Abstract
Background: The design, development, and testing of a small-thruster system with additively-manufacturing key components is presented. The primary issue associated with conventionally-manufactured small thruster systems is the assembly complexity, where the motor case, injector, ignition electrodes, nozzle retainer, nozzle, fuel grain, insulting liner, and other components are fabricated individually and then assembled. For very small thruster systems, this detailed fabrication and assembly process is extremely labor intensive and time-consuming. Proposed "all- additive" designs reduce component fabrication and procurement cycle time, and may significantly reduce overall system complexity. Before committing to hardware, a student-lead design team reduced the trade-space to 2 design-options. Each option employs multiple additively-manufactured components including the oxidizer delivery system attachments, motor cap, motor casing, insulation, and the fuel grain. Components are additively manufactured using one of three different methods, fused-deposition modeling (FDM), stereo lithography (SL), and non-galvanic nickel plating (EN). Both designs feature an FDM-fabricated ABS fuel grain, with 1) a two material combustion chamber assembly fabricated from Veroclear® plastic using Polyjet 3-D SL printing technology, and 2) a chamber/fuel assembly additively fabricated from ABS, but plated with an external nickel coating. For simplicity the student prototype employs gaseous oxygen (GOX) and additively manufactured acrylonitrile-butadiene-styrene (ABS) as propellants. ABS has been previously demonstrated to be a highly efficient hybrid fuel material. The research campaign emphasized multiple objectives including hot and cold material testing burn lifetime survivability, system restart capability, and overall performance. Performance comparisons with hydrazine are presented.