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Hedgepeth, J. M.

Publications and source records attributed to Hedgepeth, J. M..

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Considerations in the design of large space structures

Several analytical studies of topics relevant to the design of large space structures are presented. Topics covered are: the types and quantitative evaluation of the disturbances to which large Earth-oriented microwave reflectors would be subjected and the resulting attitude errors of such spacecraft; the influence of errors in the structural geometry of the performance of radiofrequency antennas; the effect of creasing on the flatness of tensioned reflector membrane surface; and an analysis of the statistics of damage to truss-type structures due to meteoroids.

Hedgepeth, J. M.↗
NASA NTRS1981

Conceptual design studies for large free-flying solar-reflector spacecraft

The 1 km diameter reflecting film surface is supported by a lightweight structure which may be automatically deployed after launch in the Space Shuttle. A twin rotor, control moment gyroscope, with deployable rotors, is included as a primary control actuator. The vehicle has a total specific mass of less than 12 g/sq m including allowances for all required subsystems. The structural elements were sized to accommodate the loads of a typical SOLARES type mission where a swam of these free flying satellites is employed to concentrate sunlight on a number of energy conversion stations on the ground.

Hedgepeth, J. M.↗
NASA NTRS1981

Foldable beam

A foldable beam possessing superior qualities of light weight, compactness for transportation, quick deployment with minimum use of force, and high strength is described. These qualities are achieved through the use of a series of longitudinally rigid segments, hinged along one side and threaded by one or two cables along the opposite side. Tightening the cables holds the beam extended. Loosening the cables permits the segments to fold away from the threaded side. In one embodiment the segments are connected by canted hinges with the result that the beam may be folded in a helix-like configuration around a cylinder. In another embodiment the segments themselves may be hinged to fold flat laterally as the beam is folded, resulting in a configuration that may be helixed around a shorter cylinder.

Hedgepeth, J. M.↗
NASA NTRS1981

Free-flying solar reflector spacecraft

Results of investigations of requirements and design concepts for large solar-reflecting spacecraft are given. The emphasis is on the one kilometer diameter self contained spacecraft that can be packaged and launched in the space shuttle. The configuration consists of a compression rim stabilized by stays coming from each end of the central compression hub. The stays are stowed on reels on the ends of the hub. The hub consists of two Astromasts which are deployed after launch. The reflector membrane is a two micron thick Kapton film with a vapor deposited aluminum coating.

Hedgepeth, J. M.↗
NASA NTRS1981

Design concepts for large antenna reflectors

A type of antenna reflector was studied in which a stiff structure is constructed to hold a membrane like reflector mesh in the correct position. An important basic restriction is that the mesh be controlled only by the structure and that no additional local shaping be employed. Furthermore, attention is confined to structures in which no adjustments would be made on assembly. Primary attention is given to the tetrahedral truss configuration because of its outstanding stiffness and dimensional stability.

Hedgepeth, J. M.↗
NASA NTRS1981

Critical requirements for the design of large space structures

The requirements for the design of a large space structure which will be deployed, erected, assembled or fabricated in space are delineated in terms of operational loads, stiffness requirements, structure-control interaction, deformations, precision requirements and member slenderness. Design examples for a truss antenna reflector, interorbit propulsion loads and free-flying solar reflectors are given. It is concluded that the demand for dimensional accuracy and stability form the primary requirements.

Hedgepeth, J. M.↗
NASA NTRS1981

High performance silicon solar arrays employing advanced structures

Specific design features to reduce cell mass, lower panel operating temperatures, and improve power to mass ratios for silicon solar cell arrays in space applications are presented. Because mass constraints limit payload capacity for launch into GEO, graphite/epoxy structures combined with high performance Si cells are needed to deliver a power/mass ratio of 265 W/kg, notably for Solar Electric Propulsion systems, compared with existing level of 65 W/kg. Shallow diffusion and back surface field cell technology have raised cell efficiencies to 15%, with a back emissivity of 1.64. Structural design requirements comprise Shuttle interface compatibility, full ground test capability, low mass, and high stiffness. Three array alternatives are discussed, and the STACBEAM configuration, which consists of a triangular truss and a piston deployer with folding accomplished on simple hinges, provides 0.2 Hz stiffness and achieves the design power/mass goals.

Rockey, D. E.↗
NASA NTRS1980

Influence of interorbit acceleration on the design of large space antennas

The characteristics of the acceleration-induced loading in structures consisting of triangular lattices are investigated and some initial quantitative results on the effect on the design mass and stowage volume are presented. The approach used defines the structural design that would be used if no interorbit acceleration were required and then determines what strengthening would be required to accommodate the loads due to acceleration. The basic zero acceleration design can be based on the stringent accuracy requirements placed on the antennas.

Hedgepeth, J. M.↗
NASA NTRS1980

Accuracy potentials for large space antenna structures

The relationships among materials selection, truss design, and manufacturing techniques in the interest of surface accuracies for large space antennas are discussed. Among the antenna configurations considered are: tetrahedral truss, pretensioned truss, and geodesic dome and radial rib structures. Comparisons are made of the accuracy achievable by truss and dome structure types for a wide variety of diameters, focal lengths, and wavelength of radiated signal, taking into account such deforming influences as solar heating-caused thermal transients and thermal gradients.

Hedgepeth, J. M.↗
NASA NTRS1980

Efficient structures for geosynchronous spacecraft solar arrays

Structural concepts for deploying and supporting lightweight solar array blankets for geosynchronous electrical powr are evaluated. First, the requirements for more mass efficient solar arrays is established by describing future needs. Then analytical results are set forth which show that not only must lighter weight blankets be developed but also the supporting structure must be improved proportionately. The SEPS configuration is taken to be the state of the art point of departure for improved structural concepts. Several directions for improvement are indicated.

Hedgepeth, J. M.↗
NASA NTRS1979

Extendable mast

Extendable mast is constructed from mutually supporting members that unfold as mast is deployed from compact package. Extendable mast is sturdy and can be compared to conventional rigid structures.

Coyner, J. V., Jr.↗
NASA NTRS1979

Structural design of free-flying solar-reflecting satellites

A promising spacecraft configuration for utilizing solar radiation is the large flat mirror. Very thin membranes with a reflective coating can be stretched to form such a mirror; the mirror mass density can therefore be very small. The purpose of the presentation is to examine the fundamentals of providing structural support for a free-flying membrane mirror. The objective of the examination is to determine what the masses of the structure might be to support membranes of areas from thousands to millions of square meters operating at altitudes from low-earth orbit to geosynchronous orbit.

Hedgepeth, J. M.↗
NASA NTRS1979

Expandable modules for large space structures

There is a need for means to construct large complex structures without having to spend a large amount of time for assembly. One approach to meeting this requirement is to erect the overall structure using highly efficient structural modules. The individual modules can then be packaged for launch, so as to utilize the volume of the Shuttle properly, and then expanded in orbit. The present paper describes several types of such modules that have been designed and tested.

Hedgepeth, J. M.↗
NASA NTRS1978

Practical design of low-cost large space structures

The practical design of low-cost space structures involves the use of approaches that reduce the cost of the design and development effort itself. Such approaches include: (1) design with criteria arrived at rationally; (2) design for simplicity, repeatability, and modularity; (3) assembly without adjustments; (4) design for testability on the ground; (5) the attainment of structural efficiency by configuration and material choice rather than by squeezing down on the design margins; and (6) prefabrication and preassembly before launch. Attention is given to truss platform designs, and the Seasat Extendible Support Structure is discussed as a particular example.

Hedgepeth, J. M.↗
NASA NTRS1978

Foldable beam

Articulated beam becomes rigid triangular truss when deployed and is stored by folding it flat as it is heliced about cylinder. Beam is composed of longerons, diagonals, and scissors arms. Folding produces flat envelope that allows more beams to be stowed on cylinder than would be possible if beams did not fold flat.

Coyner, J. V.↗
NASA NTRS1976

Survey of future requirements for large space structures

The future requirements for large space structures were examined and the foundation for long range planning of technology development for such structures is provided. Attention is concentrated on a period after 1985 for actual use. Basic ground rule of the study was that applications be of significant importance and have promise of direct economic benefit to mankind. The inputs to the study came from visits to a large number of government and industrial organizations, written studies in current literature, and approximate analyses of potential applications. The paper identifies diverse space applications for large area structures in three general categories: (1) large surfaces for power, (2) large antenna to receive and transmit energy over the radio frequency bandwidth, and (3) space platforms to provide area for general utilizations.

Hedgepeth, J. M.↗
NASA NTRS1975

Spoked wheels to deploy large surfaces in space-weight estimates for solar arrays

Extensible booms were used to deploy and support solar cell arrays of varying areas. Solar cell array systems were built with one or two booms to deploy and tension a blanket with attached cells and bussing. A segmented and hinged rim supported by spokes joined to a common hub is described. This structure can be compactly packaged and deployed.

Crawford, R. F.↗