Great opportunities to obtain low values of for close to 1 are provided by elements whose attenuation coefficient varies on the forward and reverse courses. The attenuation coefficient on the forward course is chosen to obtain the maximum value of (close to 1) and on the reverse course, the attenuation coefficient is increased to a value which provides the required recovery coefficient. This method can be used for hydraulic and electromechanical dampers. Other characteristics of energy absorbing elements can be analyzed in the same way. The efficiency of other energy absorbing elements may be evaluated from their specific energy capacity the energy absorbed per unit mass of the element or the shock absorber as a whole. As analysis has shown, the springs have a relatively low and . For example, the set of springs of the longitudinal shock absorber of the Soyuz docking mechanism has a mass of 3.9 kg and may absorb up to 660 J of energy, that is, . In this mechanism the recoil energy must be absorbed, since in a direct impact with maximum velocity, even considering the electromagnetic brake s = 0.7-0.8. Thus, (see section 1.5.1) the docking mechanism uses an additional spring shock absorber with a mass of 0.8 kg. For shock absorption of the direct impact, it is substantially more effective to use a friction brake. Tn the Soyuz-Salyut docking mechanism this brake, which has a mass of 1.18 kg, absorbs up to 600 J of energy, that is, . The shock absorbers are units of the docking mechanism which are difficult, and in many cases, impossible to duplicate. Thus, it is important to insure fail safe work. A11 four basic types of potential failures are characteristic for shock absorber elements: 1) breakdowns; 2) deformations or decrease in force; 3) Jamming; 4) rubbing. Tn planning one should make a detailed analysis of all potential failures, their criticality, and physical reasons for them to appear; it is necessary to take measures to increase the reliability of critical elements and details. 6.2. Spring Mechanisms Despite the low specific characteristics of the spring, they are widely used in the shock absorbers of docking mechanisms. The spring mechanism, in the general
RkJQdWJsaXNoZXIy MTU5NjU0Mg==