An Alternative Approach to Contact-Based CubeSat-Pod Structural Interface

Abstract

This study presents the dynamic behavior of a 3U CubeSat structure under launch conditions, proposing an alternative boundary condition to bring test and finite element analysis (FEA) results closer together. The assumptions of bottom fixation, bottom-top fixation and rail fixation seen in the literature can represent the real system as being either too soft or too rigid, potentially making designs either overly conservative or overly optimistic. With this motivation, the CubeSat–pod interface was modeled with 6-degree-of-freedom spring (CBUSH) stiffnesses derived from Hertz–Mindlin–Popov contact theories. The proposed approach was verified with a part-to-whole strategy: (i) Printed Circuit Board (PCB)-standoff set (test 360 Hz, analysis 365 Hz; 1.4% difference), (ii) PCB-standoff-dummy mass set (test 246 Hz, analysis 250 Hz; 1.6% difference), and (iii) whole CubeSat was applied test and analysis for different boundary conditions. For proposed boundary condition, the analysis results were 96/126 Hz along the lateral axes, the test results were 96.7/120 Hz; along the longitudinal axis, test and analysis results were 137.9 Hz and 138 Hz, respectively. The test-analysis difference was minimum 14.7% with common boundary conditions in the literature, whereas a maximum deviation of 4.7% was observed with the proposed contact-based boundary condition, which yields an enhancement of better than 10% in natural frequency predictions. The results indicate that the analyses performed using the proposed boundary condition show a high level of agreement with the actual test data. Based on this finding, the proposed approach can lead to low-cost and time-effective satellite testing and design processes.