Making ejection charges ahead of time?

[Joe Bruce]

There's an L2 exam question that highlights the risk of induced current causing unexpected ignition of BP charges. On the other hand, Modern High Power Rocketry 2 explains various ejection charges that could only be made ahead of time.

Is it safe to make my glove-tip ejection charges before the launch for DD? I measured the BP ahead of time, but then spent time filling glove tips, inserting the e-matches, taping it closed, and shortening the wires for the 4 charges in my new redundant DD 5.5" Patriot. I'm not saying I want to completely prep the rocket at home, i.e. ejection charges installed. But can I make them and keep them in an ammo can or similar for use at the launch? With the leads either still insulated or twisted together?

 

[seth_cooper]

completely prep the rocket at home, i.e. ejection charges installed.

I do this routinely and have for many years.

Unless you have a system that mixes the BP and e-match a split second before apogee, aren't all of your ejection charges made ahead of time?

It's just a matter of how far ahead of time are you comfortable with.

 

[Orien]

I used to be a professional pyrotechnician who fired display fireworks shows. We had a strict policy of NOT "squibbing" (e-matching) any live fireworks until they are set up on-site. This was due to their sensitivity to shock. That said, if you protect them from shock (like you said by carrying them in an ammo can), and twist the ends together (ALWAYS) to prevent a static charge, it is perfectly safe.

FYI:

I've seen a string of 3 6" shells fire during the fireworks squibbing process due to static charge. Remember, wind builds up static electricity on your clothes.

A crew on another company's shoot were all killed when pre-loaded and squibbed mortar racks that were being unloaded from a semi trailer suddenly fired. It just takes a good pinch between hard surfaces to fire an e match.

 

[seth_cooper]

We had a strict policy of NOT "squibbing" (e-matching) any live fireworks until they are set up on-site.

I've seen a string of 3 6" shells fire during the fireworks squibbing process

squibbed mortar racks that were being unloaded from a semi trailer suddenly fired.

Are you implying ejection charges should only be assembled at the launch pad?

 

[Orien]

That said, if you protect them from shock (like you said by carrying them in an ammo can), and twist the ends together (ALWAYS) to prevent a static charge, it is perfectly safe.

Couldn't be bothered to read all seven sentences?

 

[seth_cooper]

I'll dumb it down for you. When and where do you put ejection charges in your DD rockets?

 

[OverTheTop]

I have always made my ejection charges ahead of time. Months in some cases. They are treated with great respect and kept away from static charge situations.

I prepare my rockets as much as possible at home, including loading the charges. Far easier and more reliable there than on the field.

 

[Orien]

I'll dumb it down for you. When and where do you put ejection charges in your DD rockets?

You're going to dumb it down for me? Your question was answered before asked in my original post, and answered again when asked. Maybe I could dumb it down for YOU a little:

"That said, if you protect them from shock (like you said by carrying them in an ammo can), and twist the ends together (ALWAYS) to prevent a static charge, it is perfectly safe."

 

[seth_cooper]

Do you ride along inside of your rockets so that you can untwist the wires at apogee?

 

[Orien]

Do you ride along inside of your rockets so that you can untwist the wires at apogee?

Yep. PRO TIP: ride standing on your head. Otherwise the g forces drain the blood from your brain and you pass out right before you need to connect the ejection charge wires.

 

[Joe Bruce]

Mini flame war aside, I believed it was fine to prep charges ahead of time until I read that L2 exam question. Made me wonder, since I know many charge methods MUST be done ahead of time. But that L2 question made we wonder how close my prepped charges should be to things like motors or cans of extra BP. Separation seems warranted, i.e. separate ammo can.

I HAVE heard different opinions on the safety of installing charges before transporting the rocket to a launch in your vehicle. I've heard anecdotes of charges firing inside the car while driving, but maybe the electronics were energized?

The rocketry analogy to fireworks would be more like installing the motor igniter before the rocket is vertical on the pad. An HPR motor going off, anywhere unintended, would be bad news. Of course, I've done ground testing enough to know that I wouldn't want my Patriot charges going off even in the truck bed, let alone inside a car!

 

[OverTheTop]

I have heard of somebody preping a rocket in a car and the charge going off. Not a good scenario. I guess if that had been done earlier it might not have been such a confined space.

 

[David Schwantz]

For the most part I like to have my rockets RTF when I arrive at the field. Short of igniters installed and electronics powered up.

 

[Orien]

The rocketry analogy to fireworks would be more like installing the motor igniter before the rocket is vertical on the pad. An HPR motor going off, anywhere unintended, would be bad news. Of course, I've done ground testing enough to know that I wouldn't want my Patriot charges going off even in the truck bed, let alone inside a car!

I was just making the point that a prepped ejection charge is susceptible (spelled that first try, thank you very much) to shock and static. Taking steps to mitigate those dangers is easy enough.

 

[JimJarvis50]

I have always assembled charges ahead of time. I can see what I'm doing, don't have wind, don't have people talking to me, and I'm not in a hurry. After I'm done, I store the charges in a secure place (inside the rocket). The idea of doing this at the field seems to me to be hazardous. Regardless of the approach, the important thing is to not be "in the line of fire" of BP or any energized system. I don't ever stand in front of nosecones.

Jim

 

[Blackbird1936]

I was just making the point that a prepped ejection charge is susceptible (spelled that first try, thank you very much) to shock and static. Taking steps to mitigate those dangers is easy enough.

In your experience are there practices that help reduce static electricity? also concern with electronics.....

 

[cwbullet]

No issues from our club but we do request you not hook them up and shunt or short the wires.

 

[Orien]

In your experience are there practices that help reduce static electricity? also concern with electronics

Dry, windy days are the worst for static buildup. Non-synthetic clothes help. Simply keeping the wires together until use will prevent premature ignition. As for electronics, find a piece of aluminum or copper that can be placed on the ground. Touch the metal to discharge any static before touching electronics.

 

[Joe Bruce]

Thanks for all the suggestions. Good to know the safe way to do this now that I've started DD!

 

[Orien]

I have always assembled charges ahead of time. I can see what I'm doing, don't have wind, don't have people talking to me, and I'm not in a hurry. After I'm done, I store the charges in a secure place (inside the rocket). The idea of doing this at the field seems to me to be hazardous. Regardless of the approach, the important thing is to not be "in the line of fire" of BP or any energized system. I don't ever stand in front of nosecones.

Jim

This 1000%
"Okay, I'm now going to pour in my carefully measured BP... aaaaand it's dumped out on the ground 12 feet away."

 

[Jmhepworth]

I try to do what Jim does. I remember trying to weigh black powder at AirFest when it got a bit too breezy and had to weigh it in my car. That’s when I decided to measure by volume and do as much prep at home as I can.

 

[MClark]

Black powder should measured by volume not weight.
But with what we are doing it really doesn’t matter.

 

[Joe Bruce]

All of the ejection charge calculators use grams, not milliliters, of FFFFg. That said, I have heard that there's a consistent density, so it'd actually be nice to have volumetric scoops rather than using a popsicle stick and milligram scale!

 

[teepot]

I reuse the vials that the BP comes in for high power motors.

 

[Joe Bruce]

I reuse the vials that the BP comes in for high power motors.

I've been saving them for that reason, though I'll need to 3D print a skinnier funnel! I think if I try to pour it even on a fold of paper, I'll end up covering my desktop with BP!

 

[Orien]

All of the ejection charge calculators use grams, not milliliters, of FFFFg. That said, I have heard that there's a consistent density, so it'd actually be nice to have volumetric scoops rather than using a popsicle stick and milligram scale!

1/4 teaspoon equals almost exactly one gram of BP.

 

[rcktnut]

I use this to measure: Amazon.com : Traditions Performance Firearms Muzzleloader Powder Measure for Black Powder Revolvers 5-45 Grains (Brass) : Gunsmithing Tools And Accessories : Sports & Outdoors
This to dispense into measure: https://www.usplastic.com/catalog/item.aspx?itemid=35567&clickid=search

No problems!!! 15 grains= 1 gram

 

[Jmhepworth]

I use this. https://www.midwayusa.com/product/101284828

 

[DaHabes]

For FFFFg BP, 1 gram = 1 cc = 1 ml (actually it's .93 g/cc, but 1:1 is close enough, since this is kinda like hand grenades). Doesn't get any easier than that. Centrifuge tubes are measured in ml. They are the easiest way to measure out BP in advance, no scoops needed.

 

[Kelly]

Measuring by weight is more accurate. Measuring by volume is accurate enough, and usually faster/easier.