Long term APCP storage.

Discuss your favorite methods for storing APCP fuel grains. I have recently discovered this Food Saver thingy works on rocket fuel too. It vacuum seals the fuel. I used to just leave it lying around for months.

Usually I just leave the motor unopened until I'm preparing for a launch.
If the motor is built, I stick the cap on and "seal" the nozzle with electrical tape until it's used.

Andrew_ASC said:

Discuss your favorite methods for storing APCP fuel grains. I have recently discovered this Food Saver thingy works on rocket fuel too. It vacuum seals the fuel. I used to just leave it lying around for months.

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I use zipper-top mylar static-free bags, the kind used for electronics. Mylar keeps out the moisture quite well; I've had grains that were five or six years old that looked like they had just been cut from the mandrel. Loaded in a motor, they lit right away.

Best -- Terry

Do what the Russians do, slather them in cosmoline so they don't oxidize.

I’ve heard Russian Cosmoline comes off Makarov handguns in an oven. I’m not certain of putting APCP in an oven for removal of wet cosmoline dripping everywhere is a good idea. Mom would like snap. It’s a thermador!

Personally, I would keep AP motors in a airtight container with some silica gel packets, if I was storing them for several (10+) years. Otherwise, I prefer to keep my AP motor stock low so they don't get very old before use.

I leave them unopened. This helps a bunch. If I have one built that has to sit for a while I tape the nozzle closed- usually with aluminum tape as it is quite sticky and moisture is not likely to get through the aluminum.

Heh. I have a 98-mm N2000 in my garage, built, in the hardware, that has been sitting, well, standing there since March. As soon as we get back to Higgs Farm, I'm going to let her rip. I have done absolutely nothing to protect the grains. If it won't light. I'll scrape some propellant from the top grain core.

Bat-mite said:

Heh. I have a 98-mm N2000 in my garage, built, in the hardware, that has been sitting, well, standing there since March. As soon as we get back to Higgs Farm, I'm going to let her rip. I have done absolutely nothing to protect the grains. If it won't light. I'll scrape some propellant from the top grain core.

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I load a lot of my motors prior to a launch. You rarely see me do that at the field. I slide ziploc bags over the aft end, tape the edges of the bag around the case. That seals it just like it never left the original bag. I always have a few left over for the next launch. They last a long time.

what's your experience with electrical tape sealing the nozzle cap? That's what I've done when putting together a motor more than a couple weeks prior

Another hint: cereal bags are free and very good at keeping air out, if you have a heat sealer. Heat sealers are quite cheap these days. Great for sealing bags of chemicals, motor starters, etc.

I use cling-wrap if it is going to be stored for a while after assembly. I have used this up to 18 months successfully so far. I suspect years would be ok too.

Nytrunner said:

what's your experience with electrical tape sealing the nozzle cap? That's what I've done when putting together a motor more than a couple weeks prior

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I've found I can leave all the grease from assembly on the aft end because you have to clean it, easier for me to clean a ring around the case and tape the bag to it. As long as it's sealed, either way, that's all that matters.

Andrew_ASC said:

I’ve heard Russian Cosmoline comes off Makarov handguns in an oven. I’m not certain of putting APCP in an oven for removal of wet cosmoline dripping everywhere is a good idea. Mom would like snap. It’s a thermador!

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Ah, yes... Memories of being a college student, living with parents when not at school, being restricted because you don't own stuff....

Someday you'll have the luxury of being able to do whatever you want, between work hours and bedtime. However, enjoy those times because before you know it, you might be married.

Bat-mite said:

Heh. I have a 98-mm N2000 in my garage, built, in the hardware, that has been sitting, well, standing there since March. As soon as we get back to Higgs Farm, I'm going to let her rip. I have done absolutely nothing to protect the grains. If it won't light. I'll scrape some propellant from the top grain core.

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Same here. I have a M1810 that I assembled for Red Glare last spring and it has been in the corner of my shop for 7 months. The cap has been on the nozzle so at least I know there are no mouse nests in there. Next week at Higgs we'll see if it will burn.

Nathan said:

Same here. I have a M1810 that I assembled for Red Glare last spring and it has been in the corner of my shop for 7 months. The cap has been on the nozzle so at least I know there are no mouse nests in there. Next week at Higgs we'll see if it will burn.

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Should fun!

Keep in mind that APCP can be hydroscopic. I've seen white lighting grains (29mm reloads) swell so much that the core was nearly closed and the ends looked like a muffin. That was after about 15 years in an open package in a garage. Other formulas don't seem to be affected as badly. I would at least seal the nozzle if an assembled motor is left somewhere like a garage. Not only will the grain be harder to light but the performance will likely be affected as well.


Tony

I looked up the core of my M1810 with a light and it looks normal. It has been stored in an air conditioned room all summer so humidity was not bad. But the last time I flew a M1810 it was pretty slow to light so well see what happens (this video says M1800 but it was a M1810 Red Lightning) . . .

manixFan said:

Keep in mind that APCP can be hydroscopic. I've seen white lighting grains (29mm reloads) swell so much that the core was nearly closed and the ends looked like a muffin. That was after about 15 years in an open package in a garage. Other formulas don't seem to be affected as badly. I would at least seal the nozzle if an assembled motor is left somewhere like a garage. Not only will the grain be harder to light but the performance will likely be affected as well.

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I'm pretty sure that WL has a high magnesium content, it's part of what gives it that white cloud of exhaust. Magnesium really, really likes oxygen and water vapor--and nitrogen, for that matter--- so propellants with a high proportion of magnesium don't age well unless they're kept dry and away from air as much as possible. The Mg turns into MgO and Mg(OH)2 which occupy more volume than the Mg and cause the swelling. Aluminum doesn't react as readily.

You don't want to let the really fast-burning propellants that use catocene or n-butyl ferrocene as a burn rate catalyst sit unused for a long time (years) either, but for a different reason. Those catalysts are liquids at room temp, and they can migrate from the inside to the surface of the propellant if it's allowed to stand for a long time.

Best -- Terry