Aerospace Engineering Research Works

Permanent URI for this collectionhttp://hdl.handle.net/1903/1655

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Author: search.filters.author.Coffey, Shannon

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Now showing 1 - 4 of 4
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    Deterministic Studies of Debris Hazards with Parallel Processors
    (European Space Agency, 1993-04-05) Healy, Liam; Coffey, Shannon
    A new generation of parallel processing computers makes possible the ability to propagate all objects in the space surveillance catalog with simulated objects, and detect close approaches. With this capability, it is possible to test deterministically debris scenarios, without resorting to statistical models. To compare the positions of objects we have developed two methods, an all-to-all comparison and a one-to-all comparison. For the former, a seive significantly reduces computation time; for the latter, direct comparison is possible in parallel. We show results from several simulations, including simulated multiple sources of debris, hazard to the space station, and close contacts amongst the catalog itself, to show potential for debris studies. The techniques described here have potential application the general problem of catalog maintenance.
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    Parallel Computing for Space Surveillance
    (MIT Lincoln Laboratory, 1992) Healy, Liam; Coffey, Shannon
    This paper reports on an application of massively parallel processors to multiple satellite propagation and the calculation of miss distances between objects (COMBO). Unlike serial computations, we do not pre-filter the data but rather sort the data set in a way that dramatically cuts the number of comparisons required in order to be assured of a complete catalog-to-catalog comparison. The same general algorithm allows two logical sets to be compare to each other. Run time for this demonstration code on an 8K Connection Machine is about one second per time step, including propagation, complete catalog-to-catalog calculation of miss distances, plotting satellite positions, and recording of the miss distances to a file. Propagation of the objects is performed with an analytic propagator, using J2 only at present, though the code may easily be extended to other propagators. We demonstrate a second application of parallel computing to the problem of debris propagation resulting from a satellite breakup. The spread of such debris into n pieces is simulated by replicating the element set for the original satellite n times, then altering each to represent a distribution of velocities to the center of mass.
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    A Toolbox for Nonlinear Dynamics
    (Springer-Verlag, 1991) Coffey, Shannon; Deprit, André; Deprit, Eitenne; Healy, Liam; Miller, Bruce
    Using the main problem of artificial satellite theory as an illustration, we review several developments which have had a significant impact on research in nonlinear dynamics. On the mathematical front, we point to the theory of Lie transformations; in the area of computational software, we explain how massively data parallel machines open the way for symbolic solution of large problems. Finally, we show how color graphics assist in the qualitative analysis of dynamical systems.
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    The Phase Space Portrait of an Integrable Dynamical System
    (Science, 1990-02-16) Coffey, Shannon; Deprit, André; Deprit, Etienne; Healy, Liam
    For an integrable dynamical system with one degree of freedom, "painting" the integral over the phase space proves to be very effective for uncovering the global flow down to minute details. Applied to the main problem in artificial satellite theory, for instance, the technique reveals an intricate configuration of equilibria and bifurcations when the polar component of the angular momentum approaches zero.