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  1. #1
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    5th December 2013
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    Exclamation The cato to end all catoes!!!

    Well, the bottom half of my Formula 200 is no more.

    Yesterday was the first flight with my new EX motor hardware, and the forward end of the motor blew to smithereens. I am assuming hardware failure, since the propellant was a very well-known formula, third time I've used it. My motor mentor supervised the whole thing, and nothing was out of the usual with the mixing, casting or assembly.

    The motor case was made by one vendor, and the closure, nozzle and rings by someone else. I am just chalking it up to minor incompatibility. O-rings were abundantly greased and all four were assembled.

    The booster was completely scorched, and since the epoxy holding the G12 together melted, the G12 frayed. Looks like spaghetti! The G10 CRs also came apart in layers. In the center of the second-to-last picture, that's the exploded motor casing.

    Enjoy the pics. She will be rebuilt! She will again!

    Click image for larger version. 

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    John S. ---- NAR #96911 ---- TRA #15253 ---- MDRA #067 ---- BARC #028
    L1, 3/15/14: Aerotech Sumo, CTI H133BS
    L2, 6/21/14: Giant Leap Vertical Assault, CTI J240RL
    L3, 3/12/16: MAC Performance Radial Flyer, CTI M1101WH
    Altitude: 13,028', L3 flight; Speed: Mach ???, L3 flight

  2. #2
    Join Date
    4th August 2011
    Location
    Lincolnton NC
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    5,332
    GEEZ! What a mess. It's doubtful I've ever seen carnage of that nature. Bummer, eh? Hate it for ya man. R.I.P Formula 200.

    Thinking outside the box is normal for me. Went inside the box once and got claustrophobic.
    Can't never did!
    Inventions weren't created by skeptics.
    There's a bright side to every screwed up week.


  3. #3
    Join Date
    26th January 2010
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    Northern California
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    13,180
    Oh my gosh, that has got to be the worst damage I've seen! Did you happen to get photos and/or video of the event?
    NAR 91107, Level 2

    I really, really hate bugs.

  4. #4
    Join Date
    3rd July 2017
    Posts
    116
    Wow John - your not kidding. That was a terrible CATO. Good luck on the rebuild.

  5. #5
    Join Date
    28th June 2017
    Location
    Northern VA
    Posts
    114
    Sorry man. The thing felt like cotton fibers afterwards. But it did look like some could be saved at least. At least it was a really cool flight
    Trevor Mushung
    NAR 99446

  6. #6
    Join Date
    23rd January 2009
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    New York
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    Pics of motor that suggest “incompatibility”?


    Sent from my iPhone using Rocketry Forum
    Dan Patell
    TRA 10904 L3

    Easy Research Rocketry
    29mm Research Hardware Has Returned!!!

  7. #7
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    Quote Originally Posted by qquake2k View Post
    Oh my gosh, that has got to be the worst damage I've seen! Did you happen to get photos and/or video of the event?
    No. I was just planning to watch and enjoy the flight, and the launch was so busy that our resident videographer did not get any footage. Had I only known beforehand...

    John S. ---- NAR #96911 ---- TRA #15253 ---- MDRA #067 ---- BARC #028
    L1, 3/15/14: Aerotech Sumo, CTI H133BS
    L2, 6/21/14: Giant Leap Vertical Assault, CTI J240RL
    L3, 3/12/16: MAC Performance Radial Flyer, CTI M1101WH
    Altitude: 13,028', L3 flight; Speed: Mach ???, L3 flight

  8. #8
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    Quote Originally Posted by patelldp View Post
    Pics of motor that suggest “incompatibility”?


    Sent from my iPhone using Rocketry Forum
    I can't get the motor out due to the exploded end. I'll have to eventually, and may have to hacksaw it off to get it out. My conclusion that it was a hardware problem comes from:
    1. Known good formula
    2. Nothing odd in the motor-making process
    3. Flown in this same configuration before
    4. Only thing different was the motor hardware
    5. Casing and other hardware made by different vendors


    I am absolutely open to other suggestions, including, "It's your fault, you idiot!"

    John S. ---- NAR #96911 ---- TRA #15253 ---- MDRA #067 ---- BARC #028
    L1, 3/15/14: Aerotech Sumo, CTI H133BS
    L2, 6/21/14: Giant Leap Vertical Assault, CTI J240RL
    L3, 3/12/16: MAC Performance Radial Flyer, CTI M1101WH
    Altitude: 13,028', L3 flight; Speed: Mach ???, L3 flight

  9. #9
    Join Date
    26th November 2009
    Posts
    4,939
    My goodness John that is pretty nasty. Folks in my prefecture were really into mixing and a ground tested 76 mm case blew aluminum shrapnel all over. I wasn't there when it happened but the prefect showed me some of the aluminum projectiles.
    They say Al is the safest but that CATO left pieces that looked like they could have really sliced some one up. Thankfully it blew opposite from where they were standing.

    Yours looks like it really went. Well at least you can salvage the thrust plate and the retainer. Cleaning out the retainer is a PITA but doable if one is patient. Was that the first firing of that propellant mix in that size of motor or have others flown the
    same motor successfully with that propellant?

    No, it's not your fault. You just had a bad test flight. Cripes, rocketry is like fishing (especially Ex/Research). If you want to catch fish you're going to lose fishing lures. If you fly rockets, "stuff" is going to happen. There are those who've had less than
    nominal flights and those who are "GOING" to have less than nominal flights.
    Kurt
    Last edited by ksaves2; 19th November 2017 at 09:43 PM.

  10. #10
    Join Date
    6th June 2011
    Location
    San Diego. CA.
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    Good grief! Worst I've ever seen! Uh-that ain't gonna buff out-I don't care what you use. Mad props for the attempt tho'.
    TRA 2383
    Somebody told me I was on the watch list-I hope I get a Rolex.....
    The road to Hell is paved....you're welcome.
    I can't remember the last rocket I built, because I haven't built it yet.....

  11. #11
    Join Date
    23rd January 2009
    Location
    New York
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    5,382

    The cato to end all catoes!!!

    Quote Originally Posted by Bat-mite View Post
    I can't get the motor out due to the exploded end. I'll have to eventually, and may have to hacksaw it off to get it out. My conclusion that it was a hardware problem comes from:
    1. Known good formula
    2. Nothing odd in the motor-making process
    3. Flown in this same configuration before
    4. Only thing different was the motor hardware
    5. Casing and other hardware made by different vendors


    I am absolutely open to other suggestions, including, "It's your fault, you idiot!"
    Well let’s think about it.

    Looks like it burned through. Was it a good amount into the burn? Was the case DOM to final dimensions or was the OD turned?

    None of your points are really relevant, otherwise there would never be a commercial CATO. I am guessing that your liner to bulkhead fit was bad and you needed more grease or you had a bad liner.

    “Different manufacturers” would really only yield a failure to seal, but this looks to be in the pressure vessel.
    Dan Patell
    TRA 10904 L3

    Easy Research Rocketry
    29mm Research Hardware Has Returned!!!

  12. #12
    Join Date
    27th July 2014
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    south beloit, IL
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    2,287
    I had something like this when I had some voids in my propellant... looked ok on the outside, not so great on the inside. That was my first and only EX cato (so far).

    Did you weigh the grains? What was the result/density? Also, any chance the ignitor got stuck in the nozzle and caused it to overpressurize?
    NAR# 99285
    Tripoli# 16283
    L1- 4/26/2015 Madcow Cowabunga- H123SK
    L2- 11/1/2015 Wildman Darkstar 2.6- J355RL
    L3- 11/3/2017 Wildman V2 6" - M1780NT
    Woosh
    QCRS

  13. #13
    Join Date
    11th January 2012
    Location
    Commonwealth of VA
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    1,563
    John,

    Sorry for your loss. I was admiring your rocket as you were doing the final prep. My recollection of the flight is that is was only at roughly 100 - 200' ft when it let go.

    -Bill Riley

    TRA: 12294
    NAR: 89196

    A good rule for rocket experimenters to follow is this: always assume that it will explode.
    — Astronautics, issue 38, October 1937.


  14. #14
    Join Date
    18th January 2009
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    Virginia - Central
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    Quote Originally Posted by Bat-mite View Post
    Well, the bottom half of my Formula 200 is no more.
    Geeez.....that looks like it made some noise...definitely a REALLY cool flight as the MDRA folks like to say.

    Any post mix shots/inspection of the grains...not that that would show voids, .... just asking.
    What were the specs on the motor...and expected performance ?
    The case and closure had a good fit?

    Sorry for your loss, but hey, can't advance unless you try, and take calculated risks.

    Any upper internal components /electronics make it through?
    Last edited by MaxQ; 19th November 2017 at 10:11 PM.
    We got two categories of pilots around here. We got your prime pilots that get all the hot planes, and we got your pud-knockers who DREAM about getting the hot planes.
    Now what are you two pud-knockers gonna have?... Huh?”
    Pancho Barnes-
    The Right Stuff
    http://www.mwavs.com/0053148414/M4RS...udknockers.m4r

    Tripoli #2747

  15. #15
    Join Date
    17th February 2014
    Posts
    542
    Is that bent allthread in there? From the force of the boom? Wow! That's some big boy stuff you're doing.
    NAR
    L1: 2/2/13, Madcow 4" Patriot. CTI H143
    L2: 9/2/14, Madcow 4" AGM33 Pike. CTI J335. 2,878 ft, 418 mph
    L3: 1/7/17, Wildman Drago XL. AT M1500. 13,559 ft, 1,017 mph, Mach 1.2

  16. #16
    Join Date
    18th January 2009
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    Maryland
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    That was a truly impressive fiasco. My condolences. As mentioned above, none of the conditions you list can be 100 % excluded as the cause as AT and CTI etc have a lot more proven procedures and formulae.

    Sent from my SAMSUNG-SGH-I337 using Rocketry Forum mobile app
    Dick Stafford
    The member formerly known as the Pointy-Haired Moderator.
    The Original Rocket Dungeon
    Volunteer compiler of product news for ROCKETS Magazine

  17. #17
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    5th December 2013
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    Thanks, all, for the suggestions. I was not trying to prove that it was the hardware; it just seemed like the simplest answer. First flight of this rocket ever was with the exact same motor, but someone else's hardware. Hardware was the new factor here.

    I don't know if this matters, but when I slid the 98 -> 75 adapter ring on, it went down the tube easily until about the bottom third; from there I had to bang it down with a tack hammer. So if the outside of the casing was not perfectly straight, chance are the inside of the casing wasn't, either. Who knows?

    I think I can save the retainer and thrust plate, maybe the fins. Everything from the AV bay up is fine. In fact, I got an excellent deployment of the main chute.

    John S. ---- NAR #96911 ---- TRA #15253 ---- MDRA #067 ---- BARC #028
    L1, 3/15/14: Aerotech Sumo, CTI H133BS
    L2, 6/21/14: Giant Leap Vertical Assault, CTI J240RL
    L3, 3/12/16: MAC Performance Radial Flyer, CTI M1101WH
    Altitude: 13,028', L3 flight; Speed: Mach ???, L3 flight

  18. #18
    Join Date
    18th January 2009
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    Crofton, MD
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    686
    Sorry about your rocket. But it was an exciting and "cool" launch.


    Sent from my iPhone using Rocketry Forum
    MDRA Member
    TRA Level 2

  19. #19
    Join Date
    18th March 2009
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    Wisconsin
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    The adapter had to be banged on? This would certainly indicate that the case was likely out of round. This would likely keep you from getting a good seal.

    Did you weigh the grains to check density and for voids?


    Sent from my iPhone using Rocketry Forum
    Mark Koelsch
    Tripoli 6155 L3
    Owner of http://www.rocketryfiles.com/
    Editor of http://www.thrustcurve.org/
    Member of the Tripoli Motor Test Committee, and keeper of the motor file

  20. #20
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    Quote Originally Posted by markkoelsch View Post
    The adapter had to be banged on? This would certainly indicate that the case was likely out of round. This would likely keep you from getting a good seal.

    Did you weigh the grains to check density and for voids?


    Sent from my iPhone using Rocketry Forum
    Yes, grain weights were very reasonable.

    John S. ---- NAR #96911 ---- TRA #15253 ---- MDRA #067 ---- BARC #028
    L1, 3/15/14: Aerotech Sumo, CTI H133BS
    L2, 6/21/14: Giant Leap Vertical Assault, CTI J240RL
    L3, 3/12/16: MAC Performance Radial Flyer, CTI M1101WH
    Altitude: 13,028', L3 flight; Speed: Mach ???, L3 flight

  21. #21
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    22nd December 2013
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    Daytona Beach, FL
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    Need more specs on the hardware to tell if it was the hardware's fault...
    Clayton Birchenough
    L3
    NAR #100335
    Tripoli #15887

  22. #22
    Join Date
    20th February 2009
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    Wow, some amazing carnage! From experience, if you are going to cut into that mess, for safety's sake, make sure you use a double cut saw: https://youtu.be/wIEiUXEPIUg

    From the Ether...
    Last edited by dixontj93060; 20th November 2017 at 01:33 AM.
    L3, TRA #11847
    Tripoli Indiana #132
    Tripoli Central Illinois #59
    Central Illinois Aerospace (NAR) #527
    Chicago Rocket Mafia, "Big Bucks" Dixon
    ___________________________________

    Quiet little voices creep into my head. -- We Were Promised Jetpacks

  23. #23
    Join Date
    26th February 2012
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    Poultney , Vt
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    You may have had a small section of propelent not Bond properly to the casting tube which then in turn allowd it to burn on the backside and boom.
    You must always push your limits , because if you never fail , you will never succeed .

  24. #24
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    Quote Originally Posted by 3stoogesrocketry View Post
    You may have had a small section of propelent not Bond properly to the casting tube which then in turn allowd it to burn on the backside and boom.
    Could you describe that in a little more detail, please?

    John S. ---- NAR #96911 ---- TRA #15253 ---- MDRA #067 ---- BARC #028
    L1, 3/15/14: Aerotech Sumo, CTI H133BS
    L2, 6/21/14: Giant Leap Vertical Assault, CTI J240RL
    L3, 3/12/16: MAC Performance Radial Flyer, CTI M1101WH
    Altitude: 13,028', L3 flight; Speed: Mach ???, L3 flight

  25. #25
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    15th May 2016
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    Quote Originally Posted by Bat-mite View Post
    Could you describe that in a little more detail, please?
    You may have had a small section of propelent not Bond properly to the casting tube which then in turn allowd it to burn on the backside and boom.
    David McCann
    Dave's Rockets | My Flights
    URRG |URRF 4| Level 2 | TRA# 14210

  26. #26
    Join Date
    18th January 2009
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    Quote Originally Posted by Bat-mite View Post
    I can't get the motor out due to the exploded end. I'll have to eventually, and may have to hacksaw it off to get it out. My conclusion that it was a hardware problem comes from:
    1. Known good formula
    2. Nothing odd in the motor-making process
    3. Flown in this same configuration before
    4. Only thing different was the motor hardware
    5. Casing and other hardware made by different vendors


    I am absolutely open to other suggestions, including, "It's your fault, you idiot!"
    Seals held, you exceeded the yield of the tubing. Yield is typically greater than 2X what you expect for maximum operating pressure. In 75mm it is usually above 2,000 psi. Therefore the reasonable conclusion is a problem with the grains, typically casting tube debonding, excess voids, or mechanical failure of a grain blocking the nozzle throat. If the grains looked good and weighed what you expected, I'd suspect debonding. You may be able to extract some unburnt grains to do an inspection. Also, you should verify the nozzle measurement is actually what you designed the motor for. It's easy to pick the wrong nozzle if you have a bunch and are in a hurry, and I've also heard of instances where one nozzle throat diameter was specified, but a different one was supplied and the flyer didn't double check until after the cato. Basically check everything.
    Last edited by Binder Design; 20th November 2017 at 02:12 AM.

  27. #27
    Join Date
    7th May 2017
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    94
    Quote Originally Posted by Bat-mite View Post
    I can't get the motor out due to the exploded end. I'll have to eventually, and may have to hacksaw it off to get it out. My conclusion that it was a hardware problem comes from:
    1. Known good formula
    2. Nothing odd in the motor-making process
    3. Flown in this same configuration before
    4. Only thing different was the motor hardware
    5. Casing and other hardware made by different vendors


    I am absolutely open to other suggestions, including, "It's your fault, you idiot!"
    Sometimes...sh*t happens. And you can never really figure out why.

    I was testing a white formula. Single-grain 54 mm test at low pressure was perfect. Second test was 3-grain 29 mm at rather higher pressure. Nominal.

    It seems to be okay for the test stand. So I put another 54 mm grain (same weight within limits of error) in the same motor, same nozzle used for the first test. Lower pressure than the 29 mm, mind you. At least it was supposed to be...

    Press button. KA-WHAP! Nozzle shot who-knows-where, casing is trumpeted, forward closure wedged in casing. Propellant grain goes skittering down the slope, burning merrily and leaving a lovely trail of white smoke.

    I didn't have a spare load cell back then. "Sorry Jim, looks like any quantitative testing is over."

    Absolutely no idea why.

    Dammit.

    Terry
    The difference between science and the fuzzy subjects is that science requires reasoning, while those other subjects merely require scholarship.
    It is a truism that almost any sect, cult, or religion will legislate its creed into law if it acquires the political power to do so.
    Be wary of strong drink. It can make you shoot at tax collectors---and miss.
    ----R. Heinlein

  28. #28
    Join Date
    7th August 2013
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    362
    Quote Originally Posted by Bat-mite View Post
    Could you describe that in a little more detail, please?
    John,

    Sometimes with dryer higher solids mixes the propellant doesn't bond to the inside of the casting tube. The casting tube will no longer inhibit the flame front and allow the grain to also burn from the outside inward along with the normal burning from the core outwards and from the top & bottom. This will cause a dramatic increase in your burning area which will spike your pressure and burn through your liner.

    You can avoid this by lightly sanding the inside of your casting tube and painting the inside of the casting tube with a HTPB & Curative mix before casting the grains.

    I also doubt that the hardware was a problem, I have TruCore, Loki, AMW, Fisher, Gorilla, and Patel hardware and mix match all them without issue.
    John Haught L3
    Prefect Tripoli Pittsburgh

  29. #29
    Join Date
    1st July 2011
    Location
    Pittsburgh, PA
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    2,927
    I agree, that it was not the hardware. I managed to pop a NASSA test casing blowing out the pressure fitting with a proven formula (bad or mislabeled chemical). I could have used a chute and tracker on that test case, as it is lost in the woods . . .

    That said, the carnage is impressive. You beat my Mud Puppy that failed and caught the rocket on fire. The epoxy burned leaving behind the layers of cloth.
    Kevin Wuchevich
    Tripoli Pittsburgh
    TRA 12238

  30. #30
    Join Date
    31st December 2009
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    Las Cruces, NM
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    Two failure modes to consider, other than a casting-tube bonding issue.

    1) You had a leak in the forward end due to insufficient clearance tolerance, mixing and matching closure and casing. The highest pressure is at the head end of the propellant stack. Once a leak begins, there is mass flow and heat transfer into the casing around the forward seal. The casing weakens and blows at normal operating pressure.

    OR ---

    2) Your grain design assumed no inhibited end face, for normal bates grain config. It is common to have the grain faces too perfect, and without grain spacers they will seal against each other under acceleration. The resulting thrust curve is highly progressive with partially inhibited grain faces. (Simulate this to see the effect by inhibiting one end at a time and comparing the curve and peak pressure). The progressive burn will have a 2x+ pressure peak than the normal non-inhibited configuration with grain spacers.

    -John

    NAR/TRA L3
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