CTI J580 burned out the top

[AllDigital]

I was out at Rocstock this weekend and launched an old favorite of mine, a modified PML Endeavor, set up as an air start cluster. It fires a single L805 off the pad and then air starts 3 J580 smokey sams. This was the 6th time I've launched with this configuration in 4 years.

In the middle of the J burn, one of the J580's completely burned out the top (fore), over pressurizing the fin can and the fin can EXPLODED into a hundred pieces, while the rest of the airframe fell back to Earth with proper chutes. The cluster of motor mounts with motors was recovered.

The forensics clearly show that one J motor was burning out the top, while the other two were normal burns. The fore opening on the motor was 100% open to the size of the hole in the motor casing, so there had to be a crazy amount of fire/ejection coming out the top.

All three had charges removed in the same way (white cap removed and BP tapped/scraped out, white cap put back in, no epoxy). I'd prepped and flown 15 other J580 motors the same way on 5 previous flights.

Any thoughts as to why a CTI J580 would burn out the top in such a horrific way?

We had a lot of cameras pointed at the rocket, so the footage makes for a good fail video: https://vimeo.com/242636318/188f3e06be

Thanks,

Mike

 

[terryg]

I would suspect it was one of the pro38 reloads with the bad forward closure issue.

https://www.pro38.com/pdfs/Bulletin-Pro38_Forward_Clousre.pdf

 

[Bat-mite]

Agreed. Fill out a MESS report and get a rebate form from your dealer. I hope you still have the cardboard tube with the date code.

 

[markkoelsch]

Agreed. Fill out a MESS report and get a rebate form from your dealer. I hope you still have the cardboard tube with the date code.

This is the correct path. Always either keep the packaging until you fly it so you can get the date code, or keep a spreadsheet with them.

MESS report is a must.


Sent from my iPhone using Rocketry Forum

 

[ChrisAttebery]

I'm sorry about your rocket, but the onboard video was great.

 

[AllDigital]

I would suspect it was one of the pro38 reloads with the bad forward closure issue.

Thanks Terry. The PDF was a good reference and my motor looks like it was from a similar batch at Wildman. Like buying a car, crashing it, then finding out it had a recall notice. Next time I'll look for recall notices, before driving.