Flashbulb ignition...

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I'm going to date myself AND show my ignorance with these questions :confused: ...

Back in my youth, large clusters were ignited using a technique called flashbulb ignition, which I believe was developed by John Langford - I used it to ignite a scratch built 8 engine cluster when I was in my late teens. It was extremely reliable, though you had to make sure your launch controller was "flashbulb safe".

So my questions are...

1) Is it still used? and

2) If not, then what is?

Thanks in advance...
 

Missileman

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I have heard of flashbulbs being used like that but have never seen it.
Clip whips are mostly used on clusters up to around a dozen ,or sometimes more, motors.
Very large clusters of 30, 40 or more I have seen flashpans used.(usually not all motors lite.)
Watch the rocket challenge tomorrow on the discovery channel.
Emily lights a cluster with a flashpan.
Edit: I don't know why but I was only thinking BP motors.
I have seen clustered composits lit using low current ematches dipped in pyrogen.
 

JDcluster

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I've used it a bunch of times with nearly 100% success rate ( CLay was blocking contact with propellant: Estes D's).


E-mail me for instructions
[email protected].



Works almost all the time with an added kick of watching the flash bulbs go off from a distsance.



JD
 

powderburner

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First off, Bill, welcome to TRF

Flashbulb ignition is not used too much anymore for a couple reasons. Probably the main reason is you can't find flashbulbs anymore, at least not easily. Back in those days, every corner drug store, grocery store, and department store that sold photo film also had racks full of flash bulbs. Not any more.

Another part of the demise of this system was the fuse. Remember the stuff that you taped to the flashbulb----the fast burning fuse that plugged into the nozzle and actually lit the fuel grain? Our new, improved, modernized government has reclassified that fuse as an explosive (go figure) and you have to be a LEUP holder (low explosives user permit) to possess it.

How big is your cluster? (tell us, and we'll tell you how crazy you are!) Lots of people have had moderately good success with flashpan ignition for very large clusters. This approach also has the advantage of not requiring a huge battery and a snake-nest of ignition leads. But it roasts the lower end of your rocket, ruins the paint, and can burn away some serious fin area (right before you really need it).
 

Powderburner,

Not very big - was thinking about 5 engines (4 13 mm and 1 18 mm, as in the Fliskits 5 motor cluster mount). I just hate dragging big power supplies out when I launch :p

So one now needs a LEUP for thermalite fuses? Wow. Way back when, I didn't use thermalite; I took the ignitor stick that came with the Centuri 'Sure Shot' ignitors and used those. Don't recall their composition - are they legal without an explosives permit?

I have a few left, along with some flashbulbs, and was thinking of lighting a cluster bird with them - just out of nostalgia.

I've seen (on video) the flash pan cluster ignition - I kinda figured it would mess up the bottom of the rocket a bit. ;)
 

havoc821

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Go to pyrotek.org

They have the new stuff called thermAlite (notice the A not the O)
It is very similar to thermolite and it is not regulated. It is on their site under timing fuse. It is fairly cheap.

Are you a member of HARA? I know you live near Hobby Town because we spoke about launching togehter that one time. I was wonderg that if you ordered some of that fuse could I jump in with you and we could split shipping costs because I was wanting to get some too for myself (er... my Staurn V) and when you get it we could meet up at a HARA meeting and exchange the stuff. Of course I would pay you before you ordered it. Let me know what you think if you do get some of that!

Also, got any pics of that rocket with the cluster you were describing? We like pictures! :D
 

powderburner

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If you only need a little (for one or two launches) you might not want to mess with ordering a big pkg of thermAlite, or thermOlite, or therm anything else, but you could use a near-equivalent

You could try making your own black match fuse. That is the string dipped in "stuff"----put it inside a tight paper tube and I understand it burns very quickly. Do a search here on TRF and on the rest of the 'net to see how to make it.
 
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