Cesaroni Pro38 - 6XL (Gas Leak)

[Alby]

Motor: J330 - 6 Grain - 765J330-16A
Casing: Pro38 6XL
Spacers: (1) P38-SP + (1) P38-XL-SP


So using a 6 Grain J330 motor inside of a Pro38 6XL case using two spacers, I encountered what appears to be a liner burn through.
The aft 1/3rd of the liner was completely vaporized. The middle 1/3rd was burned through on one side and melted everywhere else.
The forward 1/3rd of the liner was pretty normal with some minor warping. The aft 1/3rd of the casing also shows heat stress markings on
the outside.

Im wondering if anybody else has encountered a similar issue or can review the attached photos to confirm if this was a case of a gas leak
between the grains of propellant?

NOTE: I discarded the nozzle before taking pictures, but it was pretty normal looking with its threads not showing any signs of a leak.

 

[rcktnut]

I've seen lots of posts with the same problem. Here's one: https://www.rocketryforum.com/threads/cti-38-6xl-normal-or-not.144552/

 

[Alby]

I've seen lots of posts with the same problem. Here's one: https://www.rocketryforum.com/threads/cti-38-6xl-normal-or-not.144552/

Thanks.. It definitely looks very similar to my issue. I see a mention of the smoke grain being a possible culprit. I think next time I'll drill out the maximum delay and remove the ejection charge since Im using electronics for the deployment.

Previously I just left the smoke grain in an untouched as an additional backup ejection.

 

[mikec]

The liner looking like that is pretty typical, but the heat damage to your case isn't.

I don't think the delay grain had anything to do with it FWIW, what did the forward assembly look like? Did you see any leakage past the O-ring?

 

[Alby]

The liner looking like that is pretty typical, but the heat damage to your case isn't.

I don't think the delay grain had anything to do with it FWIW, what did the forward assembly look like? Did you see any leakage past the O-ring?

The forward assembly was nearly perfect. Just some carbon residue, but nothing burnt. All the destruction was towards the aft section of the motor.

The flight was successful and no issues, delayed starts, or anything like that. Just that aft 1/3rd of the liner was completely burned to a crisp.

Attached are the remains that no longer formed a solid piece other than ash particles.

 

[mikec]

If it wasn't for the case (and I can't tell from the pics what that is, does it clean off? What about all those diagonal marks?) I'd say that was pretty typical for these motors. Certainly extensive melting of the plastic liner is something one often sees in all the CTI motors that use plastic liners.

 

[Alby]

If it wasn't for the case (and I can't tell from the pics what that is, does it clean off? What about all those diagonal marks?) I'd say that was pretty typical for these motors. Certainly extensive melting of the plastic liner is something one often sees in all the CTI motors that use plastic liners.

I was able to clean out the case and remove most of the fowling.
Here is an updated interior photo with a few stubborn bits remaining.

The spiral burn marks seem to be indicative of the spirals of the motor mount tube.
Looking at the motor mount tube, it appears to confirm where the massive heat built up
was located inside the case.

Something was definitely going on between Grains 1 and 3.

 

[mikec]

Seems like you have two choices:

1) Submit this to CTI as a warranty claim and see what they say; or

2) Shrug and assume this is not abnormal behavior (hard to say how hot the case got or if this was way out of spec) and the case is still OK.

It's more ambiguous than most CTI failures, which bubble or burn through the case, CATO, etc.

 

[Alby]

Oh yeah I'm not going to the trouble of a warranty claim. Especially since the case seems fine.

I'm going to fly this again with a 6XL motor and a 6-Grain (w/spacers) to see if the problem repeats. Maybe it was just a fluke event or maybe the 6-Grain in a 6XL Case w/spacers is the issue.

Seems like you have two choices:

1) Submit this to CTI as a warranty claim and see what they say; or

2) Shrug and assume this is not abnormal behavior (hard to say how hot the case got or if this was way out of spec) and the case is still OK.

It's more ambiguous than most CTI failures, which bubble or burn through the case, CATO, e

 

[3stoogesrocketry]

I was able to clean out the case and remove most of the fowling.
Here is an updated interior photo with a few stubborn bits remaining.

The spiral burn marks seem to be indicative of the spirals of the motor mount tube.
Looking at the motor mount tube, it appears to confirm where the massive heat built up
was located inside the case.

Something was definitely going on between Grains 1 and 3.

The case has lost its temper in that region. Trusting it is a gamble ( even bigger then flying CTI ) and it will fail. Is the case still round all the way thru, can a spacer slide thru easily?

 

[Alby]

Seems like you have two choices:

1) Submit this to CTI as a warranty claim and see what they say; or

2) Shrug and assume this is not abnormal behavior (hard to say how hot the case got or if this was way out of spec) and the case is still OK.

It's more ambiguous than most CTI failures, which bubble or burn through the case, CATO, etc.

I'll have to do an anomaly investigation similar to Andrew Adams.

 

[Alby]

The case has lost its temper in that region. Trusting it is a gamble ( even bigger then flying CTI ) and it will fail. Is the case still round all the way thru, can a spacer slide thru easily?

Oh yes the case is still round and spacers and another motor I test fitted all slide through with ease. Definitely a plus, so I don't need a new case .

 

[Banzai88]

If you're going to run 6 and 6XL 38mm CTI motors, I would be gluing the forward closure in and lubing the inside of the case with silicone spray lube or you're just asking for trouble.

 

[Alby]

If you're going to run 6 and 6XL 38mm CTI motors, I would be gluing the forward closure in and lubing the inside of the case with silicone spray lube or you're just asking for trouble.

Sounds like a hack is needed for a potential flaw?

Although in this case it seems like nothing happened around the forward closure. This all looks to have been between grains closer to the aft side of the motor. The aft nozzle also threaded in without any issues.

 

[Banzai88]

Sounds like a hack is needed for a potential flaw?

Although in this case it seems like nothing happened around the forward closure. This all looks to have been between grains closer to the aft side of the motor. The aft nozzle also threaded in without any issues.

Read the CTI thread (and any of the many YEARS worth of 38/54 CTI burn though issue threads). They've acknowledged issues almost 2 years ago at the top of the long 54s, issues at the bottom of the short 54s, and issues at the top end of the long 38s.........although they've done Z.E.R.O. to remedy any of those issues.

I've had issues with the longer 38s, as have many of others. The hack solution for the long motors is to glue in the forward closure. Since I started doing it in the 38s, I've not had one single issue. I refuse to purchase and light off a CTI 54 until/unless they solve the burn through at the forward end of the longs and the aft burn though above the nozzle issue in the shorts. Since there appears to be no movement on that front, I'm seriously thinking of dumping the cases (I have a whole set) in the Yard Sale.

As to your issue, your liner looks about what I get with the longer 38s, although I've never had one that basically disintegrated in the middle like you show. Certainly I think that you dodged a bullet!

 

[Alby]

Read the CTI thread (and any of the many YEARS worth of 38/54 CTI burn though issue threads). They've acknowledged issues almost 2 years ago at the top of the long 54s, issues at the bottom of the short 54s, and issues at the top end of the long 38s.........although they've done Z.E.R.O. to remedy any of those issues.

I've had issues with the longer 38s, as have many of others. The hack solution for the long motors is to glue in the forward closure. Since I started doing it in the 38s, I've not had one single issue. I refuse to purchase and light off a CTI 54 until/unless they solve the burn through at the forward end of the longs and the aft burn though above the nozzle issue in the shorts. Since there appears to be no movement on that front, I'm seriously thinking of dumping the cases (I have a whole set) in the Yard Sale.

As to your issue, your liner looks about what I get with the longer 38s, although I've never had one that basically disintegrated in the middle like you show. Certainly I think that you dodged a bullet!

Egads... Thanks for the heads up. Im actually working on a new rocket that will be 75mm. But Im now pondering if I should stick with CTI or go to Aerotech.

 

[Banzai88]

Egads... Thanks for the heads up. Im actually working on a new rocket that will be 75mm. But Im now pondering if I should stick with CTI or go to Aerotech.

No issues with the 75s, although I chose to go with the AT choice because they're still actively working on developing MORE loads, and have released a few new amazing short 75s over the last year or so.

Everything points to CTI being a brand in decline, especially when one views it through the lens of the last 6-7 years of issues with the various loads, as well as generally lack of availability of anything other than cases, and the abysmal year+ turn around for warranty service.

 

[Alby]

No issues with the 75s, although I chose to go with the AT choice because they're still actively working on developing MORE loads, and have released a few new amazing short 75s over the last year or so.

Everything points to CTI being a brand in decline, especially when one views it through the lens of the last 6-7 years of issues with the various loads, as well as generally lack of availability of anything other than cases, and the abysmal year+ turn around for warranty service.

I'm definitely getting that CTI availability feeling. Over the last few years it has seemed that motor availability as been scarce. I love the reload simplicity of CTI, but if you can't get motors, it doesn't matter how much time you save reloading if you're stuck on the pad. Lol


I think I will make that jump to AT for my 75mm.

 

[Neutronium95]

Egads... Thanks for the heads up. Im actually working on a new rocket that will be 75mm. But Im now pondering if I should stick with CTI or go to Aerotech.

The nice thing about 75mm is that the hardware is cross compatible between CTI and Aerotech reloads. Pretty much every CTI reload can be loaded into the equivalent Aerotech hardware, and most of the Aerotech motors in the 75/5120 and smaller are certified for use in CTI hardware. The longer motors should work fine, it just won't be a certified configuration with a warranty.

 

[Alby]

That is good to know, thanks...