Mutual Influence Between Performances Of Vibration Attenuation, Isolation And Characteristic Of Launch System

The whole-spacecraft vibration attenuation (WSVA) and isolation (WSVI) technique could significantly reduce the launch loads on the spacecraft during the trip to the orbit. The WSVA and WSVI must be analyzed and designed in a system-level of view, accounting for its coupling with the launch vehicle (LV) and spacecraft (SC). Actually, the dynamic characteristics of the whole LV and SC system will be changed to some extent after isolation treatments, which may bring some side-effects to the flight control system, e.g. the introduction of low frequency mode by the isolation may threat the stability of the flight control. On the other aspect, the LV typically has closely-spaced flexible modes with frequencies starting as low as 1 Hertz, and the SC may have modes with frequencies starting as low as 10 Hertz. Different from the classic isolation system design, the isolation of a flexible body from another one demands a special design methodology, specifically, from system-level. This dissertation focuses on studying the problems associated with WSVA/I design and developing design methodology at the system-level.Beginning with a literature survey of damping modeling and analysis methods, with a fully consideration of specific characteristics of the WSVA/I devices, LV and SC structure, high fidelity finite element models of PAF with/without the CDL is established. A mixture coordinate modeling method is also developed for the PAF with the CDL. An mechanical model of general isolation devices are established for further analysis of whole LV/SC System.An eigenvalue-perturbation method is developed based on Gerschgorin's Circle Theorem, and then is applied to build the relational expression of the additional stiffness/mass of CDL and the perturbed modal parameters of the whole LV/SC system. With this expression, the influence on the dynamic parameters of whole LV/SC system is studied by simulation. The results indicate that this perturbation method is efficient and accurate for the system-level analysis. It also shows that the modal parameters such as nature frequencies, modal shapes and modal shape slopes, are only slightly changed by the CDL treatment. The modal strain energy ratio of PAF to whole system is a critical variable to evaluate the contribution of the CDL to the whole system damping. As indicated by the vibration isolation theory, properly lowering the stiffness of the PAF can increase its modal strain energy ratio as well as the effectiveness of vibration attenuation in the low frequency range.With transfer functions of LV and SC coupled by WSVI device, an analytical expression of the whole system nature frequency in terms of the general WSVI devices'parameters is derived. The interrelationship between the modal parameters of whole LV/SC system and parameters of the general WSVI devices is studied. Because the LV dominates the mass of the whole coupled system, the results show that, the modal shapes and modal shape slopes, which correlate closely to the flight control system, changed insignificantly by the replacement of WSVI devices to the current PAF. In this dissertation, a"pole-zero cancellation"method is proposed to design and majorize the isolation performance, which is a parameter configuration method to eliminate a certain resonance of a certain component on the SC.Finally, a CDL engineering implementation and vibration test is introduced which is carried out on the PAF of a prototype FY-2 satellite for suppressing the load transmission to its on-board instruments. On analysis of test results, abnormal phenomenon and their root causes discovered from the test are figured out. Moreover, there are differences between the boundary conditions in the ground test and that in the actual launch. These differences may bring incorrect conclusion to the performance evaluation of damping implemented in WSVI technique.