Computational study of the effect of using open isogrids on the natural frequencies of a small satellite structure

• The design and analysis of the structure of a small satellite are both described.
• Open isogrid cutouts were implemented on some parts of the structure.
• Natural frequencies for 2 cases were calculated, with and without isogrids.
• A purely computational approach was taken, since physical testing was unfeasible.
• Isogrid use increased the natural frequencies, to an acceptable extent.

A structure for a hypothetical small satellite was developed, based on concepts taken from actual satellites currently in orbit. Parts of the design were modified by applying the open isogrid technique, which ensures a stiffness close to that of non-isogrid parts but with lower mass. The aim of the current work was to study the variation of the natural frequencies of the structure as a result of the implementation of the isogrid technique, with the results of the study giving the team enough confidence in implementing isogrids in the design during future downstream vibrational analyses (random, response spectrum, shock,…etc.). Due to resource and time constraints, no physical testing was possible, so finite element simulation was the only practical method available to investigate the variation. Hence, to ensure a reasonable level of confidence in the results, two models were analyzed for each case, non-isogrid and isogrid, using ANSYS and MSC.NASTRAN, and the results between the two solvers were compared and consolidated to arrive at specific values for each case. The results from the analyses indicated that the natural frequencies calculated for the isogrid case were higher than those for the non-isogrid case, due to the reduced mass of the isogrid structure.