EXPERIMENTAL INVESTIGATION OF THE DYNAMICS OF SPINNING TETHERED BODIES

Ground based experiments are conducted as a part of the OEDIPUS-C soun ding rocket mission, scheduled for launch in the winter of 1995. Here OEDIPUS stands for Observation of Electrified Distribution in Ionosphe ric Plasma-a Unique Strategy. The OEDIPUS-C configuration consists of two spinning bodies connected by a 1 km long tether (the spin axis is nominally along the tether line). The objective is to assess dynamic b ehaviour of the tether and the payload. The test configuration consist s of an end-body supported by a tether. The test procedure involves sl ow spin-up of the system and identifying the speeds corresponding to o nset of the tether modes or the large amplitude end-body coning. This is referred to as the critical speed and corresponds to the stability boundary of the system. Experimental results are obtained for four dif ferent bodies to study the system stability over a wide range of mass and geometric parameters. Effect of offset of the tether attachment fr om the end-body centre of mass is also investigated. The observed crit ical speeds are compared with those given by the linear theory. The te st results are generally in very good agreement with the theory, howev er several transient phenomena observed during the test suggest that s ystem nonlinearities cannot be ignored when modelling such a complex s ystem. (C) 1997 Elsevier Science Ltd.