E-matches & Static Electricity??

[JDcluster]

Has anyone had this problem especially this time of year??
I've had a couple pop with no warning at all when the altimeter wasn't even turned on.


JD

 

[DynaSoar]

Originally posted by JDcluster
Has anyone had this problem especially this time of year??
I've had a couple pop with no warning at all when the altimeter wasn't even turned on.


JD

Never saw it, never even heard of it, but it (static, as well as EM field induced current) is apparently why you shouldn't install igniters until on the pad.

Don't take this wrong, but I'm glad to hear it's for real. Sometimes I get the feeling some rules have no basis in fact. This one apparently does.

Time to consider proper grounding procedures.

 

[Rocketmaniac]

Originally posted by DynaSoar
why you shouldn't install igniters until on the pad.


Time to consider proper grounding procedures.

E-matches going off on their own with the altimeter turned off is scary. I agree, this gives a very good reason to install igniters only on the pad. But what about ejection charges? In my HRP cluster rocket, I will have 4 ejection charges. 2 apogee and 2 main. Waiting to install these at the pad puts about 40% of the prep time out there.

Neither choice seems too good. E-match going off or a lot of prep time at the pads...... Anyone else have more input of the subject?

 

[Chilly]

Our club insists on igniters being installed at the pad. From what I understand there's a very good reason for it. The story is that someone had assembled an I motor in his hotel room the night before a launch out west (maybe Black Rock), with the igniter installed. A static discharge lit the thing off with predictable results. Can you imagine being in a closed room with something like that?

 

[cdma77]

Originally posted by Chilly
Our club insists on igniters being installed at the pad. From what I understand there's a very good reason for it. The story is that someone had assembled an I motor in his hotel room the night before a launch out west (maybe Black Rock), with the igniter installed. A static discharge lit the thing off with predictable results. Can you imagine being in a closed room with something like that?

Hotel staff to hotel guest: "You burned up our room with what" ?

 

[JDcluster]

In all 3 cases they were ejection charges.
The first one occurred with an Adept ALTS25; it fired as I was loading it into the rocket. Luckly I was looking away when it happened. I later tested the altimeter & it was feeding current to the pyro channels without it even been turned on!

Next was with a G-Wiz Deluxe ; I was putting the payload on to the rocket & pop it went.

The only other thing that might have caused them to pop would be a short...



JD

 

[DynaSoar]

Originally posted by Rocketmaniac
E-matches going off on their own with the altimeter turned off is scary. I agree, this gives a very good reason to install igniters only on the pad. But what about ejection charges? In my HRP cluster rocket, I will have 4 ejection charges. 2 apogee and 2 main. Waiting to install these at the pad puts about 40% of the prep time out there.

Neither choice seems too good. E-match going off or a lot of prep time at the pads...... Anyone else have more input of the subject?

That's my thinking. I've always prepped the night before. It's tough enough at home. Out of the back of the van it's worse.

For igniters, grounding is the answer. Clamp an alligator clip on it, and tape it so it doesn't come off.

Come to think of it, the charge that went off and hurt a guy at a METRA launch *may* have been static. Not likely since it was summer, but he was working inside his van at the time.

Do ejection charge widgets have a way to ground the leads prior to use?

 

[cls]

in addition to altimeter power switches, some folks install arm/shunt switches across the ignitor terminals on the altimeter.

seems like a good idea but I've never tried it - it's one more thing to go wrong or forget to prep, and switches are unreliable which is why I use twisted bare wires outside the airframe.

 

[rstaff3]

I have always heard that static could set off an e-match. It is certainly the bane of electonics. However, I have never seen a case that couldn't be attributed to the electronics. (a small sampling, to be sure) My gut says the later is far more likely. And BTW if static could set off an ematch while attached to an altimeter I'd think I might not bee too good for the latter.

I generally do the prep whenever possible with ematches, but no charge. The match is then isolated, and the charge added. I then re-enable at the pad. I don't use enough electronic deploys to have gotten too lax. I always keep my face away from a charged tube and try to keep the rocket oriented so it doesn't stay pointed at me or others. I also NEVER power the altimeter up with the ematches hooked up.

 

[Dbarrm]

Grounding is the way to go. This is just a thought but should work. Get a metal rod with a wire attached to it (6 feet should be good) and attach a clip at the end. Stick the rod in the ground at the prep station and attach the clip to the match before hookup. After all prep is done remove clip and assemble. This should remove any charge in the circuit and as long as nothing touches the circuit that has any static charge in/on it all should be fine. Ill do some work on this and see if I can find a easier way to do this.

ESD = Electro Static Discharge is a very dangerous thing.

Dan

 

[r1dermon]

twist the leads.

 

[Dbarrm]

Originally posted by r1dermon
twist the leads.

The properties of twisted pair do help reduce the wire from inducing a field but will do nothing to stop a any static charge once attached.

Dan

 

[DynaSoar]

Originally posted by r1dermon
twist the leads.

That too.

Doesn't need an earth ground. The problem is the charge entering one lead, travelling through the pyro and going to the other lead as it tries to balance across the entire conductor. If the leads are tied together, both side of the pyro would get identical voltage. No voltage differential = no flow and no boom.

Even if you do use an earth ground, you'd still want to tie the leads. Giving one side an earth ground is just inviting the other to pick up a charge that wants to head someplace.

And, if you use an earth ground, always attach to your device first, to the rod last. If there's going to be a spark, you want it to happen at the rod.

 

[Dbarrm]

Very true. I ment to say attach the clip to both leads. to keep the potential the same.

Dan

 

[llickteig1]

Originally posted by Dbarrm
Grounding is the way to go. This is just a thought but should work. Get a metal rod with a wire attached to it (6 feet should be good) and attach a clip at the end. Stick the rod in the ground at the prep station and attach the clip to the match before hookup. After all prep is done remove clip and assemble. This should remove any charge in the circuit and as long as nothing touches the circuit that has any static charge in/on it all should be fine. Ill do some work on this and see if I can find a easier way to do this.

Sort of overkill, don't you think?

Follow anti-static protocols to avoid problems. Keep the leads shorted until the last possible moment prior to installation, don't wear synthetic clothing, touch ground on your car (an exposed metal surface on most cars) before working with electronics, don't store your e-matches in a plastic container/box, etc, rather store them in an anti-static bag. If you're really concerned, design your rockets with a shunt wire that can be clipped at the pad to open the shunt and allow normal operation.

I have witnessed problems with Adept electronics and non-flight firing. I don't know if it is characteristic of some models or if there is perhaps some defective units out there.

Most importantly, wear eye protection. Rocketry, as much as we love it, is not worth an avoidable debilitating injury.

--Lance.

 

[DynaSoar]

Originally posted by llickteig1
Sort of overkill, don't you think?

Follow anti-static protocols to avoid problems. Keep the leads shorted until the last possible moment prior to installation,

Maybe longer. Maybe until after the active leads are attached. The last steps before leaving the pad should be REMOVE BEFORE FLIGHT, then test continuity, then arm.

 

[jraice]

You guys are saying switches are unrelieble. I am sorry but I have to disagree. It is true that a switch can jolt to the other position for a spilt second but my electonics have a two second capaciter so that doesnt matter. Also the switch will only jolt positions under high G's so the shunt switch would be fine at apogee and while under drogue... sound logical???

 

[rstaff3]

Whose brand offers 2 secs of battery outage protection?

 

[jraice]

Perfectflites mini/alt has a 2 second capaciter

 

[rstaff3]

That should protect against a lot of glitch outages.

 

[jraice]

and the shunts wont get shunted in flight because the charges go off at a low G part of the flight

 

[als57]

Originally posted by Rocketmaniac
E-matches going off on their own with the altimeter turned off is scary. I agree, this gives a very good reason to install igniters only on the pad. But what about ejection charges? In my HRP cluster rocket, I will have 4 ejection charges. 2 apogee and 2 main. Waiting to install these at the pad puts about 40% of the prep time out there.

Neither choice seems too good. E-match going off or a lot of prep time at the pads...... Anyone else have more input of the subject?

Also could be a leaky/defective output device on the alt. Also some ematches are suseptable to induced currents from RF. So using a cell phone or other transmitter would be a no-no.


Al

 

[artu]

Originally posted by Chilly
Our club insists on igniters being installed at the pad. From what I understand there's a very good reason for it. The story is that someone had assembled an I motor in his hotel room the night before a launch out west (maybe Black Rock), with the igniter installed. A static discharge lit the thing off with predictable results. Can you imagine being in a closed room with something like that?

It was at a Danville Dare launch in 1990, Danville Ill.

The I-65 9 second burn motor had the ignitor installed and then tested with a volt meter.

The volt meter set the motor off, and the motor owner held the motor in his hands to keep the damage down.

It cost a $500 clean up fee for the room.

I saw the smoke pooring out the window as I left the super 8 behind the other motel.

 

[JDcluster]

The Altimeter that set it off that sparked this post was an ARTS.
I had just flown it with perfect results!
Now that you mention it, it could have been a possible cell phone?? There is no real way of positively identifying the problem without recreating the environment.......

I just hope it doesn't happen again.

Thnaks for the input though,

JD

Originally posted by als57
Also could be a leaky/defective output device on the alt. Also some ematches are suseptable to induced currents from RF. So using a cell phone or other transmitter would be a no-no.


Al