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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.

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At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS2011

Thermal Stability of a 4 Meter Primary Reflector for the Scanning Microwave Limb Sounder

The Scanning Microwave Limb Sounder (SMLS) is a space-borne heterodyne radiometer which will measure pressure, temperature and atmospheric constituents from thermal emission in [180,680] GHz. SMLS, planned for the NRC Decadal Survey's Global Atmospheric Composition Mission, uses a novel toric Cassegrain antenna to perform both elevation and azimuth scanning. This provides better horizontal and temporal resolution and coverage than were possible with elevation-only scanning in the two previous MLS satellite instruments. SMLS is diffraction-limited in the vertical plane but highly astigmatic in the horizontal (beam aspect ratio approx. 1:20). Nadir symmetry ensures that beam shape is nearly invariant over plus or minus 65 deg azimuth. A low-noise receiver FOV is swept over the reflector system by a small azimuth-scanning mirror. We describe the fabrication and thermal-stability test of a composite demonstration primary reflector, having full 4m height and 1/3 the width planned for flight. Using finite-element models of reflectors and structure, we evaluate thermal deformations and optical performance for 4 orbital environments and isothermal soak. We compare deformations with photogrammetric measurements made during soak tests in a chamber. The test temperature range exceeds predicted orbital ranges by large factors, implying in-orbit thermal stability of 0.21 micron rms (root mean square)/C, which meets SMLS requirements.

thermal distortion↗
NASA NTRSDate not supplied

Segmented, Pleat-Folded and Rib-Supported Thin-Shell Composite Antenna Reflector

A new architecture scalable to sizes greater than 10 m for a deployable solid surface reflector antenna is presented. The design makes use of radially and circumferentially segmented thin-shell composite gores interconnected on the back side by a series of flexible shape memory composite elements. The reflector surface stows like an umbrella by creating serpentine-shaped pleats in the thin shell while being supported by a simple-hinged metering rib structure. A parametric study assessed how design features affect the deployed stiffness of the reflector and are used to identify a test matrix for manufacturing, foldability, and shape accuracy assessments. Various manufacturing tooling designs and dedicated folding fixtures were built to increase the fidelity and confidence of the test articles produced. An overview of the development effort is provided.

Deployable antennas↗
NASA NTRSDate not supplied

Segmented, Pleat-Folded and Rib-Supported Thin-Shell Composite Antenna Reflector

A new architecture scalable to sizes greater than 10 m for a deployable solid surface reflector antenna is presented. The design makes use of radially and circumferentially segmented thin-shell composite gores interconnected on the back side by a series of flexible shape memory composite elements. The reflector surface stows like an umbrella by creating serpentine-shaped pleats in the thin shell while being supported by a simple-hinged metering rib structure. A parametric study assessed how design features affect the deployed stiffness of the reflector and are used to identify a test matrix for manufacturing, foldability, and shape accuracy assessments. Various manufacturing tooling designs and dedicated folding fixtures were built to increase the fidelity and confidence of the test articles produced. An overview of the development effort is provided.

Deployable antennas↗
NASA NTRS1971

The Apollo 11 laser ranging retro-reflector array

The laser ranging retro-reflector now deployed at Tranquility Base consists of an array assembly housing 100 fused-silica retro-reflectors mounted on a pallet-aiming assembly resting on the lunar surface. The array assembly serves to hold, optically align, and thermally isolate the retro-reflectors to preserve optimum optical performance at all operating temperatures in the expected range from -300 to 250 F.

Mccullough, J. E.↗
NASA NTRS1973

Experimental detailed power distribution in a fast spectrum thermionic reactor fuel element at the core/BeO reflector interface region

A zero-power critical assembly was designed, constructed, and operated for the prupose of conducting a series of benchmark experiments dealing with the physics characteristics of a UN-fueled, Li-7-cooled, Mo-reflected, drum-controlled compact fast reactor for use with a space-power conversion system. The critical assembly was modified to simulate a fast spectrum advanced thermionics reactor by: (1) using BeO as a reflector in place of some of the existing molybdenum, (2) substituting Nb-1Zr tubing for some of the existing Ta tubing, and (3) inserting four full-scale mockups of thermionic type fuel elements near the core and BeO reflector boundary. These mockups were surrounded with a buffer zone having the equivalent thermionic core composition. In addition to measuring the critical mass of this thermionic configuration, a detailed power distribution in one of the thermionic element stages in the mixed spectrum region was measured. A power peak to average ratio of two was observed for this fuel stage at the midplane of the core and adjacent to the reflector. Also, the power on the outer surface adjacent to the BeO was slightly more than a factor of two larger than the power on the inside surface of a 5.08 cm (2.0 in.) high annular fuel segment with a 2.52 cm (0.993 in. ) o.d. and a 1.86 cm (0.731 in.) i.d.

Klann, P. G.↗
NASA NTRS1972

Analysis of a dual-reflector antenna system using physical optics and digital computers

The application of physical-optics diffraction theory to a deployable dual-reflector geometry is discussed. The methods employed are not restricted to the Conical-Gregorian antenna, but apply in a general way to dual and even multiple reflector systems. Complex vector wave methods are used in the Fresnel and Fraunhofer regions of the reflectors. Field amplitude, phase, polarization data, and time average Poynting vectors are obtained via an IBM 360/91 digital computer. Focal region characteristics are plotted with the aid of a CalComp plotter. Comparison between the GSFC Huygens wavelet approach, JPL measurements, and JPL computer results based on the near field spherical wave expansion method are made wherever possible.

Schmidt, R. F.↗
NASA NTRS1973

Movable-molybdenum-reflector reactivity experiments for control studies of compact space power reactor concepts

An experimental reflector reactivity study was made with a compact cylindrical reactor using a uranyl fluoride - water fuel solution. The reactor was axially unreflected and radially reflected with segments of molybdenum. The reflector segments were displaced incrementally in both the axial and radial dimensions, and the shutdown of each configuration was measured by using the pulsed-neutron source technique. The reactivity effects for axial and radial displacement of reflector segments are tabulated separately and compared. The experiments provide data for control-system studies of compact-space-power-reactor concepts.

Fox, T. A.↗
NASA NTRS1973

Thermal distortion analysis of a deployable parabolic reflector

A thermal distortion analysis of the ATS-6 Satellite parabolic reflector was performed using NASTRAN level 15.1. The same NASTRAN finite element method was used to conduct a one g static load analysis and a dynamic analysis of the reflector. In addition, a parametric study was made to determine which parameters had the greatest effect on the thermal distortions. The method used to model the construction of the reflector is described and the results of the analyses are presented.

Bruck, L. R.↗
NASA NTRS1974

Deployable reflector design for Ku-band operation

A project was conducted to extend the deployable antenna technology state-of-the art through the design, analysis, construction, and testing of a lightweight, high surface tolerance, 12.5 foot diameter reflector for Ku-band operation. The applicability of the reflector design to the Tracking and Data Relay Satellite (TDRS) program was one requirement to be met. A documentary of the total program is presented. The performance requirements used to guide and constrain the design are discussed. The radio frequency, structural/dynamic, and thermal performance results are reported. Appendices are used to provide test data and detailed fabrication drawings of the reflector.

Tankersley, B. C.↗
NASA NTRS1974

Contoured patterns from reflector systems - A spherical wave expansion solution

Any electromagnetic field - e.g., a contoured antenna pattern may be expanded into a sum of spherical waves, similar to a one-dimensional Fourier expansion. This expanded wave could then be scattered from a source reflector to determine a resulting required feed field in the vicinity of the focal region. This is of questionable value, and the more significant information to produce would be the required feed pattern itself. Hence the required contour pattern is instead scattered from the back of the reflector, and the result is the required feed pattern with origin at the focus of the chosen reflector.

Williams, W. F.↗
NASA NTRS1974

Design tradeoff study for reflector antenna systems for the shuttle imaging microwave system

A general tradeoff is made of the symmetric Cassegrain antenna with regard to the possibility of meeting a 90% beam efficiency. The effects of aperture taper and blockage are calculated using an adjustable sidelobe circular distribution. Numerical integration is used. For the feed spillover calculation, a low sidelobe symmetric feed pattern is used with the equivalent parabola and numerical integration. Reflector cross polarization is calculated using double numerical integration. Reflector back lobes are estimated from radiation pattern envelopes of commercial common carrier dish antennas. The curves allow a range of f/D to be determined for a specified edge taper and blockage diameter ratio, and with a table of Cassegrain parameters, a range of possible designs that meet the 90% beam efficiency is obtained. It is shown that the feed and reflector design and implementation must be carefully done.

Hansen, R. C.↗
NASA NTRS1975

ATS-6 - Television camera reflector monitor

A black and white television camera was used to observe the 9-m-diameter reflector after deployment to assure proper configuration. It also observes the reflector periodically to assure that no anomalies go undetected. It has been sending excellent pictures which verify that the reflector deployed properly and remains in good shape.

Patterson, G.↗
NASA NTRS1978

A transform-pair relationship between incident and scattered fields from an arbitrary reflector

It is shown that a transform-pair relationship exists between incident and scattered fields from an infinite, perfectly conducting reflector of arbitrary shape, when the physical optics approximation is applied. As an example of potential applications, this relationship is used to synthesize a reflector feed pattern required to produce a desired far-field pattern from a given paraboloidal reflector.

Ludwig, A. C.↗
NASA NTRS1978

Primary reflector for solar energy collection systems

A fixed, linear, ground-based primary reflector is disclosed which has an extended curved sawtooth-contoured surface covered with a metalized polymeric reflecting material. The device reflects solar energy to a movably supported collector that is kept at the concentrated line focus of the reflector primary. The primary reflector may be constructed by a process utilizing well-known freeway paving machinery.

Miller, C. G.↗
NASA NTRS1979

Deployable antenna reflector

The first phase in the development of a solid surface, deployable, antenna reflector is outlined and discussed. The deployment concept is described in conjunction with illustrations and photos of the fabricated reflector models. Details and results of the thermal distortion analysis are presented. Results indicate that the discussed reflector concept is an effective approach in satisfying the requirements for large deployable antennas in the 6 GHz to 100 GHz frequency regime.

Palmer, W. B.↗
NASA NTRS1979

Primary reflector for solar energy collection systems and method of making same

Solar energy is reflected to a movably supported collector that is kept at the concentrated line focus of the reflector primary by a fixed, linear, ground-based primary reflector having an extended curved sawtooth contoured surface covered with a metalized polymeric reflecting material. The primary reflector was constructed by a process utilizing well-known freeway paving machinery.

Miller, C. G.↗
NASA NTRS1979

Calculated scan characteristics of a large spherical reflector antenna

A previously published numerical method to calculate the radiation properties of parabolic reflectors has been modified to also include very large spherical reflectors. The method has been verified by comparing the calculated and the measured results for a 120-wavelength spherical reflector.

Agrawal, P. K.↗