Trying again using KNSO with our new casting bases. We also have a real
eye-dropper now for measuring the surfactant. 4 38mm grains of
-1.875" length, using formula of
+1.875" length, 250 gram batch using formula of
-* 65% KNO3
-* 35% Sorbitol
-* 1% red iron oxide
-* 3 drops Polystep-B1
+* 65% KNO3, 162.5g
+* 35% Sorbitol, 87.5g
+* 1% red iron oxide, 2.5g, added after melt
+* 3 drops Polystep-B1, added before pour
## Process ##
* Grain 3, 52.30g net
* Grain 4, 51.23g net
-## Observations ##
-
-Pour went really smoothly. One grain looked "perfect" with the propellant
-settled evenly and a couple mm of open gap at the top of the casting
-tube. We think this one may have been slightly under-filled compared to
-the others, all of which had some evidence of propellant sticking to the
-cap and leaving an uneven top surface. This resulted in some quick trim
-work with a knife, ergo final grain masses not matching all that well.
-
-## Flight Test ##
-
-These four grains were assembled in an AT 38/480 case with a random AT
-delay grain from the pile of left-overs, and flown in Robert's Madcow
-Little John at Tripoli Colorado Spring Fling 2015. We used a Slim Gem
-igniter from Quickburst. Great flight! The motor seemed to come up to
-pressure quickly, and burned brilliantly.
+## Simulation ##
-The original simulator data:
<pre>
Propellant : propellants/knsb.xml
Nozzle diameter : 0.739 cm (0.291") (19/64")
Motor : H170
</pre>
+
+
+
+## Flight Test ##
+
+These four grains were assembled in an AT 38/480 case with a random AT
+delay grain from the pile of left-overs, and flown in Robert's Madcow
+Little John at Tripoli Colorado Spring Fling 2015. We used a
+[Slim Gem](http://www.quickburst.net/slim_gem_igniter.htm)
+igniter from [Quickburst](http://www.quickburst.net/). Great
+flight! The motor seemed to come up to pressure quickly, and burned
+brilliantly.
+
+The airframe weighed 1200 grams ready to launch, and 982 grams post-flight,
+of which 1g or so was BP in the ejection charge, and a few grams were in
+the Aerotech delay grain.
+
+Post-flight measurement of the phenolic nozzle showed approximately an
+0.330" throat, which clearly indicates some erosion from the 0.291" starting
+point.
+
+
+
+## Observations ##
+
+Pour went really smoothly. Easier than previous batches, perhaps due to
+a bit more surfactant, perhaps just getting better, perhaps due to putting
+the mandrels in post-pour. One grain looked "perfect" with the propellant
+settled evenly and a couple mm of open gap at the top of the casting
+tube. We think this one may have been slightly under-filled compared to
+the others, all of which had some evidence of propellant sticking to the
+cap and leaving an uneven top surface. This resulted in some quick trim
+work with a knife, ergo final grain masses not matching all that well.
+
+We were totally stoked that the burn time matched simulation (once we factor
+in a tenth of a second or two before the motor came up to pressure!). We
+were also pleased that the max pressure was "right on time" at about 0.4
+seconds after coming up to pressure. The regressive curve seems a bit
+exagerated in the flight accel data, which seems completely explainable by
+the nozzle throat erosion causing pressure to faill during that period.
+
+The airframe saw an average of 12 G acceleration on the way to Mach 0.6 and
+2838 feet above the laucnh site which is at 8800 feet MSL. Perfect
+recovery! Pretty cool for our first real flight test!
projects / web / gag.com / blobdiff