Chemestry 101: Rocket motors

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Aug 12, 2004
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I've been doing some research on how to fabricate rocket motors equal in size/load to Estes D and E size engines. So far, I am more confused then when I started. It looks like I need a really big press, or mix and melt some sugar. Does anyone have any links to info on this topic or experience with making these motors? Buying them off the shelf is getting very expensive for the multi-engine configurations.

Well, I would tell you to run over to the propulsion forum. However, it has recently been said that there is to be no discussions of actually making motors... There is a certain book that is popular, and im sure anyone who remembers the name will give it to you.
We are glad you joined us, but please don't ask this kind of question; we would like to see you stick with us long enough to make your 1000th post.

Believe it or not, the cheapest way to go is to buy the commercially-made motors. If you want a price break, buy in bulk (like 500 at a time). There are some internet sites with pretty good prices, certainly better than many of the brick-n-mortar retail places.

It may sound like a simple thing to mix some chemicals, pack 'em in a tube, and light it. But it is far more complex than you realize.

Take for example the first step, making a motor casing. You are going to have to roll, press, cook (dry), and trim these things, and that requires LOTS of time. Then you will have to pressure test them to collect a database of structural characteristics; you will have to know how strong your cases are before you can begin designing a fuel grain. You will have to pressure test a bunch (like hundreds) to establish a repeatable manufacturing process, so you can assure yourself that you won't slip a weak motor case through the mill, load it with a standard propellant charge, and kill yourself (or someone else) when it blows up. Once you get things going, you will have to continue the pressure testing of sample motor cases to maintain quality levels.

Now consider the fun involved in designing a ceramic nozzle, building a machine to press the ceramic in place, doing more pressure testing, etc.

I'm not even gonna bother to discuss how complicated the fuel grain itself is.

You will have to develop a slow-burn pyro mixture to use for a delay charge. You will have to press a bunch of little 'pills' into motor tubes and do a bunch (on the order of hundreds) of test burns to understand the time relationships, and to assure that the delay will indeed ignite from the fuel grain, and will in turn successfully trigger an ejection charge.

You will have to determine how to size an ejection charge that will reliably kick out a chute but will stop short of blowing up the entire rocket.

You will have to run thousands of these motors through the test stand to establish the performance parameters of your new product----just for your own use. Because if you don't know what your motor will do, it will be of little use to you.

Repeat all this for the next motor design.

And overshadowing all this activity, which falls under the heading of storage, handling, and manufacturing of explosives, are all the city, county, state, and federal requirements. You will undoubtedly have to find enough land to be X hundred yards from any inhabited structure, and Farmer Jones is not going to let you set up a factory in his cornfield. You will have to obtain approved storage lockers for the chemicals unmixed, mixed, and for the loaded motors. As an amateur attempting this task, you will be uninsurable (and you can't try to sneak by the insurance companies by simply not telling them; when they find out what you are doing, any policy you have will be invalidated).

And keep in mind that the whole time you are doing this, you are risking your backside . . . and your frontside, your topside, your bottomside, etc. Things DO blow up from time to time, just check out what happened to AeroTech a few years ago.

Does this sound like fun? Not to me. Does this sound like you could save money? Not to me.

Sorry to lecture, but yours is a really really bad idea. Please accept this advice from someone who suffered hearing damage as a child and has lived more than 40 years since the damage, not being able to hear an entire spectrum. Your eyeballs, digits, and gonads are worth far more to you than their weight in gold, or anything else.

Stick with the factory-built stuff.

And come back soon with some easier questions?
I'm with powderburner here. I've been a gas dynamicist in the solid propulsion industry working with the big ones. Our lab was up the hill behind the main building and motors were being fabricated and tested all around us. I've witnessed more than my share of motor firings, from multi-million pound thrust guys down to little flares. I've dealt with the chemists, seen the mixers, computed internal flows, scrutinized data...basically experienced most aspects of motor design and testing. That was over 10 years ago. If there's one thing I have no desire to do, its mess around with mixing propellants. Its not that it *can't* be done safely. But my company was professional, took every possible precaution, and *still* had its share of lab and manufacturing accidents...some of them quite severe. It's more a question of why bother, why take the risk when good, high quality commercial motors are readily available at a reasonable cost?
Look for the 40% or 50% coupons from Micheal's Craft Stores in the paper.

You can wind up with a "Bulk Pack" of Estes motors (24 motors) for $24!

A buck each!!! Kinda hard to beat that! Even homemade!

Also check the "cleance" stuff. I've found packs of D12-3's for $0.75 and a pack of 1/4A's for the same...not often...but it happens...

Also...sometimes the kits are absurdly cheap too!

Go to Micheal's, bring cash and coupons! Save your body parts!

Whenever I see this type of question asked I'm reminded of a time when I was in grad school at U. of Illinois ( were expecting Michigan?). We received a letter in our department that was passed to my adviser, who then passed it to his grad students (us) to answer. It was written in pencil and was asking for the thermochemical properties of some propellants. We assumed the writer was a high school kid. At one point he said, "Due to certain circumstances, I don't have access to the necessary materials to answer this question myself." He was even so kind as to provide us with a handwritten table with blanks for us to fill in the data and simply ship it back to him. We looked up the information and found that the propellants he wanted data for were highly toxic and highly energetic. In short, they'd make either a very good poison or a bomb, but would be very difficult to control sufficiently to make a rocket motor. Clearly, the writer knew what he was looking for, and the fact that he was looking for thermochemical parameters suggested he even knew a bit of engineering. We looked more closely at his address and noticed that it was kind of funny...not a normal street address. Based on the nature of the question and the odd address we called the local FBI office. Bottom line is that we found out the guy was actually a prisoner locked up in Joliet. The FBI was pretty happy to get our information. My guess is that the guy didn't make parole! :kill:
archflier asks:

Does anyone have any links to info on this topic or experience with making these motors?

1st off, welcome to the forum!

Stymye posted a link to Richard Nakka who is foremost one of the most knowlegeable AM/EX rockets scientists on the net. He can answer any of your questions as well.

Another site which works with AM/EX motors is This guy (Dan) has done some wonderfull work with clusters using large singleuse J motors...his videos are classic when things don't go as planned.

From either one of these sites you should be able to get to any other resource on the net, as they both have a great link resource.

For offline reading, I reccomend Terry McCreary's book on composite propellant...

as long as you are reading, you can't "blow yourself up..." at the beginning of Terry's book, and on the two web sites are disclaimers for safety. Read them, cause we do not wanna read about how you were not safe ;)

good luck, and come back to visit...
Originally posted by powderburner

Believe it or not, the cheapest way to go is to buy the commercially-made motors.

might be true for this size motor, however, for AP based experimental motors this is not true at all. You are going to need to buy the case anyway, and even when you add all the cost of materials, (and I mean all materials) it is still cheaper. The only variable that might make them close (with mixing your own still being cheaper) is the cost of your time. However, you dont figure time into the cost of building a rocket so we wont here.

There are multiple reasons for experimental rocketry being cheaper, I wont get into them here, because it would be long drawn out and boring.

Needless to say, making your own motors, (maybe not in this scenario didnt research the KNO3 based propellants) is cheaper. I have looked up the cost of all materials and calculated the approximate amount of money it would cost one to do EX, if you are wondering how I know this
I am aware that it is indeed possible to build your own low-cost motors using 'candy' propellants, and AN/AP-based propellants.

However, I believe the original question was in regard to Estes-style BP motors because of the reference to D and E impulse classes. Yes, I am aware that composite D and E motors are/were available but I don't think that was the point of his question.

Without going into a comprehensive listing of all the stuff you need for producing your own motors (accurate scales, mixing machines, yada yada), and without trying to start a completely unnecessary argument, I will repeat my assertion: it is cheaper to buy than to build your own.

And I am certainly not going to encourage someone to go mix and pour rocket propellants who cannot even spell the word 'chemistry.'
When I stumbled across this forum I thought it might be a good way of getting some feedback on my resurrected childhood hobby now inflated by my age and desire to "go the extra mile", and I thought I would receive unbiased, experienced and professional remarks on my questions.

So far, I have been told a story about how what might be construed as me being some sort of convict with a propensity to escape my bonds by brewing some home made explosive, watched as several members bantered back and forth, but the final straw came from the last post in regards to my spelling being somehow connected with my cognitive abilities to reason.

I assure you gentlemen that I am not a convict, I do have 2 undergraduate degrees, a licensed architect, and am a legal firearm carrier for the state I live in. While in college I received two (2) mathematic scholarships directly related to outstanding academic achievement—one for trigonometry and another for calculus. I am also 38 years of age, 6'-2" at 290# with a ring finger size of 16--which does not lend itself kindly to the keyboard sizes sold in the contemporary computer world. I am also not a very good speller, but that does not mean that I am a dolt, idiot, moron, without reasoning skills or diminished cognitive abilities, or any other euphemism—gee did I spell that one right??—you might wish to throw out to support your replies.

In short, your own inflated, or shall I say launched, egos have successfully ostracized me to the point that I will be withdrawing from this forum and discarding the input received as that originating from caddy boys in men’s clothing with nothing better to do in life but argue banal points back and forth, judge the reasoning skills of persons posing honest, inquisitive queries borne solely from brainstorming and information earlier researched and place other persons’ intelligence on trial—all the while from sitting comfortably and safely from behind a computer screen.

I assure you gentlemen—there’s another euphemism—that I will file your responses accordingly and complete my research on my own, practicing all too well known heuristic tactics. Thank you all so much for your timely, insulting, caddy remarks, which if you were the “veteran” rocket enthusiasts you claim to be would keep you otherwise occupied on the weekend engaged in launches, building or testing your creations. For those of you who did post honest replies I thank you for your input and have previously read through all the links you provided prior to my posting, but I can not and will not continue to keep the same company you endure. The world has become I bitter place where discrimination and distrust prevail and I fear that the sound moral ground and values that our great country had been based has been truly lost to ignorance, distrust and the psudo-intellect of contemporary America.
I really don't think anyone was implying you were a convict, just relating a personal experience. Also, sometimes people make typing mistakes, I do all the time (misspelling "the" as "teh" numerous times :D ), that doesn't matter, just as long as you know how to spell the word in question. I hope you stay on the forum. I have read several times and I cna say it is a good site.

archflyer, making your own motors (ie. 'EX rocketry') is a touchy subject here and in the modroc community in general. I'm a bit surprised that a moderator didn't comment as 'how to' details are prohibited on this forum.

This is one area where there are better resources, such as the arocket and chemrocket mail lists. There are plenty of people doing this kind of stuff and from what I can see the numbers are growing. Since you are intelligent and well educated, you will undoubtedly read, ask questions, and play it safe...and find those lists on the web.

Anyway, TRF is still a good source of info for all other rocketry subjects. You are obviously miffed. If you stick in you will fiind that, unlike some other un-named lists, your statements won't lead to flamewars.

BTW, he didn't comment, but there is one member who lost a close friend to 'EX' - he is rightfully wary.
If you think about it... the responses here do make sence. There are several EX people here who build their own motors, yet understand why they don't put the formula on this forum:

We don't want this hobby to be shut down

And we don't want this forum to shut down.

One reason that is a big no-no:

All it takes is one kid to get hurt before our friendly forum mods have to spend time and money to defend themselves and the forum. This is a Sue Happy country. They would sue every single mod... and every person who replied to the thread... even if it did not lead to the accident...

another reason that is a big no-no:

With the problems this hobby is having with certain gov agencys... you will be surprise how many times they quote things they find on sites such as this and use againts us. We don't add food the fire.

So... perk up my friend. It is not as grim as it seems. Contact the members who offered to help via their e-mails. Muc
WOW!!! Talk about ego!

You have the ability to read between the lines a lot better than I do.

I saw no reason to end you second post on this forum with insults.

The moderators have deemed this site is unsuitable for the discussion of EX motor making. That is all that has been said here.

You also spelled pseudo wrong.:p

Originally posted by powderburner

Without going into a comprehensive listing of all the stuff you need for producing your own motors (accurate scales, mixing machines, yada yada), and without trying to start a completely unnecessary argument, I will repeat my assertion: it is cheaper to buy than to build your own.

I suggest that you look into all the chemicals and expenses and you willl see differently
Wow! Somebody thought I was calling them a convict! It was a relevant story. Thought it was kind of interesting...maybe even funny. All I can say is...TRF is the most benign, non-argumentative, well reasoned forum I've come across. If you can't handle this advice is to stay off the internet!
Yikes! Couple of notes here:

Archflier: Speaking for the other mods (and the forum in general, I hope), we certainly hope you do come back. We're a growing community of people with a common interest and I can't think of a single member here who I would not like to meet in person and shake their hand. I truly don't believe that anyone here meant to insult you or imply that you were a convict, nor do I believe anyone meant to imply that the task was beyond your ability. I believe they were merely trying to inform you of the daunting task ahead and to let you know that it should not be entered lightly, both out of concern for you and for the perception that the public has about our hobby. Please don't be offended by the advice you received as it was not offered by "caddy boys in men’s clothing" but by people who have personal experience or at least secondhand experience with this from people they know personally.

Everyone else: Please note that archflier only asked for links on the topic and did not ask for instructions on here. His initial post did not violate the rules of the forum and his request for outside sources for EX info has been asked many times by many people (including a number of first time posters) and has been replied to with much more encouragement and positivity than archflier received.
Sandman mispelled "clearance" when referring to "cleance sales".
But seriously, Folks. I got mad at EMRR's Nick when he told us he had posted TRF's web address on one of the worst groups there is.
Turned out I was dead wrong and out of line. I even said, "I'm outa here."
But I'm still here and I think Nick and I mended the fence long ago.
Let's back off a bit and take a few deep breathes. Vapor lock can be a bad thing.
Sandman mispelled "clearance" when referring to "cleance sales".

I'm hurt, crushed and deeply offended...ahhh who cares!:kill:

If somebody will bring the hot dogs, I'll get some marshmallows to toast over this thread.

I apologize if I have inferred that anyone is a moron. I should have been much more specific. My point was that if someone is capable of slipping up on a matter so minor as spelling (and let's not go there either, guys, because that whole issue would get pretty bloody, and very quickly) then it is terrifying to think of the consequences of some other little slip in the process of manufacturing a BP rocket motor. I don't want to see anyone get themselves hurt.

And Ryan S, for what it's worth, I have indeed looked into the costs of manufacturing. If you do it legally, properly, and with any measure of common sense, it is far far more expensive to make your own. Just the purchase of several acres of land on which to operate your facility would be tens of thousands of dollars, without going into the cost of a specialty building, or the machinery, or the operating costs. I assume that you are referring to pouring your own composite fuel grains, which may be less expensive than store-bought, but even that activity is bending the rules when you do this in your garage twenty feet away from the neighbor's house. I believe the original question was in regard to building BP-type motors---a complete motor. I stand by my statement.
Originally posted by ibeblip

Hey, ibeblip, do you happen to have a copy of "Deep In The Jungle" (the kid's song where this lyric comes from)?
Please PM me
Powderburner, I have spread sheets to calculate motor costs of the propellant I make including liners and casting tubes. Reload hardware is a wash, as you need that as well for commercial loads. The only additional cost is a scale. I can make a baby J motor for under $8. Doesn’t take long to recover scale costs. However, if you’re do EX for money savings only you’re probably doing it for the wrong reason.

Originally posted by powderburner
I apologize if I have inferred that anyone is a moron. ...

Not to fan the flames further, but I think there's a valid point for further discussion here. In my opinion, powderburner was absolutely correct to raise all the flags. In the end, any would-be EX'er will do what they want anyway, as is their right. But when someone pops up out of the blue announcing an intention to dive into something potentially dangerous and asking for how to do it, what is wrong with injecting a measure of caution? This is not unlike my experience with the prisoner asking for thermochemical data...had we blindly given him the information he requested who knows what could have happened? Archflyer may not have liked it, but the flags raised were, in my opinion, absolutely appropriate. Here I'll risk a further comment which I'll retract if the mods request (although I think archflyer is long gone anyway): His response leads me to believe that this is exactly the kind of person who needed powderburner's warning most. Anyone who says "I'm so dad-gummed smart I can handle anything" is likely to be careless and a sure candidate for blowing himself up. I apologize if that last comment is out of line.
Great info, TRF'ers!!

The info you all gave archflyer is indeed "unbiased, experienced and professional". It wasn't the way you all gave it, it was the way it was received.

archflyer, convict? Stay in the hobby long enough to want to fly high power and see what the BATFE wants in return for a LEUP/LUP. If you are offended by these inocuous TRF remarks you really will be steamed when the BATFE asks you for fingerprints, mug shot and background check to participate in a harmless hobby.

I can assure you, archflyer, that these harmless fuzzballs did not mean to offend you. What they did offer you, however, is straight forward and correct information that anyone getting back into the hobby, especially at this time, should be made aware of especially when one wants to make motors. I agree, leave motors to the pros.

Come on back... no harm done and participate in the greatest rocketry forum on the web. You will be glad you did.

If you decide to come back you will find we are all guilty of "fat finger errors".
I'm coming late to this thread, but thought I would chime in anyway, since the original poster might be interested in BP and no-one appears to have mentioned "Amateur Rocket Motor Construction" by David Sleeter.

I make no recommendations about whether making BP motors is advisable, nor even if the material in the book is factually correct, as I have no practical experience with making solid rocket motors.

However, I have read the book and it appears to be very well written & presented, and comprehensively covers every aspect of making BP motors to a good level of detail.

I consider it was well worth the $30 + postage, even though I will never make any practical use of it - solid rocket motor manufacture being, to all intents and purposes, illegal where I live!
Originally posted by illini868891
He was even so kind as to provide us with a handwritten table with blanks for us to fill in the data and simply ship it back to him.

This is my favorite part. :D Nice of him not to want to put you through too much trouble.

I'll probably be driving near Joliet sometime this week. I'll let you know if I see...or hear...anything suspicious. ;)

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