Advanced Methods for Structural Machining and Solar Cell Bonding Allowing High System Integration and their Demonstration on a Pico-satellite

The constraints on mass and size imposed on pico- and nanosatellites drive spacecraft designers to seek fabrication methods allowing a large degree of integration. From a configuration point of view, as sizes decrease the notion of subsystems vanishes, the structural interfaces become unique and need to be custom-made. This paper describes the integration concept of the SwissCube pico-satellite with special focus on the state-of-the art structural machining process. It also presents a new soldering technique for solar arrays. Both technologies are well suited for pico- to small- satellite applications and introduce flexibility in the design process. The first part will introduce the configuration of the SwissCube and present the advantages of wire electrical discharge machining (EDM) to manufacture the satellites primary structure. This technique, used for the SwissCube pico-satellite, has allowed the manufacture of a complex lightweight monoblock frame that serves as primary as well as secondary structure. The frame is one of the lightest in the CubeSat community while its rigidity is very high as shown by FEA and vibration tests. The second part will focus on a new bonding technique for solar arrays. So far the common technique for solar array bonding consisted of attaching solar cells with silicon or epoxy adhesives. In the frame of the SwissCube project, an innovative assembly approach of solar cells has been investigated. It consists of soldering solar cell on a printed circuit board panel with a process of brazing. Environmental tests have been successfully performed to evaluate the reliability of this process. Non destructives tests were also done to evaluate the quality of the solder pads