Separation Simulation Studies Of A Large-Scale Payload Fairing

Separation system of payload fairing is a critical subsystem during the flight of launch vehicles, which determines whether the payload could be successfully brought into the predetermined orbit. Accompanied with the progress of China’s space technology, a new generation launch vehicle leads to a larger diameter and a higher thrust, while the dimension of the launch vehicle fairing structure also increases significantly. Since the increased dimensions of overall structure and rotational separation form would result in the reduction of stiffness of fairing and effective envelope inner cover, severe elastic deformations, as well as the increased risk of collision between payload fairing and core stage during the separation process.Furthermore, a larger dimension of fairing leads to a greater aerodynamic resistance in the ground test, which would prevent the fairing separation, and even result in separation failure. Therefore, it is extremely necessary to simulate the fairing separation and ground test by numerical method.To investigate the dynamic response problems of fairing separation with different energy inputs, a precise finite element model was established in this study, and the feasibility of simulation process was validated by comparing with the theoretical results and numerical results of rigid body simulation. On this basis, elastic fairing simulation was carried out to obtain the separation and deformation characteristics by consideration of elastic vibration. In order to simulate the ground test accurately, a fluid-solid coupling method was used to carry out the simulation considering aerodynamic loads, and obtain the flow region distribution of separation process and separation characteristics of ground test. Finally, taking into account the complexity of the initial transient impact, impact response issues of the fairing was discussed, which reveals the deformation mode under transient impact. The main contents of this paper are:1. A precise finite element model was established, and then theoretical separation characteristics based on rigid body dynamics and energy principles was calculated. Numerical results show the separation characteristics of rigid fairing and validate the correctness of finite element model parameters and feasibility to simulate the separation process of a large scale fairing using ABAQUS software.2. Fairing modal analysis indicated more possible dangerous vibration mode of separation. Elastic fairing separation characteristics, breathing distortion, energy and other parameters were obtained by different separation energy inputs, respectively. Different modeling techniques of spring system were also discussed. The results showed that the fairing could successfully separate, and no interference with the payload was observed in a vacuum environment. The more input energy, the more beneficial to separate. Spring modeling techniques had little influence on the rigid body simulation, but it had a remarkable influence on elastic body simulation. Spring rod model could restrict the breathing and axial deformations.3. Based on CEL method, a ground separation test simulation was carried out to describe the flow region variation. The results showed that aerodynamic resistance had great influence on the separation in the ground test, however, gas system had little effect on the separation. On the contrary, it may reduce the system reliability. Besides, initial negative pressure could increase the aerodynamic resistance; Subsequently, air entered the inner fairing continually, and aerodynamic resistance decreased.4. Initial transient impact response analysis of the fairing revealed that transient impact loads could result in twice dynamic amplification of fairing; The third-order mode of fairing with boundary constraint condition was excited by the transient impact.