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Estes Model Rocket Motor Propellant Type? Answered

What is the propellant in an Estes rocket motor?  Also at what ratio are the ingredients in the propellant.  Any help is appreciated.



Best Answer 6 years ago

The mfg. probably hasn't and won't release the exact recipe but there are several sites that have "fiddled" around and found a substitute and have created what looks to be good directions for making a replacement. Do I need to mention that you should be careful?

Site 1

Site 2

Thanks for the links. I just made potassium nitrate from ammonium nitrate and potassium chloride and I was wondering what would be a good rocket fuel mix that uses potassium nitrate as the oxidizer?  Is 60% potassium nitrate and 40% sugar a good rocket propellant mix?

I've opened up one of those motors before. I'm 98% sure that it's black powder, both from research, and the fact that when I burn them, they just smell like black powder.
I'm not sure of the precise ratio that they use, nor do I know if they use any additives in their mixture. When companies make a product, they're required to tell you what it's made of, but they can keep the ratio to their self. It's likely that the exact ratio is proprietary.
If all you want to do is to propel a rocket into the air though, any black powder will work.
Keep in mind though, that making black powder isn't as simple as just mixing the ingredients. There are special processes that must be done to the mixture to turn it into full-fledged fast burning black powder.

What would make the black powder burn faster? Also, where could I get sulfur for the gunpowder?

Well, I got may sulfur from a gardening store, along with some KNO3 stump remover. I believe the sulfur is used as a soil additive or something. It wasn't very expensive, if I remember correctly. Be prepared to search a lot though. the closest store to my house that had it was about 30 miles away.

As for the "special processes", basically you need to mix the KNO3 with the other ingredients very well. But, I mean VERY well. I only have ever heard of two ways of doing this, but there may be others.

The first is to run it in a ball mill for several days. This also has the effect of grinding it to an ultra fine powder that burns very well. (which may or may not be good. Some pyrotechnic formulations specifically call for coarse black powder. If you need details on this, I could tell you if you want) If you do decide to take this route, please, PLEASE use a proper ball mill and grinding media. If the ingredients somehow ignite BEFORE they're mixed, the worst you'd probably get is a ruined ball mill and some smoke. But when the KNO3 is mixed properly with the ingredients using this technique, now you have an explosive device that could potentially KILL you.
The second is to deposit crystals of KNO3 directly onto the charcoal and sulfur. This is done by dissolving the KNO3 with water and alcohol, and then allowing it to completely dry for several days or weeks. (depending on the climate) I typically use this method as I don't have a proper ball mill, and it works alright.

Side note: Black powder also burns faster under higher pressure. This is part of the reason why firecrackers work. As the black powder burns, it releases gases that increase the pressure causing the black powder to burn faster which releases more gases which increases the pressure which......well, you get the point. This keeps going until a) all black powder is consumed, or b) the container housing the reaction fails. (usually catastrophically)

My understanding is that the propellant in Estes motors is commercial (Goex) BP, a very fine granular grade known as "Meal D".  By buying the propellant in bulk they get the same results every time.

As with a cake, knowing the ingredients and their ratios is not enough to make a successful product.  Simply mixing the powdered ingredients for BP gives something that will catch fire and burn rather slowly.  By contrast, a pile of commercial granular BP will take fire and burn almost instantly.  There's a lot more to it than simply mixing the ingredients.  And Re-design is correct, there is a lot of hazard to making good BP.  The so-called 'sugar propellants' seem to be less hazardous.

What would you suggest as a good KN03/Sugar propellant ratio? Thanks

I wouldn't---because I've only made a few dozen such motors and am not an expert. Google "Jimmy Yawn" for more sugar-motor info than you can shake a stick at.

I belive that the smaller Estes motors are black powder, or something similar. If so, I would suspect the ratio of KNO3-Sulfur-Charcoal to be similar to that of black poweder. When I opened up a motor years ago, I found that it was one solid piece of propellant. I believe that this is necessary to control the burn rate and characteristics to achieve the thrust specifications you see on the back of a package. They are probably manufactured by using some kind of press, so making your own might be challenging even if you have powder of the same chemistry.

Sorry for the double post, it somehow got on your comment. Thanks for the info.