First fire jr ignition issues

[ExoResearch]

I attempted to launch a G series motor with a first fire jr ignitor. I don't have a regular launcher and am using a old 11v drill battery. (I know I can just buy a launcher, I want to try to do it this way)

However, at launch, the ignitor lit and blew out of the motor before igniting it. I suspect that the amps are too high. Its about 250mv. I can't seem to find specs on what is the proper amps. Does anyone know or have specs for what amps are needed, so I can step down the amps as needed?

Thank you in advance!!!

 

[ThirstyBarbarian]

It’s probably not the amps. Sometimes igniters just spit out. It’s always good to buy a supply of extras.

Have you used this type of igniter in a composite motor before? If you have, then you probably know this, but if not, the igniter needs to be inserted into the motor all the way to the forward end of the motor until it stops. It needs to light the forward end of the propellant grain. If it lights anywhere else, the motor can chuff and spit the igniter, then fail to build pressure and go out. So when you get the igniter shoved all the way in and touching the forward end, hold it there, bend the wires sticking out back forward alongside the motor nozzle, and use the provided cap or rubber band (or a piece of tape) around the nozzle to hold the igniter in position. That will keep it from sliding out of position or popping out before pressure starts to build.

Some motors are just hard to light. If I have more than one igniter fail to light the motor, I take a piece of wire or skinny probe and scuff up the propellant grain a bit, and I switch to an “enhanced” igniter that has been dipped in some special pyrogen.

 

[afadeev]

at launch, the ignitor lit and blew out of the motor before igniting it

What exact motor were you trying to light?
How old is it (oxidized grain cores can inhibit ignition)?
Pictures of your motor + ignitor + plug setup?

There are many plausible explanations for why a motor grain may start coming up to pressure, then spit out the ignitor, and flame out.
I would not over-analyze this, and simply insert another ignitor and try again.

Some motors are just hard to light. If I have more than one igniter fail to light the motor, I take a piece of wire or skinny probe and scuff up the propellant grain a bit, and I switch to an “enhanced” igniter that has been dipped in some special pyrogen.

Something similar happened to me yesterday - AT D24 motor spit out the ignitor and flamed out on the pad.
Very unusual. I replaced the ignitor with the same, and off it went.

 

[ThirstyBarbarian]

Something similar happened to me yesterday - AT D24 motor spit out the ignitor and flamed out on the pad.
Very unusual. I replaced the ignitor with the same, and off it went.

Yeah, it happens sometimes, especially with older motors. My last hard-to-light one was a single-use AT G78-4 Mojave Green. I think that propellant can be a bit difficult, but once it goes, it goes pretty good. I spent 2 normal a First-Fire Junior igniters without the motor igniting. Pulled it off the pad, borrowed a sharp, skinny tool from a friend to scrape the inside of the grain a bit, and got a dipped igniter. Then it went with no hesitation!

At a club launch, a failed ignition is one of the most annoying failures, in my opinion. I attend big launches, so if the rocket fails to launch, you are allowed to “recycle”, stay on the pad and install another igniter, but it can take forever to get back to your turn again. On a big day, they may run through all 20+ pads before getting back to yours. I hate the way it delays my whole day. Usually it means there at least one planned flight I can’t do.