Thermite or dipped igniters for reliably igniting 4 29mm I205's?

The Rocketry Forum

Help Support The Rocketry Forum:

DrewD

Well-Known Member
Joined
Oct 14, 2014
Messages
67
Reaction score
0
So i'm planning on flying a cluster of 4 Aerotech I205 DMS motors for an upcoming launch. And of course the question arised on how I can light them all simultaneously. I've made and experimented with some copper/aluminum thermite with good success. Does anyone see an issue with using thermite on these 29mm motors? I'm talking only 2 grams in a straw wrapper around a low current ematch. Bench testing has yielded good, consistent results.

As an alternative, I have some QuickDip that i've used on the same ematches folded over about an inch down and dipped. I wouldn't be opposed to using the dipped ematches if I know they'll get the job done. Your input is appreciated.
 

Steve Shannon

Well-Known Member
TRF Supporter
Joined
Jul 23, 2011
Messages
7,012
Reaction score
4,049
Location
Butte, Montana
I'm no expert on thermite, but I've read many accounts of overpressure from people who use it. Has your testing included using it in a motor? 2 grams sounds like a lot for such a small motor. I'd put it out farther than usual just in case.

A decent high power launch controller should be able to start all four motors quickly using the firstfire igniters that come with the motors without need for any extra inducement.


Steve Shannon
 

DrewD

Well-Known Member
Joined
Oct 14, 2014
Messages
67
Reaction score
0
I'm no expert on thermite, but I've read many accounts of overpressure from people who use it. Has your testing included using it in a motor? 2 grams sounds like a lot for such a small motor. I'd put it out farther than usual just in case.

A decent high power launch controller should be able to start all four motors quickly using the firstfire igniters that come with the motors without need for any extra inducement.


Steve Shannon
I apologize I meant .2 grams not 2 grams. That would be a lot for sure. I like the idea of instant on with thermite. But if FirstFire or dipped igniters will light them all at once, I suppose there's no need to over complicate it by using thermite.

It's also my understanding that thermite doesn't do much in the area of expanding gasses. Making it more suited for APCP ignition and at lower risk for over pressurization. I'm no expert sp please correct me if i'm wrong.

I'd love to hear of some first hand experience. Including success and failures.
 

Rocketjunkie

Addicted to APCP
Joined
Jan 19, 2009
Messages
4,525
Reaction score
696
In 29 mm motors, I'd use the dipped ematches. Secure each one to the motor it's in so it won't be pulled out if it's a little slower.
 

Dave A

Lifetime Supporter
TRF Lifetime Supporter
Joined
Jan 22, 2013
Messages
1,190
Reaction score
155
Those old Oxorals (spelling?) that came with the older CTI motors lit motors quite reliably just as well as the old black Davey fires. Someone in your club probably has some.

Best to get with a few of the club igniter pros, some ematches I have seen home-dipped when they popped just just knocked off the pyrogen, not ignite it.
 
Last edited:

DrewD

Well-Known Member
Joined
Oct 14, 2014
Messages
67
Reaction score
0
Those old Oxorals (spelling?) that came with the older CTI motors lit motors quite reliably just as well as the old black Davey fires. Someone in your club probably has some.

Best to get with a few of the club igniter pros, some ematches I have seen home-dipped when they popped just just knocked off the pyrogen, not ignite it.
Those aren't similar to the CTI dipped igniters used on their VMAX motors are they? I used one on a Loki I210 red and it failed to light it. But it's my understanding those reloads are hard to light anyways.
 

markkoelsch

Well-Known Member
Joined
Mar 18, 2009
Messages
4,364
Reaction score
151
Thermite is dangerous. It is very sensitive to static ignition. It burns very hot.

Thermite would be an option. Typical rules of thumb are a gram per 1000 NS impulse.

I understand why you would not want first fires. I would try an e-match with slivers of blue thunder propellant. Buy some matches and a small blue thunder reload. Test.
 

Dave A

Lifetime Supporter
TRF Lifetime Supporter
Joined
Jan 22, 2013
Messages
1,190
Reaction score
155
Those aren't similar to the CTI dipped igniters used on their VMAX motors are they? I used one on a Loki I210 red and it failed to light it. But it's my understanding those reloads are hard to light anyways.
The old one were not dipped but the Pro38 had the pellet at the top to light better. The small dipped ones like from Quikburst seem to work great.
 

DrewD

Well-Known Member
Joined
Oct 14, 2014
Messages
67
Reaction score
0
So far it seems like the low current ematches, folded and dipped is the best route to go. They light easily and burn hot and slow. I feel confident all 4 will light, but I don't feel confident they'll all come up to pressure at the same time before leaving the rail (past experience with some 29mm CTI's).
 

markkoelsch

Well-Known Member
Joined
Mar 18, 2009
Messages
4,364
Reaction score
151
So far it seems like the low current ematches, folded and dipped is the best route to go. They light easily and burn hot and slow. I feel confident all 4 will light, but I don't feel confident they'll all come up to pressure at the same time before leaving the rail (past experience with some 29mm CTI's).
It is almost impossible to guarantee that. CTI with the pellet was the quickest, and they could not give you that guarantee.

Dipped matches should work, or possibly my suggestion. For the blue thunder slices attached to a ematch.

I would stay away from thermite unless you know someone who can show you.
 

ksaves2

Lifetime Supporter
TRF Lifetime Supporter
Joined
Nov 25, 2009
Messages
6,264
Reaction score
490
Location
Central Illinois
Thermite is dangerous. It is very sensitive to static ignition. It burns very hot.

Thermite would be an option. Typical rules of thumb are a gram per 1000 NS impulse.

I understand why you would not want first fires. I would try an e-match with slivers of blue thunder propellant. Buy some matches and a small blue thunder reload. Test.
Simple thermite has a high heat of activation to get going and is not sensitive to percussion. That said, there are ways to modify that I'm not going to discuss out in the open.

I'll reiterate that ultra fine reagents are dangerous because if mixed thoroughly and sort of "suspended" in a very light, well mixed pellet it can go high order. That is not what's
desired in a motor. If going the thermite route, test like crazy remotely or get a thermite mentor to show you right. I am not a mentor as after that high order explosion of Lord knows how little in a 1.7gm canister, I curtailed further testing except with increasing the ease of ignition of more "courser" thermite reagents. Only rocket I tried with it still had an ignition delay and since I'm not staging with a low current ignition source am not pursuing it further. Be very careful Kurt
 

MClark

Well-Known Member
Joined
Jan 21, 2009
Messages
2,879
Reaction score
986
Location
Glendale, AZ
Whatever you decide to use test it repeatedly in a single motor configuration.
Preferably using the motor that will be in cluster.

M
 

ksaves2

Lifetime Supporter
TRF Lifetime Supporter
Joined
Nov 25, 2009
Messages
6,264
Reaction score
490
Location
Central Illinois
Whatever you decide to use test it repeatedly in a single motor configuration.
Preferably using the motor that will be in cluster.

M
First time though do it out in the open to make sure it doesn't produce a concussion then move on to motors. Shoot, if one mixes, would be a great time to kill two birds with
one stone by doing a motor ground test nozzle up with one's thermite ignition remedy. High speed video might be enlightening in that regard. Kurt
 

midpower_madness

Well-Known Member
Joined
Feb 29, 2016
Messages
145
Reaction score
25
No way.....
true Iron Oxide based Thermites are very stable and are in no way sensitive to static discharge or friction. However Copper Oxides types are impact sensitive to high velocity hits.

Thermates on the other hand are all very sensitive and are bonded with an Oxidizer.
 

GregGleason

Well-Known Member
Joined
Nov 13, 2009
Messages
4,655
Reaction score
7
The "classic" thermite is very hard to light, so that property made me move on. Sure, it's got a lot of heat and all but there are some other things that are better suited for instant on.

Have you looked into how the shuttle SRB's were ignited? They have to be ignited in less than half a second or the asymmetrical thrust would destroy the orbiter. The T-0 initiate command to actual SRB ignition was 0.008 seconds (a laser beam will travel a little less than 1,500 miles in that length of time). That to me is pretty much the "gold standard" for instant on for rocket motors.

This is a video of an SRB igniter:

[YOUTUBE]XIJG0klUVhw[/YOUTUBE]

This is the igniter being istalled:



link: https://www.nasaspaceflight.com/2012/07/final-flight-superb-performance-sts-135s-srbs/

This link might be of interest.

https://www.rocketryforum.com/showt...ight-the-solid-rocket-boosters-on-the-shuttle



link: https://www.jht.com/icuf/Space-Science/SolidRockets/PT-03-100.htm

Greg
 

thomas

Well-Known Member
Joined
Dec 16, 2011
Messages
288
Reaction score
6
The Nasa igniter uses Boron / KNO3 which is nice, but metallic Boron is expensive as hell.
Mg / Teflon / Viton was also used by the Nasa, but I would strongly recommend against it for hobby use.
You should also keep in mind, that the Nasa igniters are designed to match the motor. They create exactly the right amount of pressure for instant ignition.
In Hobby application this is not really necessary and it is extremely difficult to create the right amount of pressure. It is better to supply just a high amount of heat instead of trying to find the right pressure, because it makes over pressurization much less likely.

CuO / Al or Mg works well for igniting clusters, but it is dangerous if the particle size is small, comparable to flash powder. I would mix it only wet (aceton/alcohol) with a binder like NC and then dip low current commercial e-matches in it. The burn rate depends on the grain size, I would never use loose powder in a motor, it tends to explode if it is confined (some guys use it for exploding targets). Make sure to test igniters in the same volume as given by the motor, for example in plastic tubes. I do not know your grainsize but 2g seems way to much for an I motor. MnO2 would be an alternative oxidizer. You can check youtube for CuO thermite explosions to get a feeling for the dangers. Richard Nakka has also made some tests:
https://www.nakka-rocketry.net/thermites.html

I would also never buy one of these igniter kits. They expect you to mix unknown chemicals (probably some perchlorate) to form a pyrotechnic compound, this is a huge no go.
 

blackjack2564

Crazy Jim's Gone Banana's
TRF Supporter
Joined
Jan 18, 2009
Messages
9,150
Reaction score
1,324
Location
Savannah Ga
Well, have you flown yet?
What did you use?

I'm lucky, having acquired several pounds of BKNO3 Mil Spec. surplus grains.
I can make pellets for any size motor [well not 24-18mm] and dipped matches by mixing granules and nitro cellulose.

1gram pellet lights any M so far.

Location? If near me I can show/make some igniters for you. I previously used copper thermite, literally hundreds of them, but I feel much safer/secure using BKNO3. No where near so touchy.
 

DrewD

Well-Known Member
Joined
Oct 14, 2014
Messages
67
Reaction score
0
CuO / Al or Mg works well for igniting clusters, but it is dangerous if the particle size is small, comparable to flash powder. I would mix it only wet (aceton/alcohol) with a binder like NC and then dip low current commercial e-matches in it. The burn rate depends on the grain size, I would never use loose powder in a motor, it tends to explode if it is confined (some guys use it for exploding targets). Make sure to test igniters in the same volume as given by the motor, for example in plastic tubes. I do not know your grainsize but 2g seems way to much for an I motor. MnO2 would be an alternative oxidizer. You can check youtube for CuO thermite explosions to get a feeling for the dangers. Richard Nakka has also made some tests:
https://www.nakka-rocketry.net/thermites.html

I would also never buy one of these igniter kits. They expect you to mix unknown chemicals (probably some perchlorate) to form a pyrotechnic compound, this is a huge no go.
It was actually only .2g of thermite that I had plan on using. Just a typo. I agree 2g would be way too much.

I've tried mixing the thermite in NC. But even with such a small amount of NC (just enough to hold it together), the results were very inconsistent. It would burn in random pops and not very complete. Do you think the dip kits are really something I should stay away from? I had planned on using ML because of it's hot, fast burn rate.
 

DrewD

Well-Known Member
Joined
Oct 14, 2014
Messages
67
Reaction score
0
Well, have you flown yet?
What did you use?

I'm lucky, having acquired several pounds of BKNO3 Mil Spec. surplus grains.
I can make pellets for any size motor [well not 24-18mm] and dipped matches by mixing granules and nitro cellulose.

1gram pellet lights any M so far.

Location? If near me I can show/make some igniters for you. I previously used copper thermite, literally hundreds of them, but I feel much safer/secure using BKNO3. No where near so touchy.
Unfortunately I haven't had a chance to fly the cluster yet. The rocket is in its final stages but not yet complete.

So what is it you like about the bkno3? How does the burn differ from the thermite? I live in AZ, but you can always PM me with the info. I'm leaning towards using the ML pyrogen, but at some point t I'd really like to use the thermite. Maybe on a bigger motor cluster.
 

dlb

Sky Pyrate...
Joined
Jan 24, 2009
Messages
1,276
Reaction score
123
BKNO3 is my answer too!

compressed: longer burn and hot as hell
loose: Holy Crap, very fast and hot.
 

blackjack2564

Crazy Jim's Gone Banana's
TRF Supporter
Joined
Jan 18, 2009
Messages
9,150
Reaction score
1,324
Location
Savannah Ga
Unfortunately I haven't had a chance to fly the cluster yet. The rocket is in its final stages but not yet complete.

So what is it you like about the bkno3? How does the burn differ from the thermite? I live in AZ, but you can always PM me with the info. I'm leaning towards using the ML pyrogen, but at some point t I'd really like to use the thermite. Maybe on a bigger motor cluster.

Thermite sends a fiery ball of copper plasma particles down the motor core.When the molten copper hits the grain it lights instantly. Wonderful stuff IF YA KNOW how to use it. Without a mentor I would not try.
Mixing with nitro cellulose turns it into "just another ignition source" although a bit faster than most, not instant on,which is desired in clusters. Be extremely careful, if it goes off unexpectedly you will find your skin'clothes burnt to the bone [on hands] by molten copper. I have personally seen this, it's very scary & PAINFUL> You think hot wax hurts....ain't nothing compared to molten metal!

BKNO3 {Boron Potassium Nitrate} is the proven reliable ignition source for many military,sounding and NASA rockets. It works regardless of temperature by giving off huge amounts of extremely hot gas, which lights motors instantly. Is safer to handle, store & use during the igniter making process.

Thermite is placed 1/3 down the core from top, or you may actually blow the igniter out before lighting motor. Making the igniter involves placing powder in tube shape or "saddle" shaped charge wrapped over a dowel, then inserted into motor. This process is the most reliable I have used [in over 100 motors & drag races] and seen used. I made 17 gram charges for Vern's 1/3 Saturn project several yrs ago lighting 5 motors...M'N's

Since reading a 500 page 'Igniters for military" pdf I found BKNO3 one of the best, easiest to obtain & use. There are others.....Zirconium...Teflon/Mag..Vitron [Viton?] etc. But day in and day out you see BKNO3 being used by professionals everywhere. Just look at above post for the Saturn 5 By varying the size and amount of pellets, anything can be lit. There is no problem with heat transfer between granules, it works just as well in space as it does in atmosphere.

Problem you have is trying to light very small motors with tiny core/C-slots ...is getting something to fit.

If a match fits through the nozzle of the 205's, I would use broom straws, small skewers for shish-la-bobs to hold up my charge made from, tiny corner of baggie with 1.5 g's of thermite attached 2inches from top and inserted into motor. Do NOT test for continuity at the pad, unless you have tried it with a match before.
Try with 1 motor in a rocket first before lighting 4! You might also try making a dip with thermite and dipping a match. It will be slower, but so what, as long as all 4 pressure up at same time. If you are going to do this, learn how properly. This requires some time making and testing igniters till you find what works for your situation. A skill that requires some time.

The best way to light small motor is by pressing a BP pellet into top grain and just using a match ala CTI. But you want to use single use motors ruling that out. Reloads are a simple matter to push a BP pellet into grain & pellets can be harvested from Estes motors.No point going into all that, single use rules out using them.

Actually if you can't figure something out. I would try 4FFFF BP mixed in nitro and dip some matches, to see how well they work. I know some who make all their ignition supplies that way. Just don't dip too many coats or the match may blow the dip off. There are so many tricks & tips to making this stuff, a mentor is my best advice.
 
Last edited:

Wayco

Desert Rat Rocketeer
TRF Lifetime Supporter
Joined
Mar 23, 2011
Messages
3,710
Reaction score
750
Location
Goodyear, AZ
Thermite sends a fiery ball of copper plasma particles down the motor core.When the molten copper hits the grain it lights instantly. Wonderful stuff IF YA KNOW how to use it. Without a mentor I would not try.
Mixing with nitro cellulose turns it into "just another ignition source" although a bit faster than most, not instant on,which is desired in clusters. Be extremely careful, if it goes off unexpectedly you will find your skin'clothes burnt to the bone [on hands] by molten copper. I have personally seen this, it's very scary & PAINFUL> You think hot wax hurts....ain't nothing compared to molten metal!

BKNO3 {Boron Potassium Nitrate} is the proven reliable ignition source for many military,sounding and NASA rockets. It works regardless of temperature by giving off huge amounts of extremely hot gas, which lights motors instantly. Is safer to handle, store & use during the igniter making process.

Thermite is placed 1/3 down the core from top, or you may actually blow the igniter out before lighting motor. Making the igniter involves placing powder in tube shape or "saddle" shaped charge wrapped over a dowel, then inserted into motor. This process is the most reliable I have used [in over 100 motors & drag races] and seen used. I made 17 gram charges for Vern's 1/3 Saturn project several yrs ago lighting 5 motors...M'N's

Since reading a 500 page 'Igniters for military" pdf I found BKNO3 one of the best, easiest to obtain & use. There are others.....Zirconium...Teflon/Mag..Vitron [Viton?] etc. But day in and day out you see BKNO3 being used by professionals everywhere. Just look at above post for the Saturn 5 By varying the size and amount of pellets, anything can be lit. There is no problem with heat transfer between granules, it works just as well in space as it does in atmosphere.

Problem you have is trying to light very small motors with tiny core/C-slots ...is getting something to fit.

If a match fits through the nozzle of the 205's, I would use broom straws, small skewers for shish-la-bobs to hold up my charge made from, tiny corner of baggie with 1.5 g's of thermite attached 2 inches from top and inserted into motor. Do NOT test for continuity at the pad, unless you have tried it with a match before.
Try with 1 motor in a rocket first before lighting 4! You might also try making a dip with thermite and dipping a match. It will be slower, but so what, as long as all 4 pressure up at same time. If you are going to do this, learn how properly. This requires some time making and testing igniters till you find what works for your situation. A skill that requires some time.

The best way to light small motor is by pressing a BP pellet into top grain and just using a match ala CTI. But you want to use single use motors ruling that out. Reloads are a simple matter to push a BP pellet into grain & pellets can be harvested from Estes motors.No point going into all that, single use rules out using them.

Actually if you can't figure something out. I would try 4FFFF BP mixed in nitro and dip some matches, to see how well they work. I know some who make all their ignition supplies that way. Just don't dip too many coats or the match may blow the dip off. There are so many tricks & tips to making this stuff, a mentor is my best advice.
Hey CJ, did you transpose thermite for BKNO3 where I marked it in red?

Drew, we have 10 one pound cans of BKNO3, picked it up last year from Firefox in Idaho. Tried for quite a while to get it shipped, and finally drove up and brought it back ourselves. If you are interested in purchasing some, PM me. We live in Goodyear, AZ, and can't ship it.
 

blackjack2564

Crazy Jim's Gone Banana's
TRF Supporter
Joined
Jan 18, 2009
Messages
9,150
Reaction score
1,324
Location
Savannah Ga
Hey CJ, did you transpose thermite for BKNO3 where I marked it in red?

No.. he asked about both & mentioned he would like to use thermite on a large cluster. So I was 'splain'n.

But you COULD substitute BKNO3 now that I look at it...LOl Have you been using it for ignition?
 

Wayco

Desert Rat Rocketeer
TRF Lifetime Supporter
Joined
Mar 23, 2011
Messages
3,710
Reaction score
750
Location
Goodyear, AZ
Last year at Hellfire, we used it in a drag race. Sharon's caught but mine blew the ignitor out of the core. We didn't have a dowel holding the charge in place. As usual, Sharon won....
I'm thinking about mixing some BKNO3 with dissolved ping pong balls and painting the core of the top grain in our EX loads. They seem to take a while to come up to pressure, thought it would help.
So, do you position these enhanced ignitors 1/3 way down the core with BKNO3?
Also wondering how you make pellets with this stuff.
 

DrewD

Well-Known Member
Joined
Oct 14, 2014
Messages
67
Reaction score
0
Hey CJ, did you transpose thermite for BKNO3 where I marked it in red?

Drew, we have 10 one pound cans of BKNO3, picked it up last year from Firefox in Idaho. Tried for quite a while to get it shipped, and finally drove up and brought it back ourselves. If you are interested in purchasing some, PM me. We live in Goodyear, AZ, and can't ship it.
I'd be interested in some bkno3. One of these days I'd like to make a trip out to one of the launch sites outside of Phoenix. It would be nice to fly higher than 6500' just to change things up a bit. If I head out that way, I'll be sure to shoot you a pm.
 

blackjack2564

Crazy Jim's Gone Banana's
TRF Supporter
Joined
Jan 18, 2009
Messages
9,150
Reaction score
1,324
Location
Savannah Ga

So, do you position these enhanced ignitors 1/3 way down the core with BKNO3?
Also wondering how you make pellets with this stuff.
I place BKNO3 at top.

With a pellet press ....of course!

Ok kidding aside, yes a pellet press. I got one for 50-60 bucks [I think] Mine came from "WackyWillie" shipped in a plain brown wrapper...LOL really. 10mm size.

https://www.wackywillysweb.com/products.php?cat=172

Google pyro star press.

Called "star" press by fireworks guys. If you know any pyro's get help from them. The star process is much more user friendly than pouring 1 gram of powder into that tube..inserting the rod and whacking it it with a hammer.
Which I did kinda...

You can moisten the powder first, tap it gently, then cut star's ..... too much info for here....call me when you have time Wayco.

Here are some of the first ones I made. They were coated in ''flexible nitro cellulose" to water-proof and harden them. 2 in front were made by casting BKNO3 in West epoxy and punching straw into mixture. They also work very well, are super hard. Just tape to e-match.

Fast, but nowhere near as fast as plain pellet. It took many tries & adding stuff [probably 30-40 wasted pellets] before I figured it out. Like coating the inside of press with W-40 and letting dry before use so pellet would not stick and break.

DSCN4833.jpg

I can make pretty darn good ones now, just took some practice.
 

DrewD

Well-Known Member
Joined
Oct 14, 2014
Messages
67
Reaction score
0
If a match fits through the nozzle of the 205's, I would use broom straws, small skewers for shish-la-bobs to hold up my charge made from, tiny corner of baggie with 1.5 g's of thermite attached 2inches from top and inserted into motor. Do NOT test for continuity at the pad, unless you have tried it with a match before.
Try with 1 motor in a rocket first before lighting 4! You might also try making a dip with thermite and dipping a match. It will be slower, but so what, as long as all 4 pressure up at same time. If you are going to do this, learn how properly. This requires some time making and testing igniters till you find what works for your situation. A skill that requires some time.

The best way to light small motor is by pressing a BP pellet into top grain and just using a match ala CTI. But you want to use single use motors ruling that out. Reloads are a simple matter to push a BP pellet into grain & pellets can be harvested from Estes motors.No point going into all that, single use rules out using them.

Actually if you can't figure something out. I would try 4FFFF BP mixed in nitro and dip some matches, to see how well they work. I know some who make all their ignition supplies that way. Just don't dip too many coats or the match may blow the dip off. There are so many tricks & tips to making this stuff, a mentor is my best advice.
You don't think 1.5g of thermite would be too much for an I205? I like the idea of using an Estes motor for the ignition​ pellet. How much would you use? Would 1/4" be a good amount? I've had issues with a Loki motor (red) spitting igniters. Very good igniters. Perhaps using a dowel or placing it 1/3 from the top of the motor core could help this?
 

jsdemar

Well-Known Member
Joined
Dec 31, 2009
Messages
2,741
Reaction score
780
The amount of thermite is not simply based on the N-secs of the motor. You have to allow for the core diameter and length. The surface area of the core and the volume to pressurize are both a factor. I modeled this in Matlab a few years ago and plotted a curve to use as a better rule-of-thumb. This has been spot checked by several people and works well.

https://thrustgear.com/data/thermite_mass.JPG
 
Top