Wednesday, May 9, 2007

Motor Stats

I thought I'd post some quick stats on the motor that I flew on the 28th of April. The motor was designed to produce approximately 425 lbs of thrust for 2.2 seconds for a total impulse of nearly 950 lbs. The motor (nozzle, casing, bulkhead, snap rings, inhibitor, and casing liner) weighted in at 5.96 lbs. The propellant grain, consisting of 4 segments in a bates grain configuration, weighted in at 7.31 lbs, with a port/throat ratio of 1.5625. The propellant was mixed in a ratio of 65/17.5/17.5 (KnO3/Sorbitol/Sucrose) and cast into 3" mailing tubes that have an ID of 3" and an OD of 3.125". The casing insulation consisted of four layers of rosin paper, purchased at Home Depot. The casing and bulkhead are fabricated of 6061-t6 aluminum. Using Richard Nakka's casing.xls the design safety factor was determined to be 2.2 with a burst saftey factor of 2.94. The nozzle is fabricated from 12L14 "leaded steel" and had a throat diameter of 0.64" and an expansion ratio of 12. There was no measurable throat erosion post firing and the nozzle appears to ready for another firing. When I took the motor apart post flight the insulation was nearly intact, having been breached near the bulkhead. The casing appears to be fine and there is no measurable deformation.

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