Motor reloads with the most CATOs

After so many years with no CATOs, I experienced my first one on a CTI K300-P Classic motor on the maiden flight of a new rocket on a 10,000 foot altitude attempt. If you have had a CATO, you know that horrible feeling of loss after spending so much time and money planning, building and perhaps driving hundreds of miles to watch you project get destroyed. I've examined my own motor casing and lots others too trying to do a forensic study to determine what went wrong. In my case (pun intended) my 54mm 6 Grain XL casing burst open just below the Forward seal. I have seen lots others do the same. I also notice that it seems to have let go just forward of where the motor mount tube ends. Got me wondering if the additional support of a fiberglass motor mount all the way to the top of the casing would have prevented this. It make sense that the thicker the casing and/or anything surrounding it would make the casing stronger. Yes?
But the real question going through my head is: Is this particular reload more prone to CATOing? Will my replacement case and re-load have a CATO again?
Has anyone compiled a list of motors with the highest percentages of CATOs?

PS How the hell do I insert photos of my CATO? The old "advanced" posting link is gone and the only option I see is to "insert" from a URL.

See this thread:
https://www.rocketryforum.com/threads/small-bulge-in-rocket-motor-casing.144046/#post-1753720

I have had a couple K300s CATO myself. E9s are my other nemesis.

Steve Shannon said:

See this thread:
https://www.rocketryforum.com/threads/small-bulge-in-rocket-motor-casing.144046/#post-1753720

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Thanks, very interesting discussion.

I've had bad luck with A10s myself... 2 blew out of 5 I've flown. I've never had a reload go on me, but I haven't been flying MPR/HPR for all that long.

DavieRockets said:

After so many years with no CATOs, I experienced my first one on a CTI K300-P Classic motor on the maiden flight of a new rocket on a 10,000 foot altitude attempt. If you have had a CATO, you know that horrible feeling of loss after spending so much time and money planning, building and perhaps driving hundreds of miles to watch you project get destroyed. I've examined my own motor casing and lots others too trying to do a forensic study to determine what went wrong. In my case (pun intended) my 54mm 6 Grain XL casing burst open just below the Forward seal. I have seen lots others do the same. I also notice that it seems to have let go just forward of where the motor mount tube ends. Got me wondering if the additional support of a fiberglass motor mount all the way to the top of the casing would have prevented this. It make sense that the thicker the casing and/or anything surrounding it would make the casing stronger. Yes?
But the real question going through my head is: Is this particular reload more prone to CATOing? Will my replacement case and re-load have a CATO again?
Has anyone compiled a list of motors with the highest percentages of CATOs?

PS How the hell do I insert photos of my CATO? The old "advanced" posting link is gone and the only option I see is to "insert" from a URL.

Click to expand...

cwbullet said:

I have had a couple K300s CATO myself. E9s are my other nemesis.

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Chuck we should form a new club. I had some E9s go too so now they only go into saucers. Tired of losing birds.

cwbullet said:

I have had a couple K300s CATO myself. E9s are my other nemesis.

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I flew my first E9 in almost a decade last weekend in a 3d printed spinner, luckily it didn't go boom. Last time I flew an E9, it was in a Viper 3 and had a double CATO which destroyed the lower part of the rocket

OMG I HATE the new forum setup! YUK

Flying rockets is inherently an endeavor, where sooner or later, you will get malfunction. I cannot think of a single flier I know, that hasn't experienced a motor failure of some type.

It's just part of flying rockets.

If you fly long enough...you WILL have an issue. Look at NASA spend millions & millions, have thousands of personal , yet their track record isn't all that sterling either.

So far I think we as a hobby are doing better...LOL
Off the top of my head I recall toasting 6 rockets in 15 years...I'm sure if I really go back, thatnumber is low. But we are talking about 7-800 flights..at least!
WE do it not because it is easy....but because it is hard, & requires skill sets above the norm.
It's part of what we do, & accept it graciously. I just call it an "offering to the rocket Godz" & hopefully they leave me alone for awhile...lol

PS. As far as high power motor cato's...I think the J-350 has the record. Going back to AT's fire days & Ellis Mountain making the grains for them for around 2-3yrs. We nick-named the grains...''Sponge Bob's" There are some REALL stories back in those days about those motors...LOL

DavieRockets said:

Got me wondering if the additional support of a fiberglass motor mount all the way to the top of the casing would have prevented this.... Is this particular reload more prone to CATOing?

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I don't think the additional support will do any good at all, I had a CATO of a K300 in a minimum diameter; the pressure is all borne by the case.

With the longer CTI motors there is more risk of having the O-ring in the forward closure roll out of its slot when the reload is inserted, especially if the case has crud in it. I spray the case with silicon spray before putting the reload in. Also, CTI has had problems with liner tolerances letting gas out between the closure and the liner, which may be mitigated by gluing the closure in.

That said, I've only had a couple of CATOs with Pro54, both 6GXL, out of probably a dozen flights with this case. As a rule, the longer cases push the envelope a bit harder than the shorter ones.

Did you inspect the motor grain before flying? Since the K300 is a single long grain, moonburner, I always check it before flying to look for any cracks, bubbles, etc. That angled c-slot has to be the only burning surface area otherwise it'll over pressurize. Not saying that's what happened to you, but it's possible.

blackjack2564 said:

PS. As far as high power motor cato's...I think the J-350 has the record. Going back to AT's fire days & Ellis Mountain making the grains for them for around 2-3yrs. We nick-named the grains...''Sponge Bob's" There are some REALL stories back in those days about those motors...LOL

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Why Sponge Bob? Were they mixing air bubble into the propellant? Or did it have a high, nasally roar when it burned?

As far as CATO data, all we have as rocketeers is anecdotal info. The recipients of the MESS reports don't share.

I had 3 back to back CATO's with Econojet G35W motors back in the early 2000's. I had 2 that worked and 3 that CATO'ed.

It was a really cool motor when it worked. Had a nice long 3.5 second burn with a loud crackly roar as well. I think it was the casing material that was to blame. As soon as the motor pressurized, the nozzle popped out and shattered the rear portion of the casing.

Never had a reload actually CATO but I did have a 29/40-120 G138T load blister the casing which could have resulted in a CATO due to the forward O-ring burning through completely. It was singed badly and almost burned through.

Exactimator said:

Why Sponge Bob? Were they mixing air bubble into the propellant? Or did it have a high, nasally roar when it burned?

As far as CATO data, all we have as rocketeers is anecdotal info. The recipients of the MESS reports don't share.

Click to expand...

Well, short version. AT equipment was burned up in a fire...for the next 2 years or so...another motor manufacturer [since then now defunct] did a deal with AT to make all the grains for certain size motors. Some did not work so well.

Longer version
You bought a motor and got a Bag of parts [liner O-rings etc.] then another box or bag of grains depending on what you bought.....4-motors and you got 1 box and loose grains put in a package...then you had to buy the proper delay grain for your motor. Delay grains came in package of 3, if you only bought one motor, still had to buy 3 delays. If ya bought 1 blue thunder load and 1 white lighting you ended up with 6 delays...etc.
So instead of 1 package with everything in it, you had 3 . Many of the J-350 grains were a bit ["spongy] lol so you would drill out the grain to a larger diameter & use a different nozzle & they would fine...most of the time. Robert Ellis - spongy grains = "Sponge BoB" Just a running gag at the time. Today that would most likely considered politically incorrect. That just never counts, sit'n 'round the fire at a launch having refreshments & BSing

You got the parts AT had and the ones Ellis made. [2001-2003?] If you were not aware of the "fix" or bought one years later [not remembering or having been around] you got a "BoOM bOx"!

If you ever see me at a launch, buy me a beer and you'll here some funny stories that cannot be printed...lol
Like when the ATF bought some to...........!!!

As far as CATO data, all we have as rocketeers is anecdotal info. The recipients of the MESS reports don't share.[/QUOTE]

There is a reason for this. The MESS reports only give us the numerator of the relevant fraction. The denominator - the actual number of motors of that type that were flown in the same time period - is not available to us. For this reason, the MESS reports cannot give a statistically valid answer to the question "which reload has the most CATO's?"

For example, if I were to tell you that motor A has had 1 CATO since 2013, and motor B had 50 CATO's in the same time period, then, unfortunately, most rocket hobbyists would assume that motor B has a reliability problem. If we subsequently found that only 45 A motors were sold and flown in that time period, and 10,000 B motors were used in the same time period, then some people would realize that the picture is actually quite different. Unfortunately, most amateur rocket hobbyists would still think that motor B had a problem, because 50 is greater than 1, right?

Only a trained statistician would realize that 1/50 is such a small sample size that valid statistical comparisons are impossible, and that the data in the previous paragraph actually tells you nothing about the relative reliability of motor A and motor B. When we add to this known weakness of small sample sizes the fact that so few rocket enthusiasts actually bother to fill out MESS reports after a motor failure, we can see that MESS report data is actually a poor way to make motor-to-motor comparisons.

We use the MESS report data mainly to 1. Determine if there are specific lot or "day stamp" numbers that are having more problems than others, and 2. Spot specific problem areas with particular motors that show the same mode of failure. This is why it is important to save the packaging for any motor, reload or single-use, to be able to accurately report the lot number, and describe the nature of the motor failure in as much detail as possible in the MESS report.

Please be aware that people are looking at every MESS report in great detail and that the information is very important to us. If everybody who experiences a motor failure were to fill out a MESS report, it would become a much more useful tool for all of us.

Alan Whitmore
Chair, Tripoli Motor Testing

CzTeacherMan said:

Did you inspect the motor grain before flying? Since the K300 is a single long grain, moonburner, I always check it before flying to look for any cracks, bubbles, etc. That angled c-slot has to be the only burning surface area otherwise it'll over pressurize. Not saying that's what happened to you, but it's possible.

Click to expand...

No I never inspected the grains on this or any other motor that came pre-assembled in a liner. Perhaps I will from now on. Tonight I repaired another rocket that had a CATO due to those bad CTI 38mm forward closures. With the left over epoxy, I glued in the fwd closure on a K675 Skidmark that I want to fly soon.

Alan Whitmore said:

As far as CATO data, all we have as rocketeers is anecdotal info. The recipients of the MESS reports don't share.

Click to expand...

There is a reason for this. The MESS reports only give us the numerator of the relevant fraction. The denominator - the actual number of motors of that type that were flown in the same time period - is not available to us. For this reason, the MESS reports cannot give a statistically valid answer to the question "which reload has the most CATO's?"

For example, if I were to tell you that motor A has had 1 CATO since 2013, and motor B had 50 CATO's in the same time period, then, unfortunately, most rocket hobbyists would assume that motor B has a reliability problem. If we subsequently found that only 45 A motors were sold and flown in that time period, and 10,000 B motors were used in the same time period, then some people would realize that the picture is actually quite different. Unfortunately, most amateur rocket hobbyists would still think that motor B had a problem, because 50 is greater than 1, right?

Only a trained statistician would realize that 1/50 is such a small sample size that valid statistical comparisons are impossible, and that the data in the previous paragraph actually tells you nothing about the relative reliability of motor A and motor B. When we add to this known weakness of small sample sizes the fact that so few rocket enthusiasts actually bother to fill out MESS reports after a motor failure, we can see that MESS report data is actually a poor way to make motor-to-motor comparisons.

We use the MESS report data mainly to 1. Determine if there are specific lot or "day stamp" numbers that are having more problems than others, and 2. Spot specific problem areas with particular motors that show the same mode of failure. This is why it is important to save the packaging for any motor, reload or single-use, to be able to accurately report the lot number, and describe the nature of the motor failure in as much detail as possible in the MESS report.

Please be aware that people are looking at every MESS report in great detail and that the information is very important to us. If everybody who experiences a motor failure were to fill out a MESS report, it would become a much more useful tool for all of us.

Alan Whitmore
Chair, Tripoli Motor Testing[/QUOTE

Alan Whitmore said:

As far as CATO data, all we have as rocketeers is anecdotal info. The recipients of the MESS reports don't share.

Click to expand...

There is a reason for this. The MESS reports only give us the numerator of the relevant fraction. The denominator - the actual number of motors of that type that were flown in the same time period - is not available to us. For this reason, the MESS reports cannot give a statistically valid answer to the question "which reload has the most CATO's?"

For example, if I were to tell you that motor A has had 1 CATO since 2013, and motor B had 50 CATO's in the same time period, then, unfortunately, most rocket hobbyists would assume that motor B has a reliability problem. If we subsequently found that only 45 A motors were sold and flown in that time period, and 10,000 B motors were used in the same time period, then some people would realize that the picture is actually quite different. Unfortunately, most amateur rocket hobbyists would still think that motor B had a problem, because 50 is greater than 1, right?

Only a trained statistician would realize that 1/50 is such a small sample size that valid statistical comparisons are impossible, and that the data in the previous paragraph actually tells you nothing about the relative reliability of motor A and motor B. When we add to this known weakness of small sample sizes the fact that so few rocket enthusiasts actually bother to fill out MESS reports after a motor failure, we can see that MESS report data is actually a poor way to make motor-to-motor comparisons.

We use the MESS report data mainly to 1. Determine if there are specific lot or "day stamp" numbers that are having more problems than others, and 2. Spot specific problem areas with particular motors that show the same mode of failure. This is why it is important to save the packaging for any motor, reload or single-use, to be able to accurately report the lot number, and describe the nature of the motor failure in as much detail as possible in the MESS report.

Please be aware that people are looking at every MESS report in great detail and that the information is very important to us. If everybody who experiences a motor failure were to fill out a MESS report, it would become a much more useful tool for all of us.

Alan Whitmore
Chair, Tripoli Motor Testing[/QUOTE]

I have submitted MESS reports.

DavieRockets said:

There is a reason for this. The MESS reports only give us the numerator of the relevant fraction. The denominator - the actual number of motors of that type that were flown in the same time period - is not available to us. For this reason, the MESS reports cannot give a statistically valid answer to the question "which reload has the most CATO's?"

For example, if I were to tell you that motor A has had 1 CATO since 2013, and motor B had 50 CATO's in the same time period, then, unfortunately, most rocket hobbyists would assume that motor B has a reliability problem. If we subsequently found that only 45 A motors were sold and flown in that time period, and 10,000 B motors were used in the same time period, then some people would realize that the picture is actually quite different. Unfortunately, most amateur rocket hobbyists would still think that motor B had a problem, because 50 is greater than 1, right?

Only a trained statistician would realize that 1/50 is such a small sample size that valid statistical comparisons are impossible, and that the data in the previous paragraph actually tells you nothing about the relative reliability of motor A and motor B. When we add to this known weakness of small sample sizes the fact that so few rocket enthusiasts actually bother to fill out MESS reports after a motor failure, we can see that MESS report data is actually a poor way to make motor-to-motor comparisons.

We use the MESS report data mainly to 1. Determine if there are specific lot or "day stamp" numbers that are having more problems than others, and 2. Spot specific problem areas with particular motors that show the same mode of failure. This is why it is important to save the packaging for any motor, reload or single-use, to be able to accurately report the lot number, and describe the nature of the motor failure in as much detail as possible in the MESS report.

Please be aware that people are looking at every MESS report in great detail and that the information is very important to us. If everybody who experiences a motor failure were to fill out a MESS report, it would become a much more useful tool for all of us.

Alan Whitmore
Chair, Tripoli Motor Testing[/QUOTE


There is a reason for this. The MESS reports only give us the numerator of the relevant fraction. The denominator - the actual number of motors of that type that were flown in the same time period - is not available to us. For this reason, the MESS reports cannot give a statistically valid answer to the question "which reload has the most CATO's?"

For example, if I were to tell you that motor A has had 1 CATO since 2013, and motor B had 50 CATO's in the same time period, then, unfortunately, most rocket hobbyists would assume that motor B has a reliability problem. If we subsequently found that only 45 A motors were sold and flown in that time period, and 10,000 B motors were used in the same time period, then some people would realize that the picture is actually quite different. Unfortunately, most amateur rocket hobbyists would still think that motor B had a problem, because 50 is greater than 1, right?

Only a trained statistician would realize that 1/50 is such a small sample size that valid statistical comparisons are impossible, and that the data in the previous paragraph actually tells you nothing about the relative reliability of motor A and motor B. When we add to this known weakness of small sample sizes the fact that so few rocket enthusiasts actually bother to fill out MESS reports after a motor failure, we can see that MESS report data is actually a poor way to make motor-to-motor comparisons.

We use the MESS report data mainly to 1. Determine if there are specific lot or "day stamp" numbers that are having more problems than others, and 2. Spot specific problem areas with particular motors that show the same mode of failure. This is why it is important to save the packaging for any motor, reload or single-use, to be able to accurately report the lot number, and describe the nature of the motor failure in as much detail as possible in the MESS report.

Please be aware that people are looking at every MESS report in great detail and that the information is very important to us. If everybody who experiences a motor failure were to fill out a MESS report, it would become a much more useful tool for all of us.

Alan Whitmore
Chair, Tripoli Motor Testing

Click to expand...

I have submitted MESS reports.[/QUOTE]Alan, thank you for that!
Quick question on MESS... I CATO'd a motor because of flipping two o-rings (putting the wrong one in the opposite side, etc). Should I file a MESS on that? I know it was my fault, but only because someone knew exactly what I did... Like, is it helpful to let you guys know which motors have user error more often?

CzTeacherMan said:

Alan, thank you for that!
Quick question on MESS... I CATO'd a motor because of flipping two o-rings (putting the wrong one in the opposite side, etc). Should I file a MESS on that? I know it was my fault, but only because someone knew exactly what I did... Like, is it helpful to let you guys know which motors have user error more often?

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Yes please, because it could point to something the manufacturers should address either by emphasizing the issue in their instructions or by a redesign to eliminate the possibility.
I’ve done exactly the same thing by the way.

Steve Shannon said:

Yes please, because it could point to something the manufacturers should address either by emphasizing the issue in their instructions or by a redesign to eliminate the possibility.
I’ve done exactly the same thing by the way.

Click to expand...

Submitted

CzTeacherMan said:

Submitted

Click to expand...

Thank you!

CzTeacherMan said:

I have submitted MESS reports.
Alan, thank you for that!
Quick question on MESS... I CATO'd a motor because of flipping two o-rings (putting the wrong one in the opposite side, etc). Should I file a MESS on that? I know it was my fault, but only because someone knew exactly what I did... Like, is it helpful to let you guys know which motors have user error more often?

Click to expand...

Yes you should. It could be an issue with instructions etc. I would think all failures should be reported that way if a trend is spotted we involved in seeing the MESS reports might be able to get it identified and addressed.

Personally, I've had more catos on P54-6GXL than any other casing.

L805 - burn-through at liner / forward bulkhead joint
K300 - forward bulkhead blowout due to overpressurization
K300 - burn-through at liner / nozzle joint

Huh, I never considered that the K300 would be a highly prone CATO reload despite my avatar photo showing an onboard video still of a K300 CATO on my now cactus half scale AMRAAM. Here's the picture in question at a higher resolution.



I've flown two K300s, one successfully, one not. A full photo album of the carnage can be seen here.

https://goo.gl/photos/1Gk3Rx7gD5XfKA899

I probably spend 5 hours applying vinyl decals to the rocket so safe to say the CATO hurt from a time lost perspective.

Beyond the K300 I'd say I've seen more CATOs out of Aerotech G64 reloads than any other motor. I lost my Level 1 rocket to one (a PML 2.1 AMRAAM that time) and I've seen more than one pop since. Every time it's the forward closure that lets go or burns through.

The only other CATO I've had was a Aerotech J1999 which had in a Firestorm 54. It was flown ~ 2 weeks before Aerotech issued the recall. :/

Yes, I had an AT G64 reload CATO this spring. Sheared the end off of the forward closure. AT did replace the motor and casing when I notified them of it; however, my G-Force was toasted.

Has the J350 problem been fixed? I was planning on using that motor for my L2.

DeepOvertone said:

Has the J350 problem been fixed? I was planning on using that motor for my L2.

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The J350 problem in question was over a decade ago; they seem very reliable now. It is a very good cert 2 motor.

DeepOvertone said:

Has the J350 problem been fixed? I was planning on using that motor for my L2.

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Long ago.

Beautiful. Thank you all.

On my end I pigroasted a rocket on an AT g138 , was a forward closure failure. It melted the closure completely. Aerotech was kind enough to comp a forward closure replacement, they were great. Have heard the g138s bien a bit hotter and test the limits of the 29 40-120 case.