Hi Chris; Hmmm..... well the logical question is did the two holes on either side if the camera shroud ever function correctly ? i.e. Were they occluded in any way by the switches or was the air pressure non-laminar ? If so, then you really only had two holes total; one of which could have been momentarily blocked.
Best regards; Bob Finch On Mon, May 23, 2016 at 10:01 AM, Chris Attebery <[email protected]> wrote: > Hi Bob, > > There were 4x 1/4" holes in the altimeter bay. One on each side of the > camera shroud for the screw switches and two more spaced 120 degrees from > the center line of the camera shroud. > > My theory is that the camera shroud caused some sort of pressure wave after > it hit mach. The pressure doesn't seem to change from 3.5 seconds until 5 > seconds even though the rocket is traveling ~1100ft/sec. Then a quarter > second after it passes back though mach at ~5.25 seconds there is a pressure > spike. There is another pressure spike at ~6.5 seconds and that is when > everything went down hill. > > You're required to use redundant electronics for your L3 flight. Next time > I'll use something that is accelerometer based so I don't have to worry > about these issues. > > BTW: I figured out how to use the zoom functions in AltOS last night after I > posted this. I took a snapshot of the portion of the data relevant to this > discussion. > > On Mon, May 23, 2016 at 8:23 AM, w9ya <[email protected]> wrote: >> >> Um..... I like to have THREE pressure ports....i.e. just in case. >> Here's how (and why): >> >> It seems that this flight qualified as a "just in case" scenario. I >> generally make each hole .67-1.0 the size of the specified size of the >> single hole specification, all of them the same actual size, and space >> them equally around the circumference of the body. The idea being that >> while one hole can/may be "blocked" to incoming air pressure, blocking >> two of the three holes should not happen. >> >> I am guessing the hole located near the camera shroud was the problem. >> >> Best regards; >> >> Bob Finch >> >> P.S.... I am big fan of backup electronics but I almost never actually >> use more than one altimeter for deployment. Good electronic bay >> modelling along with good electronics seems to negate the need for me. >> >> On Mon, May 23, 2016 at 12:48 AM, Keith Packard <[email protected]> wrote: >> > Chris Attebery <[email protected]> writes: >> > >> >> I've attached a rendering of the altimeter bay and camera shroud. In >> >> hindsight I should have sealed the camera in a separate bay from the >> >> altimeters. I would probably stretch the rocket a bit more to get some >> >> separation between the electronic and the camera shroud. I need to look >> >> into getting a second accelerometer based altimeter for backup too. >> > >> > Hrm. Thinking about this some more, is it possible that the rocket went >> > sideways? It's really hard to make an ebay airtight enough so that a >> > plugged static port would read a steady, and even increasing pressure >> > while the rocket was still going up. If there was some major structure >> > failure near motor burn out, I would have expected to see more noise in >> > the acceleration data though, so it would have had to be a fairly gentle >> > failure mode. >> > >> > -- >> > -keith >> > >> > _______________________________________________ >> > altusmetrum mailing list >> > [email protected] >> > http://lists.gag.com/mailman/listinfo/altusmetrum >> > >> _______________________________________________ >> altusmetrum mailing list >> [email protected] >> http://lists.gag.com/mailman/listinfo/altusmetrum > > _______________________________________________ altusmetrum mailing list [email protected] http://lists.gag.com/mailman/listinfo/altusmetrum
