Periodic orbits for space-based reflectors in the circular restricted three-body problem

The use of space-based orbital reflectors to increase the total insolation of the Earth has been considered with potential applications in night-side illumination, electric power generation and climate engineering. Previous studies have demonstrated that families of displaced Earth-centered and artificial halo orbits may be generated using continuous propulsion, e.g. solar sails. In this work, a three-body analysis is performed by using the circular restricted three body problem, such that, the space mirror attitude reflects sunlight in the direction of Earth’s center, increasing the total insolation. Using the Lindstedt–Poincaré and differential corrector methods, a family of halo orbits at artificial Sun–Earth L2 points are found. It is shown that the third order approximation does not yield real solutions after the reflector acceleration exceeds 0.245 mm s−2, i.e. the analytical expressions for the in- and out-of-plane amplitudes yield imaginary values. Thus, a larger solar reflector acceleration is required to obtain periodic orbits closer to the Earth. Derived using a two-body approach and applying the differential corrector method, a family of displaced periodic orbits close to the Earth are therefore found, with a solar reflector acceleration of 2.686 mm s−2

Collecting solar power by formation flying systems around a geostationary point

Terrestrial solar power is severely limited by the diurnal day–night cycle. To overcome these limitations, a Solar Power Satellite (SPS) system, consisting of a space mirror and a microwave energy generator-transmitter in formation, is presented. The microwave transmitting satellite (MTS) is placed on a planar orbit about a geostationary point (GEO point) in the Earth’s equatorial plane, and the space mirror uses the solar pressure to achieve orbits about GEO point, separated from the planar orbit, and reflecting the sunlight to the MTS, which will transmit energy to an Earth-receiving antenna. Previous studies have shown the existence of a family of displaced periodic orbits above or below the Earth’s equatorial plane. In these studies, the sun-line direction is assumed to be in the Earth’s equatorial plane (equinoxes), and at 23.5∘ below or above the Earth’s equatorial plane (solstices), i.e. depending on the season, the sun-line moves in the Earth’s equatorial plane and above or below the Earth’s equatorial plane. In this work, the position of the Sun is approximated by a rectangular equatorial coordinates, assuming a mean inclination of Earth’s equator with respect to the ecliptic equal to 23.5∘. It is shown that a linear approximation of the motion about the GEO point yields bounded orbits for the SPS system in the Earth–satellite two-body problem, taking into account the effects of solar radiation pressure. The space mirror orientation satisfies the law of reflection to redirect the sunlight to the MTS. Additionally, a MTS on a common geostationary orbit (GEO) has been also considered to reduce the relative distance in the formation flying Solar Power Satellite (FF-SPS)

Konstruktion, Aufbau und Test eines NMR-Imaging-Zusatzes zur Untersuchung struktureller und dynamischer Inhomogenitaeten in polymeren Materialien

Design, construction and test of a NMR micro imaging device which is useable on any NMR spectrometer was the centre of gravity in this work. The NMR probes, gradient systems and the control and analysis software developed in the time period of this project were used on a NMR spectrometer for: (1) Application of the experience in the integral relaxation analysis (especially transversal relaxation) for volume selective study of inhomogenities in structure and dynamics in polymer materials (especially polymer networks. (2) Volume selective study of aging processes and solvent diffusion in elastomers and other technical materials. (3) Application, modification and development of special imaging techniques (especially for ''material properties imaging''). (4) Investigation of biological samples for preparation for further contacts with scientific partners and for demonstration of the potential of the self made imaging device.SIGLEAvailable from: <a href=http://sundoc.bibliothek.uni-halle.de/diss-online/99/99H334/prom.pdf target=NewWindow>http://sundoc.bibliothek.uni-halle.de/diss-online/99/99H334/prom.pdf</a> / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

A study of intermodulation interference due to non-linearities in metallic structures

SIGLEAvailable from British Library Document Supply Centre- DSC:DX78723 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

The zero, minimum and maximum relative radial accelerations along a family of periodic orbits around L4 in the Earth-Moon system

Constellations of satellites, Zero relative radial acceleration, Earth-Moon.Assume a constellations of satellites flighting close a given nominal trajectory around L4 or L5 in the Earth-Moon system in such a way that there is freedom in the selection of the geometry of the constellation. We are interested in to avoid large variations of the mutual distance between the spacecrafts. In this case, the possible existence of regions of zero relative radial acceleration with respect to the nominal trajectory will prevent from the expansion or contraction of the constellation. The goal of this paper is the study of theses regions.Postprint (published version

The zero, minimum and maximum relative radial accelerations along a family of periodic orbits around L4 in the Earth-Moon system

Constellations of satellites, Zero relative radial acceleration, Earth-Moon.Assume a constellations of satellites flighting close a given nominal trajectory around L4 or L5 in the Earth-Moon system in such a way that there is freedom in the selection of the geometry of the constellation. We are interested in to avoid large variations of the mutual distance between the spacecrafts. In this case, the possible existence of regions of zero relative radial acceleration with respect to the nominal trajectory will prevent from the expansion or contraction of the constellation. The goal of this paper is the study of theses regions

The zero, minimum and maximum relative radial accelerations along a family of periodic orbits around L4 in the Earth-Moon system

Constellations of satellites, Zero relative radial acceleration, Earth-Moon.Assume a constellations of satellites flighting close a given nominal trajectory around L4 or L5 in the Earth-Moon system in such a way that there is freedom in the selection of the geometry of the constellation. We are interested in to avoid large variations of the mutual distance between the spacecrafts. In this case, the possible existence of regions of zero relative radial acceleration with respect to the nominal trajectory will prevent from the expansion or contraction of the constellation. The goal of this paper is the study of theses regions

Zero drift regions and control strategies to keep satellite in formation around triangular libration point in the restricted Sun-Earth-Moon scenario

In this work, we are interested in avoiding large variations in the mutual distances among multiple satellites and also in controlling their geometric configuration around an Earth Moon triangular point. Previous studies about triangular libration points have determined the existence of zero drift regions with respect to the nominal trajectory, in which the expansion or contraction of the formation never take place. Our goal is to carry out two different control strategies for a formation near a given nominal trajectory around L-4: a bang-off-bang control and a minimum weighted total AV consumption. A linearization relative to the reference trajectory around the triangular libration point is carried out, and different geometrical possibilities in the zero drift regions are studied. To investigate the influence of the gravitational force of the Sun, the BiCircular Four Body Problem is considered here. According to the results obtained, some meaningful insights to allow a proper design of the geometric configuration of the formation are drawn. (C) 2015 COSPAR. Published by Elsevier Ltd. All rights reserved.Peer Reviewe