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Old 09-21-2017, 07:17 PM
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rocketguy101 rocketguy101 is offline
frustrated aero
Join Date: Sep 2006
Location: Duncan, OK
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Originally Posted by Royatl
No. Understand that the bonding that occurs between the casing and the propellant (and previously pressed nozzle) occurs within seconds under great pressure.
The de-bonding occurs, as you say, from the change in diameters. If fired within a few months after this occurs, you'll get flame propagation through that microscopic separation. My theory is that if the motor now is kept in normal storage conditions, the bonding reoccurs as a function of pressure over time. After all, there is still pressure being applied, as the diameter the casing was made at, is smaller than the chunk of propellant. This might explain why a lot of the early 90's Estes E15's, which were taken from the market due to a high probability of catos, (anecdotally) work perfectly now. The cause of their problems was slightly different. They worked fine when fired within a few months after manufacture, but 'dried out' too much, and started catoing later. But it seems the longer they're just left alone, they "settle in" to their casing.

By the way, I think your idea about the epoxy fillet would just lead to either a nozzle blow out or a split casing.

But it's still just a theory

Interesting! Could be the makings of an R&D project. Wonder if you xray-ed thermal cycled motors early on, could you see the debonding, then over time see it go away?

Yeah, right after I posted I thought about the nozzle blowing out then thought better to blow out the nozzle than blow out the forward end and torch the rocket....maybe??
David Stribling
NAR 18402 SR
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