actuators was optimized to minimize the weighted rms of the distortion using the continuum analysis. The optimal design is shown to be 13.6 percent better than a uniform design for a parabolic weighting function. It was also found that actuators located on the beam face elements were more effective than actuators located on the diagonal elements.

Burdisso, R.↗