The formula used is the same we've been using with sorbitol, but in an 875g
batch this time:
-* 65% KNO3, 568.75g
+* 65% KNO3, 568.75g, taken from the big bucket this time
* 35% Sorbitol, 306.25g
* 1% red iron oxide, 8.75g, added after melt
* 10 drops Polystep-B1, added before pour using eye dropper
to his process for 38mm, since the larger casting tubes and greater propellant
mass meant having to hold everything together more solidly. We also noted
that there was some variation (a mm or so?) in my casting tube lengths, so
-getting them uniformly filled was a bit fiddly.
+getting them uniformly filled was a bit fiddly. Our calculations led us to
+use a fill line 76.118mm from the bottom or 6.431mm from the top of the
+casting tubes. On a couple of the shortest-cut casting tubes, this led to a
+small amount of propellant contacting the inside of the pipe cap. Try harder
+to cut precisely next time!
These grains were cast on 1 September 2015.
## Results ##
+Dropped one grain at home, big chunk missing and maybe cracks. Decided not
+to use it. That left us with three "good" grains.
+
+The case, nozzle, and closure combination used left me cutting the liner to
+10.250 inches, while Loki specifies 10.375 for their 3-grain case. The total
+available propellant length was 9.459", so I had to trim the three grains
+slightly to fit. The gross masses below were post-trim. Calculating net
+masses will require approximation based on the overall casting tube length
+that remained.
+
* Grain 1, ?g net
-* Grain 2, ?g net
-* Grain 3, ?g net
-* Grain 4, ?g net
+* Grain 2, 204.0g gross, ?g net
+* Grain 3, 199.3g gross, ?g net
+* Grain 4, 198.6g gross, ?g net
+
+10.250" liner, 8.3mm nozzle throat, buna-n o-rings.
+
+calculated as a 39% J-477, 843 Ns, ~1.5 sec burn
## Observations ##
+1250g pre-launch motor mass, 664g post-flight motor mass.
+
+4830g pre-launch airframe mass.
+
projects / web / gag.com / blobdiff