Redundancy

Discussion in 'Rocketry Electronics and Software' started by dbpeirce, Jul 30, 2019.

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  1. Oct 21, 2019 #31

    cerving

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    We'll miss you Steve, I think TRA has definitely improved under your watch both in terms of governance and safety issues. I hope that TRA continues to recognize new technologies and the impact that they have upon the hobby, and adjusts the rules in a prudent manner with safety as the #1 consideration.
     
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  2. Oct 21, 2019 #32

    Steve Shannon

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    I’ll still be around. I’ll be on the board for nearly three years from now still. I agree that it’s vital that we allow for new technologies. I’m personally interested in GPS and tracking tech after spending years in application programming for a couple mapping programs.
    I’m also very interested in 3D printing and new composite methods, such as infusion.
    I also have a deep interest in the regulations that affect this hobby. If we’re not careful others will decide what those will be, but if we lead the way by policing ourselves, we may be able to keep regulations to a minimum.
     
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  3. Oct 21, 2019 #33

    Nytrunner

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    Hopefully we'll see you in HSV for student launch every now and then!
     
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  4. Oct 21, 2019 #34

    Greg Furtman

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    The Department of Reduncy Deepartment. :D
     
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  5. Oct 22, 2019 #35

    Onebadhawk

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    Why has noone answered the original posters question
    that a redundant electronic recovery set up means redundant.
    If the two batts and altimeters share a switch the set up isn't redundant.
    The not redundant set up will and should be rejected by the TAPs oking the set up for the cert flight..
    ( Or any other level 3 flight for that matter )..

    ( Or did someone say this and I missed it ?? )..

    Teddy
     
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  6. Oct 23, 2019 #36

    Steve Shannon

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    Great point!
     
  7. Oct 23, 2019 #37

    cerving

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    Redundancy means that there is no single point of failure, so the entire deployment system needs to be duplicated. Technically that includes charges too, although it's fairly common to make the charges a bit oversized and put both altimeters' ematches into the same well.
     
  8. Oct 23, 2019 #38

    SammyD

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    I don't like that setup (two e-matches in the same charge well) because an undersized charge will cause a recovery failure. If you're going to be fully redundant, you'll need two charge wells for each end of the AV Bay, usually with the backup charge being slightly larger than what ground testing indicated was adequate for successful deployment of the recovery components. In short, sometimes things get a little "tight", and a larger charge can "encourage" the separation when the first charge might not have gotten the job done...
     
  9. Oct 23, 2019 #39

    cwbullet

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    This is a concept I full agree with. I like the redundancy of 2 separate charges and matches. I like to add just a little extra charge to the second well.

    I consider deployment charges an art based on science similar to that of medicine. Like in medicine, full redundancy is good in rocketry.
     
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  10. Oct 23, 2019 #40

    SammyD

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    As stated above, a single switch makes that a single (non-redundant) point of failure. To be truly redundant, you'll need two of everything inside and outside the AV Bay: two altimeters, two batteries, two sets of wiring, two sets of charge wells, two switches, etc. See photos below of a 4" AV Bay, though I've done fully redundant this same way down to a 2.25" airframe - tight, but I got it all in there... :) Though not photographed, on either end of the AV Bays, I have two (2) charge wells too.
     

    Attached Files:

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  11. Oct 23, 2019 #41

    SammyD

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    Like Chuck said, I add a bit more black powder to the second charge. If ground testing shows that .5g of powder will do it, I add about .2g to the backup charge. For larger charges where 1g will do it on the ground, I add about .3g to the backup for a total of 1.3g on the backup. The primary charge is always the same as ground testing determined was the correct charge...
     
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  12. Oct 23, 2019 #42

    cwbullet

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    I think that goes to the old adage: “blow it out or blow it up”. I would never advocate this approach, but a little extra will not blow it up.
     
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  13. Oct 24, 2019 #43

    SammyD

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    Yep. There is a friend of mine that came to fly with us at Bayboro two weeks ago, and he subscribes to the "blow it apart or blow it up" theory. Whenever you here one of his charges go off (usually the backup), it sounds like a cannon above our heads. We call them "________ charges" (won't use his name here) LOL!
     
  14. Oct 24, 2019 #44

    cwbullet

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    Been there, done that. It is all great until you have a charge go off under your canopy. My ears still ring.
     
  15. Oct 24, 2019 #45

    SammyD

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    Oh boy... :-\
     
  16. Oct 25, 2019 #46

    cwbullet

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    I understand the concept of two initiators per charge but it is not redundant enough for me.
     
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  17. Oct 25, 2019 #47

    jderimig

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    ^ yes. What if lose containment of the charge during boost or other unplanned violent action. Not an unheard of failure mode. More common I suggest than altimeter failure.
     
  18. Oct 25, 2019 #48

    cwbullet

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    The funny thing is that you can plan for everything and the Unknown, Unknown will surprise you. Those darn unknown, unknowns bite you the behind every time.

     
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  19. Oct 25, 2019 #49

    cerving

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    Yup, I would suggest that even BP needs to be contained somewhat, if for no other reason than to prevent this failure mode.

    I know somebody who was using the Firewire ematches when they first came out, and he got some from that first bad batch. 3 of his 4 ematches didn't light the pyrogen... fortunately the one that went off was the backup drogue, so the only consequence was a bit of a hard landing. They all passed a resistance check prior to installation, so this is one of those failure modes that you would definitely not anticipate.
     
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  20. Oct 25, 2019 #50

    manixFan

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    I guess I don't see how anything other than two independent systems creates redundancy. If something is shared it's not a redundant system. Nothing on the OP, but it shouldn't even be up for discussion. Shared switch? Shared charge? Shared battery? Not redundant. Here's the 'engineering' definition of redundant:

    "not strictly necessary to functioning but included in case of failure in another component"

    So if you don't have something to cover the failure of another component, it's not redundant.


    Tony
     
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  21. Oct 25, 2019 #51

    Greg Furtman

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    I've been buying my ematches from Wildman & haven't had a failure yet. After I put the ematch & BP in the canister I stuff it with dog barf and tape the top. It works great.
     
  22. Oct 26, 2019 #52

    SammyD

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    Me neither...
     
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