Fellowship for Gilliam: Nonlinear Support Systems for Future Space Applications

Abstract Ihl: .\Ipha \lagnetic Spectrometer (A\[S) is an internatinnal space experiment that \\ill be launched \ia shuttle in July 20 I0 and installed on the International Space Station. The AMS is a partick physics detector that will search for antimatter and dark matter within the universe. The system relies on a cryogenic superconducting magnet that is used to bend the path of cosmic particles it encounters so they pass through the various on-board detectors. \laintaining a ]0\temperature environment for the superconducting magnet is critical to mission success. The magnet will be mounted inside of a vacuum chamber and supported by 16 nonlinear straps made from materials that will not provide unwanted heat transfer and \vill prevent the magnet from contacting the outer casing of the vacuum chamber. Each strap possesses a piecewise linear stiffness curve that causes the resistance to motion to drastically increase when stretched past a critical value. providing the assurance that the magnet will not contact the outer casing. Nonlinear systems such as the AMS support structure pose many interesting questions in regard to nonlinear dynamic response. Nonlinear system response strongly depends on initial conditions. Multiple steady state responses can occur for a particular arrangement and forcing depending only on the given initial conditions. Other phenomenons. such as bifurcations which lead to chaotic response, are also possible. The proposed work. motivated by the ,\\[S support straps. consists of numerical studies of bilinear spring support systems. Governing differential equations of motion will be generated for three-dimensional (multi-degree of freedom) bilinear spring mass models and integrated numerically with various computational tools. Key focus areas are in regards to the underlying nonlinear dynamics and teasible computational methods ot" analysis of such systems. Contact with AMS project manager John C. rutt will provide a rea! \vorld basis for the work effort. The AMS support structure is a new design. and thus no in-night heritage exists. An investigation of similar structures will benefit future missions which may use the .\\IS structure as legacy.