Interesting CTI Failure

[n3tjm]

http://www.youtube.com/watch?v=yIHdIMdkIPQ
I believe the I285 is the 4 grain classic propellant. Now I seen this propellant become hard to light when it gets old (chuffing a lot before going) but nothing like this. I wounder if he had mixed age grains or conditioned grains? (ie two grains in pristine condition, and a couple loose and got exposed to humidity?). Thoughts?

[alexzogh]

This happened to me with a research motor - almost like I had a 2 stage rocket. When I inspected the motor after the flight, I had a nozzle fracture.

When the nozzle failed, the loss of pressure made it look like the motor burned out. It the came back up to pressure (much lower) with the nozzle, and 'extra' big throat.

I'm guessing something similar happened here.

[jFlds]

That was an interesting flight. I am glad I caught the whole flight track on camera. The pause in thrust and the pop at re-ignition was very odd and much more pronounced than my clip caught.

Unfortunate for Larry. That was a cool bird and I really was hoping to see her go up on 9 motors this weekend.

[RocketManDan]

Maybe the weather might have something to do with it??

[jFlds]

Maybe the weather might have something to do with it??

It's been colder, wetter, brighter, and every other possible weather scenario out there. CTI has always been a more consistent performer in our season's conditions.

I have seen hundreds of these loads fly out on that field and not ever have I seen one do that.

I doubt it was weather.



Just a real strange thing that one did.

[larrykoskie]

[IMG][/IMG]
This is a photo of the nozzle and there is no cracks or damage to the nozzle. The specs for the motor say the the nozzle throat diameter is 0.344" but a 7/16 drill bit easily fits down the throat of this nozzle which makes it 0.4375". So I believe it was manufacture with the wrong nozzle.

[JPVegh]

Ouch! That was a scary failure. Could have been bad.

[Jeroen_at_CTI]

So I believe it was manufacture with the wrong nozzle.

See if this nozzle has a graphite insert. It should. It may have spit the graphite out.

We have a warranty process via our dealers. They know how this works. Please contact your dealer and everything will be sorted out. That way we will get all information and take necessary steps to prevent repeats.

Jeroen

[larrykoskie]

[IMG][/IMG]This a photo of the nozzle from the inside. Is this the graphite insert or is this what it would look like if it spit out the insert? I don't know what it should look like. There was a definite loud pop when it quit burning and started coasting before it reignited and burned the second time. That pop could be when it spit out the insert or when it spit out something anyway.

[gldknght]

See if this nozzle has a graphite insert. It should. It may have spit the graphite out.

We have a warranty process via our dealers. They know how this works. Please contact your dealer and everything will be sorted out. That way we will get all information and take necessary steps to prevent repeats.

Jeroen

Now that's awesome customer service right there.

[UPscaler]

looks like there is graphite in it to me...


This happened with a CTI motor at a Tripoli Idaho launch once, may have even been the same motor


Braden

[bandman444]

Is the case alright?

Any charring anywhere it shouldn't?

My first thought was that it depressurized (blow by the aft closure?) then it sealed itself, completing the burn.

Threads on tight? Not cross threaded? When you put the forward closure back on the Oring sat all the way inside not just on top?

CTI is great about customer support.

Anything salvageable from the rocket?

[jFlds]

See if this nozzle has a graphite insert. It should. It may have spit the graphite out.

We have a warranty process via our dealers. They know how this works. Please contact your dealer and everything will be sorted out. That way we will get all information and take necessary steps to prevent repeats.

Jeroen

Thanks Jeroen. I knew sooner or later you'd chime in on this.

CTI support in action.




Larry let me know if they need more footage or if they need it sent to them.

[Eat, sleep, and Fly]

I dont know why, but it also happenned here

[larrykoskie]

Is the case alright?

Any charring anywhere it shouldn't?

My first thought was that it depressurized (blow by the aft closure?) then it sealed itself, completing the burn.

Threads on tight? Not cross threaded? When you put the forward closure back on the Oring sat all the way inside not just on top?

CTI is great about customer support.

Anything salvageable from the rocket?

There wasn't anything unusual with the case, no damage, no charring, the plastic liner was quite melted and deformed but not too out of ordinary. The nose cone remains underground but the booster and fin unit was unhurt. The booster was blue tube and I did cut about 1/2 in off the forward end to remove some minor damage and I am almost done rebuilding the offset nose cone. It should fly again this weekend but this time with Aerotech J 340M as a central motor and four G 75M on the fin tips.

[larrykoskie]

The motor was manufactured in 2008 and I purchased it in July 2009, so I am guessing that it is past it's warranty.

[larrykoskie]

[IMG][/IMG] This is what it looked like before the crash.

[JPVegh]

Wow! That was a beautiful rocket, too bad.

[larrykoskie]

Well this is what it looks like today, ready to fly again

[nealkas]

[IMG][/IMG] This is what it looked like before the crash.

Well this is what it looks like today, ready to fly again

Looks like the damage 'buffed right out'.

[ID Rocketeer]

Well this is what it looks like today, ready to fly again

Sweet! I like the looks of the rebuild even better than the original.

So what exactly was the extent of the damage and what did you have to do to repair it? Did you already have a new forward portion under construction?

[ID Rocketeer]

[IMG][/IMG]This a photo of the nozzle from the inside. Is this the graphite insert or is this what it would look like if it spit out the insert? I don't know what it should look like. There was a definite loud pop when it quit burning and started coasting before it reignited and burned the second time. That pop could be when it spit out the insert or when it spit out something anyway.

Is the ID of that nozzle typical for that reload? None of the 10 CTI 38mm motors I've flown have had that big an opening, but I've never flown that particular reload.

[larrykoskie]

Sweet! I like the looks of the rebuild even better than the original.

So what exactly was the extent of the damage and what did you have to do to repair it? Did you already have a new forward portion under construction?

There wasn't anything left of the forward section. It was made of two LOC nose cones and some quantum tube. None of that survived and I left it buried out in the field. This forward section is all new. The nose cone is fiberglass and all the tube is blue tube. There is a 2 inch offset. There is a 6 inch tube on the nose cone and a 12 inch tube back to the booster that butt into each other with a 3/4"x2"x8" block of wood screwed into 4" of each section to make the offset. Then I split a 5" section of tube to make the transitions. It was fairly simple to make and turned out quite nice. And as you might guess, didn't take me that long to build.

[larrykoskie]

Is the ID of that nozzle typical for that reload? None of the 10 CTI 38mm motors I've flown have had that big an opening, but I've never flown that particular reload.

This nozzle measures 0.4375" and it was supposed to measure 0.344". I don't know why it is that large. I don't know if something was spit out when it popped just before it coasted or if it was too big to start with. I haven't gotten a clear answer on that one yet myself.

[Fe Dude]

Sorry bout the crash, that is indeed interesting. But on the upside, the pointier front end looks niiice.