On September 20th, LD and JVDB static tested a joint monolithic motor project. JVDB provided the design, foam cores & motor hardware. LD developed the grain casting process, assembled the motor and provided the test stand. This motor was our first try at a monolithic grain motor with a complex foam core. We believe case bonded, monolithic grains are a requirement in case we wish to scale up our APCP motors. Hence we started with smaller 10-11kNs proof of concept motor cast in a PML 3″ phenolic body tube mainly to investigate startup.
The core design was gratefully provided by AV and duly copied by us. AV had tested the design with great results in an approx 20kNs motor. The shape can be considered a finocyl or a finned core. Below regression graphs, as copied from this great page about solid fuel regression, describes the difference between finned and slotted core regression. In the finned core design the propellant itself protect the casing from the hot gasses. We did experience quite some erosive burning at the beginning. This could be due to the Slow White propellant and / or the grain design. See below thrust curve picture with comments.