Further analysis for DRM II's first flight

I was chatting with my aerospace buddy Chris at work today and, having seen the blog entry and data below, he was as confused as I about the barometric altitude curve shape. I normally plot barometric altitude as that's accepted as the official peak. Accelerometer-based altitudes can suffer from integration errors caused by wobble, spin, coning or other undesirable flight behavior. Chris asked if it might have been caused by a Mach transition effect but I only hit Mach 0.58 so I was nowhere near the transonic region (0.8-1.2). I continued to ponder this irregularity and think I can explain the difference. In this alternate plot from the Raven you can see that the accelerometer-based altitude is shaped as one would expect with air-starts (slight slope increase when they kicked in):

I remembered that the aluminum tube that connects the electronics bay to the motor area was not plugged. When I pulled the camera it had a bit of smoke residue on it and the electronics board smelled sooty. This 7.5" rocket produces a great deal of base drag that I think forms a vacuum. I think that's why the barometric curve is steeper than the accelerometer curve and why there's an inflection point after the air-starts burned out. Then base drag decreased at that point which might have increased the pressure in the electronics bay just enough to flatten out the barometric curve in that weird region. In any event the rocket turned only once and otherwise flew straight up so I'm going believe the accelerometer curve in this particular case. Let me know if you have other thoughts. I'll definitely plug up the conduit with clay next time to reduce this pressure tomfoolery.