An extremely long case with an cool result! Burnsim classifies this as a 68% J-560
Pc_max is 820Psi, and Kn is 299-414. Peak mass flux is 1.8 with the stepped core configuration shown in the picture above, but with straight cores it peaks at 2.2! Another reason to step cores on long motors is to reduce erosive burning. Erosive burning is when the core of the propellant grains gets eroded by the oncoming mass flux of the motor, exposing more surface area and skyrocketing the Kn and Pc. This motor uses a 28/64″ throat expanding to 0.73″.
There are 6 Grains, each 3.4″ long. The bottom two grains are stepped to 9/16 core, while the top four have a 1/2″ core.
The case is 23.25″ long, with 20.6″ total propellant length.
The propellant is “Soylent Green”, a moderate metals, 76% solids propellant. The propellant burns with a beautiful yellow-white flame. The green color comes from Chromium Oxide, a burn rate catalyst.
UPDATE: This motor was static tested successfully on the 19th of April, 2014. http://sojourner.me/blog/?p=242