Design of a Solar Array Drive Mechanism for CubeSats

Abstract

CubeSats have risen in popularity since its first launch in the year 2003. The low mass, lower launch cost, lower development cost, possibility for piggyback with larger satellites and lower development time involved compared to larger satellites have opened them to be commercialised by private companies. In contrast to being used for educational, research and technology demonstration purposes in their early years, they are now used for varied applications such as communications, Earth observation, military surveillance, in-orbit manufacturing, asteroid exploration, Internet-of-things and interplanetary exploration missions. Their lucrative features make them favourable over their larger counterparts. As a result, they are predicted to launch in higher numbers in the coming years, considering their preference for missions involving constellations or distributed space systems. This trend of increasing demand for CubeSats and their application in advanced missions requires more electrical power for their operation. The increased electrical power demand can be solved using a Solar Array Drive Mechanism. The SADM allows relative rotary motion of the solar arrays with respect to the satellite structure so that the solar panels are always perpendicularly positioned to the Sun independent of the payload pointing requirements. They can produce up to 185% more power than the panels just deployed in the case of a 3U CubeSat. Only a handful of six such SADM products were found in the commercial market, and four of them had a very similar design that drove two solar arrays and could be used in limited panel mounting configurations. A need in the commercial market for a SADM system that is modular and scalable was identified. Space mechanisms such as the SADM were found to be one of the major causes of mission failure after communications and unknown causes. It was found that tribological elements were the prominent root cause of such space mechanism failure. A research gap was identified to find the root causes of tribological failure in space mechanisms and design a SADM system that minimises failure caused due to tribological elements. This thesis has succeeded in designing a SADM that is scalable to multiple sizes of CubeSats (3U to 12U), applicable to more than three panel mounting configurations that were possible with the existing SADM and minimising failure chances due to tribological elements. The current SADM has minimised the chances of failure due to common tribological elements such as roller bearings and sliprings by eliminating the cause of failure. This includes eliminating rolling elements, liquid lubricants and metals in the case of bearings and a novel power and data transfer mechanism alternative to sliprings called "Flex-wrap" has been designed in this project. The current SADM is the smallest in the market in dimensions (70x50x6.9 mm) and applies to 5 different solar array mounting configurations.