3.1 Design The three panels and yoke in one wing of IRS are to deploy together in accordion fashion (Fig. 6). A redundant pyro cutter is used to cut the co-ordinating cable which initiates the automatic full deployment in a single step, along with the CCL device to render the mechanism a single degree of freedom system. Each panel in the two wings is sized at 1.3 mXl.l m, which are of aluminium honeycomb construction. The thickness of the panel is increased to 25 mm, with edges reinforced by aluminium square tubes for higher stiffness characteristics. During the launch phase, the forces in the three orthogonal directions acting on the panels are resisted by the launch restraints (Fig. 7). Apart from the clamping forces, which resist out-of-plane vibration, in-plane vibration is partly resisted by friction pairs consisting of serrated aluminium stand-offs pressing against delrin pads. The four clamps (Fig. 8) hinged on the outboard panel are tensioned by means of engaging levers and co-ordinating wires. By severing this wire at a single point by a pyro device, release of clamps is achieved. The hinges are provided with spherical self-aligning bearings (Fig. 9), to compensate for misalignments due to thermal deformations. End-of-travel locking is achieved by means of a pawl and cam arrangement. The design of the harness loop near interpanel hinges (Fig. 10) has been arrived at by looping and off-setting methods after several trials, as the harness is composed of Kapton sheathed wires which are pretty stiff and give rise to extraneous resisting torque during deployment.
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