Any interesting CATO stories?

[MarkII]

IMHO temperature cycling doesn't just mean getting hot. Cold means shrinkage (did I just say that?) and that can cause the pulling away of the propellant slug from the casing, and cracks in the grain.

I wish that sticky thread from the previous life of TRF was still here. here is some info on BP motor failures:

OK, I see. All of the stuff I had seen about temperature cycling up until now on various forums, mailing lists, etc. had only talked about the negative effects of cycling the motors in and out of high temps. These are the first references that I have seen to cold cycling. Thanks for the info. I'm surprised that a black powder propellant slug that is highly compressed and has been pressed into a thickly wound paper casing under high pressure can actually contract that much due to exposure to cold temperatures. Any idea of how long the duration of the exposure and how cold the temperature would need to be to produce this effect? If there was some moisture in the propellant, wouldn't that cause the slug to expand rather than contract, if the motors were stored in temperatures that were significantly lower than 32° F for a prolonged period?

Mark \\.

 

[shreadvector]

OK, I see. All of the stuff I had seen about temperature cycling up until now on various forums, mailing lists, etc. had only talked about the negative effects of cycling the motors in and out of high temps. These are the first references that I have seen to cold cycling. Thanks for the info. I'm surprised that a black powder propellant slug that is highly compressed and has been pressed into a thickly wound paper casing under high pressure can actually contract that much due to exposure to cold temperatures. Any idea of how long the duration of the exposure and how cold the temperature would need to be to produce this effect? If there was some moisture in the propellant, wouldn't that cause the slug to expand rather than contract, if the motors were stored in temperatures that were significantly lower than 32° F for a prolonged period?

Mark \\.

Too many questions to answer - especially without handy copies of the R&D reports I and the others have written on this subject. I will answer a few that I know I have the facts on:

Humidity: I soaked D12-5 motors in 100% relative humidity for quite a while (OK, I can't remember if it was 2 weeks or a month) by suspending them on a rack above a bunch of water inside a plastic garbage can. Some were static tested immediately after removal and others were placed into a container with dessicant to dry them (another 2 or 4 weeks)
and then static tested. The thrust time curves of the humidity soaked motors exhibited lower thrust with longer burn time and the delay times were WAYYYY long. Same total impulse. No catos. IIRC, after drying, the performance returned to normal or nearly normal, but I'm not sure I recall correctly.

I don't think the average motor will absord enough moisture in normal conditions to be able to form ice crystals inside that can cause expansion and cracking. I think the moisture in an average motor is pretty low and is not concentrated enough to form large crystals. I don;t know if anyone looked at this in an R&D report, but it could be interesting.

 

[pyrovette20]

I had an Estes space shuttle Challenger with a C6 cato about 2 months before the real Challenger blew up. Premanition maybe,wierd yes. But it happened.

 

[Pem Tech]

While not as spectacular as some of the other CATO's in this thread, this is one of the few I have experienced.

Right before NSL2007 I was rushing to get the Space Ark Jr. into production, should have known better than to put such a purdy paint job on it.
Lift off on a D12-3 of unknown age.
Well, an attempted lift off...

And a fraction of a second later here she is completing loop-de-loop.

The rocket was a total loss, charred to a crisp.

 

[Chrisn]

Who cares what a Cato is, this thread is about CATOs, catastrophes at take off, not the shorthand catastrophic failure. 2 completely different things.

Its not like EMRR is the oxford dictionary or anything, why is this always bought up?

 

[RangerStl]

Before anyone gets too uptight.. Chrisn please note the dates on these posts. Since January many things have been discussed and things have been left alone since then. I think we had all come to the agreement that many opinions exist and it really wasn't worth arguing over, especially since launching personal barbs at individuals is distracting and not permitted under our rules.

I think that agreement should stand and we should instead all mourn the loss of Layne's Space Ark.

Cue "Taps".

 

[Chrisn]

Before anyone gets too uptight.. Chrisn please note the dates on these posts. Since January many things have been discussed and things have been left alone since then. I think we had all come to the agreement that many opinions exist and it really wasn't worth arguing over, especially since launching personal barbs at individuals is distracting and not permitted under our rules.

It was a simple statement voicing my opinion on the matter, nothing more nothing less. Maybe I could have replied to this in January, if it didn't take until last week or whenever for my account to be manually approved

 

[Rocketcrab]

Back in 1988, when I was getting "back into" rocketry as a BAR, I bought and eagerly built the then-new Estes Jupiter-C model. It was released as part of the 30th anniversary of the launch of the first US satellite, Explorer-1. I put all kinds if time into that model - I even filled in the body tube sprals for the fist time! Man, I was proud of that build. It flew for the fisrt and last time in December of that year. I loaded up a C5-3 motor, which gave that model a great boost....she arc'd over...and...straight into the frozen ground, completely pulverizing the satellite and "bucket". The reason? The ejection charge never went off. The cap was still present. I was informed I'd suffered a CATO - never happened to me before. For some dumba$$ reason, I never returned the remnants to Estes for replacement. :bang:

 

[shreadvector]

:2:

View attachment cato_origin.pdf

 

[MysticalRockets]

Ok Fred, enough please? You made your point months ago.

If you still don't like it, don't read the thread.

Thank you.

 

[Chrisn]

can we just agree that CATO and Cato are 2 separate things, and add a new entry to the EMRR database?

 

[Pem Tech]

I think that agreement should stand and we should instead all mourn the loss of Layne's Space Ark.

Cue "Taps".

Thank you.....
*sniff*

She was a good ride while she lasted.