Sorry for the dumb question, but at the last launch I left behind a box with
4 igniters that came with the Cesaroni pro38 reloads. I was told not to use a "HOT" igniter to replace the lost ones, what would you recommend as a replacement e-match? I do not have an ATFE LTC so I'm stuck with few options, I however use nichrome/bp igniters for just about everything else they work with aerotech would they be ok? How about hotshot? Besides the starter grain, why would a pro-38 be any different then any other APCP reload?
The Pro38 igniter is an Oxral e-match, so assumedly any igniter which provides enough energy to initiate the BP starter pellet (and won't cause nozzle blockage) would work. Not sure quite how the regulation works for you, but a standard e-match (Daveyfire/Oxral) would seem to be an appropriate direct replacement.
The only difference I can think of (top of the head) is that Pro38 uses a thermoplastic-based fuel rather than HTPB based. Not sure how that would affect ignitor choice.
The only reference I have seen to using non-standard igniters with Pro38/54 motors was here:
From what I've heard, the only times people have had Pro38/54's fail to ignite (over here at least) is when the e-match hasn't been in contact with the starter pellet. As such I would assume that any igniter which delivers as much energy as the original e-match would light the starter grain and thus the motor.
Not all the CTI igniters are the same. You didn't say which reloads you had. Most have the standard Oxrail/Davyfire though.
Your best bet is to ask CTI. Send them an email and list which reloads you have so they can recommend an appropriate igniter. If Hot Shots are available to you ask if they would be okay to use as a replacement.
I can tell you that the igniter that came with my 5 grain I540 was not a standard igniter.
You could use an aftermarket igniter with the Pro38's, as long as you are diligent about making sure it is all the way up the core and in contact with or in very close proximity to the igniter pellet. But don't use something with 5 grams of thermonuclear goo on it, you won't change a thing about how quickly the motor ignites. Just use something that will ignite the igniter pellet, and that doesn't take much - your description of a nichrome-BP igniter sounds suitable.
The reason we tell people not to use aftermarket igniters is as follows:
(1) It is unnecessary - properly installed, the supplied e-match will light the igniter pellet every time.
(2) The main reason: Pyrogen dipped igniters will ignite the propellant directly, the e-matches will not. Using an igniter with pyrogen overdip can (and has) caused the occasional mid-port ignition and subsequent disaster. One would think that with that easily ignited pellet at the top of the core, that even if you accidentally touched off the propellant lower down the core the darn thing would still go and the motor would function nominally. This is true most of the time, however, there have been notable exceptions. Stagnated cold gas in the core above the ignition event is far more stubborn at allowing fire transfer than you might think - it is a far better insulator than you'd suspect.
One fellow sent us the remains of a 6G casing and reload parts, with an odd description of the event. What we recieved was the upper 2/3 of the casing, a hardened puddle of aluminum slag, and the remains of the upper part of the reload inert bits. Hmmm we thought... how did this happen. As he decribed it, the button was pushed, there was a pop from the ignitor, then nothing more than a road flare flame from the rear of the motor, that lasted something like 1-1-/2 minutes. Eventually molten aluminum was seen to be dripping from the rear of the motor..
We asked the usual questions, did you get the igniter all the way up the core, did you use the supplied igniter, etc etc. Yes to all.
Baffled, I scratched my head overnight on the issue, wondering if the nozzle had ejected at ignition, or if there was a blind drilled grain lower down, or had we shipped a whole batch of propellant missing most of the oxidizer (not likely), or what. But the problem was, as he described it the nozzle did not blow out, and he had said he used the stock igniter which I knew, or "knew" let's say from experience, would not ignitie the propellant directly. I came to the conclusion that it must have suffered a mid to lower port ignition somehow, sothought I that maybe the matches will on occasion ignite the propellant directly. It is not unheard of that the match might snag between grains and cause a misfire, it has happened a few times.
So, armed with some e-matches, a couple of 6G cases and J330 reloads I went out to the test stand to play. I tried getting a midport igniton with the stock e-match. Nothing, and in fact I have never successfully ignited Pro38 standard propellant directly with an e-match.
Next step - I rigged a pyrogen igniter using an Oxral match and about two inches of double over igniter cord, and put this about 2" into the core.
A 2 minute road flare, and after about a minute the nozzle just sort of fell out, and the bottom couple of inches of the casing melted away into a puddle of aluminum. The motor never even came close to reaching operating pressure, I doubt it would even have moved under its own power lying sideways on the asphalt. The reamins were hard to tell apart from those sent to us by our customer.
So, a quick email to the customer to report our findings. AHA! He confessed, after thinking about it, that he had indeed used an aftermarket igniter, and the conclusion was that it must have snagged in the core and felt like it was all the way up.
We all laughed about this, because on the very positive side we had learned something important from the event.
Now, all that said, in the installation instructions for the Oxral igniters (now supplied with all Pro38 2G and larger reloads) I describe cutting off a short piece of the red plastic tube used to shunt the bare leads, and sliding this over the match head. This single feature increases igntion reliabilty hugely - without the sleeve the output from the ematch goes in all directions except straight back of course. Problem is, we want that output to all go forwards towards the igniter pellet. The plastic sleeve accomplishes this - I did witness paaper tests to prove the idea, plus some hurried field testing when someone had problems with a Pro54 J. So do yourselves a favor and don't skip this step - it is described on the little paper instruction sheet accompanying the igniter. If this is done as described, the match will ignite the propellant reliably even when separated by a short standoff distance. But don't intentionally cause there to be a standoff distance - get that igniter right up to the top.
FYI, we used to supply Daveyfire M28F's with all motors. Now, we only supply them with the Pro38 1G G reloads, as they have nozzle throats too small for the Oxral. Everything else gets Oxrals. These are the only two types of igniters we provide.
Thanks Mike for a very informitive post! This is one of the reasons i always recomend cesaroni to friends. Great company, great suport, great product! if i say great one more time do i get a free shirt :)
Typically, people trying to ignite a large motor (especially single-throat L or M motors) will use a 1/8" dowel with several igniters taped to it, each igniter having been augmented with some sort of pyrogen. To avoid over-pressurizing the motor, the entire assembly should be able to *easily* slide up through the nozzle without blocking a significant portion of the nozzle throat.
This way, the igniters are held right at the head end of the motor, yet the entire assembly can be easily ejected as the motor comes up to pressure. If the whole thing can't slide easily out of the motor, you risk nozzle blockage and a CATO due to overpressurizing the motor.