[F-FT] Question/thought on Aerotech delays



You know Matt too!?!

Okay.
Jerry
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Jerry Irvine, Box 1242, Claremont, California 91711 USA
Opinion, the whole thing. <mail to: snipped-for-privacy@gte.net>
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As I just posted, I think this just happened to me. It was VERY different from a "chuff" and took maybe 3-4 seconds. A "chuff" is what you get from lighting the propellant somewhere other than the top, where it doesn't pressurize fully and the burn rate drops back down. The sound was VERY different.
    Bob Kaplow    NAR # 18L    TRA # "Impeach the TRA BoD"         >>> To reply, remove the TRABoD! <<< Kaplow Klips & Baffle:    http://nira-rocketry.org/LeadingEdge/Phantom4000.pdf www.encompasserve.org/~kaplow_r/ www.nira-rocketry.org www.nar.org
"To enslave men, successfully and safely, it is necessary to have their minds occupied with thoughts and aspirations short of the liberty of which they are deprived. A certain degree of attainable good must be kept before them." Frederick Douglas, "My Bondage and My Freedom," 1855
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David Schultz wrote:

I had two igniters fail on me at NSL (these were not Copperheads). In both cases, the igniter burned slightly were the 'junction wire' was, which was about 3/4 inch from the end of the igniter -- but none of the rest of the pyrogen burned. Thus, in both of these igniters, there was a 'burned spot' about 3/4 inch from the end, and no other visible damage. Now, if this is typical of a failed igniter, that means it would be typical for a misfire to NOT light the delay, because the delay will only be lit by the igniter if the whole pyrogen portion burns. Therefore, I would assert that your hypothesis is false (based on the only iginiter failures that I've PERSONALLY seen).
David Erbas-White
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David,
I think I saw a case of the delay igniting first, then the motor igniting last month at a launch. It was Bob Kaplow's rocket, so he should be able to chime in with the motor type and what igniter he used. We could see smoke from the igniter, then a little flame, then nothing, then a little more flame, and then it came to life. It wasn't a normal chuff like I've seen before, this was different. I can't tell you how many seconds it was between first smoke and liftoff, but I'd guess 4-5 at a minimum. The ejection charge fired while the thing was under thrust - or dang close to the end of it, and the rocket hadn't gotten more than a few hundred feet up. Bob did a good job building that rocket, because it didn't rip itself apart.
Bob Wiersbe
David Schultz wrote:

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I distrust him. I distrust his arguement.

Jerry
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Jerry Irvine, Box 1242, Claremont, California 91711 USA
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more
Since I

that
I asked a motor manufacture after reading this report.
he told me the ignitor does not light his delays.
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Would that be the one that has the 'bonus delays?'
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I don't think it's NARTS, it's R&D Judge Joyce Guzik who has been collecting R&D reports for many years. Of course, it's probably to facilitate putting together the NARTS summaries.
    Bob Kaplow    NAR # 18L    TRA # "Impeach the TRA BoD"         >>> To reply, remove the TRABoD! <<< Kaplow Klips & Baffle:    http://nira-rocketry.org/LeadingEdge/Phantom4000.pdf www.encompasserve.org/~kaplow_r/ www.nira-rocketry.org www.nar.org
"To enslave men, successfully and safely, it is necessary to have their minds occupied with thoughts and aspirations short of the liberty of which they are deprived. A certain degree of attainable good must be kept before them." Frederick Douglas, "My Bondage and My Freedom," 1855
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Yes.. The delay is timed so that it starts burning at the same time as the motor, so the ignitor should be at the top. Will it have much difference if it's down a bit (a small bit)(in practical use)? Probably not. Halfway down, you might run into some weird problems. The only reason that you'd do "halfway" is that the leads on the igniter are too short, in which case, you got the wrong igniter...
One big technical issue, is CrapperHeads. If you use them, be sure to have a "fallback igniter" (non Crapperhead)!

possibility?
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I maybe luckily have not had any problems with copperhead ignitors. Now I am going to qualify this with the fact I have not been at this as long as some have but still the way some talk they should never in a million years light a motor. I have only had 3 that have not worked properly (as it first appeared) but by looking over things it was my mistake that was the cause. Maybe I have been lucky but I have a bundle of them and plan on using them till I have a reliable cheaper alternative.

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The probelms would be in proper motor ignition, not from the delay.

Copperheads, for all their faults have a VERY energetic pyrogen. *IF* you can get them to fire, they do a pretty good job. If you wnat to try an interesting experiment, get a Quest Tigertail, and an Estes Solar ignitor. Fire each on your workbench on a flameproof surface, and compare the results. You'l be amazed.
That said, I use Firestar / Magnelite et al for igniting all my composite motors.
    Bob Kaplow    NAR # 18L    TRA # "Impeach the TRA BoD"         >>> To reply, remove the TRABoD! <<< Kaplow Klips & Baffle:    http://nira-rocketry.org/LeadingEdge/Phantom4000.pdf www.encompasserve.org/~kaplow_r/ www.nira-rocketry.org www.nar.org
"To enslave men, successfully and safely, it is necessary to have their minds occupied with thoughts and aspirations short of the liberty of which they are deprived. A certain degree of attainable good must be kept before them." Frederick Douglas, "My Bondage and My Freedom," 1855
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I suspect the reason the igniter is placed all the way at the end of the propellent grains has more to do with making sure all the grains light simultaneously than igniting the delay with the igniter. The solid boosters for the Titan missile had a configuration not much different than an RMS reloadable, but no delay. They were ignited with what amounted to a small engine at the top of the stack and the reason given was that this would ensure that the whole stack lit at once. If ignition occurred at the bottom, it would not propagate rapidly to the top. If the igniter is all the way to the top of the grains, it really doesn't matter whether it lights the delay directly or lights the top grain which then lights off the delay along with all the other grains. If the igniter placement is lower in the engine, the delay should not ignite until the top grain does. I'd say the bigger problem might be that full thrust would not be developed quickly and the rocket might not be going fast enough to be stable when it leaves the rod.
Larry
David Erbas-White wrote:

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Larry wrote:

Late ignition of the delay element would give you an undetermined amount of "bonus delay", regardless of thrust issues.
Motors with difficult to light propellant/grain configurations, where the delay element lights immediately, but the propellant does not, would "waste" delay time, prior to full motor ignition. Thus giving you a "short" delay in flight.
Any mechanical anomalies associated with the delay element, seen or unseen, can effect delay functionality. Small bubbles or "voids" will effectively shorten a delay, as will hot spots or "plumes" that might cause uneven erosion of the delay. "Burn through" of the delay liner will also shorten the effective delay.
With reloadables, You can add assembly anomalies to the equation, such as wrong delay element, improper installation of delay element, greasy delay element.
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I'd have to say NO. The reason for the ignitor placement is to insure proper ignition of the propellant grain, not anything to do with the delay.
Take for example, the 29/40-120 E16 reload. There's almost 2 inches between the propellant grain and the delay. The ignitor is placed at the top of the propellant grain. The delay has no problem igniting anyway.
BTW, the original instructions for these motors had the propellant placed at the delay end of the motor instead of hte nozzle end. They work fine that way too, except a WL motor ends up producing black smoke instead of the characteristic WL smoke. Probably due to the spacer erosion betweent he propellant and nozzle. or maybe due to some bizare gas flow through the empty space.
    Bob Kaplow    NAR # 18L    TRA # "Impeach the TRA BoD"         >>> To reply, remove the TRABoD! <<< Kaplow Klips & Baffle:    http://nira-rocketry.org/LeadingEdge/Phantom4000.pdf www.encompasserve.org/~kaplow_r/ www.nira-rocketry.org www.nar.org
"To enslave men, successfully and safely, it is necessary to have their minds occupied with thoughts and aspirations short of the liberty of which they are deprived. A certain degree of attainable good must be kept before them." Frederick Douglas, "My Bondage and My Freedom," 1855
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kaplow snipped-for-privacy@encompasserve.org.TRABoD (Bob Kaplow) wrote:

correct.
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Jerry Irvine, Box 1242, Claremont, California 91711 USA
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