163,897 research outputs found
Naturalization record of Pelaez, Manuel Suarez
No full textThe naturalization certificate for Manuel Suarez Pelaez of Spain. Signed by Judge Joseph B. Wall
Naturalization record of Pelaez, Timoteo Gonzalez
No full textThe naturalization certificate for Timoteo Gonzalez Pelaez of Spain. Signed by Judge Joseph B. Wall
Libros de cine
No full textPelaez Paz, A.; Cerqueiro: J .l., U. (1992). Libros de cine. Vértigo. Revista de cine. (5):76-80. https://riunet.upv.es/handle/10251/42964.Importación Masiva7680
Libration Control of Electrodynamic Tethers in Inclined Orbit
No full textAbstract - Any electrodynamic tether working in an inclined orbit is affected by a dynamic instability generated by the
continuos pumping of energy from electromagnetic forces into the tether attitude motion. To overcome the difficulties
associated with this instability, two control schemes have been analyzed. In both cases the background strategy
is the same: we add appropriate forces to the system with the aim of converting an unstable periodic orbit of the
governing equations into an asymptotically stable one. The idea is to take such a stabilized periodic orbit as the
starting point for the operation of the electrodynamic tether. In the first case, the unstable periodic orbit is taken
as a reference orbit. In the second one, we use a delay feedback control scheme that has been used successfully in
problems with one degree of freedom. To obtain results with broad validity, some simplifying assumptions have
been introduced in the analysis. Thus, we assume a rigid tether with two end masses orbiting along a circular,
inclined orbit.We also assume a constant tether current that does not depend on the attitude and orbital position
of the tether, and the Earth’s magnetic field is modeled as a dipole aligned with the Earth’s rotation axis
Sensitivity Analysis of Tether-Mediated Orbital Injection
No full textAbstract - This paper investigates the injection of a satellite from lower to higher orbit by means of the tether sling-shot technique. This technique utilizes the increment of velocity (Delta-v) imparted by a long librating tether, attached to a suitable orbiting platform (e.g., the Space Shuttle), for changing the satellite's orbit. With a scheme that mirrors a two-impulse orbital transfer, the tether is cut twice: the first time on the platform side when the tether crosses the local vertical after deployment and the second time on the satellite side at a convenient apogee passage. The two cuts increase the apogee and the perigee heights, respectively. Issues addressed in this paper, which are essential for an accurate and effective orbital injection, are the maximization of the first Delta-v and its sensitivity to uncertainties associated with tether unmotorized deployers (e.g., the Small Expendable Deployment System). The initial conditions that minimize the sensitivity to variations of the deployer's model parameters and the optimal timing of the second cut are evaluated. A specific numerical case is made for the injection of the SEDSAT satellite in order to prove that the orbital altitude after injection can be maximized and made insensitive to unpredictable variations of the deployer's tension model
[Report to Chief J. E. Curry, by an unknown author #1]
No full textReport to Chief J. E. Curry, by an unknown author. The report contains a list of officers who gave depositions to the United States Attorney
[Report to Chief J. E. Curry, by an unknown author #2]
No full textReport to Chief J. E. Curry, by an unknown author. The report contains a list of officers who gave depositions to the United States Attorney
A new kind of dynamic instability in electrodynamic tethers
No full textAbstract. Simulation of the dynamics of an electrodynamic tether on a circular inclined orbit shows a
very complex motion driven by the electrodynamic forces acting on the conductive tether. These
forces depend on the current owing in the wire, the Earth magnetic eld, the orbital velocity
and the tether position. In this paper we use a simple model to describe the dynamic eects of
these forces. The tether is modelled as a rigid rod with point masses at the ends. We also adopt
a non-tilted dipole model for the Earth magnetic eld, and we assume that the tether current is
constant. When the current is null, the sytem has a stable equilibrium position with the tether
aligned along the local vertical. When the current is dierent from zero, a periodic motion appears.
A non-linear analysis of the motion shows that the periodic solutions are always unstable (within
the limitation of the model considered in the paper). The physical reason for the instability is
that the electrodynamic forces pump energy continually into the system. The net energy increase
per orbit for the periodic solution (or state space trajectory) is zero. However, any non-periodic
trajectory in its neighborhood has a positive net energy ux per orbit so that after several orbits
the in plane libration becomes a rotation. The mechanism responsible for this instability depends
on the orbital inclination. Unlike other destabilizing mechanisms found in electrodynamic tethers,
this one is present in any kind of tether system with either a exible or a rigid tether, operating
in the generator or thruster mode and utilizing a bare tether or a large spherical termination to
collect the ionospheric electrons. The instability described in this paper is independent of the
presence of resonant force components that may be generated by the magnetic and plasma elds
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