## 1 Introduction
### Literature Review  
The primary function of a CubeSat's structure is to provide support and protection to the internal and external satellite bus system and payload components throughout the satellite's lifetime, during development on the ground, during launch, and in the orbit environment [9] (p. 133). Besides this basic requirement, the CubeSat structure is also required to provide an easy and flexible platform for quick integration during frequent testing phases [1] (p. 322), especially for missions involving mass production. Satellite assembly and integration in a mass production environment is unique from mass production of products for ground use, as it is often limited by various tight constraints, such as time due to the fixed launch and specific market windows to meet the targeted customer demand. In constellation missions, however, as reliability gradually increases, generation by generation, the first batch of the satellite often requires extensive functional and environmental testing [1] (p. 324). CubeSat structures can be developed from a custom design or procured from the CubeSat market as commercially off-the-shelf (COTS) designs. Several companies offer a set of ready-mades and verified CubeSat subsystems, including a fully assembled structural platform. This approach reduces the development time, since testing and verification requirements can be skipped in most cases, when the subsystems have already been verified and demonstrated in an orbit environment. Verification, however, is a mandatory requirement for custom structural designs to conduct rigorous screening and reliability tests/inspections [10]. The ready-made CubeSat platforms, to some extent, help to shorten the development time [9]. However, their fixed designs impose limitations on the flexibility in defining the placement of mission payloads that are unique in size. CubeSat vendors such as GOMSPACE [11], PUMPKIN [12], ISIS [13], and Complex system and small satellite (C3S) [14] provide several standard design options for CubeSat structures. These COTS structural designs have several predefined attachment points, providing freedom when mounting the internal subassembly. Some of these COTS structures are made of several modular frames or plates which can easily be expanded to other CubeSat form factors. Examples can be found in references [12; 13]. Most of these structural designs accommodate satellite subsystems that were developed on their own to satisfy their specific interface requirements. Custom structural design addresses these interface limitations by developing a structure that is tailored to specific satellite mission requirements. Despite its flexibility, the development and design verification steps take a comparatively long time. The decision to invest is mostly made based on the available budget and time. Even if these design solutions are aimed at solving a specific problem, they still utilize many structural components/parts. The number of structural parts is one of the critical issues that should be addressed, particularly for an efficiency-demanding mass production application. Therefore, a standard, flexible platform with a minimum number of parts and joints is very important for mass-producible, fast-delivery applications. The internal configuration of subsystems mostly depends on the type of electrical interface implemented. Commonly, there are two main electrical interface methods implemented in CubeSats, such as PC/104 and the backplane board interface. The first is the PC/104 interface, where PCBs are stacked one on top of the other through an extended \"stack-through\" connectors module. Images of this interface can be found in [15]. In this case, standoffs between the subsystems are used to provide mechanical support and transfer the load to the main structural frames. Many commercial companies make this PC/104 interface.