I'm sorry to read this. I know you put a lot of time and thought into this rocket. I doubt that the "gust shields" you placed around your altimeters prevented them from sensing pressure.
I agree with your skepticism whole heartedly. I wasn't worried in the slightest about this problem when I made the change. My only thought though is that perhaps the sides of the plastic were touching the edges of the body tube. Here is what the bay looked like before the shield was added:
The plastic shield I added sat on top of the wooden posts and was the same lateral width as the board. It ran from post 1 to post 4 counting left to right, so it sat right over both altimeters. I've drawn it in red:
I'm wondering if perhaps it was touching the sides of the body tube (I don't think it was but maybe...), then the only way for air to get to the altimeters would be through the end, and maybe that obstruction was enough to prevent launch detection from happening?
Did you have your EggFinder on? Did you get any usable position data from the flight? If you use the LCD receiver, I'm pretty sure it stores the last received position in memory. That last position can be looked at even after you shut off the LCD and turn it back on.
Eggfinder was on and I had a track in the Rocket Locator app. Track wasn't useful - the rocket never was slow enough for long enough to have a reasonable GPS lock. The rocket definitely ended up in the woods and the track never left the field. The predicted impact point from open rocket with all the winds dialed in was 43°18'26.6"N 70°53'36.5"W:
https://goo.gl/maps/oseXMj2fND12
Let me ask a bunch of obvious questions.. perhaps it will jog something useful here...
What common mode failure could have prevented both of them from deploying?... Bad igniters.. unlikely. Bad powder.. What type of powder do you use for deployment, 4F Black Powder? Low battery voltage? What type, voltage/mAh batteries did you use for your Quantums? How many volts were packs at after your armed the Quantums over WiFi? (I'm assuming you verified both drogue and main continuity for each quantum on the arming page.) Could something have broken off and disconnected both the altimeters during the boost?
Good questions to ask.
I used 4 charge cannisters (large size) from pratt hobbies. They are extremely reliable and have an integrated igniter. All 4 measured the correct resistance before I loaded them, and all 4 showed connectivity on the launch pad (the quantum let's me see that visually).
Black powder is the stuff supplied by AMW, I think it may be 3F. I've always used it. The same powder worked successfully that same day in my previous flight, which also used the pratt charge cannisters loaded in the exact same way.
Batteries were 2s 460maH Lipos. Same as I've used with all quantum flights. Each altimeter had two batteries, a deploymenet battery and a main battery. All batteries were charged (checkd with voltmeter) and the quantums confirmed charge (and I have a screenshot of the secondary altimeter showing battery voltage of 8.1V from right before the flight).
Your theory about something flying around in the AV bay is a good one... except (a) there isn't much that could. The batteries are on the opposite side of the board from the altimeters, each sitting in a separate little wooden well with a wooden board holding them in. (b) the plastic shield would have made it harder for anything loose to bang into the altimeters. This wasn't it's intended purpose, but it is a side effect.
I was reviewing your excellent flight video.. and though I may have noticed something just before the drogue deployment... Listen for the noise at 28 seconds in the video.. could that be a primary drogue charge going off, but not separating?.. or is that a quick link clanking on the side of the rocket at nose over just before deployment? I hope you are able to get back there and find this rocket. I can't imagine how it must feel to loose it.
WOW great observation. I will go home tonight and see if that sound is coming from the ground video or the on-rocket video. It certainly does seem like it could be a charge going off. I do remember being a bit concerned that I couldn't hear the backup charge fire after the drogue charge fired in the video, but chalked it up to being hard to hear over the wind noise.
That doesn't explain why the failsafe mode on the quantums didn't then fire the main once freefall was detected. BUT those are based on velocity measurements. I wonder if the shield was enough to mess with the velocity measurements as the rocket fell and cause the failsafes to not trigger? The theory I guess would be that the drogue charges weren't enough to separate the drogue, and then the failsafe didn't fire. I don't actually know for sure that the main's didn't fire at 600' (400' backup) since I'd lost visual sight of the rocket by then. My assumption had been that the failsafe not firing the mains meant the mains didn't fire. We also heard the rocket whistle as it came in hot, but AFAIK no one saw the impact or heard an impact, it is possible that the main did deploy right before impact and we just didn't see it happen.