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Gallardo D.,10 8th Street | Bevilacqua R.,10 8th Street | Rasmussen R.E.,Guidance Dynamic Corporation
AIAA Guidance, Navigation, and Control Conference 2011 | Year: 2011

This paper presents recent developments in designing a novel 6 degrees of freedom (DOF) experimental testbed for validation of guidance, navigation and control algorithms for nanosatellites. The main catalyst for this research is the desire to experimentally test these algorithms in a 1g laboratory environment, in order to increase system reliability while reducing time-to-launch and development costs. The system stands out among the existing experimental platforms because all degrees of freedom of motion are dynamically reproduced. The majority of the existing platforms guarantee at the most 5 DOF force-free motion, excluding the vertical motion. The sixth DOF, when considered, is reproduced only from a kinematic point of view, by using an electrical motor. The presented testbed achieves 6 DOF dynamical motion by using 12 cold gas thrusters. A condition of almost frictionless motion along the 6 DOF is realized using 3 sets of air bearings: linear air bearings for the planar translational motion of the platform over an epoxy floor, air bearing pulleys embedded in a mass balancing system for the gravity-free vertical motion, and a spherical air bearing providing the additional 3 rotational DOF. The challenges of near gravity-free vertical translation in a 1g field are addressed using a unique counterbalancing system. © 2011 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

Mehta R.J.,10 8th Street | Karthik C.,10 8th Street | Singh B.,10 8th Street | Teki R.,10 8th Street | And 2 more authors.
ACS Nano | Year: 2010

Chalcogenide nanostructures offer promise for obtaining nanomaterials with high electrical conductivity, low thermal conductivity, and high Seebeck coefficient. Here, we demonstrate a new approach of tuning the Seebeck coefficient of nanoplate assemblies of single-crystal pnictogen chalcogenides by heterostructuring the nanoplates with tellurium nanocrystals. We synthesized bismuth telluride and antimony telluride nanoplates decorated with tellurium nanorods and nanofins using a rapid, scalable, microwave-stimulated organic surfactant-directed technique. Heterostructuring permits two- to three-fold factorial tuning of the Seebeck coefficient, and yields a 40% higher value than the highest reported for bulk antimony telluride. Microscopy and spectroscopy analyses of the nanostructures suggest that Seebeck tunability arises from carrier-energy filtration effects at the Te-chalcogenide heterointerfaces. Our approach of heterostructuring nanoscale building blocks is attractive for realizing high figure-of-merit thermoelectric nanomaterials. © 2010 American Chemical Society.

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