The requirement for the “rigidity” of characteristics of the longitudinal shock absorber for peripheral docking devices is principally important. The ring with guides of the active docking assembly is extended for a significant distance on the shock absorbers (several hundred millimeters), mainly to insure sufficient mobility to perform linkage at substantial initial deviations of the spacecraft. Thus, it is optimal for peripheral docking devices to have a shock absorption system which insures mobility in the remaining five degrees of freedom without the ring approaching the docking frame. After linkage this approach should also be minimal so that the range of motion of the ring is not reduced for absorption of energy in rotations and/or in other coordinates. These very characteristics can be obtained with a combined shock absorption-drive system with differential connections between the rods. Of great importance is the choice of the parameters of shock absorbers which operate when the ring is at angles in yaw and pitch; analogous to the “rod and cone” docking device the working conditions of the shock absorbers before and after linkage differ substantially. Thus, it is expedient to use controlled elements, which can be used to optimize the shock absorption process. It is also expedient to have minimal coefficients of recovery on impacts, primarily before linkage. This requirement is less important if there is a relatively large thrust of the longitudinal engines of the jet control system which are turned on at contact (for example, in the Apollo-Soyuz project). Friction during interaction of the ring with guides before linkage is harmful, thus, it is necessary to take measures to minimize them. 5.6.2. The Statics and Dynamics of the Ring with Guides The position of the ring with guides of the active docking assembly (Figure 5.18) relative to the initial undisturbed position, in which system of coordinates 3 associated with the ring coincides with the immobile system of coordinates 1 relative to the body, may be given by 1) the length of the six shock absorbers the shift in the origin of coordinates 3 in system of coordinates and the angles of its rotation in the following sequence: yaw , pitch and roll
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