R-Candy

[TranslucentDragon]

Hey Everyone,

So I've been searching through the forums and, of course, the mighty Google and found a couple threads about RCandy but mostly they were about how they burned and not how they were made. I'm wondering if anyone can give me a tutorial or just tell me how to make rocket candy(the recrystallization process with corn syrup as well as sugar and KNO3) as well as the science behind how it all "works". This might be an odd request but I actually want this to be a thread where a bunch of people come together and describe a bunch of different varieties of how it's made(not just the before mentioned version) so there will be a place for beginners to see how they can make the glorious stuff. Thanks everyone.

[wb2754]

As a real newbie, I look forward to gleaning a lot of knowledge and advice from the wise sages of this forum. I would like to start with something simple and "safe". I will try not to ask to many boneheaded questions.

[mikeee]

If you want to watch some good tutorials check out Scott Fintel's website.

He has a lot of information on R-Candy fuel and tutorials on making R-Candy fuel grains.

Scott has built some of the largest R-Candy rockets and knows his craft.

http://www.thefintels.com/aer/rocketindex.htm

[BurritoBandito]

By no standard am I a sage, and I'm sure you will find much better info from someone else, but here goes...

 

Firstly, let me recommend that you read Richard Nakka's work on his site here http://www.nakka-rocketry.net/

Also, I have a hard time believing that you couldn't find ANY info on how it is made... Did you really look? I only ask because there is SO MUCH info about how to make it available online. I will however patronize you, because I know when there is too much info on a subject and so many different approaches/opinions it can become overwhelming until you have a bit of understanding.

 

There are many different approaches to making rcandy. The basic formula is potassium nitrate and sugar in a 65:35 ratio. To this you can optionally add 1 to 5% rust (red iron oxide, Fe2O3) to act as a catalyst. The potassium nitrate (KNO3) can be easily obtained from your local Home Depot in the form of Grants Stump Remover (other stump removers work as well, just read the bottle and look for potassium nitrate). This form of KNO3 is prilled and must be ground to a fine powder to be used. Some recipes call for adding just enough boiling water to the kno3 to completely disolve it. This solution is then added to the sugar and heated on a very low temperature until all of the water has been boiled off and the sugar is just below the point of caramelizing. The still hot mixture is then packed into an appropriate casing using either a press or mallet and a section of wooden dowel that snugly fits inside the casing. RCandy based propellants generally do not generate enough thrust to liftoff when just the end of the fuel is ignited (this is called an "End Burner" and is usually used with more powerful fuels than RCandy). To remedy this problem a hole is formed that runs through the middle of the fuel grain. This allows for more surface area to be burned at once, resulting in more thrust. The hole or "core" may be formed by either using appropriate tooling in the ramming phase of production or just by drilling it out (caution is recommended here). When the fuel is burned it produces a plume of expanding hot gasses which are forced through a small hole in the end of the casing (the nozzle). The rapid ejection of mass from the engine causes a force to be exerted in the opposite direction from the trajectory of the ejected mass... Remember that every action has an equal but opposite reaction? Well that's what's going on here.

 

I'm sure that this probably didn't really give you all of the info to go out and build a rocket, but there is a general idea laid out for you to follow. If you just do a search of google you WILL find very detailed instructions on the process of making a rocket from start to finish... I promise it's out there, and it's not even hard to find. Go visit Richard Nakka's site. It is probably the most comprehensive amateur rocketry site that I have ever found, and he specializes in RCandy.

 

I'm sorry if I came across as rude here. I'm actually a very nice person, but it is hard to accept that you really couldn't find any info on how to prepare RCandy. Now have fun and be safe. It is very easy to accidentally ignite the mixture while cooking out the water. You may want to try to just grind your kno3 as fine as possible, use confectioners (powdered) sugar, mix them thouroughly, and just dry ram it into your casing. It's considerably less effective, but is faster and easier to make.

[TranslucentDragon]

As to your first statement... I did look around and I think it wasn't actually the lack of information, it was the excess of it... I feel like it'd be simpler just to ask what the people on this forum think and get a straightforward answer and so the information isn't just jumbled everywhere, as you said. To the second one about Stump grinder: isn't it mixed with other substances? And is there any way to get a fine powder without using a machine of some sort? And no, you weren't rude at all, you're right, there is a lot of info out there. I applaud your politeness. Also, do you know of the Corn Syrup addition to the formula? Why is it used...

[TranslucentDragon]

Also, at what temperatures would you cook it? And if I don't have hot plate or electric skillet, etc, etc... what would I use to cook it?

[mikeee]

A small coffee grinder will work to grind prilled potassium nitrate into a powder.

[mikeee]

A hot oil fryer with adjustable temperature control works good for cooking R-Candy.

A deep one with a lid works good and the non-stick surface is easy to clean.

[TranslucentDragon]

Hmm... I don't have one of those either, would it be better to put oil in a metal pot, wait til it gets to the temp you want it, measure the temp, and just use a pan in the oil?

[dagabu]

By no standard am I a sage, and I'm sure you will find much better info from someone else, but here goes...

 

There are many different approaches to making rcandy. The basic formula is potassium nitrate and sugar in a 65:35 ratio. To this you can optionally add 1 to 5% rust (red iron oxide, Fe2O3) Caution: These are not the same, rust is more correctly refered to as hydrated ferric oxide. Hydrated ferric oxide will no catalyze the propellant properly, use true Iron(III) oxide or ferric oxide (Fe₂O_{3) to properly catalyze the fuel.} to act as a catalyst. The potassium nitrate (KNO3) can be easily obtained from your local Home Depot in the form of Grants Stump Remover (other stump removers work as well, just read the bottle and look for potassium nitrate). This form of KNO3 is prilled and must be ground to a fine powder to be used. Not if dissolved first which can give you faster cooking times and a longer handling time like you note below. It can be dissolved with room temp water at a rate of 360g per liter and over 2400g per liter of water when the water is boiling to supersaturate the mixture. Sucrose will dissolve at a rate of 2000g per liter of boiling water. A liter of water weighs 1000g so dissolving 2000g of either sugar or KNO3 in 1000g of water will give you 3000g per container allowing you to measure out and cook correct ratios with little guess work. Some recipes call for adding just enough boiling water to the kno3 to completely disolve it. This solution is then added to the sugar and heated on a very low temperature until all of the water has been boiled off and the sugar is just below the point of caramelizing. The still hot mixture is then packed into an appropriate casing using either a press or mallet and a section of wooden dowel that snugly fits inside the casing This method often causes air pockets that allow for a large segment of the fuel to burn at once causing a CATO, I suggest that you use a dowel no larger than 1/4 the ID of the tube to carefully push the fuel into the casing allowing for air pockets to be pushed out.. RCandy based propellants generally do not generate enough thrust to liftoff when just the end of the fuel is ignited (this is called an "End Burner" and is usually used with more powerful fuels than RCandy). To remedy this problem a hole is formed that runs through the middle of the fuel grain. This allows for more surface area to be burned at once, resulting in more thrust. The hole or "core" may be formed by either using appropriate tooling in the ramming phase of production or just by drilling it out (caution is recommended here). When the fuel is burned it produces a plume of expanding hot gasses which are forced through a small hole in the end of the casing (the nozzle). The rapid ejection of mass from the engine causes a force to be exerted in the opposite direction from the trajectory of the ejected mass... Remember that every action has an equal but opposite reaction? Well that's what's going on here.

 

I'm sure that this probably didn't really give you all of the info to go out and build a rocket, but there is a general idea laid out for you to follow. If you just do a search of google you WILL find very detailed instructions on the process of making a rocket from start to finish... I promise it's out there, and it's not even hard to find. Go visit Richard Nakka's site. It is probably the most comprehensive amateur rocketry site that I have ever found, and he specializes in RCandy.

 

I'm sorry if I came across as rude here. I'm actually a very nice person, but it is hard to accept that you really couldn't find any info on how to prepare RCandy. Now have fun and be safe. It is very easy to accidentally ignite the mixture while cooking out the water. You may want to try to just grind your kno3 as fine as possible, use confectioners (powdered) sugar, mix them thouroughly, and just dry ram it into your casing. It's considerably less effective, but is faster and easier to make.

As to your first statement... I did look around and I think it wasn't actually the lack of information, it was the excess of it... I feel like it'd be simpler just to ask what the people on this forum think and get a straightforward answer and so the information isn't just jumbled everywhere, as you said. To the second one about Stump grinder: isn't it mixed with other substances? Yes but there are only a few percentages in most cases. And is there any way to get a fine powder without using a machine of some sort? Mortar and pestle are slow but work but are not needed if you dissolve the KNO3 in water. And no, you weren't rude at all, you're right, there is a lot of info out there. I applaud your politeness. Also, do you know of the Corn Syrup addition to the formula? Why is it used... ​It makes the propellant thinner allowing for compacting and removing air pockets.

Also, at what temperatures would you cook it? And if I don't have hot plate or electric skillet, etc, etc... what would I use to cook it? Nakka's web site has all of that information. Jacobs Rocketry also has a lot of good information.

Hmm... I don't have one of those either, would it be better to put oil in a metal pot, wait til it gets to the temp you want it, measure the temp, and just use a pan in the oil? That would be the best way to do it but I found that the oil would vaporize and foul the propellant.

[mikeee]

The reason for using a hot oil cooker is you have no open flames & you can control the temperature.

An electric skillet can also be used but you want to control the temperature so make sure it has an adjustable control.

An electric hot plate will work with a teflon skillet, did I mention make sure it has a temperature control.

[mikeee]

The hot plate process is used when you want to liquify the fuel and pour each of the fuel grains.

What size of rockets do you want to build?

Larger rockets require individual fuel grains stacked in the rocket tube above the nozzle.

Smaller rockets can be pressed as one fuel grain, but the larger r-candy fuel grains run the risk of a cato.

Edited April 29, 2013 by mikeee

[TranslucentDragon]

About Nakka's description on how to make RCandy: he only goes into detail on how to cast it by just heating the two powders together, and doesn't describe how to make the method where you use water as a medium, and doesn't even mention using corn syrup. Jacob's Rocketry did go into detail about using water and corn syrup, but I've been wondering, if you're using corn syrup: what's the ratio between the KNO3/Sugar/Water/Corn Syrup? On Jacobs Rocketry's site, it gave a couple of formulas and I was confused on which was which... I'm assuming the "Jame's Yawn Method" is the correct one?And from what I understand, the only thing that corn syrup does is increase the viscosity of the Rocket Candy. Is this right? I was going to try to make bottle rockets out of them, but, to be honest, I just wanna see the stuff burn... And sorry for the beginner question,and I know it's gonna sound stupid, but what's a fuel grain.

[TranslucentDragon]

Will a fuse that comes off of any old firework work to set this stuff off or do you need a lot of energy to hit the amount of activation energy you need?

[TranslucentDragon]

Also, what's the difference between the smoke bombs you can make with KNO3 and sugar vs the rocket fuel? Sorry for the bombardment of questions.

[alexpyro101]

http://www.youtube.com/watch?v=TqWXtjBciTw

http://www.jamesyawn.net/skillet/large/index.html

[nater]

If you are curious about James Yawn's method of making sugar fuel, it is best to go straight to the source. http://www.jamesyawn.net/skillet/large/index.html

 

A fuel grain in amatuer rocketry is a pellet of fuel cast in a tube and cored. Once dry the grains are usually loaded into a reusable casing with a nozzle. This is totally different technique than pyro rockets, in which dry, granulated fuel is pressed in small increments around a spindle in a disposable paper tube.

 

Rather than use the fuse off commercial fireworks, it would be wise just to buy rolls of visco. ( sometimes sold as safety fuse, cannon fuse etc... this is the same green fuse you see on consumer fireworks) I don't use sugar fuel, but some comps will easily light with visco and others need a little hotter prime on the end of the fuse.

Edited April 29, 2013 by nater

[BurritoBandito]

@dagabu: That is interesting about the snug dowel causing air pockets. Makes sense, I just never thought about that.

@TranslucentDragon: There really isn't much difference between the smoke mix and rcandy, just the addition of "FERRIC OXIDE" (for you dagabu ). You can also add metals like aluminum or titanium to give your rocket bit of a boost as well a tail of fire to improve night visability.

[TranslucentDragon]

That was actually the first video I watched and one of the later websites I went to, the one about James Yawn. I wasn't really going to use the fuses from fireworks, I just needed something I could compare the fuse I wanted. How would I get a hotter prime? From a different fuse or from the thing the fuse is lighting? And so the hobby rockets you buy is just compacted dry powders? If I wanted to add aluminum to the composition, would it make the sparks? So the RCandy actually smokes quite a bit unless you add a catalyst? Is there a ratio difference in the reactants?

[nater]

By "hobby rockets" I am assuming you are asking about model rockets with fins, noseckne and a recovery system correct?

 

For these you have the Estes type BP motors, which are end burning motors made with black powder pressed into a cardboard tube at a high pressure. Anyone can buy these and fly them in small rockets without permits.

 

As rockets get larger, you move away from BP motors and into different composite fuels. These are cast into grains as I mentioned above. Single use motors and reload kits are available, anything "H" impulse and above is considered high powered rocketry, and there are self imposed regulations by the industry overseeing their purchase and use.

 

---

There are various means of priming fuse, and different comps might need a different technique. Basically a little comp which burns hotter than the fuse is "glued" to the end the fuse to help ignite a hard to light comp. Sorry for being vauge but your questions are all over the place and it is starting to get confusing. You are asking about two different types of rocketry, smoke bombs, and fusing methods. It might be easier and get you better answers to work on one topic at a time.

Edited April 29, 2013 by nater

[BurritoBandito]

If I wanted to add aluminum to the composition, would it make the sparks? So the RCandy actually smokes quite a bit unless you add a catalyst? Is there a ratio difference in the reactants?

@TranslucentDragon: There really isn't much difference between the smoke mix and rcandy, just the addition of "FERRIC OXIDE" (for you dagabu ). You can also add metals like aluminum or titanium to give your rocket bit of a boost as well a tail of fire to improve night visability.

 

It will still produce quite a bit of smoke even with the Fe2O3. The catalyst improves the thrust from the rocket. Pretty much (to a degree) the more sugar you have the slower the burn will be and the more smoke will be produced. You could also add a small amount of baking soda to slow the burn down in a smoke mix to improve the performance. Yes the addition of aluminum shavings will produce sparks.

 

Edit: http://www.nakka-rocketry.net/sucrose.html#Preparation

Read the section entitled "Alternate Methods". He briefly describes the water and corn syrup techniques.

Edited April 29, 2013 by BurritoBandito

[dagabu]

That was actually the first video I watched and one of the later websites I went to, the one about James Yawn. I wasn't really going to use the fuses from fireworks, I just needed something I could compare the fuse I wanted. How would I get a hotter prime? From a different fuse or from the thing the fuse is lighting? And so the hobby rockets you buy is just compacted dry powders? If I wanted to add aluminum to the composition, would it make the sparks? So the RCandy actually smokes quite a bit unless you add a catalyst? Is there a ratio difference in the reactants?

 

There is no difference in the amount of smoke produced by R-candy fuel, the catalyst just helps it burn faster.

[TranslucentDragon]

I'll stick to two topics because I was getting confusing myself about how I worded things and such : How would one set up the fuse to correctly set off a bottle rocket so said person wouldn't blow my everything up? Should I use Black Match connected to a piece of visco? And although I love all the great information on here, no one has really said anything about what they would recommend to make and which methods to use(although i probably missed a bunch of subtle recommendation)... What have you all tried? What worked well for you guys? Edited April 29, 2013 by TranslucentDragon

[nater]

For bottle rockets, BP has worked well for me. To fuse them, I just stick a piece of visco in the core of the motor. Like I said, I don't use sugar fuel, so that might not be the answer you are looking for.

[BurritoBandito]

If all else fails fusewise you can make a pretty ghetto fuse by getting a thin straw and repeatedly shoving it into your still hot fuel until the straw is completely full. Then you roll the straw on a hard surface, while applying light pressure with your hand. Keep doing this until the fuel is thin enough that it is capable of being removed from the straw. This will work, but it's kinda crappy because if a molten glob falls off it could wind up breaking of the section of "fuse" which has been lit. Also the "fuse" will be brittle. Plus you really want to ignite the grain at the back end (away from the nozzle) so that the whole core lights up quickly. Another option would be to use a sparkler as a fuse, but I would recommend just buying some fuse from skylighter.

 

Edit: you can prepare the fuse to more easily ignite the fuel by disolving 6 ping pong balls in 250mL of acetone. This will make a nitrocellulose laquer substitute that you can use to "glue" some black powder to the fuse. Then shove the fuse as deep into the core of your rocket as possible, so that it ignites the back end of your fuel grain.

 

I would suggest using the water method, if you are comfortable with cooking the fuel. If not then I'd dry ram it. If you do choose to go the water route you can add around 4% corn syrup, by weight, prior to cooking to make your fuel a little bit more pliable. The formulas I personally would use are

 

Just water or dry rammed:

64.5 : 34.5 : 1 - KNO3 : sugar : Fe2O3

 

Water & corn syrup:

64.5 : 30.5 : 4 : 1 - KNO3 : sugar : corn syrup: Fe2O3

 

The amount of water is not important as you cook it off anyhow. Just use as little boiling water as you can to completely dissolve the KNO3, the sugar will melt.

 

As for the casing, you can use a section of PVC pipe. If you go this way it is recommended that you line the inside of the pipe with a few layers of paper to prevent the grain from binding to the PVC. Otherwise, when the PVC gets hot and expands, the grain will not and will end up cracking. This results in more surface area burning (increased pressure), which can lead to an explosion (CATO).

For the nozzle and bulkhead (the top cap) you can use your dowel and mallet to ram some kitty litter (bentonite clay) into a solid plug. Then you just drill out a hole for the nozzle. The size of the hole will depend on the fuel and amount of surface area that will be burning..

I think (and please someone correct me if I am wrong on this) a good rule of thumb is the nozzle should be about 1/3 of the inner diameter of your casing. For stabilization you can glue a stick to your engine. The stick should be just long enough to balance on your finger just behind the nozzle.

Edited April 29, 2013 by BurritoBandito