AT DMS CATO: A Memorial to My Level 1

I’ve heard stories like this a few times before, but I never thought it would happen to me.

Yesterday was a big day for me. I was to attempt my NAR Level 2 cert flight and I would be making my first launch with QCRS, one of the premier HPR clubs in the country. My day started auspiciously: perfect weather (for March in northern Illinois); mile after mile of flat open ground; and greetings and introductions from some launch regulars. My first launch of the day, an Estes Leviathan on an AT I205 went well, notwithstanding a very, very late deployment. That was user error. I should have set the deployment altitude on my CR higher. The altitude per Jolly Logic Altimeter 3 was 3,790’. My Leviathan is great rocket and I love it, but it has has given me all it can, and it has been retired with honors.

Then the time came to get my NAR Level 2 certification. First, I took the written test, which was mailed to me at my request in a sealed envelope a few weeks ago from NAR headquarters. There seems to be lots of confusion about precisely how the Level 2 written test is to be administered. This is NAR’s fault. Its website is hopelessly vague about the process. Thankfully, TRFrs DWatkins and RocketRev graciously stepped in and offered to help. DWatkins graded my completed test, and I scored 100% (not much of an accomplishment when you study as much as I did)!

My intended Level 2 project has traditional dual deployment, but I was unable to finish it in time for yesterday’s launch. So, I retrofitted my motor deploy-only Level 1 rocket, a PML AMRAAM-3, to make it J motor friendly. As I have posted elsewhere (esp. post #13), I have an emotional attachment to this rocket. I added a sled to the payload bay to accommodate a Jolly Logic Altimeter 3 and a Trackimo GPS tracker, and I used a Jolly Logic Chute Release to control deployment. I had to choose my Level 2 motor carefully, because PML’s “quantum tube” (aka plastic) is scared of transonic speeds, one reason I won’t build with QT again. I chose an Aerotech J250 DMS. It proved to be a very, very bad choice.

I don't have YouTube account, so I can't post my "flight" video. Needless to say, my CATO looked like many other tragic CATOs you have seen: rocket heaves a few feet off the pad before falling lifelessly to the ground. Have you ever noticed that experienced rocketeers seem to take a lot more interest in CATOs than in solid, glitch-free flights? That means I had lots of company as I approached the pad to assess the damage. The electronics, laundry and links, payload tube and nosecone are usable, but the sustainer was horribly damaged. My AMRAAM will never fly again. Here are some post-mortem photos.






Some of the most experienced rocketeers around, TRFrs DWatkins, RocketRev, and Mad Bomber F/X, helped me pick up the pieces of my rocket (and sweet shattered dream). They offered soothing words of consolation (“It wasn’t your fault. It happens to everyone.&#8221 and analysis. Their consensus is that the forward closure blew out and not because the igniter blocked the somewhat small nozzle. That was helpful and undoubtedly right, but the ultimate cause remains a mystery to me.

Aerotech’s warranty on the motor means that I can get a new AT J250 if I want. I’m sure nobody is surprised to hear that flying another J250 isn’t very enticing right now. I’m still figuring out how many hours I spent on my AMRAAM’s wetsanding and custom decals.

The AMRAAM I once knew is gone forever.

In loving memory of my AMRAAM, tomorrow night at 9 PM I’ll be holding a candlelight vigil outside Aerotech headquarters, to be followed by a brief memorial service. Please feel free to join me if you’re available. My AMRAAM will live on only in my memory and TRF avatar.

So sorry for your loss. That hurts, especially on a cert flight. As you were probably counseled at the launch, I hope you'll save the parts, contact Aerotech customer service, and *also* complete a MESS Report, which can really help the rest of this community.

Mark

Marty,

Sorry to hear about your loss, and sorry I couldn't be there to help out. Ask if Carl can give you the equivalent motor in a reload...

Adrian

R.I.P.

I feel your pain. AT will replace the motor but not anything else that was ruined. When my L1000 failed I lost at least $400 of other things I had in upper part of the rocket. AT will not replace that. Its one thing when the flyer makes a mistake but when its the motor makers fault that seems much different to me. For sure go with a reload next time. I replace all 3 of my L1000s with reloads. Its to bad about the DMS motors I really like them. They just need to work. That's all as flyers we ask.

Sorry for your loss. You are correct in that no warranty can give you back the time and effort, and that is not inconsiderable as you move up the size and impulse ladder. And your rocket buddies are right as well in that catos happen. Our vendors do what they can to make things right, in my experience. Good luck on your next L2 attempt.

So sorry for your loss!

Sorry to hear about the cato!

Note: that rocket is very fixable; I've never personally met a rocket that couldn't be saved. I have pulled some out of the dumpster and fixed 'em. Where there's a will, there's a way!

Just sayin'; if that rocket means a lot to you, it can definitely be fixed!

-Eric-

You really should fine a MESS report at Motorcato.org so that the failure goes into the database.

John

Welcome to the club. I have two RMS cases with aft burn through one a G135 and the other an H238. I checklist when I build the motors so I couldn't figure out the problem. The G cooked the aft end of a Jart but it's well on its way to restoration. Only paint to fix.

The H238 took out my cardboard L1 Executioner Clone on a later flight. It's sad to go through all that work and have a CATO take out your cert attempt. Especially one so prepared for and if you would have had nominal motor performance,
you would have stood an excellent chance for success. Condolences. Kurt Savegnago

I've been there. Don't give up.

September of last year my dad's first L2 attempt had a J250W DMS fail basically the same way, only the case separated above the grains rather than below. Bottom of the 3 DMS motors in the picture obviously. The video is below. AeroTech was on-site and replaced the motor, we performed some serious field repairs to the rocket and he got his L2 the next day.



[video=youtube;kXOl30IIeYc]https://www.youtube.com/watch?v=kXOl30IIeYc&t=0m49s"]https://www.youtube.com/watch?v=kXOl30IIeYc&t=0m49s[/video]

What is it about DMS motors that causes them to have a high failure rate?

Want to see a DMS casing come apart up close and in slo-mo? Skip to 3:05. This was the disposal burn of a recalled L1000.

[video=youtube;Vq9c9d1XcQ8]https://www.youtube.com/watch?v=Vq9c9d1XcQ8[/video]

A lot of flyers say you should file a MESS Report. What good would that do?

crossfire said:

A lot of flyers say you should file a MESS Report. What good would that do?

Click to expand...

Gives manufacturers data about their failed products. Can help determine if a certain LOT number has a higher rate of failure, etc.

At least as much good as posting about it on Internet forums. Posting may get you some information and at least the sympathy of fellow rocketeers and reporting may help the manufacturing process. Or not, but either only costs a few minutes and keystrokes.

crossfire said:

A lot of flyers say you should file a MESS Report. What good would that do?

Click to expand...

Agreed. A MESS report won't get me a new motor, not that I want one, or a new rocket. Beyond that, I am disgusted with the lack of transparency involved. The motor manufacturers expect us to buy their motors and voluntarily tell them when their products are defective and unsafe. We're all ok with that. My issue is with the next part: having asked us to buy their defective and unsafe products, the manufacturers proceed to conceal failure rate data from us, their paying customers. Once a MESS report is submitted, the information goes into a black hole. We, the end user, have no access to the data, which makes for uninformed decisionmaking. Yes, MESS reports helps the manufacurers determine which of their products are defective and unsafe, but it's far from clear when or ever that information will trickle down to and benefit us the paying customer.

Anecdotally, it appears that AT DMS motors have disproportionately high CATO rates. Do the data warrant this? We can't know without access to the data. Aerotech will have to tell us. I don't feel like waiting for Aerotech to let me know. I have flown (and CATO'd) my last DMS motor. I think this will help:






Re-reading this post, I realize that my tone sure makes it look like I'm going through stage 2 of the grieving process: anger. But the tone is misleading because I'm already mostly at peace with what happened. The sympathetic posts from everyone here have been a big help. Thanks guys.

My condolences.

MartyS said:

My AMRAAM will never fly again. ....

The AMRAAM I once knew is gone forever....

Click to expand...

Dude, you can fix that. It's not an easy fix, but it certainly can be done.

MartyS said:

Agreed. A MESS report won't get me a new motor, not that I want one, or a new rocket. Beyond that, I am disgusted with the lack of transparency involved. The motor manufacturers expect us to buy their motors and voluntarily tell them when their products are defective and unsafe. We're all ok with that. My issue is with the next part: having asked us to buy their defective and unsafe products, the manufacturers proceed to conceal failure rate data from us, their paying customers. Once a MESS report is submitted, the information goes into a black hole. We, the end user, have no access to the data, which makes for uninformed decisionmaking. Yes, MESS reports helps the manufacurers determine which of their products are defective and unsafe, but it's far from clear when or ever that information will trickle down to and benefit us the paying customer.

Anecdotally, it appears that AT DMS motors have disproportionately high CATO rates. Do the data warrant this? We can't know without access to the data. Aerotech will have to tell us. I don't feel like waiting for Aerotech to let me know. I have flown (and CATO'd) my last DMS motor. I think this will help:

View attachment 285769




Re-reading this post, I realize that my tone sure makes it look like I'm going through stage 2 of the grieving process: anger. But the tone is misleading because I'm already mostly at peace with what happened. The sympathetic posts from everyone here have been a big help. Thanks guys.

Click to expand...

The MESS reports filed at motorcato.org do not go to the motor manufacturers, rather they go to the staff of NAR S&T, TRA TMT, and CAR MC2 for tracking. We review the data incoming data and contact the manufacturers as needed. Because we don't know the production volume, a true statistical analysis of the data isn't possible which limits our options. To state that motor H111 by ABC manufacturing was failing at a high rate without the statistics to back it would open us to legal recourse. The usual goal is to request the motor manufacturer to publish an advisory or corrective action as needed. These announcements are also archived on motorcato.org

Bat-mite said:

Gives manufacturers data about their failed products. Can help determine if a certain LOT number has a higher rate of failure, etc.

Click to expand...

Actually, a MESS report goes to Tripoli Motor Testing, NAR S & T, and CAR Motor Certification, and can trigger a number of possible actions. It helps to have independent motor testing groups accumulate these data, in addition to the manufacturer. Remember, we're supporting these organizations to help represent us, and they can't help if they don't know that these events are happening and in what quantity. Send them the info - simple to do.

Quoting from motorcato.org:

"The Malfunctioning Engine Statistical Survey (MESS) is a joint organization program that allows NAR Standards & Testing, Tripoli Motor Testing and the CAR Motor Certification Committee to track field trends in the reliability of sport rocket motors. Remember how disappointed when this happened to you?

Help your fellow rocketry community by documenting your unfortunate experience. An unusual number of consumer reported incidences on a particular engine type or lot number can trigger retesting of the product, manufacturer recall, or even decertification."

Mark

[and I see that while I was composing, there was a valuable post by Johnly in a similar direction - Thanks!]

So sad for the AMRAAM. I really like them too. The good news is that you get to make another one because PML is still alive and healthy!
Hope that you get to rebuild or replace it soon!

Great. I bought a K535 DMS thinking it would be an easy entry into 54mm. Now I am not so sure. Just read the MESS site, and now I need to make thrust ring modifications. Grrrr...

In 20 years and hundreds of flights, I have never ever had a problem with reloadables - 24mm, 29mm, and 38mm. Only the single use and econojets have failed on me. Apparently, I can build a motor better than Aerotech can...

MartyS - sorry for your loss. I did enjoy reading your postmortem and rocket eulogy.

Bat-mite said:

What is it about DMS motors that causes them to have a high failure rate?

Click to expand...

All of the DMS failures I've seen, including this one, look like the fiberglass case wasn't strong enough to contain the motor pressure.

If a motor overpressures due to some problem with the propellant -- say, voids or cracks in the grains -- the closures are supposed to blow out before the case fails.

It was sad to see knowing it was your level 1 rocket. Like Eric said, it is rebuild able!

In the aerotech thread it was stated that Aerotech had not received any of the data collected thru the MESS reports. If the mfg does not get the information and it is not available to the community, then there is not much point to the process in my opinion. The info on the most likely date ranges for catos of estes E motor only can be gleened from old thread on TRF. There have been a number of problem motors over the years that have had cato issues that you only find out about afterward from dealers. I was considering getting kit from Andy at "Whats up Hobbies" and he asked if I wanted to do a demo flight with it. I accepted of course and it catoed and it turned out that particular load had a high failure rate and he was getting rid of them in that fashion, rather then paying to return them. If anyone had them in their motor stash they would SOL unless they ran across the projected failure info somewhere.

If you think you are free from CATOs by switching to CTI you are sorely mistaken. Stuff happens and it sucks that you rocket got destroyed but it happens. You seem to be taking it much harder than others that have been through the same thing.

terryg said:

In the aerotech thread it was stated that Aerotech had not received any of the data collected thru the MESS reports. If the mfg does not get the information and it is not available to the community, then there is not much point to the process in my opinion. The info on the most likely date ranges for catos of estes E motor only can be gleened from old thread on TRF. There have been a number of problem motors over the years that have had cato issues that you only find out about afterward from dealers. I was considering getting kit from Andy at "Whats up Hobbies" and he asked if I wanted to do a demo flight with it. I accepted of course and it catoed and it turned out that particular load had a high failure rate and he was getting rid of them in that fashion, rather then paying to return them. If anyone had them in their motor stash they would SOL unless they ran across the projected failure info somewhere.

Click to expand...

One data point is not a trend of statistical significance. In most cases no data, means no action. On the other hand we just learned of a pair of identical large motors failures(no MESS reports were filed BTW) and the manufacturer was contacted as a result.

John

grouch said:

If you think you are free from CATOs by switching to CTI you are sorely mistaken. Stuff happens and it sucks that you rocket got destroyed but it happens. You seem to be taking it much harder than others that have been through the same thing.

Click to expand...

When you invest several hundred dollars and hours of labor building and painting a rocket, I would be pretty bummed out too if my rocket ended out like that. Especially on a cert because you either have to start from scratch or rebuild. Yeah, it's repairable, but will never look as good as good as before.

Want to see an L1000 CATO blow apart an L3 cert project on a test flight?

[video=youtube;K5jGPXW0rmQ]https://www.youtube.com/watch?v=K5jGPXW0rmQ[/video]