Printed PaulSat

grabcad

This entry is based on my long experience in designing and manufacturing CubeSat frames. I designed the structure of ESTCube-1 (first Estonian satellite which is in orbit) and CubeSat structure product line for my company. Designing and assembling real CubeSats and performing space qualification testing has given very good experience and know-how. This is valuable because too many other CubeSat structure designs have been inspired by Pumpkin CubeSat Kit but much more elegant and mass-efficient designs are possible. This design is based on the idea of removing stack beams and standoffs between subsystems and using on-demand 3D printing to manufacture corner slots with very small margins to keep the subsystem printed circuit boards (PCBs) in place. One of the solar panels (see the rendering) will keep the PCBs tightly fastened so the stack would not slide back out. NB! See the longer description document under files! -- DESIGN AND ADVANTAGES -- Benefits of this design: • Structure is only one single part. • Helicoil reinforced solar panel mounting holes to attach and remove side panels many times. • Possible to manufacture with current technologies. • Mass of 1U aluminium structure is only 54 grams. It really is that low. Likely can be optimized even more. • Made from aluminium. Does not cause additional thermal, radiation or outgassing concerns. • Quick and easy modifications, might just have to change PCB distances and thicknesses. • Deployment switch and separation spring are integrated as one. • Scalable to 12U and more, depending on exact configuration. • Conforms to CubeSat Specification and launcher requirements. Process of designing and assembling this structure: 1. Design CubeSat in 3D modelling software. a. Choose or design satellite subsystems and connect them with common PC104 connectors or by using a separate PCB back-plate which is like a motherboard in PCs. Both solutions are supported. b. Quickly and effortlessly modify distances between corner slots, which will hold PCBs in place and create all other modifications if necessary. 2. Send CubeSat structure model to on demand additive manufacturing. 3. Assemble PCB stack outside of the frame. 4. Attach some solar panels and antennas to the structure. Use common screws to mount them or use some compliant mechanism option in the future. 5. Start inserting the PCB stack into the frame from one of the sides specially meant for this. 6. During insertion connect solar panel, antenna, Sun sensor etc cables. Also connect the cables for panels which have not yet been mounted to the structure. 7. Attach the last remaining solar panels. One of them will fix the PCB stack securely and tightly into place (rendering with the solar panel). These (corner) slots will be the exact size as PCB boards with very small margins. -- ADDITIVE BUILD PROCESS AND MATERIAL -- Aluminium AlSi10Mg with Direct Metal Laser Sintering (DMLS) is the choice for an already common build process. Main reasons for using metals are better radiation protection and self-supporting nature of the DMLS build chambers. Downside is the build volume because common 3D printers will limit printing to 1U and 2U CubeSats but new EOS M400 has 400 mm x 400 mm x 400 mm build volume allowing printing of CubeSats up to 27U. Aluminium already complies with all the environmental requirements (incl. thermal and outgassing) as well as CubeSat standard and dispenser requirements. Future improvement expectations: • Compliant mechanism solar panels. Waiting to be able to print different materials with DMLS/SLS so that frame can be from aluminium and compliant mounting mechanism from plastic/composite. • Deployment switch and separation spring may be attached during printing by stopping the process and then continuing. Stack 3D models are from GomSpace and CubeSpace.