Topic
Shields
About: Shields is a research topic. Over the lifetime, 1456 publications have been published within this topic receiving 10896 citations.
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TL;DR: In this paper, a section of retrieved Hubble Space Telescope (HST) bi-stem thermal shields (BSTS), which experienced 8.25 years of space exposure, was analyzed for space environmental durability.
Abstract: A section of retrieved Hubble Space Telescope (HST) bi-stem thermal shields (BSTS), which experienced 8.25 years of space exposure, was analyzed for space environmental durability. The shields were comprised of 2 mil (0.051 mm) aluminized-Teflon® fluorinated ethylene propylene (Al-FEP) rings fused together into a circular bellows shape. As the circular thermal shields had solar, anti-solar and solar-grazing surfaces and were exposed to the space environment for a long duration, it provided a unique opportunity to study solar effects on the environmental degradation of Al-FEP, a commonly used spacecraft thermal control material. Therefore, the objective of this research was to characterize the degradation of retrieved HST BSTS Al-FEP with particular emphasis on solar effects. Data obtained included tensile properties, density (as-retrieved and after 200 3C heating), solar absorptance, and surface morphology and chemistry. The solar-facing surfaces of the thermal shields were found to be extremely embrittle...
6 citations
6 citations
11 Jun 2009
TL;DR: In this article, the authors presented results of measurement of electromagnetic wave shielding effectiveness by shields based on polypropylene unwoven (PP) with metallic, or oxide layer, made by means of pulsed magnetron sputtering.
Abstract: The paper presents results of measurement of electromagnetic wave shielding effectiveness by shields based on polypropylene unwoven (PP) with metallic, or oxide layer. Thin films on PP fabric were made by means of pulsed magnetron sputtering. Deposited materials were Zn and Ti, fitted on magnetron gun of the WMK-100 Type in argon and oxygen background. Manufactured shields were characterised by good adhesion and shielding effectiveness (SE) over 35 dB in frequencies range from 10 MHz to 1.3 GHz.
6 citations
TL;DR: In this article , a 3D numerical model based on a vector potential (A)-formulation was exploited to investigate the properties of superconducting (SC) shielding structures with cylindrical symmetry and an aspect ratio of height to diameter approaching one.
Abstract: Superconductors are strategic materials for the fabrication of magnetic shields, and within this class, MgB2 has been proven to be a very promising option. However, a successful approach to produce devices with high shielding ability also requires the availability of suitable simulation tools guiding the optimization process. In this paper, we report on a 3D numerical model based on a vector potential (A)-formulation, exploited to investigate the properties of superconducting (SC) shielding structures with cylindrical symmetry and an aspect ratio of height to diameter approaching one. To this aim, we first explored the viability of this model by solving a benchmark problem and comparing the computation outputs with those obtained with the most used approach based on the H-formulation. This comparison evidenced the full agreement of the computation outcomes as well as the much better performance of the model based on the A-formulation in terms of computation time. Relying on this result, the latter model was exploited to predict the shielding properties of open and single capped MgB2 tubes with and without the superimposition of a ferromagnetic (FM) shield. This investigation highlighted that the addition of the FM shell is very efficient in increasing the shielding factors of the SC screen when the applied magnetic field is tilted with respect to the shield axis. This effect is already significant at low tilt angles and allows compensating the strong decrease in the shielding ability that affects the short tubular SC screens when the external field is applied out of their axis.
6 citations
01 Jun 1986
TL;DR: In this article, the contaminant flow field produced by 10 N thrust bipropellant rocket engines used on the Galileo spacecraft was quantified using the direct simulation Monte Carlo method and the expected result was that the use of line-of-sight plume shields may have very little effect on the flux of vapor phase contaminants to a surface.
Abstract: This paper describes efforts to quantify the contaminant flow field produced by 10 N thrust bipropellant rocket engines used on the Galileo spacecraft. The prediction of the composition of the rocket exhaust by conventional techniques is found to be inadequate to explain experimental observations of contaminant deposition on moderately cold (200 K) surfaces. It is hypothesized that low volatility contaminants are formed by chemical reactions which occur on the surfaces. The flow field calculations performed using the direct simulation Monte Carlo method give the expected result that the use of line-of-sight plume shields may have very little effect on the flux of vapor phase contaminant species to a surface, especially if the plume shields are located so close to the engine that the interaction of the plume with the shield is in the transition flow regime. It is shown that significant variations in the exhaust plume composition caused by nonequilibrium effects in the flow field lead to very low concentrations of species which have high molecular weights in the more rarefied regions of the flow field. Recommendations for the design of spacecraft plume shields and further work are made.
6 citations