cluster ignition without fuse?

What type of motors are you wanting to use?

Mostly D or E BP but I might try similar impulse composites too at some point. Thanks!

for BP motors consider flash pan, or a spider or perhaps quickmatch if you can get it.... skylighter sells it but you have to pickup..

terry dean nar 16158

Use the flash pan method.

Spider?

Ted Novak TRA#5512 IEAS#75

does it involve setting a large spider like a tarantula on fire so they can run around lighting motors?

a variation on the theme of a flashpan....might be considered a directed flashpan:

terry dean nar 16158

Ya just did a high-warp flyby... I know what flashpan ignition is, though I'd probably put enough powder in to orbit the rocket without motors; though I'm sure experienced guys like yall could tell me how much you generally use for a given cluster size and the pan size or configurations. But WHAT is a spider or quickmatch?? Never heard of either of these. What do they look like, how are they set up, where do you get them, etc.

How about flashbulb ignition?? Is that used anymore or did that go out like cold propellant rockets?? I never used flashbulb; to a high schooler it looked terribly sophisticated but having re-read about it now it seems a rather elegant solution. Thanks! OL JR :)

A spider is a set of thin tubes stuck in a cap that goes over a pan of BP. This pan of BP is essentially like what you'd see for flashpan ignition--the difference is the cap with tubes. The rocket with the motor cluster sits on top of the spider such that each motor is right over one of the tubes. When the BP is lit, fire squirts up each tube and up the motor nozzle.

It's a way to make flashpan ignition safer (no "overspray"), cheaper (need less BP), and more reliable (direct and concentrate the flame where it's needed).

Flashbulb ignition is still used (saw it most recently at NARAM 47 in

4xA cluster altitude), but is used less and less as time goes by.

Would this be along the lines of a pan with a cover that has individual pipes/tubes that go directly into the nozzles? I saw something like this at our August launch and it worked great on a 5 E9 cluster.

Ted Novak TRA#5512 IEAS#75

Yes. The spider was written up in a recent SR issue. There are some pics there.

FWIW, and I know I'm swimming upstream and therefore contradicting every other post in this thread, I've had great results clustering with plain old Solar Igniters. I inspect them, looking for goodly portions of pyrogen as well as making sure they appear to be intact and not bent or bruised. Then I ohm them out to make sure the cluster set is all within a reasonable tolerance of each other, perhaps within 1/10 of an ohm.

Next, I wire them in pairs and recheck with the ohmmeter to be sure I didn't short or open something. In the past, I've connected clip whips. But in the future, I'll be instead using throwaway clip-whips - IOW, I'll be attached flying leads to the igniters which can be twisted together. This allows me to insulate the connections at the ignitors, and these connections are more reliable than the alligators of the clip-whips, and they won't touch and short each other out like alligator clips can, nor will they fall off which clips sometimes do.

Anyway, I use a relayer - ie, high power pad - to fire them. I've flown my Super Better Bertha twice now this way lighting all nine motors each time.

While inspecting, ohming and extending the leads on the igniters sounds like lots of work, building a spider and setting it up ain't no piece of cake either. Plus, getting all the spider flues lined up perfect with the nozzles might turn into a major PITA. Anyway, the direct approach works fine for me.

Doug

Thanks for the explanation. What is a PITA though?? :) I have a hunch it's a humorous anagram.

So flashbulb material is hard/impossible to come by then and regulated?

I have thought much the same thing vis-a-vis the Solar Ignitors. I know from what I've read that most writers seem to think that clustering with Solar Ignitors is a disaster waiting to happen and suggest other methods. But it would seem to me that if you had good ignitors, ohm-metered them to make sure that they were electrically sound, insured the pyrogen was intact and not cracked or chipped, and then soldered either small leads or a small 'harness' to them so you KNOW that there was a good electrical connection between the leads and the ignitor itself (thereby doing away with clip whips and the notoriously bad connections clips can have with ignitor wires) and pumping plenty of power to them when you hit the switch they should be about as reliable as anything else.

Didn't really WANT to do flashpan because I've heard it tends to roast the rear end of the rocket. The spider sounds a lot more 'elegant' as far as the flash pan method goes.

BUT how about composites or composite upper stages?? How are those ignited?

Thanks! OL JR :)

Pain In The A$$

Ground starting composite clusters requires special igniters. Air starting composites requires even more specialized igniters.

In a composite cluster, you want the igniter to come up very quick, then burn big AND hot to ensure the motors light together.

In airstarts, you typically have a limited battery. It won't be a 12V car battery, so you won't have the voltage and low output resistance (ie, current capability) of a lead acid battery. Small NiCads are probably about the best bet.

Similarly, your electronics typically don't have the current switching capability of a relay. They tend to use FETs which can have much higher on resistance thus limiting current. Usually, with a FET, the harder you drive the gate, the lower the channel resistance, but you need to drive the gate above 5V for that. Most microcontrollers are limited to

5V outputs. To go higher then would require specialized circuits such as charge pumps thus adding cost and complexity and reducing reliability.

If you get what's called a "logic level" FET and use a 5V micro, you can get a reasonably low impedance switch. I have a PerfectFlite timer which, when powered by an 8V NiCad, can light a Solar igniter. But these situations have a fairly narrow range of operation. Small changes in voltage or resistance can render it in-operable. IOW, it's marginal.

So, for airstarts, you want an igniter built around a low-current e-match which can be lit without need for big batteries and ultra low resistance FETs.

has made several products which will work well for these applications. As soon as he has his licensing issues resolved, he will be a good place to look if you're doing a composite cluster or airstart.

Doug

Agreed. ALL my BP cluster launches involve Solar igniters.

I use lamp cord (18ga ?) clip whips, though, and scrape the propellant grain on every motor to ensure no clay is present. I also take an emery board or nail file to *copper* clips (not the silver colored ones) to ensure good connectivity. The club launcher uses a large 12v lead-acid battery and my personal controller uses a 12v sealed gel-cell motorcycle battery. Very high reliability. I believe a low resistance current path is the biggest factor in BP cluster reliability, rather than the igniter type. YMMV.

I agree with Doug that clustering with standard Estes igniters works fine. I follow the same procedure with a digital ohmmeter, but take it a step further: I write down each igniter's resistance, then calculate the combined resistance of the cluster and then verify it once the igniters are connected together. Works OK for up to four igniters or so (larger clusters drop the combined resistance below the limit of my ohmmeter.) When I get around to doing larger clusters I will use a combination of series and parallel wiring to overcome this limitation and to keep the amperage requirements under control.

You don't need to solder leads, in fact you will find it difficult to solder to the nichrome legs of the Estes igniters. Use a wire wrap tool and 30ga wire wrap wire. I wrap a red wire to one leg and a blue wire to another so that when I twist the leads together I don't get confused.

Good addition. I forgot to mention that. It's important for clusters AND staging.

Yep. Same here. Every range box should have some emery boards.

Exactly. We want most of the resistance to be the ignitor and not some bad connection elsewhere.

My move away from clip whips was prompted by two things - seeing someone else using extender wires (with insulating tape on the junctions) and struggling too often to get all the clips to stay attached and not touch each other.

Doug

I was sorta doing that. When I twist the igniters in pairs, I re-ohm and make sure they're ~1/2 of what I was previously reading.

I don't know. Doing the combo will make measuring easier, but you run the same risks as any series ingiter scheme. I'm thinking a new ohm-meter might be a better idea :)

Steve, I think the legs are steel and only the bridge is nicrhome.

Actually, I made up 20 or so igniters with extended leads doing this. The problem I ran into was that the wire wrap doesn't bite the round igniter lead nearly as well as it does a square wire wrap post. They can slide off. So I then hit the wraps with a dab of solder. Worked great.

That's paramount. Just imagine standing at the pad with 9 white wires inone hand and 9 more white wires in the other, trying to figure out if more than one wire in either hand goes to the same igniter :)

Doug

Yeah, doing a 7 motor BT-80 cluster gets tight. I used to have some heavy gauge jumper wires with the plastic insulator covers over the clips. "Great!", I thought, "A solution to shorted clips." Worked like a champ. Once. ;)

Yeah, you ever price one of the good ones? :-)

I think series wiring will work with Estes igniters, but I must add that I haven't tried it except in bench testing. That paper on the current requirements of various igniters--darned if I can find it now but it was mentioned here recently--showed that burning igniters continue to conduct through the plasma ball. The early bare-nichrome igniters would break when they got hot enough to light the motor, thus breaking the chain in a series wiring, so early cluster experimenters quickly gave up on series wiring. But blasters use series wiring, though not with Estes igniters. :-)

After wrapping the wire--down near the paper strip--bend the free end of the Estes igniter leg back up over the wrap to keep the extension lead from sliding off.