Lightweight composite reflector panels

The Hexel Corp. has produced additional composite panels, based on JPL designs, that: (1) have increased the panel size from 0.15 to 0.40 meters, (2) have improved the as-manufactured surface precision 3.0 to approx. 1.0 micron RMS, (3) have utilized different numbers of face sheet plys, (4) have improved face sheet fiber orientation, (5) have variations of aluminum honeycomb core cell size, (6) have combined graphite/epoxy (Gr/Ep) face sheets with E-glass honeycomb cores, and (7) have used standard aluminum core with face sheets composed of combinations of glass, Kevlar, and carbon fibers. Additionally, JPL has identified candidate alternate materials for the facesheets and core, modified the baseline polymer panel matrix material, and developed new concepts for panel composite cores. Dornier designed and fabricated three 0.6 meter Gr/Ep panels, that were evaluated by JPL. Results of both the Hexel and Dornier panel work were used to characterize the state-of-the-art for Gr/Ep mirrors

Optimizing The Design Of Chilled Water Plants In Large Commercial Buildings

The design of chilled water plants has a very large impact on building energy use and energy operating costs. This thesis proposes procedures and analysis techniques for energy efficiency design of chilled water plants. The approach that leads to optimal design variables can achieve a significant saving in cooling cost. The optimal variables include piping sizing, chilled water temperature difference, and chilled water supply temperature. The objective function is the total cooling energy cost. The proposed design method depends on detailed cooling load analysis, head and energy calculations, and an optimization solver. The pump head calculations including piping, all fittings, valves, and devices are achieved by using the Darcy-Weisbach Equation and given flow parameters. The energy calculations are done by using generic chiller, fan, and pump models. The method is tested on an existing four-story building located in Greensboro, NC, equipped with a packaged water-cooled chiller. A whole building energy simulation model is used to generate the hourly cooling loads and then the optimal design variables are found to minimize the total energy cost. The testing results show this approach will achieve better results than rules-of-thumb or traditional design procedures. The cooling energy saving could be up to 10% depending on particular projects

Intergalactic Gas in Groups of Galaxies: Implications for Dwarf Spheroidal Formation and The Missing Baryons Problem

Radio galaxies with bent jets are predominantly located in groups and clusters of galaxies. We use bent-double radio sources, under the assumption that their jets are bent by ram-pressure, to probe intragroup medium (IGM) gas densities in galaxy groups. This method provides a direct measurement of the intergalactic gas density and allows us to probe IGM gas at large radii and in systems whose IGM is too cool to be detected by the current generation of X-ray telescopes. We find gas with densities of 10^(-3)-10^(-4) per cubic centimeter at group radii from 15-700 kpc. A rough estimate of the total baryonic mass in intergalactic gas is consistent with the missing baryons being located in the IGM of galaxy groups. The neutral gas will be easily stripped from dwarf galaxies with total masses of 10^6-10^7 solar masses in the groups studied here. Indications are that IGM gas densities in less-massive systems like the Local Group should be high enough to strip gas from dwarfs like Leo T and, in combination with tides, produce dwarf spheroidals.Comment: 9 pages, 7 figures, accepted for publication in Ap

Optimizing The Design Of Chilled Water Plants In Large Commercial Buildings

The design of chilled water plants has a very large impact on building energy use and energy operating costs. This thesis proposes procedures and analysis techniques for energy efficiency design of chilled water plants. The approach that leads to optimal design variables can achieve a significant saving in cooling cost. The optimal variables include piping sizing, chilled water temperature difference, and chilled water supply temperature. The objective function is the total cooling energy cost. The proposed design method depends on detailed cooling load analysis, head and energy calculations, and an optimization solver. The pump head calculations including piping, all fittings, valves, and devices are achieved by using the Darcy-Weisbach Equation and given flow parameters. The energy calculations are done by using generic chiller, fan, and pump models. The method is tested on an existing four-story building located in Greensboro, NC, equipped with a packaged water-cooled chiller. A whole building energy simulation model is used to generate the hourly cooling loads and then the optimal design variables are found to minimize the total energy cost. The testing results show this approach will achieve better results than rules-of-thumb or traditional design procedures. The cooling energy saving could be up to 10% depending on particular projects

Five meter diameter conical furlable antenna

An investigation was made to demonstrate that a 5-meter-diameter, furlable, conical reflector antenna utilizing a line source feed can be fabricated utilizing composite materials and to prove that the antenna can function mechanically and electrically as prototype flight hardware. The design, analysis, and testing of the antenna are described. An RF efficiency of 55% at 8.5 GHz and a surface error of 0.64 mm rms were chosen as basic design requirements. Actual test measurements yielded an efficiency of 53% (49.77 dB gain) and a surface error of 0.61 mm rms. Atmospherically induced corrosion of the reflector mesh resulted in the RF performance degradation. An assessment of the antenna as compared to the current state of the art technology was made. This assessment included cost, surface accuracy and RF performance, structural and mechanical characteristics, and possible applications

A technology development program for large space antennas

The design and application of the offset wrap rib and the maypole (hoop/column) antenna configurations are described. The NASA mission model that generically categorizes the classes of user requirements, as well as the methods used to determine critical technologies and requirements are discussed. Performance estimates for the mesh deployable antenna selected for development are presented

Mariner Venus 67 structural developmental and qualification vibration test report

Mariner 5 forced vibration test progra

QUASAT: An orbiting very long baseline interferometer program using large space antenna systems

QUASAT, which stands for QUASAR SATELLITE, is the name given to a new mission being studied by NASA. The QUASAT mission concept involves a free flying Earth orbiting large radio telescope, which will observe astronomical radio sources simultaneously with ground radio telescopes. The primary goal of QUASAT is to provide a system capable of collecting radio frequency data which will lead to a better understanding of extremely high energy events taking place in a variety of celestial objects including quasars, galactic nuclei, interstellar masers, radio stars and pulsars. QUASAT's unique scientific contribution will be the increased resolution in the emission brightness profile maps of the celestial objects

Bent-Double Radio Sources as Probes of Intergalactic Gas

As the most common environment in the universe, groups of galaxies are likely to contain a significant fraction of the missing baryons in the form of intergalactic gas. The density of this gas is an important factor in whether ram pressure stripping and strangulation affect the evolution of galaxies in these systems. We present a method for measuring the density of intergalactic gas using bent-double radio sources that is independent of temperature, making it complementary to current absorption line measurements. We use this method to probe intergalactic gas in two different environments: inside a small group of galaxies as well as outside of a larger group at a 2 Mpc radius and measure total gas densities of $4 \pm 1_{-2}^{+6} \times 10^{-3}$ and $9 \pm 3_{-5}^{+10} \times 10^{-4}$ per cubic centimeter (random and systematic errors) respectively. We use X-ray data to place an upper limit of $2 \times 10^6$ K on the temperature of the intragroup gas in the small group.Comment: 6 pages, 1 figure, accepted for publication in Ap