Size and Topological Optimization of a CubeSat Structure

Abstract

CubeSats are a class of Nano Satellites that is defined by the CubeSat Design Specification (CDS). They are built to standard dimensions of 10 cm x 10 cm x 10 cm which is known as a 'Unit or U'. Each unit typically weighs less than 1.33 kg. For a successful CubeSat mission, several Subsystems work together to achieve the mission objectives. These subsystems occupy the majority of the CubeSat' total mass leaving a very minor portion/percentage of it for the structure. Therefore, mass reductions shall be made to a CubeSat structure to allow for additional weight to be used elsewhere. Furthermore, throughout its lifetime, a CubeSat is subjected to harsh operational loads such as extreme heating and cooling cycles and harsh launch loads such as high g-forces and vibration during lift-off. In order for a CubeSat qualify acceptance and function properly, it is expected to withstand the harsh conditions during launching. As a result, it is essential to optimize the design of the CubeSat structure to minimize the mass and volume while maximizing the stiffness. This type of optimization is known as Topological optimization, which basically includes the introduction of holes or cuts into the structure to minimize weight. This advancement plays a great role in the applicability of the generated designs since it allows for enhanced structural performance such as a high strength to weight ratio. Topology Optimization is approached in this research by first studying the geometric constraints retrieved from the CDS. Then, existing CubeSat Designs were compared to each other in terms of structure geometry and layout. A new CubeSat design was then developed based on ISIS' 1U CubeSat with altered ribs that were used in the optimization module. The Ribs of the CubeSat structure were topologically optimized at 4 different volume fractions (60,70, 80 and 90%) using two different designs; including a concave center and a hollow one. The Quasi-Static and Modal analysis of these designs were compared to ones of ISIS' and ones of the initial design which is considered as the maximum physical extent of the ribs geometry. These analyses were conducted on the structure alone and on structure with 5 subsystems to simulate a worse case launch scenario at 14g. All analysis and optimization processes were conducted using Abaqus. The new optimized designs were verified by confirming the margin of safety and meeting the launch vehicle frequency requirements. In Addition, the results were verified by the design of the existing 1U CubeSat Structure of ISIS since all values of maximum von Mises stress and deflection were similar to ones of ISIS.

Date of Award	May 2020
Original language	American English