+++ /dev/null
-# Batch 2020-batch-01 #
-
-8 grains of 75mm KNSB, intended to be a reload for my long purple case.
-with Loki-style #58 nozzle. Grain length 5.125" with 0.125" spacing per
-grain planned using o-rings. Delrin coring rods of 0.75" diameter since
-that's what I have bases and caps for, then bored out to 0.875" final ID
-before assembly.
-
-Kuker's Motorsim says this should be a 43% M-2690 with a slightly progressive
-burn about 2.5 seconds long, using 5355g of propellant or 73% volume loading,
-and a max pressure of 825 psi.
-
-Since this is too much propellant to handle in one batch, we'll plan to use
-two 2700g batches, the formula for each of which is:
-
-* 65% KNO3, 1755g
-* 35% Sorbitol, 945g
-* 1% red iron oxide, 27g, added after melt
-* 41 drops Polystep-B1, added before pour using eye dropper
-
-This formula is completely fluid with 225F indicated on the Presto Multicooker,
-but viscosity is noticeabley lower making for easier pouring at 250-275F.
-
-These grains were cast on 2020.08.31.
-
-## Results ##
-
-The 5.125" grains were poured to a 119mm fill line, and then an 0.75" Delrin
-coring rod was twisted down into the goo puncturing foil over the coring rod
-hole at the grain base. About 18 hours later, the grains were "topped off"
-and smoothed level to compensate for shrinkage. The coring rods were pulled
-about 48 hours after casting, and each grain was observed to have some bubbling
-around the base of the coring rod, presumed to be due to air below the foil on
-the casting base pushing up as the rod went down. We should arrange for
-explicit venting of that in the future. The top faces of the grains were knife
-scraped smooth, the cores were bored out to 0.875", and the bottom of each grain
-was chamfered around the core to eliminate the bubbly bits. Thus, the grain
-masses were highly likely to be less than anticipated.
-
-* Grain 1, 630g gross, 16.21g casting tube, 613.79g net
-* Grain 2, 634g gross, 16.20g casting tube, 617.80g net
-* Grain 3, 640g gross, 16.14g casting tube, 623.86g net
-* Grain 4, 632g gross, 16.17g casting tube, 615.83g net
-* Grain 5, 626g gross, 16.34g casting tube, 609.66g net
-* Grain 6, 628g gross, 16.11g casting tube, 611.89g net
-* Grain 7, 628g gross, 16.17g casting tube, 611.83g net
-* Grain 8, 636g gross, 16.28g casting tube, 619.72g net
-
-Average casting tube weight 16.2g. Measured total propellant mass of 4924g,
-or about 616g per grain, which is 92% of what Kuker's simulator projected.
-
-Borrowed Terry's Loke #58 nozzle, which is a few thousandths over-sized.
-
-The as-built motor is projected to be a 30% M-2300 or so.
-
-Flight attempted at Airfest 2020 on Monday morning, CATO just off the rail.
projects / web / gag.com / blobdiff