1,721,360 research outputs found
Novel Tether-Connected Two-Dimensional Structures for Low Earth Orbits
No full textAbstract - This paper proposes novel tether-connected two-dimensional structures with a size of several hundred square kilometers for low earth orbits. The attitude of these structures is gravitationally stabilized with respect to an earth-oriented reference frame. A stable shape is obtained by utilizing environmental forces such as differential air drag or electrodynamic forces which stiffen the system. Configurations which differ in geometry and in the number of connecting tethers are presented in the paper. The static stability of each configuration is analyzed as a function of design and orbital parameters. A brief discussion of the applications of such tethered systems is provided at the end of the paper
A Three-Mass Tethered System for Micro-g/Variable-g Applications
No full textAbstract - This paper describes a Space-Station-attached tethered system for micro-g/variable-g applications. The
system consists of three platforms: the Space Station, an end mass anchored at the end of a 10-km-long kevlar
tether, and a micro-g/variable-g laboratory with the capability of crawling along the tether. Control strategies
are devised for performing both the deployment and the stationkeeping maneuvers of the system. Effective
algorithms are identified for damping out the major oscillations of the system
Active Gravity-Gradient Stabilization of a Satellite in Elliptic Orbits
No full textAbstract - A tether can be utilized as an efficient actuator for the purpose of satellite attitude control. The tether tension generates a strong passive gravity stabilization effect. The combination of tether tension with a movable attachment point mechanism results in an effective and low cost active controller. This paper reviews the concept and presents the dynamical characteristics of the configuration. It then demonstrates that a feasible three-axis control can be achieved by means of only two actuators. The primary contribution is the development of a control law that works for eccentric orbits. In this case, the dynamical system that represents the configuration becomes periodic in time, and thus impossible to control by using constant gains. The solution is a periodic control law. A combination of Floquet transformation and sampled state periodic hold feedback control is proposed as an effective pointing method for small-eccentricity orbits
Electrodynamic tethers in space: dynamical issues, solutions and performance
No full textElectrodynamic tethers are a promising new technology for a variety of applications ranging from
deorbiting of spent satellites and upper stages in low Earth orbits to propellantless propulsion
around any planet (inclusive Earth) with a magnetic field and a plasmasphere. However, the
continuous application of electrodynamic forces/torques over a relatively long period of time raises
dynamical issues related to the tether attitude dynamics that need to be solved for achieving longterm
dynamical stability. The paper addresses firstly the fundamentals of the dynamical motion
forced by the electrodynamic forces/torques and secondly reviews the techniques used to control the
motion generated by those forces/torques. The paper also presents the techniques that were used
successfully in simulation to control the dynamics of a tethered system designed for deorbiting
spent satellites in low Earth orbits and shows its deorbiting performance at all orbital inclinations. Copyright © European Space Agenc
Analytical formulation of a complex mutual gravitational field
No full textAbstract. The mutual gravitational potential for proximate bodies with an arbitrary mass
topology is investigated. The current research is motivated by an experiment
for the verification of the equivalence principle in gravitation. The gravitation
model for the experiment is complex and requires high precision. The proposed
methodology is to formulate the potential in terms of inertial integrals and
the so-called outer integrals. The method is general and can represent any
gravitational configuration. Approximating the outer integrals by radial basis
functions reduces the complexity for a real-time dynamical simulation
Dynamical Effects of Radar Reflectors Attached to the Small Expendable-Tether Deployer System (SEDS)
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