theoratically best cheap r-candy?

[modelrocket]

Keep in mind I didn't look into chemicals like sorbitol because that is way too expensive for me

 

The mass ratio is 90.29g KNO3, 33.51g glucose (C6H12O6) and 1.2g Fe2O3

 

I haven't tested it yet, but I will soon (and compare it to alot of other compositions).

 

Glucose because: when you melt tablesugar it turns into a 50/50 mix of glucose and fructose, glucose is an aldose sugar whilst fructose is a ketose (placement of the aldehyde group). Aldose sugars are better in redox reactions.

conclusion glucose is the best fuel (that isnt expensive).

 

 

What do you guys think?

Edited October 24, 2014 by modelrocket

[Mumbles]

When you melt or dissolve sucrose, it does not necessarily split into fructose and glucose (invert sugar).

[modelrocket]

When you melt or dissolve sucrose, it does not necessarily split into fructose and glucose (invert sugar).

Please elaborate, im interested

[Mumbles]

I'm not sure what more there is to elaborate on.

 

When you dissolve sucrose in water, it stays as sucrose

You can melt sucrose it undergoes much more complicated chemical reactions than just splitting. See caramel, which actually results in higher molecular weight compounds.

 

You may want to look more into invert sugar to see how it's actually split. It's usually done via acid catalyzed hydrolysis at elevated temperatures, or via enzymatic processes. You need water around to split it anyway. The easiest way to tell is that invert sugar doesn't crystallize well at all (a la honey, corn syrup, etc). The ability to make rock candy should be proof enough that you dissolve it in water, and even heat it, without causing it to disproportionate.

[stix]

Depends what your burn rate and motor configuration requirements are.

 

This is my standard and 'best' r-candy recipe:

 

64 : KNO3

33 : Dextrose/Glucose Powder

3 : Dextrin

.1 Carbon Black

 

The reason I use glucose powder is that it melts at around 145C as apposed Sucrose at 185C - saves a lot of burnt fingers. When maintained at around 125C it's more manageable as it stays softer longer especially with the introduction of dextrin. No need to rush to make your motor.

 

This fuel burns slower that the standard 65/35 KNSU but that's exactly what I want because I make bates grains. The carbon black is there because I read somewhere that it stops transmission of heat through the somewhat translucent fuel. Might be complete garbage, but I prefer my fuel to look black, ie. black powder

 

The glucose is a bit more expensive than white sugar but that's a compromise I'm happy to make.

 

btw. technically I'm using the 'melted' method where the KNO3 has been milled, which in my experience is more consistent than the re-crystalised method.

 

I'm also getting a specific impulse of around 95 which is pretty respectable.

 

 

Cheers.

Edited October 24, 2014 by stix

[Oinikis]

I do my rcandy like so. 2 parts of KNO3 1 part of sugar, and 1 part of water. This gives O/F ratio of 66.7% which is just about right. I put nitrate and water in the pan, heat and mix untill it's dissolved, and only then put sugar. Sugar melts on it's own, while nitrate doesn't thus it needs water, and doing this allows me to use least amount of water. Anyway, then you heat, mix, and do the regular cooking procedure. Using this fuel I hit 80s Isp, using low chamber pressure. Also via calculations I found that my Rcandy follows Kn vs. chamber pressure graph found on Nakka's website, so it means my Rcandy performs well. I don't use glucose or syrup, becouse I don't think it raises Isp, and only thing it does is lowers melting point and i'm not really interested in it, becouse I have no problems with handling hot rcandy and casting it. Also I don't think Fe2O3 is really a game changer, becouse it only catalyses reaction, making it burn faster, and increasing chamber pressure. Same thing can be achieved by increasing Kn, thus increasing chamber pressure, and increased chamber pressure increases burnrate, giving the same effect. I think the most important thing when making Rcandy is cooking it correctly, becouse you can really spot the difference between correctly cooked rcandy, and incorrectly cooked one (not mixed correctly, burnt, or whatever).

[modelrocket]

 

 

I'm not sure what more there is to elaborate on.

 

When you dissolve sucrose in water, it stays as sucrose <--- Fact

You can melt sucrose it undergoes much more complicated chemical reactions than just splitting. See caramel, which actually results in higher molecular weight compounds. <--- Also fact

 

You may want to look more into invert sugar to see how it's actually split. It's usually done via acid catalyzed hydrolysis at elevated temperatures, or via enzymatic processes. You need water around to split it anyway. The easiest way to tell is that invert sugar doesn't crystallize well at all (a la honey, corn syrup, etc). The ability to make rock candy should be proof enough that you dissolve it in water, and even heat it, without causing it to disproportionate.

So does this happen to 100% of the sugar? or to just a little bit?

 

And what actually hppens when you burn it? the exact same but more rapidly? or do you then skip the caremelization

Edited October 24, 2014 by modelrocket