CubeSat Advanced Technology Propulsion System Concept

One of the many challenges when it comes to small satellites is low cost, especially when it comes to propulsion. At Aerojet Rocketdyne a CubeSat propulsion system was developed utilizing the advantages of the additive manufacturing process. This design reduces the part count by 50%, eliminates all 22 final assembly welds and reduces the projected recurring propulsion system cost by 75%. Starting with the CubeSat envelope of 1000 cubic centimeters, a typical satellite hydrazine mono propellant propulsion system was created for a baseline comparison. The goal of the advanced technology low cost propulsion system was to minimize part count by taking maximum advantage of additive manufacturing. This innovative concept combines 22 parts into two additive manufactured parts; literally, a “plug and play” final assembly approach. The propulsion system components (i.e., thrusters, valves, regulator, isolation valves, service valves, burst disks, etc.) are all installed into the two additive manufactured parts at final assembly. At Aerojet Rocketdyne, design guidelines were developed for the Direct Metal Laser Sintering (DMLS) process. These guidelines (i.e., part accuracy, overhangs, cavity features, floor features, wall features, minimum feature size, wall thickness, etc.) were used when designing the CubeSat DMLS parts. The parts initially were rapid prototyped with a multi-color 3D printer. The parts were then fabricated with both Inconel 625 and Titanium 6-4 using the Concept Laser M2 machine. Material test specimens form the same machine used to make the CubeSat parts were fabricated and tested for material properties (i.e., ultimate, yield, ductility, etc.). After fabrication the parts went through powder removal, clean, stress relief, wire Electric Discharge Machining (EDM) from the build plate and a Hot Isostatic Pressing (HIP) heat treat process. To verify that the parts met all the dimensional requirements, a white light inspection was performed and compared to the original Computer Aided Design (CAD) model. The final step was post machining operations on all the sealing surfaces and threaded interfaces. Due to the continuing improvement in additive manufacturing capability, low cost satellite propulsion systems are now possible.