CTI Motor Ignition

Are there any differences with CTI propellants in the speed of igniting the motor? Any propellants that take longer to ignite than others?

I need the information to decide which motors to use for air start ignition in a 2-stage rocket.

Thanks.

CTI motors usually have a special "pellet" to assist with motor ignition built-in to the top of the grain closest to the delay.

Every CTI motor I have ever used (24,29,and 38mm) ignited promptly on the first attempt with the supplied igniter.

Not all CTI propellants use the pellet. I have successfully airstarted their Smoky Sams using a Perfectflite Minitimer.
-Ken

No, not all of their propellants and not all motor sizes use the pellet. Most of the small ones do --54mm on-down. That said, the ones without still light very quickly.


Later!

--Coop

I didn't know that. I'm using 29mm reloads.

I'd like to use a Smokey Sam but am somewhat hesitant.

Leo said:

Are there any differences with CTI propellants in the speed of igniting the motor? Any propellants that take longer to ignite than others?

I need the information to decide which motors to use for air start ignition in a 2-stage rocket.

Thanks.

Click to expand...

Any CTI motors with pellets (nearly all of them in 29mm) you can be confident will light virtually instantly. I've flown a 2-stage with CTI 29mm loads in the sustainer; I forget the exact number but the time the altimeter fired the 2nd stage igniter to when the unit read >5g's (motor completely up to pressure and accelerating the rocket) was less than 0.05 seconds...

An Aerotech H115 DMS with stock (firstfire jr.?) ignitor, on the other hand, took a hair over a half second.

EDIT: I do not have any hard data for smokey loads, but I have flown clusters of the CTI 3G 24mm F-impulse smokey and skidmark loads with a central 29 or 38mm H/I blue/red/white, and they all light well before the rocket is even halfway up the rail - the two F79-SS were actually faster lighting than the central CTI red I motor...

Thanks for the answers everyone. I feel more confident now.

Using a Smokey Sam in a sustainer is really cool, I saw a video of one and the black smoke starting at altitude was pretty neat.

I'm planning on something similar for my magnum, what timer are you using and does that also detect G?
Think of K660SS then starting 2 H175 SS right after the K burnout.
Just not sure what timer to use that is safe and how I'm going to mount it all up yet

I haven't done the 2 stage HPR yet, some here have and can recommend Altimeters with airstart capability that meets NAR/TRA requirements.

Nick@JET said:

I'm planning on something similar for my magnum, what timer are you using and does that also detect G?
Think of K660SS then starting 2 H175 SS right after the K burnout.
Just not sure what timer to use that is safe and how I'm going to mount it all up yet

Click to expand...

I'm using my home-made altimeter.

rharshberger said:

Using a Smokey Sam in a sustainer is really cool, I saw a video of one and the black smoke starting at altitude was pretty neat.

Click to expand...

Like this?
https://vid424.photobucket.com/albums/pp321/new2hpr/Rocketry/Excess%20In%20Moderation/ExcessInModeration-airstartflight.mp4

CTI Smokey Sam is pretty much instant-on and great visibility for airstarts!
-Ken

new2hpr said:

Like this?
https://vid424.photobucket.com/albums/pp321/new2hpr/Rocketry/Excess%20In%20Moderation/ExcessInModeration-airstartflight.mp4

CTI Smokey Sam is pretty much instant-on and great visibility for airstarts!
-Ken

Click to expand...

EXACTLY!, not the same video I saw but the same effect, that would look abso-freakin-lutely awesome for a Nike Hercules 2 stage.

I've flown CTI several times....no ignition problems at all.

At an earlier launch this year there were several red motors that took a few seconds to ignite, including one of mine, which was a CTI I255RL. I don't know if the others were all CTIs, but all the ones I noticed taking a few seconds to light were all red flames. My launch video shows it was about 3 seconds from the click of the relay until the motor really ignited. It's in this video, the third launch around 2 minutes in (the on-board camera shot is the most obvious since you can hear the relay click). This was my first CTI red, I've fired several AT reds without noticing any unusual delay, this was long enough that I was thinking I had my first ignitor failure until it finally lit.

woferry said:

At an earlier launch this year there were several red motors that took a few seconds to ignite, including one of mine, which was a CTI I255RL. I don't know if the others were all CTIs, but all the ones I noticed taking a few seconds to light were all red flames. My launch video shows it was about 3 seconds from the click of the relay until the motor really ignited. It's in this video, the third launch around 2 minutes in (the on-board camera shot is the most obvious since you can hear the relay click). This was my first CTI red, I've fired several AT reds without noticing any unusual delay, this was long enough that I was thinking I had my first ignitor failure until it finally lit.

Click to expand...

You're using relays in your rockets? I thought that was problematic in rockets.

SpaceManMat said:

You're using relays in your rockets? I thought that was problematic in rockets.

Click to expand...

I suspect he's referring to the launch controller relay at the pad - not on the rocket, itself.

markjos said:

I suspect he's referring to the launch controller relay at the pad - not on the rocket, itself.

Click to expand...

Soory I thought we were talking about staging, makes more sense.

woferry said:

At an earlier launch this year there were several red motors that took a few seconds to ignite, including one of mine, which was a CTI I255RL. I don't know if the others were all CTIs, but all the ones I noticed taking a few seconds to light were all red flames. My launch video shows it was about 3 seconds from the click of the relay until the motor really ignited. It's in this video, the third launch around 2 minutes in (the on-board camera shot is the most obvious since you can hear the relay click). This was my first CTI red, I've fired several AT reds without noticing any unusual delay, this was long enough that I was thinking I had my first ignitor failure until it finally lit.

Click to expand...

If the igniter is good and in contact with the BP starter pellet, the motor should ignite in 0.1 seconds or so.

You could get a slow start if the e-match was not contact with the starter pellet and the propellant was barely ignited by the e-match, or if you had one of the e-matches from a weak batch that CTI received and didn't catch before the motors were shipped.

Bob