Engineering topics
Publications and source records attributed to Agan, W. E..
Study of concepts for large space structures will interest those designing scaffolding, radio towers, rescue equipment, and prefabricated shelters. Double-fold, double-cell module was selected for further design and for zero gravity testing. Concept is viable for deployment by humans outside space vehicle as well as by remotely operated manipulator.
The Teleoperator Maneuvering System (TMS) is a Shuttle launched, free-flying, remotely controlled reusable propulsive stage capable of performing spacecraft and payload placement services, retrieval functions, assembly/servicing support for large space systems, dexterous manipulator operations for planned or contingency satellite servicing, satellite viewing, and subsatellite science support. The basic TMS segments, subsystems and performance are described, beginning with the criteria and requirements derived from mission models. Examples of TMS benefits to the STS and user communities are demonstrated. TMS applications such as support and servicing of Space Station, materials processing and subsatellite missions are presented.
Design features of components for space erectable/deployable concepts are described along with the neutral buoyancy testing with the shuttle remote manipulator system. The basic structural configuration is a double folding cubic module. It is 3 meters by 3 meters in crosssection by 6 meters long. The first folding operation results in a 3 meter by 6 meter planar configuration. The second folding operation results in a 9 meter linear configuration. Folding (deployment) is achieved by single and double pivoting joints and telescoping diagonal members. Deployment and retraction is accomplished by an external force. Two joining devices, the module to module coupler and the automatic coupler, were designed and fabricated for test. The module to module coupler features angular and axial locking compliances of 10 deg and 2.5 mm, respectively. It also has a linear zero free play stiffness characteristic.
Large erectable and deployable space structures have been studied extensively in the past few years with a view toward usage in the near future for space platforms. The paper covers in particular the operational testing of a double-cell, double-folding cubic aluminum module at the Marshall Space Flight Center Neutral Buoyancy Simulator. Joining methods, deployment kinematics, configurations and operation time lines were analyzed using the Shuttle Remote Manipulator System (RMS) and EVA crewmen. Results of the test were considered successful, with crew tasks accomplished and the structural design adequate for flight design.
Erectable/deployable space structure concepts particularly relating to the development of a science and applications space platform are presented. Design and operating features for an automatic coupler clevis joint, a side latching detent joint, and a module-to-module auto lock coupler are given. An analysis of the packaging characteristics of stacked subassembly, single fold, hybrid, and double fold concepts is given for various platform structure configurations. Payload carrier systems and assembly techniques are also discussed.
This paper presents the development of a stability analysis for the nose cap of the NASA Space Shuttle Orbiter. Stability is evaluated by the differential stiffness analysis of the NASTRAN finite-element computer code, addressing those nonstandard characteristics in the nose cap such as nonuniform curvature, asymmetrical and nonuniform loads, support fixity, and various combinations of membrane and bending stresses. A full-sized nose cap, thinner than production, was statically tested and stability analyzed. The failing load level correlated to within 30%. The region and mode of buckling that occurred during test was accurately predicted by analysis. The criterion for predicting instability is based on the behavior of the nonlinear deflections. The deflections are nonlinear elastic in that the stresses are well within the elastic range of the material, but the geometry-load relationship produces nonlinear deflections. The load-deflection relationship is well defined by differential stiffness analysis up to the zero-slope portion of the curve, the point of neutral stability or where the shell 'snaps through' just prior to general instability.