Terry,
An altimeter is unlikely to be able to directly fire anything requiring
more current than an ematch (the Quest Q2G2 counts as an ematch). So, the
issue becomes, "How do I get an ematch to light an APCP motor?"
Depending on how much room you have in the core and nozzle throat, you've
got a few options:
1) Copper thermite. It's easy to ignite, and throws molten copper at the
motor core, lighting it easily. Drawback is that you need a big enough
throat and core to accommodate a "package" containing the powder. Great for
K and up, but hard to use on anything much smaller.
2) Magnalite, Igniterman, or similar pyrogen "dips". These can be good, but
tend to dry out on the bottle, requiring constant thinning with acetone or
MEK. May be hard to come by nowadays.
3) Pyrodex pellet or black powder motor piece wedged or glued into the top
grain core. If it will fit, a Pyrodex pellet or the unwrapped black powder
grain from an Estes mini motor can be pushed into the top end of the upper
grain core. If it's too big, break one gently with a hammer, and use a
small chunk the same way. Place the ematch against the Pyrodex or black
powder chunk, and it will light it easily.
Hope this helps!
Rick Dickinson
On Wed, May 23, 2018, 10:16 PM Terry McKiernan <terry@xxxxxxxxxxxxx> wrote:
Hello all,
Still trying to get my 2-stage high-power rocket project ready for the
June launch. I have a question about igniters I hope you can all help
me with. Basically I am looking for a recommendation: should I use the
igniter that comes with the motor, or buy an igniter more suitable for
airstarts, if there is such a thing?
My design uses two 3" rockets which are outfitted with Aerotech motor
retainers, and I have Aerotech casings, so I've only used Aerotech
motors with them. These are 38mm motor mounts and I'll be using class H
or I motors for the sustainer stage.
I am concerned that the Aerotech motors will be hard to start with a
small battery that can fit in a payload bay. I found a few posting
online indicating that Aerotech's igniters require 12V and can pull 15A+
momentarily when they short & burn. This is OK I guess for a ground
control system with a big fat car battery or marine battery attached.
But, it seems like an awful lot for an altimeter battery.
The airstart will be controlled an a Raven altimeter, and it does
support having a small 1S LiPo for the altimeter and a second battery up
to 20V for the pyro channel. And, yes, I can get a 2S 30C 12V LiPo on
Amazon. So, theoretically it should be able to start the motor using
the Aerotech igniter.
Alternatively I could buy some other igniter, or ematch, or make my
own. Any recommendations?
I am tempted by this ClusterFire kit, which promises 1 second burn at
5400F, using 6V and 2.3A:
https://www.rocketflite.com/store/index.php?route=product/category&path=61
Or maybe H-3 Compound?
https://www.apogeerockets.com/Rocket-Motors/Motor-Starters/H3-Igniter-Dip
Or MJG?
https://electricmatch.com/pyrotechnics/see/6/5/mjg-firewire-initiator
Note that at the March launch my Aerotech igniter on one launch failed,
and I tried an MJG ematch I had bought from buyrocketmotors.com as a
replacement and it failed, and then I bought a FirstFire and it worked.
But, that was a ground launch not an airstart. In any case my only
experience with MJG was not good.
Or Slim Gem?
https://www.apogeerockets.com/Rocket_Motors/Motor_Starters/Slim_Gem_Starters
One thing i note about Slim Gem is they also require 12V just like
Aerotech. Also according to the Apogee site they burn at 1400F, vs. the
5400F claimed for ClusterFire. Quite a difference...
Or Quest Q2G2?
http://www.buyrocketmotors.com/quest-q2g2-3-initiators-6-pack/
Or ... probably lots of other choices out there?
Thanks for any suggestions!
Terry McKiernan
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