Ok,
I've done a lot of testing of different igniter schemes. Were they ematches
like Double-ended E-match-Initiated with Dual-End Burn
Shown here when you scroll down: ttp://www.berfield.com/igniters.html
Or was it a variation of a standard nichrome igniter? If a variation of say a
"first fire" type igniter, one has to have enough current
and I would have suspected the project team would have ground tested these
igniter with the electronics that
was going to be used to start them in flight. Is that what you mean by "he
tested 6"? Did he use the altimeter that was going to fly to test
them or just a plain battery?
I doubt the theory of "thin pyrogen". If the nichrome is too fine, it may heat
up unevenly and more intensely
in some spots as opposed to others. The overlying pyrogen can react locally in
a violent fashion and "pop"
off the wire. In the process of "popping" off it fractures the wire and since
there is no more current flowing
there is no longer any heat flux, the rest of the igniter remains unburned.
Three ways around this: 1. Use a thicker gauge nichrome wire. Only problem
there is it requires more battery current to heat up
and might not be able to be
supplied by the staging electronics.
2. Experiment like crazy and try to
find the optimum (smallest) nichrome gauge that will reliably
work so you can get away with
smaller and lighter battery capacity
3. Use a little trick I learned when
a batch of my igniters seemingly turned into "poppers". It's very simple.
I take my fingers, small hemostat
or needle nosed pliers and gently crack the igniter head along its
length. I do it very gently
because I just want to introduce some transverse cracks along the length
of the pyrogen head in several
spots tip to base. I don't want the pyrogen to fall off but crack it just a
"little bit".
What I think now happens is the cracked pyrogen allows any rapid buildup of
gases to safely "vent" and allow just a fraction more time
for the pyrogen to catch. It seems that the igniter might start from the
"cracks". Once the head is burning the tough part is over.
I've had "bad" batches of homemade igniters that would work nicely after I
started cracking them. In fact, I just routing "crack" all my
homemade igniters now out of habit 'cause I hate walking back to the pad.
Yeah, I know for staging it's a different story but if using a nichrome wire as
opposed to a ematch augmented the theory should be the same
as I expressed above.
Kurt
--------------------------------------------
On Tue, 6/30/15, Casey Barker <[email protected]> wrote:
Subject: Re: [altusmetrum] Update and Questions about TeleMega on 100K Attempt
To: "Altus Metrum" <[email protected]>
Date: Tuesday, June 30, 2015, 1:48 PM
Our pyro
guy dissected it and determined that the pyrogen was too
thin in one spot, so it didn't ignite all of it. Out of
his batch of 10, he tested 6, flew his own rockets on 2, and
lit the booster with 1. Figures the sustainer would be the
one that failed.
Casey
On Tue, Jun
30, 2015 at 11:13 AM Kurt <[email protected]>
wrote:
Homemade
igniter? If so it might have popped and fractured the
nichrome wire.
Was it ematch/pyrodex or a dipped ematch augmented pyrogen
or did you have
sufficient battery juice to use a standard nichrome dipped
pyrogen igniter.
Kurt
_______________________________________________
altusmetrum mailing list
[email protected]
http://lists.gag.com/mailman/listinfo/altusmetrum
