Alternative Ejection Charge?

Ok, here's the deal. I have a short time to get my rocket flight ready (like a day, but anytime within a few weeks would be good too!). I make my own 3/4" pvc casing, r-candy motors. However, all retailers in the my area seem to be out of black powder due to supplier shortage. Question is: is there a good alternative that will pop out a parachute? Would it be worth trying straight up r-candy? Any other methods/strategies?
I realize I can order black powder online, but the handling charge is ridiculous for the amount I need.

Randy ...... Most of the time these are launched at group launches. If you already know the size of charge you need(Amount of BP) Would you not be able to talk to someone going to be there, and buy a charge or two. Other than that, I would recommend Motor ejection and a Chute Release........

You can use smokeless powder. You just need to be aware of the requirements of tight, enclosed packing if that for a good pop.
If you are launching with a club, ask to buy some BP from a member. We always have a bunch on hand.ihjt want to ask ahead of time.
I usually bring along a few prepped 1.5 g eppendorf tubes with ematches ready to use for anyone who needs them.

PVC casings may not be the best choice here: those can't fly at any TRA research / EX launch, and certainly not at a commercial TRA or any NAR launch.

If you do decide to keep running those, please remember PVC makes very sharp relatively heavy shrapnel if there's a miscalculation, and is not quite as easy to detect in the human body as aluminum.

Finally, your local sporting goods store probably has a black powder substitute. It's not as good as FFFF, but if you measure it like FF and restrain it well you should have good success. eMatch at the bottom of a deeper narrower charge well, dog barf, good tape.

Please do not attempt, under any circumstances, to make powdered rcandy.

dhbarr said:

PVC casings may not be the best choice here: those can't fly at any TRA research / EX launch, and certainly not at a commercial TRA or any NAR launch.

If you do decide to keep running those, please remember PVC makes very sharp relatively heavy shrapnel if there's a miscalculation, and is not quite as easy to detect in the human body as aluminum.

Finally, your local sporting goods store probably has a black powder substitute. It's not as good as FFFF, but if you measure it like FF and restrain it well you should have good success. eMatch at the bottom of a deeper narrower charge well, dog barf, good tape.

Please do not attempt, under any circumstances, to make powdered rcandy.

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Excellent post. Thanks!

As dhbarr said, people have used Pyrodex successfully, and it's more widely available than black powder.
https://en.wikipedia.org/wiki/Black_powder_substitute

First thing first, are you using the BP in your motor as an ejection charge or are you talking altimeter deployment?

Not an alternative - but we are getting ready for Tri-Cities launch in a couple of weeks and FFFF (4F) is available in Puyallup Washingtion at Muzzleloaders Supply (253-922-1717). I picked up a pound of Goex Black Powder FFFFg for about $30.

Since you are already cooking your own r-candy motors, why not make Crimson Powder?
https://www.google.com/search?q=crimson+powder

PLEASE stay safe!

Second "Graduator's" suggestion.
SG

I appreciate all the suggestions and safety concerns. I'm not a member of a rocketry club, don't have the time, but I'm aware of the risks and laws in my area and take reasonable safety precautions. For those still concerned, your conscience can rest assured that any devastating injuries from PVC shrapnel are not your responsibility. Given that I limit propellant to < 4 oz, I expect to survive a catastrophic failure and will post pics of injuries .

UPDATE, I tried using smokeless, with dismal results. Since the BP shortage in my area (major US metro area, very gun-friendly) persists, I did try using straight up r-candy as the ejection charge in a test launch. Parachute ejected with a little more force than necessary, but it survived. I like the idea of crimson powder. However, I'm not sure I see the point if r-candy works - I would simply reduce the charge quantity to get a good result. Any problems I'm not seeing here? The only thing I could think of is that the heat might be higher than BP, and thus risk damaging the rocket interior. My paper heat shielding and ceramic fiber wadding seemed to handle it ok for one test launch.

I have tired smokeless also. I gave up and had 10 pounds shipped to me.

I have no idea how sensitive such a low bulk density mixture might be to adiabatic compression and/or confinement.

I suspect no such studies have been done; nor any about static, impact, friction, etc.

Please just be extremely careful with a relatively unknown compound which is substantially more energetic than gunpowder.

https://www.grafs.com/retail/catalog/product/productId/5450
I got mine from Grafs and Sons. Took 3 days after the order. $18 per pound and I ordered three pounds before I felt ok with $18 in shipping.

Black powder is similar to gasoline in that it burns at standard atmospheric pressure. Smokeless powder is similar to diesel fuel in that it won't burn properly unless contained and pressurized. I used smokeless powder successfully for ejection charges on several flights and then I had a catastrophic failure. I was quite ill when I made the charges for that flight and clearly didn't do something correctly. However, when made correctly, smokeless charges work quite well. The key is to make the charge container strong enough to allow enough of the smokeless powder to burn to create the pressure you need to eject the parachute. If the smokeless powder is not properly contained it will simply smolder and not produce much pressure. For the record, I have switched to BP charges as they are easier to make and easier to assemble.

I know you will ignore this, but PVC pipe is a terrible motor casing. There was a discussion on the properties of PVC pipe a few years ago on this forum. One thing that I remember from the discussion is that as you pressurize PVC pipe close to its maximum pressure rating it loses strength. So the next time you pressurize the same pipe it can only handle about 80% of the rated max pressure. The weakening is cumulative, so each time you take it close to its max rating it drops another 20%.

Zeus-cat said:

I know you will ignore this, but PVC pipe is a terrible motor casing. There was a discussion on the properties of PVC pipe a few years ago on this forum. One thing that I remember from the discussion is that as you pressurize PVC pipe close to its maximum pressure rating it loses strength. So the next time you pressurize the same pipe it can only handle about 80% of the rated max pressure. The weakening is cumulative, so each time you take it close to its max rating it drops another 20%.

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Wait? What the wha? Do you mean if you heat and pressurize PVC pipe beyond it's intended operating range? I don't know in that case, but in normal use this is false. I design large infrastructure systems that use Class 200 PVC in sizes from 2" to 24" (they become C905 in the larger sizes). These systems are cycled from 0 to 180-200 PSI 10-15 times per day, 300 days a year. I've had systems installed for 25 years without failure. On the low end that is 75,000 cycles on the infrastructure.

Edward

Zeus-cat said:

I know you will ignore this, but PVC pipe is a terrible motor casing. There was a discussion on the properties of PVC pipe a few years ago on this forum. One thing that I remember from the discussion is that as you pressurize PVC pipe close to its maximum pressure rating it loses strength. So the next time you pressurize the same pipe it can only handle about 80% of the rated max pressure. The weakening is cumulative, so each time you take it close to its max rating it drops another 20%.

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If you mean that I will ignore your implication that I should stop using PVC, then you are correct. However, I will take up and challenge the rest of your statement, and you can respond to my challenge if you have better information .
Why would you say categorically that PVC is a terrible motor casing? Even if the 80% number is correct, I think it is a terrific casing for 2 simple reasons - it is accessible and easy to work with. I can get it at Lowe's anytime, and finish a motor in 15 minutes when all materials are on hand. Even if it is a one-time use, that is a welcome compromise for the casual hobbyist who is a busy working dad, such as myself. As for the 80% number, I have strong doubts, because I have actually flown the same motor 3 times. The problem was not failure under stress, but roughness of the interior, which made it difficult to pack in powder with a dowel. Nevertheless, I maintain that the right PVC casing, used as a disposable rocket motor, has it's time and place, and is a great choice when safety precautions are taken seriously.

Crimson powder is pretty good. Richard Nakka has a good procedure for making it on his website. I've used it in several model sized flights. I actually prefer it to BP, it doesn't burn as hot, and no sulfur smell at the end. It's just the effort to make it that slows me down, but if you're making your own motors that probably doesn't bother you.
I've only watched others use smokeless powder. From what I've observed you've got to confine it pretty good; better than I think a motor ejection charge could be confined. So unless you're doing an electronics payload, where you can seal it in a nice package with an e-match, I don't think smokeless will be an option for you.