Has anyone tried arc ignition for black powder engines?

[Kelly]

My point about Estes motors is that the "black-powder" that Estes is using is not the same thing as the BP that we often use for recovery device deployment charges with our electronic in our Av-bays. Its not the same thing as cramming a bunch of Dupont 2F, 3F, or even 4F into an empty motor case and calling it "propellant." Chemically they have mostly the same ingredients, but in differing proportions thus creating a propellant rather than low explosive. Am I saying that well enough? Or am I completely in left field?

The difference between the blackpowder (BP) you use in an ejection charge and that you would use in a motor is actually more about how the motor is prepared. The composition of the powder is - or can be - identical. What enables BP to burn so fast when used as an ejection charge is the space between the grains. When an individual grain ignites, it generates an enormous amount of hot gas, which quickly expands through the interstices between the BP grains, igniting more. This leads to an almost instantaneous chain reaction. When used to prepare a rocket motor, the BP is packed very tightly into the casing, leaving no space between grains. When the first surface is ignited, there are no interstices for the flame front to spread through, and so the burn is much slower and more controlled - leading to propulsion rather than deflagration.

 

[rharshberger]

https://www.skylighter.com/blogs/fireworks-information/black-powder-grades-sizes-meshAll the different sizes from FA to X-fine Meal are made from the same batch. After thorough mixing the powder is "corned"---pressed into cakes and allowed to dry, then broken up---and sieved into the different sizes. I think they may tumble each batch to round off the edges and give more uniform particles, and they get a coating of some sort.

The finer stuff like Meal D requires less pressure to consolidate it into a propellant grain. Finer grades could be used but I'd guess that they're even more sensitive to spark than Meal D.

Fireworks enthusiasts often use a similar method, but the mixture is higher in coarse charcoal to give a nice tail. Such mixtures usually burn much more slowly, so their rockets are almost always coreburners, for maximum thrust.

I'm not certain where I saw the statement that Estes uses Meal D as the propellant. Memory again...

Best -- Terry

IIRC Black Powder is "glazed" with graphite, which serves two purposes, increased safety in handling after manufacture and it makes it " free flowing" when dispensed from various devices like powder measures, powder horns and the container its in. My guess though is that the powder Estes uses is not glazed as it might make it more difficult or even impossible to press into a homogeneous motor grain. Initiator01 might know the answer to that.

 

[Kelly]

IIRC Black Powder is "glazed" with graphite, which serves two purposes, increased safety in handling after manufacture and it makes it " free flowing" when dispensed from various devices like powder measures, powder horns and the container its in. My guess though is that the powder Estes uses is not glazed as it might make it more difficult or even impossible to press into a homogeneous motor grain. Initiator01 might know the answer to that.

Sporting grade (but generally not blasting grade) BP's are polished with graphite. This improves flowability, as you say, but actually slows the burn rate, and so I would doubt that Estes uses it.

 

[DaveW6DPS]

IIRC Black Powder is "glazed" with graphite, which serves two purposes, increased safety in handling after manufacture and it makes it " free flowing" when dispensed from various devices like powder measures, powder horns and the container its in. My guess though is that the powder Estes uses is not glazed as it might make it more difficult or even impossible to press into a homogeneous motor grain. Initiator01 might know the answer to that.

The "black powder" used as propellant in these motor is similar to the black powder used for firearms, but formulated to give a consistent "slow" burn. It isn't powder at all, rather formulated as a clay-like consistency that is then cast and dried.

There is really no point in comparing them to actual black powder.

 

[prfesser]

I guess the whole BP topic is moot. I just got an email from Estes, saying that the propellant is proprietary information. So we're all guessing... (though I was *sure* that I'd read on one of the pyrotechnics lists or sites that Estes used Meal D. Then again... memory... )

Best -- Terry

 

[dhbarr]

I guess the whole BP topic is moot. I just got an email from Estes, saying that the propellant is proprietary information. So we're all guessing... (though I was *sure* that I'd read on one of the pyrotechnics lists or sites that Estes used Meal D. Then again... memory... )

YORF has a discussion about goex/Dupont
https://www.oldrocketforum.com/archive/index.php/t-7425.html