12" Talon on a P

[speedyweasel]

So these photos are neat and cool but we can't trust them enough to make our analysis?

 

[jsdemar]

So these photos are neat and cool but we can't trust them enough to make our analysis?

Yep. Take away my technobabble, and that's what's left.

 

[rocketsaway]

Sometimes peoples remarks come off as criticism. Deep at heart, most of us are only evaluating the failures and the successes of others for our own.
What not to do and what to copy. The flight wasnt perfect, but Im sure there were many more successes from it. For one, the motor. That in itself was outstanding.
Some day, when Im building an O or P powered project and scratching my head, Ill remember something I read in these forums, from someone who took the risk first..

 

[stickershock23]

OK, here's a sampling of the pictures my dad got. First, the pretty one:




Now, the less pretty ones:



The first picture shows right about where the upper fins let go, and it's kind of hard to tell if they're in line or not. The next several show the upper fins quite clearly flapping all over the place, and although the coupler also fails at this point, the coupler failure was almost definitely caused by the enormous sideloads of the fin failure, rather than directly causing the shred (these are at 0.1 second intervals by the way).

Wow those pictures are AWESOME. Thanks

Chris Charley Joe.. The project was just way cool. I am glad to have been a small part of it! hey remember your decals are covered when you rebuild LOL

 

[Sandy H.]

OK, here's a sampling of the pictures my dad got. First, the pretty one:




Now, the less pretty ones:



The first picture shows right about where the upper fins let go, and it's kind of hard to tell if they're in line or not. The next several show the upper fins quite clearly flapping all over the place, and although the coupler also fails at this point, the coupler failure was almost definitely caused by the enormous sideloads of the fin failure, rather than directly causing the shred (these are at 0.1 second intervals by the way).

Could you post links to some pictures a little before those to validate the digital scan artifact issue? If that is it, then the fins should still look like they are fluttering, correct?

Great project, though, guys. In my mind, this was an airframe loss, not a failure. One of the best threads ever, BTW.

Sandy.

 

[SpartaChris]

One of the best threads ever, BTW.

Sandy.

Thanks, tell your friends!

 

[cjl]

You may be seeing aliasing artifacts from the digital camera's scan rate. The rocket appears to be bending but that is most likely a result of the digital line scanning as the rocket moves during exposure. This is the same affect seen in the onboard fin-flexing videos which people misinterpret. The photos are also highly compressed and the rocket is a relatively small object in the frame. The details are missing because of the compression artifacts. It's nearly impossible to do photo interpretation under these two conditions.

-John

Bull. Those are from a top end DSLR made for high-speed sports photography. There are no scan rate artifacts, since unlike cheap digital video cameras, there is no scanning. The entire image is exposed at once. Those pictures show exactly what is happening. If there was high enough speed motion that it would move significantly during the exposure (which in this case was 1/3200 second), there wouldn't be an artifact of it curving, it would just blur (exactly the same as a film camera). In general, still cameras will not show scan rate artifacts, as they don't tend to scan. It's video cameras that you have to watch out for.

Besides, those don't look anything like scan rate artifacts. Scan rate artifacts generally make something look like it is bending with a smooth curve. It won't make it look like it has a kink (like the body tube), nor will it make a fin appear to still be straight, but at a different angle from the tube.

As for compression artifacts? There aren't any, at least not any significant ones. The reason that the details are missing is because those are all a 2x upsize of the originals, which makes them somewhat easier to see (but they won't look perfectly sharp because you're looking for details the original didn't have).

 

[cjl]

Could you post links to some pictures a little before those to validate the digital scan artifact issue? If that is it, then the fins should still look like they are fluttering, correct?

Great project, though, guys. In my mind, this was an airframe loss, not a failure. One of the best threads ever, BTW.

Sandy.

They look perfect up to that point.

 

[cjl]

So these photos are neat and cool but we can't trust them enough to make our analysis?

You can absolutely trust them. 100%.

 

[jsdemar]

Bull. Those are from a top end DSLR made for high-speed sports photography. There are no scan rate artifacts, since unlike cheap digital video cameras, there is no scanning. The entire image is exposed at once. Those pictures show exactly what is happening. If there was high enough speed motion that it would move significantly during the exposure (which in this case was 1/3200 second), there wouldn't be an artifact of it curving, it would just blur (exactly the same as a film camera). In general, still cameras will not show scan rate artifacts, as they don't tend to scan. It's video cameras that you have to watch out for.

Besides, those don't look anything like scan rate artifacts. Scan rate artifacts generally make something look like it is bending with a smooth curve. It won't make it look like it has a kink (like the body tube), nor will it make a fin appear to still be straight, but at a different angle from the tube.

As for compression artifacts? There aren't any, at least not any significant ones. The reason that the details are missing is because those are all a 2x upsize of the originals, which makes them somewhat easier to see (but they won't look perfectly sharp because you're looking for details the original didn't have).

What make/model is the camera? The scan and compression artifacts are fundamental problems, even in high-end cameras.

The "noodle" effect in the bending body tube is good evidence of scan artifacting. Also, zoom in on the details and you will see non-optical lossy blurring. That is, if you haven't already made up your mind.

-John

 

[cjl]

1) There is non-optical blurring. As I said, that's a result of the software I used to enlarge the photos, not the camera itself.

2) It's a Canon EOS-1D Mark III. Trust me, it doesn't have scan artifacts. When set to lower quality Jpg, it can have compression artifacts, but that's not the case here. As for the bent body tube? As I said, that's not scan artifacting, that's the body tube bending. As I said, very few decent still cameras will exhibit scan artifacts, as they tend to expose the entire frame at once. It's almost exclusively video cameras that scan line by line.

(Oh, and if you still don't believe it, here's a photo taken with the same make of camera that would show tremendous scan artifacts if the camera were prone to it: https://www.airliners.net/photo/Air...21050/L/&sid=3e307c34e7c7709a915788f15b8f87f4)

 

[stickershock23]

Trust me, Ray's photos are TOP quality.. Check this shot out taken at several hundred MPH from pretty close.. Look Closely, everything is square, no distortion. what you see is what was there.. period.

 

[cjl]

Wow - you really like that pic, don't you

 

[stickershock23]

Wow - you really like that pic, don't you

Yes I know everyone has seen it, but it seems to fit this conversation..

NO DISTORTION, NOTHING JUST A CLEAR SHOT..

Is this one better?

or maybe this one..

or even this one..

All photos taken by Ray lapanse,

 

[Reinhard]

2) It's a Canon EOS-1D Mark III. Trust me, it doesn't have scan artifacts.

Even a single digit EOS camera can experience scan artifacts, because it uses a focal-plane shutter. It's minimum X-sync time is 1/300 second, which gives you an idea how fast the shutter actually moves.

See:
1: https://en.wikipedia.org/wiki/Focal-plane_shutter
2: https://en.wikipedia.org/wiki/Flash_synchronization


However, I don't believe that the pictures of the Talon are significantly distorted by scanning artifacts.
The camera followed the rocket, therefore no significant skewing or compression (see the car in link 1) is to be expected.
For the rocket to appear bent, one of two things needs to happen. Either the rocket rotates fast (see the helicopter in link 1), or it oscillates perpendicular to the shutter movement at a significant frequency (>>10Hz) and amplitude (>>1"). Neither movement was observed, the latter is not even plausible in any imaginable cases.

Reinhard

 

[cjl]

Fair enough. It wouldn't exhibit the artifacts shown with a 1/3200 shutter speed though, and any scanning artifacts would be much, much smaller and more subtle than the ones that are commonly shown with digital video cameras. The helicopter sample in the wikipedia article is bizzare - I've seen pictures taken with my dad's camera of extremely fast rotating objects (namely aircraft propellers), and none of that distortion was visible.

 

[Reinhard]

It wouldn't exhibit the artifacts shown with a 1/3200 shutter speed though, ...

Read the articles again.
Shorter exposure does not mean the shutter moves faster, just that the slot becomes narrower. Therefore I believe the picture of the helicopter was shot at a very short exposure time (No blur, but very "sharp" distortion).

...and any scanning artifacts would be much, much smaller and more subtle than the ones that are commonly shown with digital video cameras.

This sounds plausible. The shutter scans the picture in something along the lines of 1/300 second whereas a video camera, especially a cheap one, may be slower by a magnitude.

The helicopter sample in the wikipedia article is bizzare - I've seen pictures taken with my dad's camera of extremely fast rotating objects (namely aircraft propellers), and none of that distortion was visible.

The distortion is not always clearly visible. The blur in the photo of the A400M that you posted makes it hard to distinguish between a complex propeller shape and distortion. Some kind of distortions are particular hard to notice. If the rocket appears a few percent shorter on a picture than in it is, nobody will notice.

Reinhard

 

[cjl]

Read the articles again.
Shorter exposure does not mean the shutter moves faster, just that the slot becomes narrower. Therefore I believe the picture of the helicopter was shot at a very short exposure (No blur, but very "sharp" distortion).

Agreed. I wasn't referring to scanning artifacts in general though - I was referring to the specific things seen in the Talon picture. I don't know the exact details of the camera shutter though, so I don't know what the scan time is (it is definitely quite short though).

This sounds plausible. The shutter scans the picture in something along the lines of 1/300 second whereas a video camera, especially a cheap one, may be slower by a magnitude.

Definitely. I've seen video cameras that scan slowly enough to cause very noticeable artifacts in even relatively slow moving objects.

The distortion is not always clearly visible. The blur in the photo of the A400M that you posted makes it hard to distinguish between a complex propeller shape and distortion. Some kind of distortions are particular hard to notice. If the rocket appears a few percent shorter on a picture than in it is, nobody will notice.

Reinhard

In that case, the complex prop shape is the reason that the prop blades look bent, not distortion. I agree that if a rocket is a few percent shorter, nobody will notice though. I'll have to experiment a bit at some point and see if I can determine the actual sweep speed. It sounds like an interesting project.

 

[SpartaChris]

In an effort to un-hijack this thread and turn it back to Talon talk instead of Digital Camera talk, here's the altimeter data.

The data from the MAWD. It's my belief this unit lost power during the flight as the unit is showing it's default settings of altitude at 20,000' and 700' for main altitude deployment:

The ARTS 2 data:

And the data graph:

Enjoy!

 

[5x7]

Enjoy!

Can you post the ARTS motor thrust curve?

 

[SpartaChris]

Can you post the ARTS motor thrust curve?

I tried inputting the data into the program, but it kept giving me errors, indicating corrupted data there too. I'll keep trying.

 

[jsdemar]

(Oh, and if you still don't believe it, here's a photo taken with the same make of camera that would show tremendous scan artifacts if the camera were prone to it: https://www.airliners.net/photo/Air...21050/L/&sid=3e307c34e7c7709a915788f15b8f87f4)

That photo has scan artifacts on the prop tips.

Seeing that you are 100% confident, I'm not sure if it's worth further discussion. Having an open mind is the first step in the learning process. I could suggest an engineering approach with a design of experiment, but that would take some curiosity and doubt. It would be a fun Father's Day activity for you and your Dad, or at least you and your Dad's camera.

-John

 

[DAllen]

*steering thread away from photo discussion* I just want to say that I really appreciate all the time and effort that has been put into posting all of the information on this thread. This has been a great read and an epic thread to boot even in spite of SpartaChris' silliness. Hopefully, I will get to meet all of you in person when you get your next insane project done. LDRS30 maybe?

-Dave

 

[cjl]

That photo has scan artifacts on the prop tips.

Seeing that you are 100% confident, I'm not sure if it's worth further discussion. Having an open mind is the first step in the learning process. I could suggest an engineering approach with a design of experiment, but that would take some curiosity and doubt. It would be a fun Father's Day activity for you and your Dad, or at least you and your Dad's camera.

-John

I see no artifacts - what are you seeing that you believe is an artifact? The tips do look bent, but that's because they are bent, not because of an artifact: https://www.airliners.net/photo/Air...69816/L/&sid=1ebc604467903f5dfaa5d26fc434ac79.

As for the experiment, I mentioned above that I would be very curious to do an experiment to determine the scan rate of the camera. I'm pretty busy right now though, so it might not happen soon.

 

[SpartaChris]

Guys-

With all due respect, while the conversation about digital cameras has been great for those who know what the heck you guys are talking about, can I ask you to move it over here instead?

https://www.rocketryforum.com/showthread.php?t=12724

Thanks!

 

[cjl]

Sorry Chris

I'll head over there with camera discussion instead.

 

[SpartaChris]

Thanks man, I appreciate it.

 

[jsdemar]

Sometimes the primary cause of a flight failure could be hidden in the noise of all the other secondary observations and speculation. Here's something I've been thinking about as a primary cause. This was going through my mind while driving back from LDRS after watching the flight.

A CG shift during motor burn will make a rocket over stable. A heavy over-stable rocket will have a large polar moment of inertia, making it slow to react from disturbances. Add to that the compound fin plan and it's difficult to predict the dynamic stability. A common observation is a coning action with the aft end wagging around. We're used to seeing somewhat smaller rockets do this at a higher rate due to the lower inertia and relatively higher corrective forces. But with this size/mass of a rocket, the coning rate will be much smaller, as observed.

Early in the flight with the CG further aft, the large fins will be closer to the CG (like aircraft wings). Any flapping would have a smaller affect closer to the CG, plus the velocity is lower. Once the motor burns, both the increased velocity and the shifting CG will deflect the aft end more. Also, there is feedback into the fins from this motion, causing a resonance, making the deflection build up.

Once the angle of attack is high enough, the side forces will rip apart the weakest link which is usually the coupler. That's pretty common in larger heavy rockets with dynamic stability problems (as observed at BALLS several times).

So, as others have mentioned, stiffer fins attachments would have helped. But other imbalances (thrust vector) or external disturbances (wind gust) could have caused the same coning dynamics due the forward fins and the shifting CG. You could build the same rocket with stiff tip-to-tip laid up fins and it might have the same dynamics.

-John

 

[speedyweasel]

Freshly removed from the motor casing - the Forward Closure

Face of the Fwd Closure

Side view of Fwd Closure

G-10 Seal Disc just inside the forward closure

Inside Face of the G-10 Seal Disc

The only one of the four O-rings to sustain any damage. VERY minor scorching on one side.

Side View of Aft Closure/Nozzle

Inside Face of the G-10 aft ring (surrounded the graphite nozzle and kept the propellant grains from resting on the graphite ring)

Small section of the phenolic liner was torched, but no visible damage to the casing itself.

The phenolic liner broke in a couple of places as we knocked it out of the casing.

An S.O.S. pad, degreaser and water - the only way to clean a gigantic motor casing.

The (nearly) final product of all that scrubbing... and a shameless plug for Joe's Rocket Shop of the Apocalypse on my t-shirt. Yes, that's the self same shirt my beloved wife bought for me before we were on the Discovery Channel the last time we flew the Talon. For those of you who're Canadian, you probably already know and love this shirt.


And finally, we near the last photo of the casing teardown -- and a new requirement for the naysayers and second-guessers -- when you fly a rocket that has a motor casing that you can just BARELY reach half-way through in order to clean... come talk to us.

I wear 37" dress shirt sleeves... a human/orangutan hybrid...

@#%$$ That's a big motor! :y:


p.s. You have no idea how challenging it is posting build thread updates while you're serenaded with songs about cheesy Doritos and smelling like butt. Don't ask. :bangpan:

 

[speedyweasel]

Forgot to mention - we're having a formal wake for the Talon next Saturday.

For those of you who thoroughly enjoyed the build thread, the flight, the aftermath and/or the discussions of digital photography, hinge action and Fat Tire, please observe a moment of silence at 5:00pm Pacific on Saturday, June 26, 2010.

Chief Associate Beer Wench of the Apocalypse ("Tennille" to some) has pointed out that the Talon's funeral happened when it landed in the dumpster and has no idea why we're having a wake AFTER the funeral.