Interesting Discovery with Igniters

[GregGleason]

I was looking through the photo of a launch of a composite motor from last weekend and found something interesting: unexplained dots on the image near the base of the rocket. These were not visible at launch time, and can only be seen under a higher resolution image.



TH002_2011-03-12_043 by D.Laney, on Flickr

Greg

[GregGleason]

I looked at a pic of another flight and saw the same thing, except more of them.


TH002_2011-03-12_063 by D.Laney, on Flickr

In the next photo, a fraction of a second later, they are almost all gone:


TH002_2011-03-12_064 by D.Laney, on Flickr

[GregGleason]

I believe these objects to be an element that I added to my igniter dip for the first time, in hope that the white hot substance would itself into the AP to help it light. Apparently it burns very hot, but only for a brief time.

If there is not a name for this phenomena, I'll give it one:
Extra Motor Igniter Transients or EMITs.

Greg

[cjl]

1) Holy cow. Those pictures are enormous - I have a 30 inch monitor, and they still extend off the side. In the future, could you use clickable thumbnails or something instead of filling the thread with enormous images?
2) I do think that those could be igniter pyrogen. It's hard to say, but that does sound like a definite possibility.

[GregGleason]

Sorry c!

I didn't know how to do that or I would have done that. Maybe a mod can throw me a "how to" to fix.

But a 30 in monitor to see it would be sweet!

Greg

[Pantherjon]

The 2nd and 3rd pics looks like could be the extra 'stuff' from the ignitor..The 1st picture looks as if the exhaust flame is kicking off residue off the blast deflector..Awesome pictures, a bit big, unsure exactly how to make them resizable thumbnails tho...

[jadebox]

I think that almost every type of motor and igniter combination produces little sparkles at ignition. My guess is that it's mostly bits of pyrogen from the igniter. We generally don't see them because they are hard to see in sunlight and they are short-lived.

I've managed to capture ignition fairies in few photographs and videos. My favorite is the little sprite that falls out of the nozzle and bounces around on the blast deflector in the high-speed video at http://www.payloadbay.com/video-7949.html.

-- Roger

[GregGleason]

I may need to make an igniter test video a "without element X" and a "with element X", to see if there is a discernible difference. A high-speed video would be great, but I don't have access to one of those.

I am going to check David Laney's launch photos from that day if the EMITs are visible on anyone else's rocket. My guess would be a "no", since I believe I was the only one using this igniter formula at the launch.

Greg

[jadebox]

I may need to make an igniter test video a "without element X" and a "with element X", to see if there is a discernible difference. A high-speed video would be great, but I don't have access to one of those.

I'm sure the igniter formula makes a big difference - just as stuff can be added to the propellant to make "sparky" motors.

Thinking about it, I'm having second thoughts about what I said about the sparks being "mostly" from the igniter. I've taken high-speed video of Estes igniters burning by themselves and didn't see any sparks. But, when used to ignite a motor, the sparks are visible in some still photos and videos. It might be that they only form when bits of the pyrogen are blown out of the nozzle or they might be from the propellant starting to burn.

I may play around and make some high-speed videos of other types of igniters burning.

-- Roger

[ClayD]

are those copperheads?

I would say, the slag being kicked off the blast deflector, and the ignitor being slammed against the deflector before fully burnt *or after its turned into a molten ball* are the two best plausible answers. *(maybe a combo of the two)*

NICE PICTURES!

[luke strawwalker]

I've seen this sort of thing before, in video images I got by setting the launch pad up on a milk crate and setting the camcorder down on the ground below the launch pad, looking upward past the launch rod at about a 30 degree angle from vertical... I was flying a scratchbuilt D motor powered rocket at the time... I slowed the video down with my early model digital Toshiba VCR and redubbed it back to the camcorder to get some EXTREMELY SLO-MO video... when the engine ignited, there was a SHOWER of glowing sparks that blow out of the nozzle, bounce off the deflector plate, and fly out across the camera's field of view as the motor comes up to pressure (next frame) and begins lifting off, tugging the ignitor leads with it for a frame or two...

I've caught the same phenomena on several different videos and rockets, so it's not just a transient thing. Night launches are particularly good for seeing this phenomena.

I chalk it up to loose bits of material either embedded in the propellant grain itself or on the surface of the nozzle, IE foriegn material, which is superheated and becomes molten as the surrounding propellant burns and dislodges it and expels it in the exhaust jet from the nozzle. When the motors are 'pressed' it seems that the clay and the BP tend to 'co-mingle' in the nozzle/throat area of the motor when the motor is pressed, embedding small inflammable particles of clay into close proximity with the flammable BP, so that when the BP ignites and burns, these particles then melt into "glass" and are ejected from the nozzle-- sort of like thermite welding (I read how they used to weld railroad rails together by abutting the rail ends with a specific gap in between them, clamping a steel-jacketed ceramic-lined 'pot' over the two rail ends, and then pouring a mixture similar to BP and iron filings into the pot (some kind of thermite) and then igniting it... the BP burns SO hot that it melts the iron filings into a liquid, and melts the end of the rails as well, and the heavier liquid iron flows down into the gap between the rails, completely filling it and welding the rails together. Later the pot is removed and the "flash" of metal cut/ground off leaving a smooth joint).

With APCP motors, it's probably bits of pyrogen and molten metal from the bridgewire or ignitor leads being expelled from the motor, since there should be virtually NO foriegn matter inclusions in the propellant grain or nozzle, unlike "pressed" BP motors. That would explain the smaller number of 'sparks' as well...

One time at my nephew's 4H rocket launch in Indiana at the county fair, I was sitting on the lowest aluminum bleacher seat closest to the launch pads, which were set up pretty darn close to the bleachers anyway. I was watching a rocket take off and suddenly felt a sharp burning pain in my thigh, like I was being stung by a wasp or hornet-- thought maybe I'd inadvertantly sat on one or something-- I leapt up, and swatted at my leg, and turned to look-- There on the seat, bouncing like a drop of water dripped into a HOT skillet, was a small white-hot glowing glass bead about the size of a BB, or maybe a hair smaller-- evidently some kind of "inclusion" of foriegn matter that had become molten as the BP of the motor burned around it in intimate proximity, causing it to become liquified, and expelled it from the rocket nozzle at high velocity, and bounced it off the blast deflector at just the right angle to end up wedging it between my thigh and the aluminum bleacher seat on which I was sitting... When I looked, it had burned a hole through my denim shorts and into my leg, about the size and depth of a BB.... OUCH!

What are the odds?? BUT that's the only explanation I have for it... I was only maybe 10 feet from the pads...

Later! OL JR

BTW... shuttle SRB's expel globs of molten aluminum from the fuel grains as they burn on ascent... some can be quite large...

[GregGleason]

are those copperheads?

I would say, the slag being kicked off the blast deflector, and the ignitor being slammed against the deflector before fully burnt *or after its turned into a molten ball* are the two best plausible answers. *(maybe a combo of the two)*

NICE PICTURES!

These are "home brew" bridge-wire igniters, with an eclectic pyrogen mix (something here and something there, for a two-stage dip pyrogen). It was my first time using this formula in the igniters. The molten objects, I believe, are one of the additives. But it's hard to know with any degree of certainty without high-speed movie imagery. That said, the molten objects are consistent with the behavior I have seen in other applications.

Greg

[atxcple]

hey i know that airport

excellent pictures wish i could get mine that clear

[rockets4kids]

These are "home brew" bridge-wire igniters, with an eclectic pyrogen mix (something here and something there, for a two-stage dip pyrogen). It was my first time using this formula in the igniters. The molten objects, I believe, are one of the additives. But it's hard to know with any degree of certainty without high-speed movie imagery. That said, the molten objects are consistent with the behavior I have seen in other applications.

Yup, that sure looks like the result of a little [REDACTED] over top of a little [REDACTED]!

[JDcluster]

Yeah, they even run off of my screen: a 1920 x 1080 LCD tv.


You need to reduce them before posting them.
a good size for this forum is 600 x 400.




Most cameras come with some kind of editing software...
Especially a 5k Canon Body....

JD

1) Holy cow. Those pictures are enormous - I have a 30 inch monitor, and they still extend off the side. In the future, could you use clickable thumbnails or something instead of filling the thread with enormous images?
2) I do think that those could be igniter pyrogen. It's hard to say, but that does sound like a definite possibility.

[Sandy H.]

Not entirely 100% relevant, as the pictures you posted had a custom igniter, but:

Slow Motion of an Estes A8-3 has a decent amount of sparkiness upon ignition.


http://www.youtube.com/watch?v=PUy7iBA7mZw

A regular Estes igniter in slow motion doesn't seem very energetic in this video.


http://www.youtube.com/watch?v=AC_9wOhhU7Y

I think I have a few close-ups of rockets launching that are HPR motors. I'll see it there is something interesting.

Sandy.

[rockets4kids]

A regular Estes igniter in slow motion doesn't seem very energetic in this video.

It doesn't need to be. BP motors will generally light from a bridge wire alone if it is in contact with the propellant.

AP needs much more oompf to ignite, and core-burners need to ignite all surfaces evenly in order to develop their proper thrust curve.

[edit: formatting]

[UhClem]

1) Holy cow. Those pictures are enormous - I have a 30 inch monitor, and they still extend off the side. In the future, could you use clickable thumbnails or something instead of filling the thread with enormous images?

Since our attention is called to a specific and small portion of the image, a better plan would be to crop it.

As an example I cropped the first 2741X4111 image to 592X464. I used xv to do this (a Unix image program I have used for a decade or two) but almost any image editing program will do this simple job.

[bobkrech]

Since our attention is called to a specific and small portion of the image, a better plan would be to crop it.

As an example I cropped the first 2741X4111 image to 592X464. I used xv to do this (a Unix image program I have used for a decade or two) but almost any image editing program will do this simple job.

These pictures are 11 Mb files and are really bigger than they need to be.

FastStone Image Viewer 4.0 made this 640x480 crop of your second photo in 3 clicks. The resulting file is 31 Kb. Download it free from http://faststone.org/

Bob

[daveyfire]

Slow Motion of an Estes A8-3 has a decent amount of sparkiness upon ignition.

Oh, my turn!


http://www.vimeo.com/21502243

This was one of the motors we lit using qquake2k's pyrogen. It's a dual layer grain, hence the drastically different flame structures. Same sparkles, though.

(Does that sparkle with all?)

[rockets4kids]

Ooh. Nice mach diamonds!

[GregGleason]

Here is a second attempt with the presentation.

The first pic is the one where the motor is apparently at full pressure and at the point of first motion with several (I count about a dozen) of the EMITs still visible.

The second one is a moment later, with them almost all gone. Maybe I can find out what the frame rate was.

Greg

[SteveF]

some of those, especially in the second picture, look like they could be flare and/or ghosting from the lens of the camera

[bobkrech]

Here is a second attempt with the presentation.

The first pic is the one where the motor is apparently at full pressure and at the point of first motion with several (I count about a dozen) of the EMITs still visible.

The second one is a moment later, with them almost all gone. Maybe I can find out what the frame rate was.

Greg

some of those, especially in the second picture, look like they could be flare and/or ghosting from the lens of the camera

You need to realize that the rocket exhaust flow is supersonic, exceeeding 1150 fps speed of sound by a significant amount. This high speed flow acccelerates the igniters and the plugs away the motor very quickly.

The distance from the base of the rocket to the blast deflector is less than 6". So if we guess that moving that distance requires 30 milliseconds (one video frame) it's really only an average speed of 10 mph which is really not that fast The acceleration would be ~35 G which is not very high for such a light object.

Bob

[GregGleason]

some of those, especially in the second picture, look like they could be flare and/or ghosting from the lens of the camera

Well, that could be. However, in any of the other launch photos (from the same camera on the same day) the phenomena is not present.

Here are a few pics from other flights that day (no EMITs detected).

Greg

[GregGleason]

I found one more pic that was earlier than the others. The red cap on the nozzle has just pressurized away from the motor, but only smoke with no flame is present. And yet, there are already 2 EMITs some distance away from the nozzle. For something so small they sure give off a lot of light. My guess is that they impinged off the blast plate, which gave it a vector to the side.

Sure wish I had some super slo-mo imagery of this event.

Greg

[jadebox]

I have found some evidence to support the hypothesis that at least some of the little sparkies are metal from the blast deflector.

At the last ROCK launch we had temporary blast deflectors made of a softer metal than we usually use. At the end of the day, we could see that the motors had burned through the metal.

During the day, I managed to capture a few photos like this one:

Click on the picture for a larger version then again for the full-size one.

Here's a detail from it:

The sparkly thingies seemed to be more prevalent when using the temporary blast deflectors.

-- Roger