Root Cause Help on a CTI Pro-54 CATO

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Swany

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I recently experience a CATO on the pad using a Cesaroni 54mm 2-Grain Skidmark motor. The forward closure was ejected through the motor casing and out the top of the rocket and the recoil smashed the retaining ring against the launch pad standoff (I got a pretty spectacular photo sequence of the event!). It turns out that aside from the motor retainer assembly needing to be replaced, the rocket is fine. After a little motivation with a hammer and screwdriver, I managed to get the reload out of the casing. I found a little wad of some "debris" inside the nozzle. It almost looks like masking tape or a plug of some sort. The only thing I inserted into the nozzle was the e-match, so this was inside the reload when I purchased it. Does anyone know if something like this is a component of a Pro-54 reload ? Has anyone else seen anything similar? My theory is that this wad of debris plugged the nozzle and created enough back pressure to blow the forward closure out. Any thoughts ???

R51A3967.jpgIMG_6925.jpgIMG_6948.jpgIMG_6950.jpg
 

Cameron Anderson

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Do any of the grains show sign of ignition or does it look like the overpressure was just the result of the ignition pellet?
 

WoShuGui

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Some background info on Pro54 forward closure sealing that may relate to your CATO is in the CTI discussion thread.
 

Steve Shannon

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That’s a different kind of failure than the forward burn throughs that others have experienced. This looks like a piece of casting liner plugged the nozzle.
 

Swany

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Do any of the grains show sign of ignition or does it look like the overpressure was just the result of the ignition pellet?
It looks like there was ignition for a fraction of a second based on the photo sequence I have, but it’s hard to tell from inspecting the grains.
 

Cameron Anderson

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It looks like there was ignition for a fraction of a second based on the photo sequence I have, but it’s hard to tell from inspecting the grains.
A nozzle blockage would explain the forward closure taking flight the way it did...and clearly there is something in the nozzle. But what is it and how it get there are the real questions. I don't know enough about the ignition pellet CTI uses but I can't imagine that alone could deform a case.

What was the blockage made of?
 

cerving

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Did you use the ematch that came with the J145, or another igniter (maybe one with additional pyrogen...)? I've flown plenty of these, it's one of my favorite motors, but it IS a PITA to get the ematch up in the offset core.
 

Swany

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OK. So I spent some more time looking at the debris and it turns out to be...

IMG_6952.jpg
an ~18" long strip of of 1/2" of rolled up masking tape !!! Is there any reason that this should have been in the reload from CTI ? Like I said in the top post, the only thing I placed in the motor was the e-match. I have know idea why there would a rolled up piece of masking tape inside the propellant core. It looks like a quality escape to me.
 
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Swany

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Did you use the ematch that came with the J145, or another igniter (maybe one with additional pyrogen...)? I've flown plenty of these, it's one of my favorite motors, but it IS a PITA to get the ematch up in the offset core.
I used the igniter that came with the motor.
 

T34zac

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Interesting. I’ve witnessed about four or five J145 catos this year alone. I think I’ve only seen two fly successfully. Every single one I’ve seen cato was through the forward closure like yours.
 

Steve Shannon

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There are three recorded for the J145 in the mess reports in September and November, but ten J145 failures in all. The last five were all reported in 2021.
FBFC38C4-0FE7-4DCA-BBC6-E53350D9A3FD.png
 

ECayemberg

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Had the exact same thing happen with a J145...the nozzle looked identical with paper in the throat. Casting tube was sucked into the core, clogged the nozzle, CATO occurred almost immediately at ignition. Note that although it is a 2 grain case, the J145 is a single moonburner grain.

I suspect gluing the grain to the liner...especially on the cored side would solve the issue.
 

Neutron95

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I've seen the aftermath of what looks like an identical failure to yours, it was a J145 as well. I love the idea of a longburn sparky motor, but I'm not planning on flying one anytime soon. I was honestly surprised to see one work at Rocstock.

There is definitely something wrong with a batch of these motors, I'll wait until CTI issues a fix and I see a few fly before putting one in one of my rockets.

A pair of them popping earlier this year at MDRA:

Photo of the remains of one I saw CATO last June.
20200606_124309.png
 
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jnmiller

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I've seen the aftermath of what looks like an identical failure to yours, it was a J145 as well. I love the idea of a longburn sparky motor, but I'm not planning on flying one anytime soon. I was honestly surprised to see one work at Rocstock.

There is definitely something wrong with a batch of these motors, I'll wait until CTI issues a fix and I see a few fly before putting one in one of my rockets.

A pair of them popping earlier this year at MDRA:

Photo of the remains of one I saw CATO last June.
View attachment 491529
 

jnmiller

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I've seen several J145 CATO's, two of them being MINE! (One is in the video in the last post!).

The problem is with the huge pellet. Since the last of my CATO's, I have removed the pellet and used a standard ignitor for all subsequent J145's. All have been successful! Lose the pellet!!
 

woferry

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Wow. Just flew one on Saturday, no issues (12 May 2021 date code). Love the ~4s of sparks and rumble. Flew one other one several years back when I was working on my L2 (up part was fine, but the main never deployed and it landed on drogue-only). My only CTI CATO was a K300CL in 2018, and what seems to be a known issue with not bonding the forward closure in the longer 54mm motors, even though the instructions don't call for bonding.
 

Neutron95

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I've seen several J145 CATO's, two of them being MINE! (One is in the video in the last post!).

The problem is with the huge pellet. Since the last of my CATO's, I have removed the pellet and used a standard ignitor for all subsequent J145's. All have been successful! Lose the pellet!!
I wonder if it's an issue like what happened with the G33, where they accidentally put in too large ignition pellets in a batch.
 

T34zac

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Wow. Just flew one on Saturday, no issues (12 May 2021 date code). Love the ~4s of sparks and rumble. Flew one other one several years back when I was working on my L2 (up part was fine, but the main never deployed and it landed on drogue-only). My only CTI CATO was a K300CL in 2018, and what seems to be a known issue with not bonding the forward closure in the longer 54mm motors, even though the instructions don't call for bonding.
Even bonding the forward closure doesn’t ensure you are safe from a cato. Although my cato was related to the rear closure rather than the forward closure.
 

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Banzai88

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The long 38s and 54s have an issue. CTI has acknowledged it, and claims to be investigating it......but has said that they are awaiting new testing fixtures to really get things going to find answers.
 

jnmiller

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I wonder if it's an issue like what happened with the G33, where they accidentally put in too large ignition pellets in a batch.
Yes, I believe so, but I even tried cutting the pellet in half once and still had a CATO. I've had ZERO CATO's since eliminating the pellet entirely and just using regular 'aerotech type' ignitors (with the pellet removed you can't use the electric match supplied by CTI). It's a slower ignition but it will save your reload case and rocket!
 

Swany

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Had the exact same thing happen with a J145...the nozzle looked identical with paper in the throat. Casting tube was sucked into the core, clogged the nozzle, CATO occurred almost immediately at ignition. Note that although it is a 2 grain case, the J145 is a single moonburner grain.

I suspect gluing the grain to the liner...especially on the cored side would solve the issue.
Interesting and thanks for the info. So the casting tube is what surrounds the starter pellet ? Are these tubes made using a rolled up piece of masking tape ? How would gluing the grain to the liner prevent this ? Wouldn't the casting tube still get sucked into the nozzle and plug it ?
 
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