AP cluster ignition - help needed

[Gillard]

I need some help with a project.
i want to do a simple cluster using low/mid power AP RMS motors.
i've done several BP clusters and never had a major problem, occasionally one motor might not ignite.

here's my problem, when i ignite aerotech RMS motors there ia a greater time lag between pressing the button and lift off than with BP, and this time lag differs quite a bit.
i use a 12v battery, freshly charged etc. the igniters i use are the supplied copperheads.

how can be sure that both motors in an AP cluster will ignite?

I'm in the UK and my choice of igniters is limited.


Any suggestions?

 

[Pantherjon]

If available, I would go with the FirstFire Jr ignitors..Paint the top grain of the reload with pyrogen, sand the top grain with an emery board and try to leave the fine propellant 'dust' in the grain slot..Sacrifice a blue thunder reload and put s small sliver of that propellant at the top of the top grain with ignitor making contact or wrap the head of the ignitor with the blue thunder sliver..Why blue thunder, you may be wondering, it, in my experience, is the easiest propellants to ignite...Just some ideas..

 

[timothyterpsalot]

I agree with everything said above, especially using the first fire jr. igniters. I have noticed the lag you are talking about with copperhead igniters but the delay is MUCH decreased with the first fire igniters.

 

[hardinlw]

One alternative to a true cluster where all engines are equal is a large central engine which is capable of lifting the rocket alone and outboards that are fired by a g-switch after liftoff. Using the g-switch eliminates the possibility that the outboards will fire without the center engine. If the outboards don't fire, the center engine should have enough thrust for safe flight.

Another concern is that even if all engines fire, they might not come up to thrust at the same time, resulting in the rocket flying in a low arc. Altimeter deployment can save the rocket in that condition where the delay that might be correct for a straight up flight may not fire until after impact.

Think of everything that could possibly go wrong, and then design to minimize the chances that it could happen or to reduce the consequences.

 

[quickburst]

Clustering Copperheads is very un-reliable. Use better igniters if possible, I understand that your options in the UK are limited.

I need some help with a project.
i want to do a simple cluster using low/mid power AP RMS motors.
i've done several BP clusters and never had a major problem, occasionally one motor might not ignite.

here's my problem, when i ignite aerotech RMS motors there ia a greater time lag between pressing the button and lift off than with BP, and this time lag differs quite a bit.
i use a 12v battery, freshly charged etc. the igniters i use are the supplied copperheads.

how can be sure that both motors in an AP cluster will ignite?

I'm in the UK and my choice of igniters is limited.


Any suggestions?

 

[blackjack2564]

I also use 6 ft long "leads" attached to the igniters, laid out at the bottom of the pad, usually loosely coiled or if room permits laid out so that upon ignition they can follow the rocket up off the rail. This gives some extra time for all the motors to ignite should one or two fire off first causing movement of the rocket.

I use old e-match leads 22 gauge wire. Any small gauge you have access to will work. The extra lead time has made all the difference in several flights.

Make sure to securely attach the igniter to motor or rocket with tape so they cannot pull out.

 

[THier]

Copper thermite.

Tom

 

[Gillard]

Copper thermite.

Tom

As a chemist, i like the idea, but i'd never get it past the RSO.

 

[THier]

As a chemist, i like the idea, but i'd never get it past the RSO.

Why not? it is very accepted method of lighting APCP on this side of the pond. No igniters in the motors until on the pad,, but copper thermite is actually pretty safe. We use 1gram per 1000ns of motor, 10,000ns = 10gr, 6000ns = 6 gr. ect ect ect. If you need to, measure out the ingredients, then mix and prepare out at the pads.

Use copper thermite with a "Davey fire or equiv, and you are good. We lit 8N motors and a P motor in Steve Eves Saturn V last year, all appeared to light at one time.
Tom

 

[MarkII]

I believe that Aerotech advises against using Copperheads to ignite clusters.

Has anyone mentioned Quest's new long-lead Q2G2's?

MarkII

 

[blackjack2564]

Copper thermite.

Tom

I have been unable to use it on anything smaller than 38mm.

It's very hard to package it and the e-match in a small enough bundle to fit through smaller nozzles.

If you have please elaborate.

 

[Gillard]

Why not? it is very accepted method of lighting APCP on this side of the pond. No igniters in the motors until on the pad,, but copper thermite is actually pretty safe. We use 1gram per 1000ns of motor, 10,000ns = 10gr, 6000ns = 6 gr. ect ect ect. If you need to, measure out the ingredients, then mix and prepare out at the pads.

Use copper thermite with a "Davey fire or equiv, and you are good. We lit 8N motors and a P motor in Steve Eves Saturn V last year, all appeared to light at one time.
Tom

i'll have to check. thanks for the advice

 

[THier]

I have been unable to use it on anything smaller than 38mm.

It's very hard to package it and the e-match in a small enough bundle to fit through smaller nozzles.

If you have please elaborate.

I did use it once with a 38mm, you will be using a small amount, so there are a couple of ways, one is lay match on tape, put thermite on it and wrap tight. You can use celophane, masking or vinyl, I used celophane. Or use tissue paper and do it the same way, tape is easier. The Match can be just over the thermite, to reduce diameter, just make sure it is in contact with the base of match. Use only enough tape to package the thermite.

Tom

 

[Bazookadale]

Clustering Copperheads is very un-reliable. Use better igniters if possible, I understand that your options in the UK are limited.

I believe that Aerotech advises against using Copperheads to ignite clusters.

Has anyone mentioned Quest's new long-lead Q2G2's?

MarkII

A friend of my relatively new to rocketry used to ignite 2 G80's with copperheads. He called his rocket "Quivering Dale" since I ran and hid every time he brought it out. Amazingly he got perfect ignition the first 6 -7 times he flew it, but the reliability of copperheads caught up with him and the rocket is now a twisted pile of wreckage

 

[THier]

I have been playing with making my own igniters, I use Telephone Cat5 wire for leads, and Nichrome wire for the bridge wire, I wire wrap it, (same procedure we use in the telecom industry, no soldering or flux to worry about) and I use ping pong balls dissolved in acetone, with a BP - alum pyrogen. I am testing for the reliability before I use them for clusters. So far they have lit APCP everytime, both using Thermite and no thermite.

Tom

 

[Handeman]

I have been playing with making my own igniters, I use Telephone Cat5 wire for leads, and Nichrome wire for the bridge wire, I wire wrap it, (same procedure we use in the telecom industry, no soldering or flux to worry about) and I use ping pong balls dissolved in acetone, with a BP - alum pyrogen. I am testing for the reliability before I use them for clusters. So far they have lit APCP everytime, both using Thermite and no thermite.

Tom

I've made my own igniter the same way. I use a mix of KNO3 (saltpeter bought at the drug store), charcoal and magnesium shavings. I made different sizes and they have worked on E to M motors without fail.
Like most igniters, they take a while to ignite the motors. If you are using any igniter for a cluster, painting the grains with a pyrogen or a pyrodex pellet in the top grain like CTI motors can help a lot.
You can also use the cellulose lacquer (ping pong balls in acetone) and fine black powder to paint the grains with.

 

[bobkrech]

I believe that Aerotech advises against using Copperheads to ignite clusters.

Has anyone mentioned Quest's new long-lead Q2G2's?

MarkII

They work well on small APCP motors.

You might have to add pyrogen to the upper grain bore in a larger motor.

Bob

 

[bobkrech]

Why not? it is very accepted method of lighting APCP on this side of the pond. No igniters in the motors until on the pad,, but copper thermite is actually pretty safe. We use 1gram per 1000ns of motor, 10,000ns = 10gr, 6000ns = 6 gr. ect ect ect. If you need to, measure out the ingredients, then mix and prepare out at the pads.

Use copper thermite with a "Davey fire or equiv, and you are good. We lit 8N motors and a P motor in Steve Eves Saturn V last year, all appeared to light at one time.
Tom

Tom

Copper thermite igniters have very short ignition delays, but your comments on being "pretty safe" is a subjective evaluation. While handling the assembled ingiter might be safe, I believe that mixing and making a copper oxide igniter is a dangerous process, and most rocket folks don't realize what can happen if something goes wrong.

I just finshed sitting on an incident review committee to determine how to prevent a reoccurance of the detonation of 0.8 g of nano-aluminum/nano-copper oxide thermite being processed in one of our labs yesterday. Fortunately no one was hurt but it shook the lab and the individual involved and a nearby co-worker had ringing ears for several hours.

To put this in perspective, a military M-80 contains 1.5 grams of flash powder and can blow off a hand. Copper thermite is just a energetic, and is as friction and ESD sensitive as flash powder. A detonation of 1 to 2 gram is capable of removing body parts, and a detonation involving 3 grams or more can be fatal to anyone holding it, so you really have to be careful about ESD and friction when mixing multiple gram quantities.

Bob

 

[THier]

Tom

Copper thermite igniters have very short ignition delays, but your comments on being "pretty safe" is a subjective evaluation. While handling the assembled ingiter might be safe, I believe that mixing and making a copper oxide igniter is a dangerous process, and most rocket folks don't realize what can happen if something goes wrong.

I just finshed sitting on an incident review committee to determine how to prevent a reoccurance of the detonation of 0.8 g of nano-aluminum/nano-copper oxide thermite being processed in one of our labs yesterday. Fortunately no one was hurt but it shook the lab and the individual involved and a nearby co-worker had ringing ears for several hours.

To put this in perspective, a military M-80 contains 1.5 grams of flash powder and can blow off a hand. Copper thermite is just a energetic, and is as friction and ESD sensitive as flash powder. A detonation of 1 to 2 gram is capable of removing body parts, and a detonation involving 3 grams or more can be fatal to anyone holding it, so you really have to be careful about ESD and friction when mixing multiple gram quantities.

Bob

I was led to believe it was NOT ESD sensitive,, but,, I do not take anything lightly, BP, APCP, thermite, all fall into the category of "be careful while playing with it"

Thanks for the heads up on ESD,

Tom

 

[quickburst]

Great advice here.

I also use 6 ft long "leads" attached to the igniters, laid out at the bottom of the pad, usually loosely coiled or if room permits laid out so that upon ignition they can follow the rocket up off the rail. This gives some extra time for all the motors to ignite should one or two fire off first causing movement of the rocket.

I use old e-match leads 22 gauge wire. Any small gauge you have access to will work. The extra lead time has made all the difference in several flights.

Make sure to securely attach the igniter to motor or rocket with tape so they cannot pull out.

 

[blackbird67]

I use a chunk of a Pyrodex Pellet,the kind you buy at Bass Pro for Black Powder Rifles.Break a piece off,wedge it in the slot or silicon it in the core.The Pyrodex takes nothing to light and will burn for a second to get the Propellant lit.It helps to sand the grain a bit first as well.Hope this Helps.