KNO3/Sugar rockets!!!

[KinneticEnergy]

I noticed this question was asked earlier, but no one answered it. Has anyone had any experience using other sugar forms? Say Sucralose for example, or even saccharin? I realize the ratios between oxidizer and fuel would definitely change. Any thoughts on this?

Sorbitol makes a unique fuel. In a Kn/Sb 2:1 ratio it is quite potent. It does not tend to cato nearly as much, due to the slightly slower burn rate. It dries much quicker, and as nearly impossible to caramelize. So it can be safly made by melting them together.

[Mumbles]

Sorbitol has a melting point a bit lower than the boiling point of water(95C). I'd suggest using a double boiler to melt it, instead if direct heat. It will melt much more evenly. As far as being able to safely melt it together, that is still up in the air without any other data, and the person doing it.

[KinneticEnergy]

Check out this site for more "data".

Main site:

 

http://www.nakka-rocketry.net/

 

Kn/Sb page:

 

http://members.aol.com/riccnakk/sorb.html

[devilman]

Ive been trying to make some sugar rockets with a 75/35 mix. The tubes im useing are 20mm id. Ive tryed both 95mm and 70mm lengths, different core sizes and corless rockets, but 99% of them have exploded the nozzle out. What could i try to stop this, smaller tubes or a different mix?

 

any help is appericated, cheers

[KinneticEnergy]

Niether, it sounds like you need a new nozzle mix. What are you using atm?

[devilman]

kitty litter rammed. I did a little more research and found the problem. I was casting the fuel directly into the pvc tube. The tube was flexing but the fuel was not, so it cracked and cato'd. I have added 3 layers of paper inside the tube and i can now use a 5mm nozzle on a 25mm od rocket without a cato.

[KinneticEnergy]

Do you re-crystallize your propellant? Or do you just melt it?(Just to clarify, I'm asking what you do, not asking for suggestions as to myself)

[devilman]

i havent bothed making any rcandy yet, it takes ages to make and i dont have the time, so i have just been melting the kno3 + su. It works pretty good, gets em of the ground. The only problem i have now is making them go straight up, i added a guide stick and weighted it properly ( balance on finger just behing the nozzle) but the all want to fly straight accross, insted of up.

 

Im useing a bit of abs pipe in a sizzor jack to launch them, stick goes down the pipe with the fuse on the outside.

 

any thoughts on how to make them go straight up?

[KinneticEnergy]

Care to post any pics of your rockets? Or a vid of a sample of propellant could help(maybe even a vid of a launch)... The finger balance trick is a myth, it all depends on the length of the stick, the longer the better(No pun intended). Do your rockets have a slow liftoff? If so, how long does it take for them to get into the air? Because if the liftoff is slow enough, the rocket will stall, tilt sideways, and travel parallel with the ground. Do you use a hand drill for your nozzle? If you do, than you could be drilling the nozzle at a slight angle, causing the rocket to fly slightly sideways.

 

As you can see, you should elaborate on your contruction alot before asking very vague questions..

 

EDIT: I forgot to mention one thing -- Safety.

If you're not already, you should be wearing a full face mask, thick gloves, and a welders apron. Not to mention cooking this stuff outside... Simply melting these ingredients together is INTENSELY DANGEROUS, and IMHO is something unnecessary and foolish. It's better to take the extra 25 minuets to recrystallize this stuff... Melting is much more dangerous, and provides quite poor propellant as compared to the former method.

 

Thanks in advance for considering my advice, and stay safe .

-Kinnetic

[ecko]

Mine never work with just kno3 and sugar, no matter the ratio.

 

So I use

 

kno3-63

Sugar-27

Sulfur-10

 

Works perfect, but I ram half with that, fill up the other half with bp.

[KinneticEnergy]

Mine never work with just kno3 and sugar, no matter the ratio.

 

So I use

 

kno3-63

Sugar-27

Sulfur-10

 

Works perfect, but I ram half with that, fill up the other half with bp.

I'm assuming you are dry mixing this stuff... Have you tried grinding them together? Milled 65/35 kno3/Sugar propellant is definitely fast enough to get a rocket off the ground. There's a vid on youtube demonstrating such, I just cant seem to find it...

[spdreader]

Does anyone know how dissolving the KNO3 and sugar, then evaporating off the water compares with dry mixing and melting? I know its sure a lot easier than melting.

 

Also, would adding iron oxide increase the burn rate, and if so, about how much should i use?

[Tweetybird88]

I would assume that all you would be left with is just poorly mixed KNO3 and sugar. They really wouldn't combine together in any way I could imagine. In fact you would probably see one just crash out of solution first and the then the other, and once dry, this would be layered, and worse then just mixing them dry. I'm no chemistry wiz but thats what I would assume would happen.

[KinneticEnergy]

Does anyone know how dissolving the KNO3 and sugar, then evaporating off the water compares with dry mixing and melting? I know its sure a lot easier than melting.

 

Also, would adding iron oxide increase the burn rate, and if so, about how much should i use?

The method you described is called re-cystallization, the only thing that differs from the usual, is the lack of karo syrup. If you want some info on it, check out this link

 

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

 

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

 

As explained in the video, 1 gram of red iron oxide for a 100 gram batch is about right.

 

If you would rather make a powdered propellant, and not use any karo syrup, you can try this method.

 

http://www.pyroguide.com/index.php?title=R...Candy_Powder%29

 

If you still have any questions, throw me a pm.

 

-Kinnetic

[ActionTekJackson]

I would assume that all you would be left with is just poorly mixed KNO3 and sugar. They really wouldn't combine together in any way I could imagine. In fact you would probably see one just crash out of solution first and the then the other, and once dry, this would be layered, and worse then just mixing them dry. I'm no chemistry wiz but thats what I would assume would happen.

actually, I dissolved kno3 and sugar in water once and left it in a jar all summer (the solution) and came back and there were these really cool crystal growths that when I broke a piece off and lit it it burned pretty well, so not sure that is actually what would happen... I'm not chem wiz either tho...

[justanotherpyro]

Does anyone know how dissolving the KNO3 and sugar, then evaporating off the water compares with dry mixing and melting? I know its sure a lot easier than melting.

 

Also, would adding iron oxide increase the burn rate, and if so, about how much should i use?

Your best bet would be to saturate a boiling solution with the KNO3/Sugar mix and then move the pot/pan directly into an ice bath. Usually the main goal of crystallization is to purify a particular chemical. Slower recrystallization tends to do a better job separating two chemicals if they both crystallize out of solution. Your best bet to get around this is to crystallize as fast as possible which will form finer crystals as well. I don't really think that recrystallizing the two together is the best way to go, but it could turn out pretty well.

[ActionTekJackson]

I think for most people a true technical recrystallization is highly impractica. The common method referred to as recrystallization, is more dissolving a modified sucrose composition adding karo syrup (I think this helps with mouldability more than anything), and evaporating off the water at a controlled rate while mixing it. This allows for a much more intimate mixture of the chemicals, while keeping it warm which keeps the sugar soft and much easier to press into a grain once its dry enough. *the amount of water left in your propellant is extremely important, none is preferred, but good luck with that, just stick to the snap test as shown on the youtube vid posted earlier and you should be ok.*

[Yankie]

I don't know why people bother with recrystalisation and melting as the dry milled powder makes some awesome rockets. mine went about 150 metres (2cm by 7cm) is the only benefit a 20% extra burn time?

[psyco_1322]

Its a more homogeneous mix also. I agree with you that the dry mix is just about as effiecent. But most people making recrystallized fuel are doing it for high powered rockets. They are molding grains to reload into expensive metal casings that are used over again. I dont think they would like to have to try and set one of those cases up in a press and risk runing something. So its a good choice for them, for the small guys like us its just extra work. Paper is cheap....sometimes.

[DIYMark]

Some people have used KNSU with sulfur and others have used KNSU with Fe2O3 and that works good too. So why not use KNSU with a percentage of sulfur AND Fe2O3? Anything bad with this?

[Deceitful_Frank]

From my experience with this propellant the one flaw that immediately strings to mind is the very high burn rate of KNSU whether recrystalized, dry mixed or melted.

 

If you are intending to send your craft up vertically then you want to extend the burn rate as long as possible (within reason) given the same total impulse available as all things being equal, we all know that the slower rocket with 100Ns goes higher than the faster one with same total impulse.

 

Sure, if absolute speed is what you are after for instance in a 200m horizontal sled with on-board camera then the quicker you can spit out those 100Ns the better as the rocket will be exposed to those crucial frictional and aerodynamic forces for a shorter time.

 

Unless you are making very small motors then adding anything that would reduce Isp (sulphur, although it does make it easier to ignite) or speed up the burn (Fe2O3) is going to be counter-productive.

 

Uncatalyzed rcandy under chamber pressure can burn at half an inch per second. In my 1.25" Aluminum motors this equates to >0.4 second useful burn time when burning an unrestricted free standing 27mm cored grain!

 

With fire up and tail off its all over in 0.7 seconds, great for sending a cam in video mode to 400mph but not ideal when altitude is what you are after.

 

Best to stick to 65/35 melted or 60/40 recrystalized nice and pale. Forget the catalysts and use a wide motor tube or investigate the bates grain.

[DIYMark]

Thank you so much!

 

Ive also just got back from tests and in order of ascending 1 atmosphere burn rates the results are...

 

KNSU

 

KNSU + Sulfur (1% S)

 

KNSU + Fe2O3 + Sulfur (0.5% S and 0.5% Fe2O3)

 

KNSU +Fe2O3 (1% Fe2O3)

 

KNSU catalyzed with iron oxide is about 2 times as fast as regular KNSU but the burn is completely different. Plain KNSU has a nice hiss with a purplish flame where as the Fe2O3 batch is quieter and more has more flame/sparks. It seems that although the KNSU burn rate is faster - it seems to be "worse" for lack of better words.

 

So what your saying by a wide motor tube is for core or end burning engines?

 

And am I right in thinking this - 50N thrust for 2 seconds WONT send up the same rocket as high as if 100N for 1 second was used?

 

My theory is that from 50N, the amount of thrust needed to over come the rockets mass makes up a greater percentage than it would out of 100. So say to rocket needs 10N of thrust to be "weightless" and any more makes it accelerate up.

 

Now say you have 2 rockets. I that delivers 50N for 2 seconds and one that delivers 100N for 1 Second. 10N/50N is 20% of the thrust is needed to lift the rocket. Where as 10N/100N is only 10% of the rockets thrust is needed...

 

Am I right or for this should I use the Impulse for this "calculation" which then would mean 50N for 2s or 100N for 1s would send a rocket up equally as high.

[Deceitful_Frank]

What I am basically saying is that for KNSU, forget the cardboard tube. If you want to make small rockets with cardboard then stick to BP as your fuel and use core burners or end burners depending on your BP formulation and the weight of the rocket to be propelled.

 

I personally would not bother with a core burning engine using KNSU. If I am going to go to the trouble of making cast KNSU or rcandy then why would I throw it all down the shitter with an inefficient engine design?

 

I personally believe that when using fast sucrose, rcandy is better. it is denser and does not contain air voids and this for me more than makes up for the slightly less than ideal 58-60% KN in the mix. 70% is in theory the stoichiometric ideal but forget this as max Isp peaks at the lower 65% I don't know exactly why but this is apparently true.

 

Yes you do have a point that the rocket's weight will act against thrust before upward acceleration is achieved but I disregrded this because the mass should be very small compared with a motor kicking out 40 pounds of thrust. In your example you say 10N/50N for 2 seconds. would you really put a 100Ns motor in a rocket weighing near to 1 kilo?!

 

Doubling your velocity through the atmosphere requires EIGHT times the effort. 50N for 2 seconds will be slower and 100N for 1 second will be faster but all other variables being equal will NOT send a rocket up as high.

 

A rocket that developes twice the thrust for half the time will not accelerate to twice the speed to make up for the short burn time... unless it is being fired in a vacuum!

[DIYMark]

Awesome thanks for that reply.

 

Now that I know its eight times as hard, well Ill take the 50N for 2 seconds Also my numbers were an example as was my thinking! In school all they crap on about in physics is "Ideal" conditions (Vacuum etc) - good luck finding that!

 

So from here it'll be UNcatalyzed KNSU rockets. Now, my rockets will be 16mm ID and the "larger rocket" will have 19mm ID. For the 16mm one I'll use the tooling I made (Cored) and just either pack Rcandy down and around it or use Rcandy dust (coffee grinder) and dry pack it. However for the larger 19mm rocket I will make tooling to form nozzles and tooling to cast grains. As for grains Bates seem as a good idea but ill have to re-revise some stuff on them. If I'm not mistaken wasn't it like 1.6 times the ID is the length of each grain (in order for near flat thrust graphs?)

 

EDIT - Ive got a hold of some Bates Grain Calcs however I was wondering is there any "ideal" Kn I should be aiming for when using uncatalyzed R Candy? 120? 140? or is more the better as long as I can stop a CATO happening?

[Deceitful_Frank]

I prefer my bates grains to have the following proportions:

 

core ID to be 1/3 grain OD and with a length of 5/3 or grain OD.

 

These for me are the ideal proportions as it looks good, keeps calculations simple for working out Kn and your peak thrust isnt too much higher than the beginning and end... which in theory are identical.

 

As an example in my 1 1/4" OD 16swg Al tube I use 27mmOD with 9mm ID core and 45mm long. without the inhibitor each slug weighs about 39 grams.

 

Kn really needs to be over 200 at start and finish of burn. I've taken it over 300 in Al tubing but to be honest anything more than 250 isn't going to increase your Isp by much and will just be getting close to burst pressure which is not good. If you are using PVC and not going over 19mm I'd shoot for 200 at the start and finish bearing in mind that mid-burn it will go a little higher... maybe 230 ish.

 

Don't use rcandy dry-packed dust. Even if it all doesn't turn into a pipe bomb you can never reproduce good results with any degree of accuracy.

 

At the moment I am looking to get the most impulse I can from my 1 1/4" tubing for a wire guided rocket sled. Obviously for mine its all about speed so no bates grain for me. Just a free standing grain as long as the design will allow lit as quickly as possible. If I can get it all burned and spat out the back in >0.4 seconds I'll be happy!