Rotable accurate reflector system for telscopes Patent
Development of reflector system for application to line-of-sight pointing and tracking telescopes
Wells, W. H.↗
SEARCH · Search NASA
Results for “reflector”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Static Analysis of the 64-m (210-ft) Antenna Reflector Structure
NASTRAN program used to calculate gravity load distortions in 64-m antenna reflectors
Katow, M. S.↗
NASTRAN-GAP: an Integrated Approach to the Analysis of Radiation Patterns of Distorted Reflectors
NASTRAN-GAP programs for analyzing antenna radiation patterns of reflectors distorted by gravity and thermal loads
Cook, W. L.↗
A study of the near fields of reflector antennas using the geometrical theory of diffraction
Calculation of near fields of reflector antennas by geometrical theory of diffraction
Roberts-Horsfield, W. C., III↗
Far-field diffraction pattern for corner reflectors with complex reflection coefficients
Far field diffraction pattern of corner reflector for normally incident monochromatic light, considering polarization characteristics
Alley, C. O.↗
Large spacecraft antennas: Conical ring-membrane reflectors
A 1.83-m diameter furlable conical Gregorian antenna based on a novel spoke-supported ring-membrane concept has been successfully demonstrated. Mechanical measurements of the conical reflecting surface, as well as BE gain measurements at Ku-band, show an rms surface deviation from the proper conical surface of 0.3 mm and a repeatability after multiple furling-unfurling cycles of + or - 0.05 mm. Design features and performance characteristics of this antenna indicate that the spoke-supported ring-membrane concept is a promising approach for producing large, furlable, lightweight, conical reflectors for spacecraft high-gain antennas.
Oliver, R. E.↗
High-gain antenna with singly-curved reflector
Reflector collects energy over large region of space and focuses it toward small region where antenna feed is located. When incident energy is in form of plane wave, logical choice for shape of reflecting surface is paraboloid which converts plane wave into spherical wave that converges at a point.
Ludwig, A. C.↗
Collapsible structure for an antenna reflector
A collapsible support for an antenna reflector for use in supporting spacecraft antennas is described. The support has a regid base and a number of struts which are pivoted at the base. The deployment of the struts and their final configuration for supporting the antenna are illustrated.
Trubert, M. R.↗
Graphite epoxy reflector support truss for applications technology satellite /ATS/.
The design, development, fabrication, and qualification load testing of the reflector support truss for Applications Technology Satellites F and G are described. Because the truss is stability-critical, high modulus graphite epoxy composite was used to provide a minimum weight structure. The work was performed under the sponsorship of the NASA Goddard Space Flight Center with Fairchild Industries as the prime contractor.
Randolph, R. E.↗
Computer design of antenna reflectors.
Performance of paraboloidal antenna reflectors is adversely influenced by surface distortions from a perfect paraboloid, which cause pathlength variations of the RF energy beam. The structural design objective for the surface backup structure is to minimize the rms pathlength deviations for gravity loading. Two design approaches are illustrated and applied to sample antenna structure designs. These are a sectional search method and a virtual work/Lagrange multiplier method. Both are shown to provide useful performance improvements. The second, however, appears to be more suited for application to design of large antenna structures.
Levy, R.↗
Thermal shielding by subliming volume reflectors in convective and intense radiative environments.
The behavior of dielectric materials having densely packed internal scattering centers subject to extreme convective and radiative environments is analyzed. Experiments have shown that these materials act as volume reflectors of incident radiation even when the exposed surface is being eroded by thermochemical ablation. The analysis was applied to interpret experiments of subliming Teflon models exposed to combined radiative and convective fluxes up to 1.7 kW/sq cm for several seconds. Results show that, although the exposed surface receded at an apparently steady rate, the internal temperature climbed continually, due to internal absorption of radiation and would have caused failure internally if the test duration were extended a few seconds. Thus, performance is time-limited by the internal absorption coefficient. Results were obtained for larger configurations and other materials. Typically, Teflon shells may withstand radiant fluxes up to 20 kW/sq cm for about 5 sec and fritted quartz up to 50 kW/sq cm for about 8 sec (corresponding to the Jupiter entry).
Howe, J. T.↗
Astigmatism in reflector antennas.
Astigmatic phase error in large parabolic reflector antennas is discussed. A procedure for focusing an antenna and diagnosing the presence and degree of astigmatism is described. Theoretical analysis is conducted to determine the nature of this error in such antennas.
Cogdell, J. R.↗
Lightweight 3.66-meter-diameter conical mesh antenna reflector
A description is given of a 3.66 m diameter nonfurlable conical mesh antenna incorporating the line source feed principle recently developed. The weight of the mesh reflector and its support structure is 162 N. An area weighted RMS surface deviation of 0.28 mm was obtained. The RF performance measurements show a gain of 48.3 db at 8.448 GHz corresponding to an efficiency of 66%. During the design and development of this antenna, the technology for fabricating the large conical membranes of knitted mesh was developed. As part of this technology a FORTRAN computer program, COMESH, was developed which permits the user to predict the surface accuracy of a stretched conical membrane.
Moore, D. M.↗
Reflectance and unsteady temperature distribution of diffuse reflectors
The applicability of a previously derived solution of the Kubelka-Munk differential equations for the reflectance of an absorbing and scattering material for the case of a zero absorption coefficient to the description of the reflectance of a weakly absorbing, highly scattering material is examined. A solution for the transient heating of a one-dimensional volume reflector is obtained, and the error incurred in the use of the zero absorption coefficient solution is assessed for early times appropriate to the entry heat protection system application. It is found that the small difference in reflectance causes a significant difference in internal temperature.
Weston, K. C.↗
Secondary reflectors for economical sun-tracking energy collection system: A concept
Mechanism is simpler and lower in cost because it moves heat-collector pipe to stay in focus with sun, instead of moving heavy reflectors.
Miller, C. G.↗
Spurious signals generated by electron tunneling on large reflector antennas
Large reflector antennas are currently fabricated by assembling a large number of small light aluminum panels onto a superstructure. A large number of aluminum-to-aluminum joints are inherently exposed to RF radiation on such an antenna. It is shown in this paper that the natural oxide layer on aluminum is of the correct thickness to permit electron tunneling through the Al-Al2O3-Al junctions. The nonlinearity due to the junctions then generates spurious signals when these antennas are used for simultaneous transmission and reception of signals at different frequencies. Moreover, the large number of junctions (rivets) on an antenna can combine to produce serious interference in these diplexed systems.
Higa, W. H.↗
Experimental evaluation of a stationary spherical reflector tracking absorber solar energy collector
This article presents experimental data for the thermal performance of a stationary, spherical-reflector, tracking-absorber solar energy collector (SRTA). The principle of operation and details of thermal performance of such an SRTA have previously been described. These experimental results were compared with the predictions of a thermal analysis previously published. Experimental results were compared with the prediction of Kreider's computer model. Within the range of the temperature of the experiments, the predicted performance of the unit agreed well with experimental data collected under clear sky conditions. In addition, the extrapolation of the efficiency to higher temperature is shown so that the potential of an SRTA solar collector as a means of providing high temperature steam to operate an electric power facility or for process heat can be evaluated. As a result of the tests conducted by NASA, and an economic analysis not yet publicly available, it appears that the SRTA solar collector concept will be economically viable in competition with any other existing solar system in providing electrical energy.
Steward, W. G.↗
Lightweight conical antenna reflector
Conical antenna reflectors using knitted mesh materials for aluminized film eliminate problem areas in thermal distortion and long term stability when film is subjected to ultraviolet radiation. Meshes may be selected from wide selection of yarns to form mesh membrane.
Moore, D. M.↗