Mechanical Frame Design of the Satellite

3d view of four frame panels in a line

As part of the design of our CubeSat satellite, a 10x10x10cm cube, a frame is required, to stabilise solar panels and hold circuit boards among other things. This blog covers the design process of this frame.

line drawing of half of a cross on one side ofthe frame with dimensions

The frame is made out of aluminium as this is a light-weight material that can be added to the extra payload of the rocket. Aluminium is a cheap material and, therefore, the best material when the budget is considered. The thickness of the aluminium is 1.5mm to withstand the forces within the rocket during launch (we have a rocket launch coming up in a few months to test our design). The thickness of the aluminium sheets couldn’t be any thicker than 1.5mm as we have a size constraint of 10×10 cm to adhere to and it is easier to bend 1.5mm sheets. The aluminium has metallic properties where it can spread the heat energy generated from the printed circuit board (PCB). The structure is crafted to reduce the possibility of overheating whilst in orbit.

The PCBs, which are used to power the satellite while the satellite is in orbit, will be layered on top of each other. The PCBs will be attached with the solar panels and all securely fastened by a bolt. The bolt has a 3mm diameter with a length of 100mm.

full sketch of one face of the frame, a square with a cross in the midle

The BLUEsat Power Team has replicated parts of previous models of CubeSats that have been successful in launch and the design has been tested. As seen in the illustrations, the crosses in the frame are used to stabilise the solar panels. The circle in the middle reduces the concentration of stress being applied to the frame. The possibility of material failure is, therefore, reduced as there is less stress being applied to a specific point.

The satellite is a one-unit CubeSat satellite made from aluminium sheets with layered printed circuit boards within the structure. The printed circuit boards will be stabilised during launch through the use of nuts in a layered format. The frame will be designed by bending the aluminium sheets using a specialised bending machine. The sheets will be fastened together using a rivet gun. The top and bottom of the frame will have an arc to be bended to connect the top and bottom to the main frame. The connection will be fastened together using bolts and nuts.

The mechanical frame will be made through a CNC machine as this is the most cost-effective and efficient method of producing the mechanical frame. The sides of the frame will be made one at a time since the CNC machine used to produce the frame doesn’t have the current capacities to produce a three-dimensional finish. The screw holes, that will hold both the bolt to connect the sides together and the bolt that will hold the printed circuit boards together will have a diameter of 3.5mm. The hole within the centre of the sides of the frame measures to be 150mm. Other measurements that are needed will be presented in the CAD diagrams below. The size of the sheets is 95x95mm sheets with four sides that have four solar panels as well as two sides on the top and bottom to access the printed circuit boards.

four panels of the frame put together

The solar panel will be fastened down, through the use of bolts, on the side of the aluminium frame. The solar panel will be placed on top of the frame so that the solar cells can absorb all the light whilst in orbit. Photos of the frame are documented below for visuals of what the frame will look like.

For the solar panel, a temperature sensor is used to analyse the temperature of the solar panel and this is sent back if any heating problems need to be addressed. There are two pads on the PCB that will hold the solar cells as well as the temperature sensors stated above. The solar cells will be soldered onto the pads and there will be a small gap in between the solar cells to prevent breakage.

one face of the satellite frame coloured in with a gradient

Another design to be considered, if the design above is to fail during testing is to have the sheets to have tabs at the ends of the sheets that can attach to other sheets in the frame. This feature in the aluminium sheets will reduce the sliding of the sheets and increase strength of the frame. The sheets will be held together by an inner bracket that is a three-axis bracket. The three-axis bracket will be fastened together using bolts and nuts with the bolt being 3mm by diameter and 10mm by length. The top and bottom will also have tabs to connect to the other sides of the frame. Since these two sides aren’t attached to the layered printed circuit boards, the bottom and top of the frame can be easily detached from the main structure if the satellite needs to be dissembled for maintenance. The CAD designs of the second frame to use as back-up if the first one fails is illustrated below.

The dimension of the frame is 97x97mm and the thickness if 1.5mm.

3d view of one side of the frame

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