Using the following definitions, is a cato a detonation or a deflagration?
'deflagration' - exothermic chemical decomposition of a material in which the reaction front advances into the unreacted material at less than the speed of sound;
'detonation' - a chemical reaction that progresses through an explosive at
sound in the reaction zone;
Are there different forms/types of a CATO?
shockie B)
From an online version of the RMR FAQ (probobly outdated, by the date at the top)
"1.8 When a consumer rocket motor fails (i.e., CATOs) does it explode or detonate?
To be precise, consumer rocket motors do NOT 'detonate'. Black powder rocket motors 'deflagrate'. Detonation involves the creation of super-sonic shock waves. Use the term 'explode' when discussing CATOs involving split motor casings, holes blown out the sides of models, etc."
I've heard CATO in refrence to many types of failure, not just explosive ones. Motors failing to burn completely, for example. (A recent launch had a Big Daddy pitch over just after takeoff and nosedive into the ground a few hundred feet downrange. After recovery the clay cap of the D12-3 was still in place.)
deflagration?
I don't know about BP motors, but for APCP motors, it's neither. A cato is simply an over-pressurization of the containment vessel.
explosive at
According to at least one source, deflagration is more precisely defined as progressing at a speed of meters per second.
Most catoes of APCP sport rocket motors are the result of internal pressure exceeding the strength of the hardware. There are many possible causes of this. For instance, if the propellent has excessive voids, the additional surface area produces more gas than the nozzle was designed for. Using a smaller nozzle by mistake can cause the same problem. Casings can also fail due to manufacuring flaws (mainly in single-use motors) or after being damaged by a previous incident.
Some "catoes" would more accurately be called "burn throughs" or "blow-bys". For instance if an o-ring is installed incorrectly, or left out during assembly, the hot gases can escape through the gap and/or burn through the casing. Or the gas gets past the delay column and blows out through the forward closure.
Neither. A catosthrophic failure is a failure not necessarily a pyrotechnic event.
This should be in the FAQ.
Really.
Point.
Most CATOs are neither. THey are the result of overpressurization blowing out the forwarad or aft end of the motor.
Yes! THe most common I memtioned, blowing one end out. Occasionally a casing will rupture along the length. There can be a burn through the side of the casing. ANd of course there can be a delay malfunction, either no ejection, early ejection or late ejection. ANd probably othere I've forgot.
In all my years of rocketry, I can recall exactly ONE motor going "BANG" like a rifle shot. It was in one of my competition models at an old ETR back in the 70s. A 1/4A3 IIRC and it was the LOUDEST cato I ever heard, especially being 15' away. My ears rang for quite a while.
Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD" >>> To reply, remove the TRABoD!
Substances detonate or deflagrate. Devices explode. CATO is just a colloquial term.
Motors that fail catostrophically sometimes do so by exploding due to the pressure caused by deflagrating propellant causing a structural failure due to a defect or design flaw.
But motors can fail catostrophically in other ways, such as burning through the wall but yet not exploding. Or puking a nozzle without doing so violently. It's still "catostrophic" and CATO is just a cute term for a bad failure of one sort or another.
Mike D. CTI
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