In attendance: Eric Hettinger, Brian O’Neel, Jim Ward, Evan Waymire
What we did today:
We discussed the possible reasons surrounding our low chamber pressure and low thrust levels from the last test fire. We hypothesized that our thrust coefficient could likely be in error due to an incorrect ratio of specific heats for oxygen/paraffin. This may have lead to us calculating an over sized nozzle. The other possibility we considered is that our oxidizer to fuel ratio is not optimal.
We have decide to do another round of parametric testing where we will vary both our nozzle sizes by 10% and 20% smaller in diameter and also adjust the metering orifice to be 25% and 50% larger in diameter. We will conduct another round of static firing were everything else is held as it was in the last test fire except for these two variables (nozzle and metering orifice diameters) and individually vary these to see their effect on chamber pressure. This will hopefully tell us enough to point us in the right direction.
We also discussed Jim's preliminary plans for building a spin caster. He brought in some prototype components he has been working on and they look very good. We will attempt to pour the liquid paraffin in a sealed cylindrical mold and spin this between 1000-3000 rpm until the paraffin has solidified and the shrinkage has created the right diameter port in the center of the grain.
We discussed pouring the new fuel grains for the upcoming static test and the additional hardware that needs to be made to accommodate the new changes we want to try.
We will be static firing approximately ten motor will we our out at the Black Rock desert for the upcoming launch Sept 10-13th.
K vs Dia. Throat sensitivity analysis
- Machine new nozzles (10% and 20% larger dia.)and premix chambers.
- Machine new metering orifice (25% larger dia.).
Machine new combustion chamber. chamber and flanges (Jim will get it welded up).
Work on spin caster prototype.
Work on remote Labview server.
Start pouring new paraffin grains (10 total).
Never underestimate the power of a rocket motor