From: Bdale Garbee Date: Wed, 9 Sep 2020 22:22:35 +0000 (-0600) Subject: KNSB M for Airfest - CATO X-Git-Url: https://git.gag.com/?p=web%2Fgag.com;a=commitdiff_plain;h=adc039d4e2945695e2a019baa8c9e96375235af9 KNSB M for Airfest - CATO --- diff --git a/rockets/research/2020-batch-01.mdwn b/rockets/research/2020-batch-01.mdwn new file mode 100755 index 0000000..f66091a --- /dev/null +++ b/rockets/research/2020-batch-01.mdwn @@ -0,0 +1,56 @@ +# 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.