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[web/gag.com] / rockets / research / 2017-batch-09.mdwn

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+# Batch 2017-batch-09 #
+
+8 grains of 75mm using sorbitol, intended to be a reload for my CTI Pro75 6xl 
+case with Loki nozzle and forward closure.  Grain length 4.375" with 0.125" 
+spacing per grain, so we'll make the casting tubes 4.5" long.  Delrin coring 
+rods of 0.75" diameter.  
+
+To overcome shrinkage noticed in the last batch, fill lines set based on the
+total 4.5" casting tube length, on the assumption that any shrinkage will
+provide sufficient inter-grain spacing.
+
+Formula for a batch size of 4800g:
+
+* 65% KNO3, 3120g
+* 35% Sorbitol, 1680g
+* 1% red iron oxide, 48g, added after melt
+* 72 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 15 October 2017.
+
+## Results ##
+
+This batch made for a pretty full Presto, and a fairly long time coming up
+to temperature.  It seems like 5kg might be the most propellant I should try
+to melt at one time.  As an aside, that means for my 6" O project, we'd be
+melting and casting one grain at a time...
+
+Average casting tube weight 15.3g.
+
+* Grain 1, 542g gross, 527g net
+* Grain 2, 548g gross, 533g net
+* Grain 3, 552g gross, 537g net
+* Grain 4, 546g gross, 531g net
+* Grain 5, 544g gross, 529g net
+* Grain 6, 540g gross, 525g net
+* Grain 7, 528g gross, 513g net
+* Grain 8, 538g gross, 523g net
+
+Total propellant load 4218g.  That's enough lower than the anticipated mass
+that I decided to "top off" the grains with more melted propellant from the
+left-overs in this batch.  Will re-weigh after they cool/cure.
+
+