Not quite sure if this was a cato or shred...

A shred or fin flutter event will result in a sharp or oscillatory deviation in trajectory but no "forward fire." Whereas a CATO/blow-by will 99% of the time have the characteristic "forward fire." One of my "fond" memories of the later below:



The final 1% are CATO's that completely over pressurize and blow out the case so any observable fire is near extinguished. Those are pretty spectacular and extremely loud!

bobkrech said:

I have to ask a really stupid question so don't get insulted. You used a 5G reload in a 6G casing. You did remember to insert the 1G spacer into the casing before you inserted the 5G reload?

Click to expand...

I don't believe there's such thing as a stupid question - only 'logical lines of inquiry' But yes - I did use a spacer.

dixontj93060 said:

A shred or fin flutter event will result in a sharp or oscillatory deviation in trajectory but no "forward fire." Whereas a CATO/blow-by will 99% of the time have the characteristic "forward fire." One of my "fond" memories of the later below:

View attachment 293464

The final 1% are CATO's that completely over pressurize and blow out the case so any observable fire is near extinguished. Those are pretty spectacular and extremely loud!

View attachment 293466

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Thanks for the explanation and the visuals - very helpful. It looked like the bottom picture, not the top one.

DavidMcCann said:

The way the smoke trail ends when the event took place leads me to believe CATO. Bob's got a great point on the spacer (can happen to anyone).
The third photo you posted in the OP seems to match what I've seen on motors that blew up in one manner or another.

On early deployments from either blow-by or electronics getting fooled I've typically seen the smoke trail continue usually veering quickly off vertical.

At LDRS34 I grabbed a little over 700 photos of various "abnormal" flight patterns.

I believe these were early deployment/blowby issues, note the smoke trail continues-

These appear to be CATOs to me, and the smoke trail ends-

Shreds seem to follow the pattern of continued smoke as well, here's an airframe failure at URRF2:

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Thanks for posting these - yes, in terms of what I saw, it most closely resembled images #8 and #10 of those you've supplied. There was no 'nuclear fireball' effect as in some of the other pictures, but the b-bang was significant.

Tim51 said:

Thanks for posting these - yes, in terms of what I saw, it most closely resembled images #8 and #10 of those you've supplied. There was no 'nuclear fireball' effect as in some of the other pictures, but the b-bang was significant.

Click to expand...

Those were extreme examples.... likely 4-6" motors, so a 38mm would be much less nuclear.

Ok so to revive this thread - yesterday I received the SLCF USB download kit courtesy PerfectFlite, USPS and Royal Mail.. Below I've posted screenshots showing the data plots for the cato/shred of 5 June (first image), and one of a nominal flight in April with exactly the same rocket - but a different motor - for comparison (second image). Obviously I'd welcome any further thoughts/analysis from anyone, please.

Just a summary recap on the details of the rocket:
This was a 4" LOC Fantom EXL weighing 3.3kg flying on a CTI I540.
The altimeter bay is a stock LOC EXL 3.9" long bay, with 4 evenly spaced static ports each of the size recommended by PerfectFlite (0.101").
The altimeter was a Stratologger CF with 2 x 1.5g charges of 4F BP, with the drogue deploying at apogee and the main at 700'. This altimeter had flown with no problems previously on both CTI I236, and on a CTI J410*. I heard normal continuity beeps before the launch in question.

(*One thing that I've just noticed on accessing this plot is that the SLCF recorded a far higher peak velocity - Mach 0.71 - than that OR sim suggested (i.e. Mach 0.6) for the J410 flight, although the max altitude is more or less the same. I don't know how relevant that might be but thought I'd mention it.)

The scorching / residue is definitely from Cato. As is melted epoxy. Looks like a Cato out the side of the case venting between the motor mount and body. This would have the overpresurised the body and caused the lower airframe to fail. From the data it looks like things went wrong at about .3 sec into the flight.

SpaceManMat said:

The scorching / residue is definitely from Cato. As is melted epoxy. Looks like a Cato out the side of the case venting between the motor mount and body. This would have the overpresurised the body and caused the lower airframe to fail. From the data it looks like things went wrong at about .3 sec into the flight.

Click to expand...

Thanks for the analysis - it's been 'a steep learning curve' as the saying goes, but it's useful to know what one looks like - hopefully it'll be a long time before I see / experience another one...any thoughts on what might have caused it?

Tim51 said:

Thanks for the analysis - it's been 'a steep learning curve' as the saying goes, but it's useful to know what one looks like - hopefully it'll be a long time before I see / experience another one...any thoughts on what might have caused it?

Click to expand...

Liner out of place perhaps, as it happened so quickly it's not just from burn through. probably happened aft as I expect the motor sticks out longer than the upper CR. Other possible fault could be issue with aft seal. Guessing here really need the motor to confirm.

Am I reading your graph wrong? It looks like a peak velocity of 1,400 feet/sec.

Dale

DEmery said:

Am I reading your graph wrong? It looks like a peak velocity of 1,400 feet/sec.

Dale

Click to expand...

That's what the graph says but it's simply the result of aerodynamic effects during the breakup of the rocket. The graph also shows a number of apogee's, clearly the altimiter is not going up, coming down and going back up again.

SpaceManMat said:

That's what the graph says but it's simply the result of aerodynamic effects during the breakup of the rocket. The graph also shows a number of apogee's, clearly the altimiter is not going up, coming down and going back up again.

Click to expand...

This may have been a shred and a CATO at the same time. The velocity spike on the CATO graph looks too sharp (like the non-cato graph) before quickly dropping in speed due to the CATO/shred. If you look closely there is an altitude loss at around 1.3 seconds, which I assume is the effects of mach transition. All at the same time you see the negative drop in velocity due to the break up.

Compare this with the non-cato graph the velocity spike slowly drops in speed as the rocket is slowing down after motor burn out at around 2.4 seconds into the flight.

It could have been possible that the motor had a quick burst in speed due to over pressurization before CATOing.


Alexander Solis - TRA Level 1 - Mariah 54 - CTI-I100 Red Lightning Longburn - 6,345 Feet

SinfulDarkLord said:

This may have been a shred and a CATO at the same time. The velocity spike on the CATO graph looks too sharp (like the non-cato graph) before quickly dropping in speed due to the CATO/shred. If you look closely there is an altitude loss at around 1.3 seconds, which I assume is the effects of mach transition. All at the same time you see the negative drop in velocity due to the break up.

Compare this with the non-cato graph the velocity spike slowly drops in speed as the rocket is slowing down after motor burn out at around 2.4 seconds into the flight.

It could have been possible that the motor had a quick burst in speed due to over pressurization before CATOing.


Alexander Solis - TRA Level 1 - Mariah 54 - CTI-I100 Red Lightning Longburn - 6,345 Feet

Click to expand...

I believe the speed is derived from altitude, so is subject to errors if the baro is being fooled. Take a look at at this Cato on my original L2 attempt. In this case the motor shut down (blocked nozzle) so no further thrust occurs. Despite this after the Cato the altitude is recorded as rapidly increasing. But the reality is the rocket is rapidly slowing. Both the baro and accelerometer are fooled, I believe due to rapid spinning.

you can see from the graphs you vent pressure from the fin can into you ebay. This is seen by the dip in altitude when your events occur - even on the normal flight graph, just to a lesser extent (due to lower pressures)

gotta wonder if you didn't inadvertently pop the delay / top off the motor case. Happens sometimes if the liner is sticky and you push on the nozzle end to get the darn thing up. Did you do that? One of my biggest "ah ha" moments was doing that and hearing the delay rattle in the spacer... then i found out that if I have a sticky liner I take the nozzle off and use an old one to push it up far enough to be able to clear a couple of threads, then use the nozzle and closure

Thanks very much guys for your input and shared experience - all really useful. To supplement the points / informed speculation each of you have kindly offered -

SpaceManMat:

probably happened aft as I expect the motor sticks out longer than the upper CR.

Click to expand...

Thanks - actually in this instance the end of the CTI casing was well inside - this portion of the booster was built stock, and the MMT for the LOC Fantom 438 nearly 20" long (I guess to accommodate 6GXL cases..)... I was just using a standard 6G case. But your point stands generally - there seemed to be no evidence of burning forward of the fore CR.

I believe the speed is derived from altitude,

Click to expand...

If that's the case, I'm thinking that could lead to the SLCF reading of velocity having quite wide discrepancies in recorded speed and actual(..? re. my earlier point about the recorded velocity on J410 normal flight being a lot higher than the sim)

SinfulDarkLord:

If you look closely there is an altitude loss at around 1.3 seconds, which I assume is the effects of mach transition. All at the same time you see the negative drop in velocity due to the break up.

Click to expand...

Thanks Alexander - yes, you're right that the altitude loss lines up with the drop in velocity at 1.3s.

SpaceManMat:

Both the baro and accelerometer are fooled, I believe due to rapid spinning.

Click to expand...

Thanks for posting your graph. From what we saw this would seem to be the case here also. (btw if you originally posted a thread for the build / cato I'd be interested in reading it).

cbrarick:

you can see from the graphs you vent pressure from the fin can into you ebay

Click to expand...

Do you mean gases actually entering the ebay? It's sealed pretty tightly, both with all thread, nylon washers and a ring of silicone sealant.

gotta wonder if you didn't inadvertently pop the delay / top off the motor case. Happens sometimes if the liner is sticky and you push on the nozzle end to get the darn thing up. Did you do that? One of my biggest "ah ha" moments was doing that and hearing the delay rattle in the spacer... then i found out that if I have a sticky liner I take the nozzle off and use an old one to push it up far enough to be able to clear a couple of threads, then use the nozzle and closure

Click to expand...

All good points. It seemed a smooth fit, without any stickiness. The Pro 38 case doesn't have a detachable forward closure. As you can imagine I've gone over what I did when loading the motor a few times in my head since (particularly whilst paying out for replacement hardware and recovery gear..). This was my first 5G motor, so I was particularly paying attention to using the spacer and the casing. I also checked the inside of the casing to ensure there was no residue from the previous flight. Since the motor eject was back up I didn't remove the delay grain module to drill any delay adjustment, and at the time I was pretty sure everything was fine and dandy there. I've also wondered whether (for example) when I was inserting it, the igniter did not reach all the way up the core and get seated in the head end, but I did my usual checks to ascertain that. At the pad I made the usual finger loop before putting the yellow nozzle cap back on, and wrapped the crocodile clip leads loosely around the base of the launch rail to take some of the strain and avoid pulling the igniter lead down.

Hopefully later in the summer after the harvest the casing and fin can will turn up. If it does I'll post pictures.

Tim51 said:

Ok so to revive this thread - yesterday I received the SLCF USB download kit courtesy PerfectFlite, USPS and Royal Mail.. Below I've posted screenshots showing the data plots for the cato/shred of 5 June (first image), and one of a nominal flight in April with exactly the same rocket - but a different motor - for comparison (second image). Obviously I'd welcome any further thoughts/analysis from anyone, please.

Just a summary recap on the details of the rocket:
This was a 4" LOC Fantom EXL weighing 3.3kg flying on a CTI I540.
The altimeter bay is a stock LOC EXL 3.9" long bay, with 4 evenly spaced static ports each of the size recommended by PerfectFlite (0.101").
The altimeter was a Stratologger CF with 2 x 1.5g charges of 4F BP, with the drogue deploying at apogee and the main at 700'. This altimeter had flown with no problems previously on both CTI I236, and on a CTI J410*. I heard normal continuity beeps before the launch in question.

(*One thing that I've just noticed on accessing this plot is that the SLCF recorded a far higher peak velocity - Mach 0.71 - than that OR sim suggested (i.e. Mach 0.6) for the J410 flight, although the max altitude is more or less the same. I don't know how relevant that might be but thought I'd mention it.)

Click to expand...

Barometric altimeters measure external pressure only: they do not measure either altitude or velocity! In a standard uneventful flight, the pressure monotonically decreases thru apogee and then monotonically increases during the descent to ground. In a normal flight, the pressure measurement is representative of the static pressure around the rocket, and thus can be converted to a pressure altitude quite easily. If the altitude smoothly increases with time, the dH/dt can be used as a crude measurement of velocity. A better estimate of the velocity is obtained if the altitude versus time is plotted and curve fit. The first derivative of the curve fit with respect to time is the velocity versus time curve. If you take the velocity curve fit and take another derivative versus time you will obtain the acceleration of the rocket as a function of time.

If you take a close look at the failed flight, you will see the first pressure fluctuation at ~120' altitude @~300 fps about 0.45 seconds into the flight . That's where the failure occurred and most of the data after that time is garbage as the dynamic pressure of a sideways rocket is polluting the pressure measurement. It look like the altimeter compartment got to ~300' before beginning descent, and from that point ~ 5 seconds into the flight, the barometric altimeter is providing reasonable pressure measurement that can be converted into pressure altitude. So the maximum velocity your rocket obtained was likely ~300 fps and the maximum altitude of the payload was approximately 300 ft with 0 upward velocity.

The velocity was not high enough for a shred. The motor CATOED. Either the forward closure failed, or the nozzle spit, or the casing over-pressurized, blew up and took out the fincan. If the forward closure failed or the nozzle spit, the fincan should be largely intact. If the motor over-pressurized and blew up, the fincan would be destroyed. Since you don't have a photo of the lower end of the rocket after the flight, I'll assume the motor overpressurized, blowing up the casing and the fincan.

Bob

SpaceManMat said:

I believe the speed is derived from altitude, so is subject to errors if the baro is being fooled. Take a look at at this Cato on my original L2 attempt. In this case the motor shut down (blocked nozzle) so no further thrust occurs. Despite this after the Cato the altitude is recorded as rapidly increasing. But the reality is the rocket is rapidly slowing. Both the baro and accelerometer are fooled, I believe due to rapid spinning.

Click to expand...

Edit: take back what I said.

Hm I think I'll take back all I've said lol. Nah not really anyways after reading Bob's post I just realized that there is no increase in altitude until 1.3 seconds. So yeah pretty much it was messed up readings from the CATO.


Alexander Solis - TRA Level 1 - Mariah 54 - CTI-I100 Red Lightning Longburn - 6,345 Feet

bobkrech said:

Barometric altimeters measure external pressure only: they do not measure either altitude or velocity! In a standard uneventful flight, the pressure monotonically decreases thru apogee and then monotonically increases during the descent to ground. In a normal flight, the pressure measurement is representative of the static pressure around the rocket, and thus can be converted to a pressure altitude quite easily. If the altitude smoothly increases with time, the dH/dt can be used as a crude measurement of velocity. A better estimate of the velocity is obtained if the altitude versus time is plotted and curve fit. The first derivative of the curve fit with respect to time is the velocity versus time curve. If you take the velocity curve fit and take another derivative versus time you will obtain the acceleration of the rocket as a function of time.

If you take a close look at the failed flight, you will see the first pressure fluctuation at ~120' altitude @~300 fps about 0.45 seconds into the flight . That's where the failure occurred and most of the data after that time is garbage as the dynamic pressure of a sideways rocket is polluting the pressure measurement. It look like the altimeter compartment got to ~300' before beginning descent, and from that point ~ 5 seconds into the flight, the barometric altimeter is providing reasonable pressure measurement that can be converted into pressure altitude. So the maximum velocity your rocket obtained was likely ~300 fps and the maximum altitude of the payload was approximately 300 ft with 0 upward velocity.

The velocity was not high enough for a shred. The motor CATOED. Either the forward closure failed, or the nozzle spit, or the casing over-pressurized, blew up and took out the fincan. If the forward closure failed or the nozzle spit, the fincan should be largely intact. If the motor over-pressurized and blew up, the fincan would be destroyed. Since you don't have a photo of the lower end of the rocket after the flight, I'll assume the motor overpressurized, blowing up the casing and the fincan.

Bob

Click to expand...

Thanks very much for taking the time to talk me through that Bob - I really appreciate your input and expertise on this. I'll refer fellow club members to this thread and file a MESS report on this incident.

bobkrech said:

Barometric altimeters measure external pressure only: they do not measure either altitude or velocity! In a standard uneventful flight, the pressure monotonically decreases thru apogee and then monotonically increases during the descent to ground. In a normal flight, the pressure measurement is representative of the static pressure around the rocket, and thus can be converted to a pressure altitude quite easily. If the altitude smoothly increases with time, the dH/dt can be used as a crude measurement of velocity. A better estimate of the velocity is obtained if the altitude versus time is plotted and curve fit. The first derivative of the curve fit with respect to time is the velocity versus time curve. If you take the velocity curve fit and take another derivative versus time you will obtain the acceleration of the rocket as a function of time.

If you take a close look at the failed flight, you will see the first pressure fluctuation at ~120' altitude @~300 fps about 0.45 seconds into the flight . That's where the failure occurred and most of the data after that time is garbage as the dynamic pressure of a sideways rocket is polluting the pressure measurement. It look like the altimeter compartment got to ~300' before beginning descent, and from that point ~ 5 seconds into the flight, the barometric altimeter is providing reasonable pressure measurement that can be converted into pressure altitude. So the maximum velocity your rocket obtained was likely ~300 fps and the maximum altitude of the payload was approximately 300 ft with 0 upward velocity.

The velocity was not high enough for a shred. The motor CATOED. Either the forward closure failed, or the nozzle spit, or the casing over-pressurized, blew up and took out the fincan. If the forward closure failed or the nozzle spit, the fincan should be largely intact. If the motor over-pressurized and blew up, the fincan would be destroyed. Since you don't have a photo of the lower end of the rocket after the flight, I'll assume the motor overpressurized, blowing up the casing and the fincan.

Bob

Click to expand...

Thanks Bob, much better explanation than me.

Tim, my build thread is here along with details of the Cato.

https://www.ausrocketry.com/forum/viewtopic.php?f=6&t=4161

FYI Cato is on page 8

Tim, my build thread is here along with details of the Cato.

https://www.ausrocketry.com/forum/vie...php?f=6&t=4161

FYI Cato is on page 8

Click to expand...

Thanks very much for posting that.

Hi! Casing has been found by the farmer. Looks like it blew out the top end/forward closure as it's opened up both spacer and casing. Nozzle looks normal to me and all grains burnt. Malc has it so give him a call to talk about it. The casing is otherwise normal in all respects. Fin can got nobbled by the farm machinery.



Cheers

Andy

I wonder if your motor happens to be one of the CTI motors with the faulty forward closure.

markkoelsch said:

I wonder if your motor happens to be one of the CTI motors with the faulty forward closure.

Click to expand...

We checked that. It was made earlier than the affected batches.

If you had at least some video. My rockets except video of the ground have onboard video which most times survives even rocket have a crash. Especially оnboard video immediately is visible reason of the crash.And so I'm not Nostradamus to guess.
P.S . O, this is an old topic.

amell said:

Hi! Casing has been found by the farmer. Looks like it blew out the top end/forward closure as it's opened up both spacer and casing. Nozzle looks normal to me and all grains burnt. Malc has it so give him a call to talk about it. The casing is otherwise normal in all respects. Fin can got nobbled by the farm machinery.

View attachment 300674View attachment 300675

Cheers

Andy

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Thanks Andy - interesting! I wish I could've made it today but just got out of hospital (I should emphasise I was there for non-cato related reasons.. :wink:!) I think at least some of the fin can must have survived as I got a call during the week from Josh, one of the junior EARS members, who'd found the part of it with my mobile number on. I do hope that lovely anodised Rowes 38mm retainer hasn't been mangled...
Anyway, I'll speak to Malc, and hopefully be there in person next month.

Cheers