Head-end ignition through a smoke grain?

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Some of us are not as enamored with wireless devices as you are, and hope there is no intent to mandate them in the foreseeable future.
 
The only thing that needs to be mandated are the means to make complex multi staged projects as safe as possible
to avoid a severe ground accident. That might include outlawing them from given venues due to fear.
You may not care if you burn yourself up in a mishap but your widow and survivors of anyone you kill or maim
will be gunning for someone, something and $$$$$ from anyone attached to the situation. Peace. Kurt
 
The only thing that needs to be mandated are the means to make complex multi staged projects as safe as possible
to avoid a severe ground accident.

That's why I recently am redesigning my HEI for my coaxial motor to use the ET Quantum. I believe that's the safest option currently available for remote arming.
 
The only thing that needs to be mandated are the means to make complex multi staged projects as safe as possible
to avoid a severe ground accident.

They don't let you fly it if you lack a way to safely arm it. The RSO will prefer shunts or magnetic switches. The scrutiny a complex multistage gets is way more intensive than an certification flight starting with pages of emails with the RSO of the exact setup, electronics, flight profile, programming logic for staging, and also any rocketry sims. Along with a visual done with multiple people. If you are going for a high altitude record buster, they will recommend first or last flight of day to minimize the amount of spectators. The questioning began fiercely before you even showed up to fly. They want to know inside and out about that particular project as much as you know. They start with requests for the device instruction manuals to confirm what your doing.

For that SEDS project we had to develop a checklist procedure of assembly on ground without ignitor inserted into sustainer stage until nearly ready to fly then arm the electronics without disassembly on the rail to reduce risks. The only electronic I remember having on was an TeleGPS before a raven or igniter was ever touched. I don't think complex rockets should be outlawed. They require a bit of care with attention in preflight,during inspection ,and approval. Everyone gets very attentive when you have one. It's treated differently and not brushed over. Usually these involve multiple very experienced certified members reviewing the rocket before it even flies. It's already not as simple as put it on a pad and light it. People want to completely disassemble it, look at everything, take twenty minutes to an hour and help you on the flight line after its cleared by the RSO. The actual arming is next to/on the pad with sustainer pointing away from people.

And if there's still any doubts they stick it further out. And they don't just call a pad number and light it. You get some priority when you want it to launch. So maybe a huge formal process could be added but right now the RSO\LCO and others are doing everything they can to make sure it's safe.
 
Sorry for the necromancy, but I have a question on the HEI topic.

Assuming you are using a normal, open Aerotech forward closure. Could you purchase the appropriate size delay insulator from RCS (example: https://www.rocketmotorparts.com/Delay_Insulator,_2938mm/p1577809_7824126.aspx), and then cast your ematch wires in an epoxy plug filling the insulator as the delay grain normally would?

Assuming you strip the wires for say 1/2 the length of the plug facing the "internal/aft" side would there be any reason to expect the plug to leak in flight assuming the motor is built with the normal forward o-rings?

Yes, I know this makes it research.

Also, CJ, what is the black material in your closure pic?

Ok,so setting aside the safest way to arm the system, does anyone think my plan would work, or am I asking for a burn through.?
 
We had one complex rocket sit on a pad for four hours armed as weather conditions deteriorated then slowly improved until okay to launch it. And once armed on the pad no one had permission to touch it. No one has get there itis about a complex rocket launching.
 
The mistake we made was leaving the wire insulated into through the forward closure and epoxy selection. The insulated wire was visibly burnt on recovery with the burnt epoxy plug remanents.
 
Just a black G-10 disc,[top & bottom] holds the 2 rods perfectly centered in their holes. One rod is wrapped in teflon plumbers tape, then covered with shrink wrap tube to insulate the rod from metal part of closure electrically. Also provides a nice flat surface for nuts to bind against when tightened.

Hole in center is then injected with high temp epoxy [800] to fill the closure cavity. [3/4 in. deep epoxy. Disc gets charred but one with 20+ firings is still fine.

Just finished casting some BKNO3 pellets directly to ignition wire. Used 40 ga nichrome for bridge wire. [same as E-match bridge wire]. Pre tested with 9v battery and lit just fine.

Where is the e-match wire going into the system you built? And what brand of epoxy do you use?
 
Does the 40 gauge wire with match head touch the rods with nuts on inside of casing? Then on outside the circuit is completed? No holes for the wire through the closure??? Is the black cylinder the casing liner?
 
Just a black G-10 disc,[top & bottom] holds the 2 rods perfectly centered in their holes. One rod is wrapped in teflon plumbers tape, then covered with shrink wrap tube to insulate the rod from metal part of closure electrically. Also provides a nice flat surface for nuts to bind against when tightened.

Hole in center is then injected with high temp epoxy [800] to fill the closure cavity. [3/4 in. deep epoxy. Disc gets charred but one with 20+ firings is still fine.

Just finished casting some BKNO3 pellets directly to ignition wire. Used 40 ga nichrome for bridge wire. [same as E-match bridge wire]. Pre tested with 9v battery and lit just fine.

Thanks for the info. I need to convince myself I can make it all fit in the 38 mm smoke well of an Aerotech closure, but this definitely looks like the most fool-proof way to do HEI. If flame gets through this, your rocket is already confetti.
 
If flame gets through it. Rocket explodes. Violently. Feel free to ask more questions.
 
It was a H123W skidmark with the black CTI delay grain piece completely swapped for an epoxied H118 once fired variant (no powder) drilled through center with igniter and insulated wire inserted through this center hole then epoxied that closure area before inserted into casing. Not kidding about the we blew up a motor on a SEDS flight this year. I don't blame the fuel propellant. I blame a lack of knowledge about proper HEI construction. Second multistage and HPR flight of year by novice college team no mentors. We picked two H's to meet a waiver alt on a MD. It stopped climbing at 3,703ft I was on the ground station with the FCC license. We ball parked 11kft in sims without the kaboom.
 
I plan on getting an L-2 next spring/summer before I mess with Hei. I want to learn how to do this properly as next semester/year team is wanting HEI and they have zero experience. They don't want to blow up a motor like we did.
 
It's customary to use accurate terms to describe this sort of thing. Just because fire comes out both ends doesn't mean it didn't merely burn very quickly.
 
We only had rocketpoxy and Cotronics 4700 epoxy on hand at time of assembly. 4700 was ruled out by oven cure not possible with igniter live and inserted through closure. Post flight-Old O-rings were admitted reused by a dude on the team who thought it "didn't" matter. Exterior surface of O-rings looked fine. He's still convinced the epoxy on the inside of the closure had a slight air gap about the size of diameter of a pencil on the inside of the closure, halfway deep. I thought it was the TG of rocketpoxy was too low. We didn't have any R45 or a custom machined closure. I never saw the CTI motor assembly so I'm trusting the guy's recall of incident.

The forward plugged closures for a 38/480 RMS had Cotronics which survived. ( we had converted open closures to plugged previously in Utah). I didn't do any of the CTI motor assemblies. I did the Aerotech ones which worked and I assumed the others used new o-rings. We weren't doing HEI in Utah on any Aerotech...That's all the details I got.
 
Where is the e-match wire going into the system you built? And what brand of epoxy do you use?

This is a 54 CTI closure. 2 matches are used. Pellet passed into top grain has a hole in it.
One match goes through hole/bent upwards to fire into pellet.
2nd match sits on top of pellet, So in perfect world both fire ...from both sides into pellet.
If one fails, other is backup.

DSCN0119.jpg

The 29CTI version both matches [I always use 2] are on top of pellet.

Most users just go with one match..

AT version,I use either a pyrodex pellet pushed into top grain, then Match on top.
For 75's/98's the cores are big,, so match [2] are taped to [1] each side of pellet [BKNO] and lowered into top grain.
All closures are built basically the same & allow for attaching 1 or 2 match wire leads.

Top side the long lead wire goes into a slip fit molex connector on the av-bay.

Our cast pellet onto ignition wire was tested with 9v battery today, [several] and worked great. We even stuck one [tiny 1/3 gram] in a 54 soda can motor today & used the 12v launch system. Again...it worked.
So after getting a bit further, I will figure out casting 2 ignition leads into pellet for redundancy.


The epoxy....wish I could tell ya, but....since this has been an ongoing project & they are being sold, no for now. I will tell ya this, it's for potting electronics in high temp environments ,costs 400.00 gal. and is 1 part heat cure . Closures are placed in a special built oven and cured under several different temp ramp ups for 10 hrs.

The eyebolt is for recovery attachment/threaded into solid aluminum in all sizes. They are all re-usable.
The AT version is single use and requires the special umbilical cord which is large and bulky& costly.

AT standard 54mm tapped closure is 70.00 one of these is 54.00
 
It's customary to use accurate terms to describe this sort of thing. Just because fire comes out both ends doesn't mean it didn't merely burn very quickly.
Normally casings and airframe sustainer tubes are recoverable. This wasn't found after searching. We don't even have slight confetti pieces to show for it.
 
This is a 54 CTI closure. 2 matches are used. Pellet passed into top grain has a hole in it.
One match goes through hole/bent upwards to fire into pellet.
2nd match sits on top of pellet, So in perfect world both fire ...from both sides into pellet.
If one fails, other is backup.

View attachment 334483

The 29CTI version both matches [I always use 2] are on top of pellet.

Most users just go with one match..

AT version,I use either a pyrodex pellet pushed into top grain, then Match on top.
For 75's/98's the cores are big,, so match [2] are taped to [1] each side of pellet [BKNO] and lowered into top grain.
All closures are built basically the same & allow for attaching 1 or 2 match wire leads.

Top side the long lead wire goes into a slip fit molex connector on the av-bay.

Our cast pellet onto ignition wire was tested with 9v battery today, [several] and worked great. We even stuck one [tiny 1/3 gram] in a 54 soda can motor today & used the 12v launch system. Again...it worked.
So after getting a bit further, I will figure out casting 2 ignition leads into pellet for redundancy.


The epoxy....wish I could tell ya, but....since this has been an ongoing project & they are being sold, no for now. I will tell ya this, it's for potting electronics in high temp environments ,costs 400.00 gal. and is 1 part heat cure . Closures are placed in a special built oven and cured under several different temp ramp ups for 10 hrs.

The eyebolt is for recovery attachment/threaded into solid aluminum in all sizes. They are all re-usable.
The AT version is single use and requires the special umbilical cord which is large and bulky& costly.

AT standard 54mm tapped closure is 70.00 one of these is 54.00

Are there plans to produce an AT38 closure for sale? If so, available before Airfest?
 
Thanks for the info. I need to convince myself I can make it all fit in the 38 mm smoke well of an Aerotech closure, but this definitely looks like the most fool-proof way to do HEI. If flame gets through this, your rocket is already confetti.

The standard screw on closure is a pain. You must be extremely careful during assembly, so whatever you use doesn't get twisted up, catching on top grain, when screwing the closure. Ideally I would think you want your pyrogen centered inside top grain.

May I suggest using the "floating" closure that comes with the RAS system, and modifying it. No need to rotate it, slide down to top grain & screw the ring closure on.

Screen Shot 2017-12-16 at 11.42.58 PM.png

This is the type we make, since being machined from scratch, the top is flat with room for eyebolt.


I'll take some pictures tomorrow and post.
 
The only thing that needs to be mandated are the means to make complex multi staged projects as safe as possible
to avoid a severe ground accident. That might include outlawing them from given venues due to fear.
You may not care if you burn yourself up in a mishap but your widow and survivors of anyone you kill or maim
will be gunning for someone, something and $$$$$ from anyone attached to the situation. Peace. Kurt

I understand your concern, Kurt. The worst accident that happened at a Tripoli launch was a ground accident involving a multi stage rocket. That’s exactly why our Safety Codes attempt to create layers of protection. Our recent rule change that prohibits spectators from accessing the HPR range is one layer. The rule requiring that the rocket be pointed safely downrange or safely vertical before inserting any motor starters is another level. The rule that prohibits arming any energetics or inserting starters except when the rocket is the safe distance away from anyone other that required personnel or safety personnel is another layer. By all means, wireless switches (or any switches that can be operated safely) and which are reliable enough to protect your rocket in flight are vital. The whole system of rules has been designed and tweaked over time to try and make sure that we never encounter the nightmare scenario you imply. The strategy of having multiple layers of protection is so that when our imperfections result in a mistake the other layers work as backups to prevent serious injuries.
I think we have enough rules, but any Tripoli member may certainly suggest rules if they think they’re needed. But they must be specific.
Thanks,
Steve


Steve Shannon
 
You can PM with where to buy CTI 29mm HEI closures Jim. I know a team that could use a pair. You have the experience at making these work.
 
Are there plans to produce an AT38 closure for sale? If so, available before Airfest?

Yes they are 38.00 for the "floating'' closure. You will need to purchase the screw on ring as shown in pic.
A run of 6 was done in each size, there is 1 left in 38 as of now in stock. The way these things are going, there will be larger runs made. Over 50 of varying sizes and types [from 29-98CTI- AT-Snap ring types] are currently in field and being used.

I'll put up some pics of most of them Sunday.

Prices are simple: 29mm = 29.00 38mm=38.00 54mm=54.00 and so on. Unless some custom work required.
 
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That's why I recently am redesigning my HEI for my coaxial motor to use the ET Quantum. I believe that's the safest option currently available for remote arming.

That's why I mentioned it as a possibility. I have nothing against shunts. There has been some intelligent discussion on the forum here about shunts but unless one tests out the failure mode, it's nothing more than a false sense of safety.
Lithium batteries can pound a lot of current through a parallel shunt and can light off an ematch augmented igniter anyways.

Unless of course one is counting on their FETs to burn up and act as a fuse. I for one do not want to be standing next to
A research L and up motor if there is an accidental ignition event. Kurt
 
There was a lawsuit against TRA where a woman as spectator was standing 30ft away from a LDRS launch and she got burnt 5% of body by the exhaust. There's a good reason they don't allow spectators around HPR launch pads. Maybe she really didn't understand rockets have hot combustion processes. It was likely her lack of respect and experience around motors that size. They don't let passengers on light general aviation flight lines without crew, because people have walked into whirling propellers which appear nearly invisible when turning. There's a faint red plaque of a reminder of that at every airport. You see a faint outline of an arc. And in New Jersey people get snark when you're from out of state and pump own gas. I told em if you can't pump gas into a car you shouldn't drive. They called me a hick. But I guess someone somehow blew up a car and sued there now it's a law. Touch the metal car it grounds it from static electricity before pumping. Sheesh. I'll never live in Jersey.

We used a magnetic switch on our second multistage rocket this year and never looked back. There's always a risk with anything. Your goal in rocketry or aviation is risk reduction. And you will face daily risks higher than normal.
 
There was a lawsuit against TRA where a woman as spectator was standing 30ft away from a LDRS launch and she got burnt 5% of body by the exhaust. There's a good reason they don't allow spectators around HPR launch pads. Maybe she really didn't understand rockets have hot combustion processes. It was likely her lack of respect and experience around motors that size. They don't let passengers on light general aviation flight lines without crew, because people have walked into whirling propellers which appear nearly invisible when turning. There's a faint red plaque of a reminder of that at every airport. You see a faint outline of an arc. And in New Jersey people get snark when you're from out of state and pump own gas. I told em if you can't pump gas into a car you shouldn't drive. They called me a hick. But I guess someone somehow blew up a car and sued there now it's a law. Touch the metal car it grounds it from static electricity before pumping. Sheesh. I'll never live in Jersey.

We used a magnetic switch on our second multistage rocket this year and never looked back. There's always a risk with anything. Your goal in rocketry or aviation is risk reduction. And you will face daily risks higher than normal.

Without actual knowledge, please do not comment on incidents that you heard about. Nobody needs false rumors.


Steve Shannon
 
It was a H123W skidmark with the black CTI delay grain piece completely swapped for an epoxied H118 once fired variant (no powder) drilled through center with igniter and insulated wire inserted through this center hole then epoxied that closure area before inserted into casing.

That's just APCP. It's not explosive, we proved it in a protracted, expensive court battle against the ATF. APCP motors do not explode even in failure mode. They over pressurize. It's a big difference and a very important one. For future reference "cato" is the correct term.
 
I don't know how it ended. But here's an external link to a news website that google picks up. Kurt's comment of not wanting to stand next to an L when it ignites made me cringe a tad.
https://www.sandiegoreader.com/webl...t-filed-over-injuries-suffered-at-large-and-/
People like this woman put rocketry at risk. Maybe this media incident is a false rumor. Or spectators really don't know better.

And it should make you cringe. An over pressurization event is not to be taken lightly especially if you were standing close to the rocket.

To Steve, I am not promulgating rules here. The suggestion of using proven Electronics can make it a little easier and safer for the newly experienced to do a two-stage flight safely. Simply sticking a big fat wire shunt in parallel to an ignition circuit and saying it's good without testing it directly is a false sense of security. I don't care how much math anyone does unless it's tested in the failure mode, it's unproven.

I'm not saying that a shunt can't work, I'm saying that one needs to be certain it will work. With the electronics makers making bulletproof circuits on their outputs that can handle High current loads that lithium batteries can provide, the current can bypass the parallel shunt and activate the ignition process. That's bad mojo my friend. Kurt
 
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