more info about our second batch of igniters

[web/gag.com] / rockets / research / 2017-batch-05.mdwn

diff --git a/rockets/research/2017-batch-05.mdwn b/rockets/research/2017-batch-05.mdwn
index e16404b4ceae565b56e2b02945495bda56905f64..c0e50699ece0cc318db4aee7ac21c95f352be52f 100755 (executable)
--- a/rockets/research/2017-batch-05.mdwn
+++ b/rockets/research/2017-batch-05.mdwn
@@ -13,8 +13,8 @@ Made up a 15g batch with the following formula:
 * 7% magnesium powder, 1.05g
 * 1% air float charcoal, 0.15g
 * 24% West Systems 105+206 epoxy, 3.60g
-** 3.03g 105 resin
-** 0.57g 206 hardener
+    * 3.03g 105 resin
+    * 0.57g 206 hardener
 
 Two folded papers were used to weigh out the KNO3 in one, and a mixture of
 the magnesium powder and charcoal in another.  The epoxy was mixed in a small 
@@ -49,5 +49,32 @@ Mg particle size.  It could be that we need to go back to using the finer Mg
 powder when making smaller igniters, and reserve the "chunky" stuff for large
 ones?
 
+At NCR's Mile High Mayhem 2017, we used a 12V battery to test one of the
+larger igniters, and the bridge wire burned and burned a small amount of
+the pyrogen, but then it fizzled out without doing anything really 
+useful.  That made us skittish about trying them on the rail, and we used
+up the rest of our commercial igniters and bought a couple more that weekend 
+instead. 
+
+Once home, we tested the rest of the batch.  About 2/3 ignited and burned ok,
+but fairly slowly and not very evenly.  About 1/3 did what the one we tested
+at the launch did, burning slightly then fizzling out. 
+
+The burn time was at least 5 seconds on each igniter, with about 1" length
+of pyrogen.  That really seems too slow.  1-2 seconds would be better?
+
 ## Observations ##
 
+We think the larger magnesium particles, which make nice "spitty" igniters
+when the igniter actually ignites, would probably help start big sugar motor
+grains, but we really can't call this batch successful.  Our theory is that
+the failed igniters hit a big chunk of magnesium that they didn't have enough
+energy to ignite before enough of the epoxy-based pyrogen was burning to 
+sustain combustion.
+
+Robert noted that large magnesium particles also seem to raise the risk of
+starting a grass fire around the launch pad if the motor does light and the
+rocket takes off before the igniter completely combusts.
+
+Next, we'll try going back to the powdered magnesium with bridge wires.
+