more text

[web/gag.com] / rockets / research / test5.mdwn

diff --git a/rockets/research/test5.mdwn b/rockets/research/test5.mdwn
index ca27d89bdbbbf68c109a0d20e137ee3e6c5c57a7..23f80a1ce2cf9c9f5b539fd5786ea198a1d65595 100755 (executable)
--- a/rockets/research/test5.mdwn
+++ b/rockets/research/test5.mdwn
@@ -24,24 +24,8 @@ cap installed and grain tapped down.
 * 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 ##
+## Simulation ##
 
-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.
-
-The original simulator data:
 <pre>
 Propellant             : propellants/knsb.xml
 Nozzle diameter        : 0.739 cm (0.291") (19/64")
@@ -74,3 +58,41 @@ Average Thrust : 169.555 N
 
 Motor          : H170
 </pre>
+
+![simulation data](test5-sim.png)
+
+## 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.
+
+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.
+
+![flight acceleration data](test5-altosui.png)
+
+## 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.
+
+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.
+
+Pretty cool for our first real flight test!