KN Sucrose cooking incognito

[w55561]

Hi, Im trying to make rocket candy with KN and sucrose with no success. I tried many times, other methods, other cooking temperatures, and the products all fail to burn properly.

This is what Im using to cook:

- Yara fertilizer Krista K 25kg bag, not powder, but very fine granular form;

- Icing sugar (contains a bit of corn starch) and granulated sugar;

- Electric skillet with iron pot above to homogenize the heat;
- Infrared thermometer, dimmer to control the electric skillet power (I bypassed the safety of the electric skillet, which works with 2 options: 100% or 0% power, when it heats to the desired point, it turns off, so with it bypassed, it is always on and wont turn off via the thermostat);
- Corn syrup (Karo);

- Silicon spatula;

 

Cooking method i have used:
65% krista k, 35% sugar, cooked for a few minutes (5-8min) with pot pre heated to 180ºC and stabilized temperature (356ºF) till it become "liquid", trying to not caramelize the sugar, ending with light brown propellant.
I also tried 160ºC, 200ºC, 60/40 rate, powdered Krista K, granulated sugar, refined sugar, icing sugar, with karo, without karo, with water, and all burn tests failed.

All grains where very sticky after a few minutes after the cooking process.
The burn tests where conducted at normal atmospheric pressure (not inside a motor), in small batches.
The propellant ignites with some resistance, not easy. It burns slow, not uniform like some videos ive seen, where the flames produced are constant and uniform, make white bubbles in liquid form, and left a black coal-like residue.

 

Inside the test "motor", which consists of a steel pipe with closed with caps, but one cap with an 10mm hole, which is the nozzle, just to test if it creates enough pressure to give some thrust.
All the motor tests failed, taking long times to burn and producing a lot of white smoke. Only one worked well, which is the propellant i cooked on the gas stove (outside with precaution, small batch).

The one cooked on the gas stove, burned kind of fast (5-8s), and the cooking time was fast, 3-4minutes, not controlled temperature. I noticed steam/smoke during the cooking in the gas stove.

There is a video of one burn test attached to the post.

 

So my question is, which part of the process could be going wrong? Could my KN be wet (at least it doesn't seem)?

Edited December 31, 2015 by w55561

[MadMat]

I looked up the MSDS for your Krista K, apparently it's fairly pure potassium nitrate (have you tried making BP or anything else with it with success?).
Cooking Rcandy without water means the chemicals need to be milled very fine to get intimate mixing. If you dissolve your ingredients in water and boil off the water, milling isn't necessary. Because of this I always use water for my Rcandy. If you plan on casting your Rcandy in the rocket tube, you don't really need the Karo syrup. Karo is added simply to make the grain less brittle. If you're cooking to 160c there won't be any moisture left. So, if you mix 65% KNO3, 35% granulated sugar, add enough water to dissolve the chems completely (add water slowly and let it heat up before adding more, it's surprising how little water will be needed to dissolve everything when it's hot). Cook it to 160-170c stirring often. You should get a good fairly fast burning rocket grain. If not, I would suspect your Krista K of being bad for pyro work.

Edited December 31, 2015 by MadMat

[w55561]

I looked up the MSDS for your Krista K, apparently it's fairly pure potassium nitrate (have you tried making BP or anything else with it with success?).

Cooking Rcandy without water means the chemicals need to be milled very fine to get intimate mixing. If you dissolve your ingredients in water and boil off the water, milling isn't necessary. Because of this I always use water for my Rcandy. If you plan on casting your Rcandy in the rocket tube, you don't really need the Karo syrup. Karo is added simply to make the grain less brittle. If you're cooking to 160c there won't be any moisture left. So, if you mix 65% KNO3, 35% granulated sugar, add enough water to dissolve the chems completely (add water slowly and let it heat up before adding more, it's surprising how little water will be needed to dissolve everything when it's hot). Cook it to 160-170c stirring often. You should get a good fairly fast burning rocket grain. If not, I would suspect your Krista K of being bad for pyro work.

I haven't tried to make BP yet.

I tried cooking with water today, but the results where even worse (wont ignite, extremely hygroscopic) and now, about 8 hours after cooking, it is very wet and still flexible.

I find strange that it works when i cook on gas stove, and fails when e follow the steps on nakka and other rocketry websites (all similar) on the electric skillet.

[MadMat]

Hmm... There shouldn't be any water left if you cook it to that high of a temperature. Try going as high as 175c. Stir constantly (it helps the water to evaporate faster). Yes Rcandy is hygroscopic, but you shouldn't be having that many problems. Maybe you are getting bad temp. readings from your infra-red thermometer? I usually don't use a thermometer. Is there any boiling action going on when you think you are done? I have also noticed that when the water is just about gone, the Rcandy starts to actually smell like carmel candy and you won't see any boiling type action going on. The mixture should get pretty hard upon cooling, if not, it's probably not cooked long enough. Or your maybe your Krista K just won't work. FYI, good Rcandy does produce a large volume of white smoke when it burns. Another thing you could try is to just cook a small amount of it until it actually does start to caramelize (turn a tan-brown color) and see what happens. Caramelized Rcandy will have a slight loss of power, but at this point, I would like to see if you can just get the stuff to burn decently. One more thing.... cooking Rcandy over a gas flame is rather dangerous. As it's boiling small drops of it do float up in the air, which could be ignited by the flame

Edited December 31, 2015 by MadMat

[MrB]

Inside the test "motor", which consists of a steel pipe with closed with caps, but one cap with an 10mm hole, which is the nozzle, just to test if it creates enough pressure to give some thrust.

 

That should work great as a pipebomb.

 

 

I looked up the MSDS for your Krista K, apparently it's fairly pure potassium nitrate (have you tried making BP or anything else with it with success?).

-/Snip/-

If not, I would suspect your Krista K of being bad for pyro work.

 

Krista K Plus has been my only source of KNO3 for the last... 15 years or so. There is no issues with it. Krista K seams to be the same product, but sold in a different region?

B!

[MadMat]

 

Krista K Plus has been my only source of KNO3 for the last... 15 years or so. There is no issues with it. Krista K seams to be the same product, but sold in a different region?

B!

 

 

 

Well that's good to know. It has got to be a problem with lack of cooking then. ...Or... badly contaminated sugar??

Edited December 31, 2015 by MadMat

[lloyd]

You should review Jimmy Yawn's R-candy method, here:

 

http://www.jamesyawn.net

 

Lloyd

[Nessalco]

Another excellent resource is Nakka site - he's a part of the SugarShot to Space project - launching a sugar propellant motor to 100km.

 

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

 

If you look under "Propellants" you'll see methods for KNSU, KNDX, and KNSB - all slightly different. There is also a lot of information about performance characteristics.

 

Kevin

[MadMat]

Lloyd

That's a website I've missed... very informative!

[stix]

The KNSU 65/35 ratio is pretty much the standard. If your KNO3 is pure enough - which does seem to be the case according to others, and unless your sugar is somehow badly contaminated, then that only leaves the method.

 

Looking at your video the slow "spluttering" burn is characteristic of fuel that's not incorporated enough because the KNO3 isn't fine enough. Although it could also be too wet if the moisture wasn't driven out.

 

My first suggestion is to follow the "dissolved/re-crystalised" method as Lloyd suggested from jimmy yawns website. The exact instructions are here (although I would be inclined to drop the karo): http://www.jamesyawn.net/skillet/large/index.html

This is the simplest method if you don't have a ball mill or grinder. If you follow these steps you should have success.

 

Alternatively you could use the "melted" method. If you don't have a ball mill, get yourself a coffee grinder and mill up the KNO3 until it's about the consistency of icing/confectioners sugar. Combine with (pure) icing/confectioners sugar and mix in a container shaking it around for a few minutes. Pour into your electric skillet and stir until melted (186C). Cast.

 

Cheers.

 

Scott Fintel is another good source of info: http://www.thefintels.com/aer/protected/castingsugar.htm

Edited January 1, 2016 by stix

[navyou14]

Hello! Im new to this forum but have hard gaining access to Potassium Nitrate. I wanted to make a K & Sugar rocket but have only access to sodium nitrate. Does sodium nitrate work well to make r-candy rockets?

[MadMat]

I've never tried Sodium nitrate, but I imagine it would work, unfortunately, sodium nitrate is rather hygroscopic itself. Making a mixture of two hygroscopic components is going to spell double trouble with it absorbing moisture.

Edited January 21, 2016 by MadMat