KNO3 / Sugar Rocket Safety?

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scubaru

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Hey all, New to the forum! Also a re-new to rocketry.

I used to do model rockets as a kid, build the kits, light off the little Este's C engines. It was a lot of fun, but life went the other way.

Here I am some 10 years later and looking to get back into it...but with a different approach. I am looking to build rockets based on my own fuel. I know, its gonna be a lot simpler to go out and buy a pack of engines, but what fun is that.

I am in school for Manufacturing Engineering so I can machine about any part of a rocket to create my completely custom design. Don't worry, right now I'm just doing chemical testing for fuel and working with cheap engine models to demonstrate thrust and burn time.

Anyone who does this, care to chime in on a few questions?

- My biggest worry right now is I am using PVC pipe as the casing for the combustion chamber, with a concrete plug. I use 3/4" ID PVC pipe and a 1/8" Dia nozzle. Burned one off and it was awesome. Worry is, I understand PVC when burned can be toxic, although the PVC never catches fire it sure does withstand a high level of heat that I'm sure is burning off traces of the inner walls, is this something to be concerned about or maybe just take precautions anway? I was thinking if i introduce a cardboard or even Aluminum foil sleeve I might be able to produce enough of a barrier all the PVC would suffer would be heat instead of direct flame contact.

- How can I reduce any chance for explosions of issues if/when I start manufacturing an aluminum nozzle? I'd imagine a thick enough wall would help to reduce the effects of a blow out, but maybe a special cap I'd have to design that would blow out at high pressure?

- Is the smoke from the typical Sugar Rocket mixture (most basic formula) toxic or at all dangerous? I do have an older painters mask (with the 2 carbon filled canisters for purity) laying around that I'm considering using for another precaution.

Anything else I should be worried about with this type of engine? I've made a few different mixtures and worked with different designs, so far still getting into it but want to make sure I'm not building a device that could blow out and cause damage or injury to something around me.

Attached is my video of my first engine with a nozzled tip

Burn time: 22s
Thrust: uncalculated

[video=youtube;FH5LhkgvZ1I]https://www.youtube.com/watch?v=FH5LhkgvZ1I[/video]
 
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Aksrockets

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I would be less worried about the smoke being hazardous from the PVC and more about the PVC casing shattering and killing you.
A Manufacturing engineer should know that PVC shatters instead of deforms. Aluminum is a much better choice.

Read the forum rules. We can't talk about motor formulas here.

Alex
 

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I'm just gonna drop this off here in case it's needed.
a dead horse.jpg
 

scubaru

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I would be less worried about the smoke being hazardous from the PVC and more about the PVC casing shattering and killing you.
A Manufacturing engineer should know that PVC shatters instead of deforms. Aluminum is a much better choice.

Read the forum rules. We can't talk about motor formulas here.

Alex
Yes I am aware PVC will shatter under high pressure, however due to the long burn time of mine you wil notice I had an expansion of the main body. I am working on a design for an engine made for Aluminum (still looking into exact material choice), but for right now till I can figure out mixtures and nozzle size I am using PVC with a concrete nozzle. I did light this engine next to a concrete sidewalk with 2 blocks of aluminum to hold it stead, I am working to build a simple housing that will encase the engine in concrete walls and a shatterproof piece of clear acrylic. I also ALWAYS ALWAYS ALWAYS wear safety glasses with all my trials!



(BTW, my eduction is primarily in metals, we don't touch PVC as that is not a component typically machined.)

Also if you notice I am NOT talking about motor formulas, I am ONLY talking about safety concerning this "type" of engine. I talked to one of the mods prior to posting to this make sure my posting would be within the limits of the forum and I feel it is. But thank you for checking.

I'm just gonna drop this off here in case it's needed.
View attachment 107138
Thanks for the info....
 
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Dwatkins

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Safety concern #1, when PVC shaters and inters your body x-rays will not find it! Switch to aluminum 6061 T6. Use snaprings and a graphite nozzle. Liners and casting tubes will help insulate case. Have fun and be safe.

Dennis
 

scubaru

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Safety concern #1, when PVC shaters and inters your body x-rays will not find it! Switch to aluminum 6061 T6. Use snaprings and a graphite nozzle. Liners and casting tubes will help insulate case. Have fun and be safe.

Dennis
Alright thanks! I wasn't thinking of switching to Aluminum yet but I get the concern. I've seen a number of guys on Youtube build rockets within a PVC pipe with little issue, however this type of fuel can be unpredictable at times and therefore can cause issues. I assumed with proper protection it should be okay for testing. I'll have to order in some Aluminum bar stock for machining.
 
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Aksrockets

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Yes I am aware PVC will shatter under high pressure, however due to the long burn time of mine you wil notice I had an expansion of the main body. I am working on a design for an engine made for Aluminum (still looking into exact material choice), but for right now till I can figure out mixtures and nozzle size I am using PVC with a concrete nozzle. I did light this engine next to a concrete sidewalk with 2 blocks of aluminum to hold it stead, I am working to build a simple housing that will encase the engine in concrete walls and a shatterproof piece of clear acrylic. I also ALWAYS ALWAYS ALWAYS wear safety glasses with all my trials!

(BTW, my eduction is primarily in metals, we don't touch PVC as that is not a component typically machined.)

Also if you notice I am NOT talking about motor formulas, I am ONLY talking about safety concerning this "type" of engine. I talked to one of the mods prior to posting to this make sure my posting would be within the limits of the forum and I feel it is. But thank you for checking.
Instead of building a "housing" to put your engine in, just step back a hundred feet or more. That will be safer then any housing you could make.
Safety glasses, although a step in the right direction, will do little against flying shrapnel and peices of burning propellant.

https://lokiresearch.com/secure/store.asp?groupid=5520031443530
I would check out Loki rocket motors. Get a 38/240 case. Comes with a casing, closures and a reusable graphite nozzle.

Thanks for checking with the mods about the content of your post.

Alex
 

troj

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Also if you notice I am NOT talking about motor formulas, I am ONLY talking about safety concerning this "type" of engine. I talked to one of the mods prior to posting to this make sure my posting would be within the limits of the forum and I feel it is. But thank you for checking.
Yep, indeed, he did.

I actually think discussing safety publicly is a very good thing.

-Kevin
 

scubaru

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Instead of building a "housing" to put your engine in, just step back a hundred feet or more. That will be safer then any housing you could make.
Safety glasses, although a step in the right direction, will do little against flying shrapnel and peices of burning propellant.

https://lokiresearch.com/secure/store.asp?groupid=5520031443530
I would check out Loki rocket motors. Get a 38/240 case. Comes with a casing, closures and a reusable graphite nozzle.

Thanks for checking with the mods about the content of your post.

Alex
Alright I'll look into using a better casing from them, I'm still going to be building my own from Aluminum because my end goal is to manufacture my own engine with the best optimized ratio of combustion chamber ID to nozzle ID, along with the best exhaust cone shape I find for my build.

As for the safety glasses, I know its not full body protection but for the first few trials I did I was burning just a raw piece of the fuel on a block of aluminum, no combustion chamber or any sort of restriction, just to see its burn rate. Even then the flame was spitting a good deal of fuel. The only trial I have run under compression of the nozzle was the one I have the video of. I was probably 10' back with zoom on the camera and had the entire length of the engine below the siding of the sidewalk to build a somewhat barrier between me and it. I know it wasn't the smartest setup but when you finally craft that first engine and you want to see if the mix of homemade fuel and homemade engine will actually produce thrust its a bit exciting.

The only reason I want to remain close is because I am only burning under 50g of fuel, in some instances a mere 20g. I want to be close to watch the dynamics of the thrust profile and anything else that might show me an improvement I need to work on. I am working on building 2 or 3 simple boxes for my camera's to be mounted in so I can watch via video tape to keep myself at a safe distance. I am also working on producing a block of aluminum with the size of the engine bored into it, so I can drop the engine down into the bore, allowing the casing to be surrounded by solid Aluminum.

This is why I posted this thread, so I can get idea's from those who have worked with either this type of engine or just high power engines that they too have all the capabilities of blowing out and creating a hazard. I am realizing some things I didn't before.
 
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Aksrockets

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This is why I posted this thread, so I can get idea's from those who have worked with either this type of engine or just high power engines that they too have all the capabilities of blowing out and creating a hazard. I am realizing some things I didn't before.
"Creating a hazzard" is putting it lightly. Motor catos (explosions) are extremely dangerous, especially at the distance you were at. If there is a crack in the propellant or some other flaw. You end up getting a pipe bomb instead of a rocket motor.
[YOUTUBE]X3V5LJuQeXA[/YOUTUBE]
There are tons of videos on TY of idiots blowing up PVC motors.

When you static test, treat the motor like it is going to explode (cato). You'll be much safer.

Alex
 

CarVac

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If you rest the raw fuel on aluminum, you increase the rate of burn because the aluminum will conduct heat faster than the propellant itself, giving an inflated estimate. Just so you know. The standard for testing burn rates is (I believe) coating a piece of natural fiber string with it, hanging it, and lighting the bottom.

There is no one ideal case ID to nozzle throat diameter. It all depends on the propellant and the burn surface area.

Regarding safety, your plans seem to be pretty good; the mixing of the propellant is where you ought to be very careful.
 

G_T

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#1 - I'll suggest, as others have, of starting with a commercial motor. It will be safer and better engineered than your first attempts. Learn from what is done in that motor.

#2 - Are you high power certified with NAR or TRA? If you are up to level 2, then take a class on making your own motors. You have some misconceptions that I don't want to clear up in this open forum as I'm not exactly sure where the bounds are, but those misconceptions will cause you to blow up hardware. If you are not up to level 2, I'd suggest getting up to level 2. At that point you will likely receive a lot of help on EX motors if you want it at that point.

#3 - As has been pointed out, distance is your friend. There are recommended safety distances based on the size of the motor. These are to render testing and operation reasonably safe for people. Always assume a motor will fail in the most nasty annoying way possible, and arrange any test so that such failures are not a problem. Doing anything else is bordering on reckless and irresponsible. Now if you are adult and choose to take risks that is your business, but if something goes wrong then it reflects on the rest of us and that is our business. I do not think you know enough right now to have an idea of what is safe and what is not, so follow the distance guidelines as tested for Level 1 cert.

#4 - I can't tell for sure in your video, but those object near the motor look to likely be somewhat flammable if something goes wrong. You want the area around your test stand to be free from things which can burn. If your hardware fails and burning grains are spewed around, I guarantee you they have the potential to start a fire.

#5 - There are subtle but very important details for making safe reliable EX motors. IMHO you need to either take a class on doing so, or get mentored with someone who has experience at doing so. Actually, doing both is even better.

#6 - You can gain some valuable insight into rocket motors by reading through (studying) some of the textbooks on the subject. Rocket Propulsion Elements is one often mentioned. https://www.amazon.com/dp/0470080248/?tag=skimlinks_replacement-20 There are others of course. Plus there is a lot of info online if one does some research.

#7 - IMHO one can go three ways. One is to go through Level 2 certification and take a class and/or get mentoring, which is the usual way one would do it in TRA. One can do a lot more research and experimenting to re-invent the wheel so to speak, while likely being less safe and producing less certain results. Or one can go the professional route. These are not mutually exclusive of course.

Gerald
 
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scubaru

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"Creating a hazzard" is putting it lightly. Motor catos (explosions) are extremely dangerous, especially at the distance you were at. If there is a crack in the propellant or some other flaw. You end up getting a pipe bomb instead of a rocket motor.
[YOUTUBE]X3V5LJuQeXA[/YOUTUBE]
There are tons of videos on TY of idiots blowing up PVC motors.

When you static test, treat the motor like it is going to explode (cato). You'll be much safer.

Alex
I certainly should have with the first run and will from here on out. I had an itch to see it burn and jumped the gun. However its the only one I've lite so far, now that I know my mixture is at least able to produce thrust now I'm looking for more efficient mixtures and better engine designs.


If you rest the raw fuel on aluminum, you increase the rate of burn because the aluminum will conduct heat faster than the propellant itself, giving an inflated estimate. Just so you know. The standard for testing burn rates is (I believe) coating a piece of natural fiber string with it, hanging it, and lighting the bottom.

There is no one ideal case ID to nozzle throat diameter. It all depends on the propellant and the burn surface area.

Regarding safety, your plans seem to be pretty good; the mixing of the propellant is where you ought to be very careful.
I am aware of that, however given the nature of the rules of this thread I am not going to discuss any form of mixture of additives for my fuel.

Mixture I did find is key, the first batch I made I was trying to measure everything with a kitch scale (you know, the mechanical $8 ones, haha). Needless to say it burned, but it got hotter than hell and burned 3x as long as the proper mixture (via a $11 digital 1000g scale :D ). Well I've always been worried even at a faster burn rate, if in a theoretical world the fuel burned evenly and up the cylinder, it should produce XXX pressure, if my nozzle can only handle XX pressure I could be looking at a serious detonation of explosion.


I'll see your crispy horse and raise you.. well... Me!
View attachment 107146
Krusty
Can we please treat me thread with respect? I know, its the internet, but I'm trying to talk about Safety with something that can be very dangerous and I'd respect if my thread can be treated as such. Thank you.
 

krusty

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Alright I'll look into using a better casing from them, I'm still going to be building my own from Aluminum because my end goal is to manufacture my own engine with the best optimized ratio of combustion chamber ID to nozzle ID, along with the best exhaust cone shape I find for my build.
I turned up a motor out of aluminium a few years ago. Got a few flights out of it. I also tried PVC but with little success.

Personally, I have found that simply purchasing a commercial motor to be easier and safer.

As for the safety glasses, I know its not full body protection but for the first few trials I did I was burning just a raw piece of the fuel on a block of aluminum, no combustion chamber or any sort of restriction, just to see its burn rate.
Don't be complacent with any propellant - confined or not. I've seen RCandy, when rolled into a strip about the size of a pencil and an inch or two long, leap off the ground.

The only reason I want to remain close is because I am only burning under 50g of fuel, in some instances a mere 20g. I want to be close to watch the dynamics of the thrust profile and anything else that might show me an improvement I need to work on.
See my comment above.

Krusty
 

scubaru

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#1 - I'll suggest, as others have, of starting with a commercial motor. It will be safer and better engineered than your first attempts. Learn from what is done in that motor.

#2 - Are you high power certified with NAR or TRA? If you are up to level 2, then take a class on making your own motors. You have some misconceptions that I don't want to clear up in this open forum as I'm not exactly sure where the bounds are, but those misconceptions will cause you to blow up hardware. If you are not up to level 2, I'd suggest getting up to level 2. At that point you will likely receive a lot of help on EX motors if you want it at that point.

#3 - As has been pointed out, distance is your friend. There are recommended safety distances based on the size of the motor. These are to render testing and operation reasonably safe for people. Always assume a motor will fail in the most nasty annoying way possible, and arrange any test so that such failures are not a problem. Doing anything else is bordering on reckless and irresponsible. Now if you are adult and choose to take risks that is your business, but if something goes wrong then it reflects on the rest of us and that is our business. I do not think you know enough right now to have an idea of what is safe and what is not, so follow the distance guidelines as tested for Level 1 cert.

#4 - I can't tell for sure in your video, but those object near the motor look to likely be somewhat flammable if something goes wrong. You want the area around your test stand to be free from things which can burn. If your hardware fails and burning grains are spewed around, I guarantee you they have the potential to start a fire.

#5 - There are subtle but very important details for making safe reliable EX motors. IMHO you need to either take a class on doing so, or get mentored with someone who has experience at doing so. Actually, doing both is even better.

#6 - You can gain some valuable insight into rocket motors by reading through (studying) some of the textbooks on the subject. Rocket Propulsion Elements is one often mentioned. https://www.amazon.com/dp/0470080248/?tag=skimlinks_replacement-20 There are others of course. Plus there is a lot of info online if one does some research.

#7 - IMHO one can go three ways. One is to go through Level 2 certification and take a class and/or get mentoring, which is the usual way one would do it in TRA. One can do a lot more research and experimenting to re-invent the wheel so to speak, while likely being less safe and producing less certain results. Or one can go the professional route. These are not mutually exclusive of course.

Gerald
I understand the basics of how the simple Estes motors work, I can't imagine building another $20 rocket and shooting off some of those will help me. I've been all over forums, threads, databases etc looking for information. I know solid state engines are simple..yet complex. Its something I sorta want to tackle on my own. Yes, that sounds stupid. But I'd rather the thrill of watching a rocket soar into the sky in another year or two knowing its my motor, engineering, design, fuel that is pushing it up into the air. I know it sounds like I'm trying to reinvent the wheel but as simple as it might be its something I want to do. Build one from the fuel to the rocket tip.

I can't afford any major certs in high propulsion rocketry and for such reasons am currently only building motors, not rockets. I am building motors to eventually build a thrust rig and see what kind of propulsion I am producing. Then go from there to tweak my formula, change my nozzle, etc. This is more a fun little challenge I've given myself.

As for the safety aspect, I understand now that distance is my friend, I'll assure you the next video posted will be via a stationary camera and me wayyy behind it. I will also have a better cleared and prepared field and I can spare an extra $20 for a good fire extinguisher if the event rises.
 
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CarVac

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I take it you are planning on endburning? Now I see why you are thinking about diameter versus nozzle throat.

Usually that requires an incredibly fast-burning propellant: like black powder in Estes motors, or like Aerotech's super-fast-burning Warp Nine composite propellant.

If this is true, a commercial case, which is designed for core-burning, might not have a nozzle with a small enough throat available for you.

Additionally, you will need some SERIOUSLY good case insulators, because end-burning motors have very high heat loads, which over the course of several uses can ruin the temper of the aluminum and sap its strength.
 

scubaru

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I take it you are planning on endburning? Now I see why you are thinking about diameter versus nozzle throat.

Usually that requires an incredibly fast-burning propellant: like black powder in Estes motors, or like Aerotech's super-fast-burning Warp Nine composite propellant.

If this is true, a commercial case, which is designed for core-burning, might not have a nozzle with a small enough throat available for you.

Additionally, you will need some SERIOUSLY good case insulators, because end-burning motors have very high heat loads, which over the course of several uses can ruin the temper of the aluminum and sap its strength.
I have been toying with making both models that have a 1/8" Dia hollow down the center of the fuel. I am also trying solid, still gotta see what I like more.

This is why I am researching, haha! :blush:
 

krusty

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I can't afford any major certs in high propulsion rocketry and for such reasons am currently only building motors, not rockets. I am building motors to eventually build a thrust rig and see what kind of propulsion I am producing. Then go from there to tweak my formula, change my nozzle, etc. This is more a fun little challenge I've given myself.
Making your own motors isn't the way to save money.

Do you have a metal lathe or access to a metal lathe? If not, here's one that will get you started -
https://www.harborfreight.com/7-inch-x-12-inch-precision-mini-lathe-93799.html

Do you have a safe area to make your motors or are you doing this in your kitchen?
kitchen-fire-image-from-cnettv.jpg
This can really spoil your day.

These things aren't cheap and may not be covered by your health insurance...
080422112942-large.jpg
But it would make you look like the Terminator, which is cool, I guess?

I can spare an extra $20 for a good fire extinguisher if the event rises.
I would really consider a decent 2.5Gal Water extinguisher. The $20 1kg ABC dry chem extinguishers are no good for anything bigger than a waste paper basket.
Here's one on Amazon - https://www.amazon.com/dp/B001ECQ5M0/?tag=skimlinks_replacement-20

I haven't been keeping track of prices, but I'm sure it's starting to add up....

Krusty
 
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CarVac

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Actually, for rocket propellant, since it has its own oxidizer, nothing BUT water will work.
 

scubaru

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Making your own motors isn't the way to save money.

Do you have a metal lathe or access to a metal lathe? If not, here's one that will get you started -
https://www.harborfreight.com/7-inch-x-12-inch-precision-mini-lathe-93799.html

Do you have a safe area to make your motors or are you doing this in your kitchen?
View attachment 107149
This can really spoil your day.

These things aren't cheap and may not be covered by your health insurance...
View attachment 107151
But it would make you look like the Terminator, which is cool, I guess?


I would really consider a decent 2.5Gal Water extinguisher. The $20 1kg ABC dry chem extinguishers are no good for anything bigger than a waste paper basket.
Here's one on Amazon - https://www.amazon.com/dp/B001ECQ5M0/?tag=skimlinks_replacement-20

I haven't been keeping track of prices, but I'm sure it's starting to add up....

Krusty
I am in school for manufacturing engineering, my school has over 30 lathes, 40 mills, CNC lathes and CNC mills, Wire EDM, grinding and a heat treatment area. I can produce about anything (oh and free metal for small products). I am also fluent in using AutoCAD, MasterCAM, solidworks and more, I can design and build it :).

I made the first batch in the kitchen however I have a single unit burner I now cook this outside with.

Alright I wasn't sure if a regular ABC extinguisher would work, I already have 5 one gallon containers filled and ready for this.

Actually, for rocket propellant, since it has its own oxidizer, nothing BUT water will work.
Good to know, thanks!
 
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krusty

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Actually, for rocket propellant, since it has its own oxidizer, nothing BUT water will work.
You're going to struggle to put out the propellant even with water. It's really more for the exposures that will be involved.

Krusty
 

krusty

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I am in school for manufacturing engineering, my school has over 30 lathes, 40 mills, CNC lathes and CNC mills, Wire EDM, grinding and a heat treatment area. I can produce about anything (oh and free metal for small products). I am also fluent in using AutoCAD, MasterCAM, solidworks and more, I can design and build it :).
Cool :)

I have a single unit burner I now cook this outside with.
Gas or Electric?

Krusty
 

JordanT

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Personally, I find mixing anything on a hobby scale at elevated temperatures mindbogglingly stupid. (Note: I've gotten a helicopter ride and a 9 day guest stay in a room where they scrub your skin off twice a day.)

If you're just dabbling with formula, especially low pressure, go find a pyrotechnic supplier and look for convolute wound tubes. That's the same type of cardboard/paper tube which Estes uses, and is most frequently used in end or partial core burning drivers. If/when you have an issue, the results are less dangerous. If you have access to EX folks, they can probably get you on a track which is closer to correct. If not, consider making yourself a test pit and fill it with sand, or at least a large container. The ability to absorb energy is key. Nobody I've heard of uses HDPE for engine casings, but if you need a little more containment than just a paper casing, an outer casing of HDPE is a safe alternative as it turns to cotton candy in an explosion.

I won't argue that making your own propellant is fun, but please assume that anything you see on youtube has a good chance of getting you injured, and that mistakes are extremely expensive even with what might appear to be small quantities. Keep reading...and lay off the sugar - what you're looking for is out there in far better formulae.
 

scubaru

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Personally, I find mixing anything on a hobby scale at elevated temperatures mindbogglingly stupid. (Note: I've gotten a helicopter ride and a 9 day guest stay in a room where they scrub your skin off twice a day.)

If you're just dabbling with formula, especially low pressure, go find a pyrotechnic supplier and look for convolute wound tubes. That's the same type of cardboard/paper tube which Estes uses, and is most frequently used in end or partial core burning drivers. If/when you have an issue, the results are less dangerous. If you have access to EX folks, they can probably get you on a track which is closer to correct. If not, consider making yourself a test pit and fill it with sand, or at least a large container. The ability to absorb energy is key. Nobody I've heard of uses HDPE for engine casings, but if you need a little more containment than just a paper casing, an outer casing of HDPE is a safe alternative as it turns to cotton candy in an explosion.

I won't argue that making your own propellant is fun, but please assume that anything you see on youtube has a good chance of getting you injured, and that mistakes are extremely expensive even with what might appear to be small quantities. Keep reading...and lay off the sugar - what you're looking for is out there in far better formulae.
I'll get away from the PVC piping.

I just see potential to explore a field I first knew nothing about and now have a very slight and ever evolving understanding of all of this. The biggest thing that would keep me from exploring other mixtures is being on a government watch list for suspicious activity. We all know how America has become over the past 11 years, and buying any higher strength chemicals would appear to me to cause issues.

I would image there are ways to capture his chemical mix and operate it safely. I know it has potential to be explosive but with the right precautions I see at least testing mixtures on the ground being safe. If its not going airborne I can contain it's desire to blow outwards.
 
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bill2654

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I dont know why but it seems that KN03 + sugar propellants are the bastard child of rocketry. I dabbeld around with it a couple years ago and I had great results. You sound like you are taking all the right precautions when making it although I would add face shield and gloves when cooking and handling. It can be done safely. The motors I built are mostly 38mm and 29mm. I found using snap ring cases are the best hardware and simplifies things alot. Liners and casting tubes are easy to get also. I stored my motors in a section of PVC pipe that was permantly capped at one end and a screw on cap on the other. I added a small bag of rice inside also. As you know sugar propellants are hydroscopic and will turn to mush if left in the open air. I have motors that I made 2 yrs ago the are still good. Have fun and be safe.
 

G_T

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Generally speaking, in EX rocketry we AVOID working with things which have decent potential to make explosives. What we make are flammable solids which contain their own oxidizers. Their burn rate is intended to be low at low pressures, but it does accelerate when under pressure. We typically characterize propellant using a simplified formula that really isn't all that accurate in many cases but works well enough in practice enough of the time. The characterization gives us an "a" and an "n" value from which one can estimate the regression or burn rate based on the pressure. Though under really lousy conditions such as a plugged nozzle the burn rate can get rather high, it is still very low compared to even low explosives such as black powder. the propellant types we make generally cannot be detonated. That is probably part of why we are allowed to make them.

A CATO is an overpressurization phenomenon not an explosion in the normal sense. Not that the difference might make all that much difference if one is standing very close. But the difference is that were it an explosion, all of the propellant would be consumed in the blast. Instead, in a CATO of a solid propellant, grains might be thrown around or left in the case. They may even be blown out by the sudden depressurization. It is likely at least some grains will be expelled from the failed hardware and still be burning.

The exception to this sort of behavior is a N2O hybrid. Nitrous Oxide is a monopropellant, and if contaminated with organics, or under the right conditions, it can go monoprop in the tank and essentially all combust along a propagation wave. That can literally fragment a tank. Nitrous hybrids are relatively safe except for this low probability failure mode. Note - professionals have been killed by this one.

Actually, that might be a point worth noting. The safety procedures used for testing motors and launching rockets are based on a lot of experience. The safety procedures for making propellant of any sort are also based on a lot of experience (much of it from professionals developed over decades and thankfully we got to inherit it). In some cases people died teaching us those lessons. As amateurs we haven't been dying and that is in large part due to inheriting a lot of sound methodology from professionals and from experienced amateurs that preceeded us. Without knowledge and proper methodology, working with propellants is rather more dangerous than it need be.

BTW, not going airborn... Suppose the upper bulkhead fails? Then in an inverted test the test motor is likely going airborn. Just FYI. A rocket motor contains a lot of potential energy. If something goes wrong, a piece of the hardware could get a few thousand pounds of pressure behind it and in that case, it is going to MOVE!

Personally I wish you the best of success with your endeavor. I have been doing a lot of EX myself for the past little while and learned a great deal in the process. That has included countless hours reading everything from textbooks to research papers to patent applications, to private discussions. Any source of knowledge, and the more vetted the better. I also took a class in this sort of work, and did get excellent mentoring. I did it all within the system. That is really what I'm encouraging you to do. It is not necessary of course, and the choice is yours.

Gerald
 

scubaru

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I dont know why but it seems that KN03 + sugar propellants are the bastard child of rocketry. I dabbeld around with it a couple years ago and I had great results. You sound like you are taking all the right precautions when making it although I would add face shield and gloves when cooking and handling. It can be done safely. The motors I built are mostly 38mm and 29mm. I found using snap ring cases are the best hardware and simplifies things alot. Liners and casting tubes are easy to get also. I stored my motors in a section of PVC pipe that was permantly capped at one end and a screw on cap on the other. I added a small bag of rice inside also. As you know sugar propellants are hydroscopic and will turn to mush if left in the open air. I have motors that I made 2 yrs ago the are still good. Have fun and be safe.
I am always looking for advice on how to build a better engine. I think you make a valid point that PVC does have a place in rocket engines...to keep them dry, that's it. I will definitely add the face shield and gloves to my cooking, that does make a lot of sense since I have the fuel at its closes natural state to ignition and a lot of it. Thanks!

Generally speaking, in EX rocketry we AVOID working with things which have decent potential to make explosives. What we make are flammable solids which contain their own oxidizers. Their burn rate is intended to be low at low pressures, but it does accelerate when under pressure. We typically characterize propellant using a simplified formula that really isn't all that accurate in many cases but works well enough in practice enough of the time. The characterization gives us an "a" and an "n" value from which one can estimate the regression or burn rate based on the pressure. Though under really lousy conditions such as a plugged nozzle the burn rate can get rather high, it is still very low compared to even low explosives such as black powder. the propellant types we make generally cannot be detonated. That is probably part of why we are allowed to make them.

A CATO is an overpressurization phenomenon not an explosion in the normal sense. Not that the difference might make all that much difference if one is standing very close. But the difference is that were it an explosion, all of the propellant would be consumed in the blast. Instead, in a CATO of a solid propellant, grains might be thrown around or left in the case. They may even be blown out by the sudden depressurization. It is likely at least some grains will be expelled from the failed hardware and still be burning.

The exception to this sort of behavior is a N2O hybrid. Nitrous Oxide is a monopropellant, and if contaminated with organics, or under the right conditions, it can go monoprop in the tank and essentially all combust along a propagation wave. That can literally fragment a tank. Nitrous hybrids are relatively safe except for this low probability failure mode. Note - professionals have been killed by this one.

Actually, that might be a point worth noting. The safety procedures used for testing motors and launching rockets are based on a lot of experience. The safety procedures for making propellant of any sort are also based on a lot of experience (much of it from professionals developed over decades and thankfully we got to inherit it). In some cases people died teaching us those lessons. As amateurs we haven't been dying and that is in large part due to inheriting a lot of sound methodology from professionals and from experienced amateurs that preceeded us. Without knowledge and proper methodology, working with propellants is rather more dangerous than it need be.

BTW, not going airborn... Suppose the upper bulkhead fails? Then in an inverted test the test motor is likely going airborn. Just FYI. A rocket motor contains a lot of potential energy. If something goes wrong, a piece of the hardware could get a few thousand pounds of pressure behind it and in that case, it is going to MOVE!

Personally I wish you the best of success with your endeavor. I have been doing a lot of EX myself for the past little while and learned a great deal in the process. That has included countless hours reading everything from textbooks to research papers to patent applications, to private discussions. Any source of knowledge, and the more vetted the better. I also took a class in this sort of work, and did get excellent mentoring. I did it all within the system. That is really what I'm encouraging you to do. It is not necessary of course, and the choice is yours.

Gerald
I understand completely what you are getting at with working with chemical mixes that when a blast occurs can stay lite (seems a bit like napalm). I am ever working with ways to secure the engine safely for testing. I have already understood there is an inherent risk to making engines hence the reason for creating this thread seeking further knowledge. I will look into take some classes over the summer once I have funding to afford such things. In the mean time I will be working to make my processes safer and more under control.

What I am working on right now is to take a 4" x 4" stock piece of aluminum, and bore out the center to fit the ENTIRE engine inside, the create somewhat of a semi cover to hold the engine in the holder. This way if there is a detonation the shrapnel will only be able to go UP, which by the time it comes back down it will have cooled, lost speed, and I'll be far enough away to avoid any issues. The fuel however may still spray upwards and out and I'll be sure to follow the guidelines set for distance my the closest model engine I think my engines compare to. I'll also have water set next to me to prevent any issues if the fuel is launched upwards and starts a situation.


I want to make it clear to everyone that yes, I do want to continue my research and experimentation with this type of fuel, I feel given my skills, resources and brain I should be able to create a safe environment to work with these engines. I am doing all my research and always looking for safer alternatives and let that be known I am not taking creating these lightly. I want a challenge, sure its easier to buy a motor pre-made but what would the world be if all we had was people that took the simpler route, some of us need to try things out for ourselves (with guidance).
 

G_T

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The classes on propellant manufacturing that I was thinking of do not need to cost much. But they do have a requirement of L2 certification. Without L2, TRA will not allow EX... Essentially, it is an insurance thing. Nobody will let you burn an EX under your name if you are not at least L2 at a TRA research launch. Doing things on your own doesn't have that limitation but you lose a lot of advantages as well.

You live close enough to be able to take one of the classes, but you would need the cert first.

You live close enough to MDRA to check out one of their launches (like this weekend for instance, weather permitting I'll be there Saturday with two others for three EX N projects). It is about a 4 hour drive for you. L1 cert can be fairly inexpensive - it is essentially just a model rocket on steroids. Some manufacturers have certification specials for motors, and the small motors are not all that expensive. No electronics are required and motor ejection is fine. The requirements are intended to be pretty easy. I'd recommend considering it. L2 is more work of course but it doesn't have to be expensive. Get that far and I or others can recommend a good and affordable course that is within driving distance for you.

There are other launch locations not super far from you. It would be worth your time to check one of them out.

Gerald
 
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