Deslgn And Thermal Analysis For Deployabl Space Truss Structures

The space deployable structure is a new type of foldable structure which appears with the development of space navigation technology in recent 30 years. It is folded during launching, and is deployed to keep in working state in the orbit. Its appearance broadens the application realm of large space structures, and makes the deployable structures develop very quickly.Usually, the shapes of space structures should be stable. Whether the outer temperature changes much or not, the variation of their shapes should be very little. Flexible structures such as large deployable truss structures are required to have high sensibility and thermal stability. But deployable antenna always enters into and leaves the earth shadow periodically when it orbits the earth, and it is affected by the shadows of itself (such as the shadows of reflector mesh and members). So high temperature gradient and severe temperature variation in this structure will induce thermal expansion, thermal stress and thermal deformation. On the other hand, thermally induced deflections of reflector have much effect on the electric performance of antenna, and rapid changes of thermal load may result in vibration, even this affects the position control of antenna. Thus a key design for the antenna structure is to control its deformation in a limited range. Obviously, thermal analysis is very important for such structure to maintain its high thermal stability.A 5-m diameter large deployable cutting-parabolic antenna model is designed. It is composed of a supported backbone (deployable truss) and a reflector surface (flexible mesh). All analysis in this dissertation is based on this model, such as temperature field analysis, thermal deformation analysis, thermal stress analysis, thermal vibration analysis, and so on.In the design of supported backbone, a key technology, the deployable mechanism of eachtetrahedral element, is discussed. And the mechanism of spider nodes, middle nodes and torsional springs in these nodes are also illustrated.In any orbits, whether the satellite is self-rotating or not, there is always an angle between the deployable antenna and the sun radiation, and this angle decides temperature distribution and thermal cases of the antenna. Thus in this design, types of orbits and position of satellite needn't to be considered, but only the angles between sun radiation and antenna are considered, this can simulate any state in the whole orbit. Given the angle between sun radiation and horizontal plane, the angles between sun radiation and all kinds of rod elements and membrane elements are obtained, then the incident radiation flux on these elements can be computed.Any antenna structure in arbitrary orbits will be affected by the shadow of itself. According to the periods and altitudes of GEO (Geosynchronous Earth Orbit) and LEO (Lower Earth Orbits), and according to the time when antenna transverses the penumbra and umbra, the effects of earth shadow can be decided. Also, the difference between horizontal shadowed members and non-horizontal shadowed members, and the method computing shadow factor (SHAD), are proposed.Transient radiation-conduction differential equations of each 2-node rod element and each 6-node triangular membrane element are deduced. Based on the differential equations and conditions, functional formulation of each element is founded. According to the functional extreme value, equations in the entire solving area can be resolved, and the temperature field of the antenna can be computed. A temperature analysis procedure has been programmed. The result shows that the temperature field in the whole structure is reasonable. The obvious change in temperature happens when the antenna enter into the earth shadow, so this case should be studied to decide whether the temperature of the structure and its components are in the limited range or not. If not, passive heating and active heating should be used to keep the antenna in stable state.In thermal-structural analysis, the matrix of equivalent node the...