Test 2

Trying again using the same formula as test 1, but different handling logistics for pouring the grains.

Tru-Core casting set with two bases each set up with 0.5 inch mandrels. Four pieces of casting tube cut to grain length of 1.875 inches.

Process

The grains were cast on 31 May 2015.

The multi-cooker was preheated to about 250F with the lid on. Temp was increased during melting to 275F indicated.

When the 200g batch of propellant was nearly ready to pour, we put in enough bits from the void-plagued grains of test 1 to re-melt that we'd be able to cast 4 grains plus a burn rate test rod.

We poured one grain at a time, leaving the multi-cooker heating and putting the lid back on between grains to keep the propellant at temperature. The first 3 grains poured pretty easily, the viscosity was higher when pouring the last grain so not clear how well it filled. Two grains stacked on each mandrel, for 4 grains total. That left enough to form a test burn rod about 3/8" diameter and in excess of 4" long.

Results

• Grain 1, 55.42g net
• Grain 2, 54.57g net
• Grain 3, 55.90g net
• Grain 4, 56.33g net

Observations

Went much better than trying to pour one large "grain" to cut later, but we still seemed to have lots of bubble inclusions. Either need to use more surfactant or keep everything warmer to get better grains. Possibly pour on a vibration table?