Best powder rocket fuel?

[Lrsnsam]

What do you guys think the best powder rocket fuel is? I'm looking for most reliable and overall best. I want to have some rockets last up to a year.

[ddewees]

Black powder

[AzoMittle]

What size rockets?

[dagabu]

I second the BP motors, all the others have issues with storage and seem to undergo "the relaxation theory".

[Lrsnsam]

3/4" rockets, about 75cm long... I've seen people add potassium perchlorate and MgAl to black powder before to make a propellant. I've also seen just nitrate and powdered sugar without melting and that looks like it works pretty well but I'm not sure how long they can be stored... Also, what is the best mandrel?

[Redrocketman]

KNO3/Su dry propellant is ok if ground / blended sufficiently, tho barely ok compared to recrystallised method. Best to keep propellant preparation in an airtight container with some of those moisture absorbing silica bags. When I had a run a E class dry motors found it really has to be rammed hard. I packed the motors & then hand cored them with a drill bit. Pain in the ass so I have concentrated larger hot cast motors. Good luck

[AzoMittle]

3/4" rockets, about 75cm long... I've seen people add potassium perchlorate and MgAl to black powder before to make a propellant. I've also seen just nitrate and powdered sugar without melting and that looks like it works pretty well but I'm not sure how long they can be stored... Also, what is the best mandrel?

 

Wait what? 75cm is 29.5 inches, almost 2 and a half feet long. Did you mean 75mm? Going off of Skylighter's Intro to Rockets page a 3/4" I.D. rocket should be around 7.5 inches, a 1 Lb.'er.

 

For a 1 Lb.'er I'm seeing a typical fuel to oxidizer ratio ranging from (0.35 fuel 0.65 oxi) to (0.45 fuel 0.55 oxi). For example, the hottest and slowest (respectively)1 Lb. BP-based rocket propellants I have listed are:

 

Hot....Slow

68.......44.....Potassium Nitrate

17.......34.....Charcoal (For the latter: 16 Airfloat, 18 Midsize Mesh)

10.......09.....Sulfur

05.......00.....Aluminum (Coarse, can be subbed with Titanium or other spark metals)

 

Fuel Percentage

0.320....0.494 (Respectively. This is counting the coarse charcoal as a fuel.)

 

I am also seeing an average of 5-7% metal content (Aluminum, magnalium, titanium, steel, etc. I am not including coarse charcoal in that count) in the formulas that do have metals; the colored magnalium propellants are closer to 25-30% metals but that is because they do not have charcoal. You should be fine with around 5-10% of the composition being coarse metal, coarse charcoal, or lampblack. No guarantees, that's just what I'm seeing for 1 Lb. rockets specifically.

Edited July 8, 2016 by AzoMittle

[Seymour]

I agree firstly with "Black powder" being the fuel of choice for "overall best" when it comes to fireworks rockets. It's far from the most powerful, but it's relatively cheap, relatively forgiving in terms of safety (specifically it's low sensitivity to shock and friction) and if made properly, and stored properly will work perfectly for a lot longer than a year.

 

I used quotation marks around "Black powder" because I also agree with AzoMittle that the ratios of Potassium nitrate, Charcoal and Sulphur, as well as the processing methods can vary a lot.

 

First you have to decide what type of motor you are making. The three main types of BP type rockets are End Burners, Core burners (with a clay nozzle) and finally, Nozzleless (also cored).

 

End burners have less thrust at any given instant but have a long burn. Cored rockets have a much shorter burn time, but much more thrust during that time, and are therefore able to carry bigger payloads. The fact that they don't burn for so long is not a problem if you are just trying to get a shell a hundred meters up. You don't want it to keep going for five to ten seconds because the shell won't be so impressive.

 

Nozzleless core burners tend to have even shorter burn times than ones with clay nozzle because they work by having such a high burn rate that with a core they don't need a clay plug with a hole through the middle to get enough pressure for them to work. Whistle rockets tend to be this type of motor, but using fast BP also works.

 

End burners and Nozzleless core burners work with similar fuels. This essentially means you want to use the fastest burning stuff you have for both types. Well milled 75/15/10 with a good charcoal is what you should start with. Many people process it further by adding 1 or 2% oil or wax to cut down dust, or even wetting, screening and drying it for the same reason. It's much easier to work with.

 

For cored rockets that have a clay plug you want to use a fuel that is slower than hot Black Powder. I'm pretty sure that the formulas AzoMittle posted are for this type of rocket.

 

Personally I have tended to use 60% Potassium nitrate, 30% Charcoal and 10% Sulfur, though personal preference and core dimensions are important considerations and so you have to decide what works for you after you've made some. Because you don't need such a high burn speed these fuels don't need to be ball milled, though many people still do (but if metal powders are added, add them after milling). Some people mill it with some of the charcoal and add the rest of the charcoal later to give a longer tail.

 

I've made many of them will ball milled 6/3/1 and also with milled KNO3 and already fine sulfur and -40 mesh charcoal screened together. Overall I prefer to mill it for 30 minutes, so it's a bit more powerful and reliable but still has a bushy tail, but that's just my taste.

 

Some Questions:

 

What are you wanting these rockets for? Model rockets? Lifting a small salute half a kilometer in the air?

 

Lifting Payloads? What are the payloads? A 2" shell? a 3"? even 4" and bigger can be lifted on a good, well tuned BP type 19mm core burner.

 

Do you want a pretty spark tail?

 

Do you want a rocket motor to set off 15 times a week attached to a stick but with no header, just because it's what you have to do to stave off pyro withdrawals?

 

All types can have pretty tails. You can add spark producing materials to hot BP, commonly Titanium, Aluminium or charcoal, to hot BP for end burners and nozzleless rockets. Core burners (with nozzle) usually have extra charcoal in the fuel so you get charcoal sparks which I actually prefer to usually not ad metals to, but that's personal taste and you can add Al and/or Ti to get several kinds of sparks if you wish. Often the metals are added above the core in the delay section to reduce tool wear and/or sensitivity issues when making them but still get the effect.

 

If you want to lift quite large headers then core burners are what you need. However if you're happy with a smaller headers, short end burners can work well too. 19mm end burners can be made powerful enough to lift a 3" shell, but for reliability I'd say 2" or smaller could be a better choice.

 

As for adding Potassium perchlorate and MgAl to BP type rockets I have done this quite a lot. I usually add Dark Flake Aluminium and wax too. However I don't think that this is a better fuel than Black Powder overall. When cost and safety are factored in, the benefits don't necessarily outweigh the issues that come with it. Black powder is already dangerous enough, but it's safe enough that people ram them by literally pounding the BP in to a solid lump. BP + Flash must only ever be pressed, and even then, I'm not sure how safe that is. I personally consider in an experimental fuel that has many unknowns. Not only will adding KP and metal powders (especially flash aluminium and fine MgAl) certainly increase the sensitivity quite a lot, and make those freak accidents much more likely, but also much more serious. This stuff can explode with a lot more force than BP, and I think that a 19mm diameter rocket with BP igniting during manufacture is already a scary possibility.

 

That being said, I will still carefully make them, though I don't feel like I should recommend doing so for others. They are more powerful than plain BP but not necessarily by as much as you might expect. The main thing that I feel this fuel has going for it is the flame and sound they make. They can be made to look more powerful than they are from the bright flame and roar from the high temperature and the vastly excessive solids/liquids in the exhaust from all the metals adding to the already about 50% solid products from BP.

 

They certainly won't last as long as BP motors but they certainly work for at least a few years if made properly. In the last few years I've made some very reliable end burning rockets with a 5cm long motor tube. One increment of clay for the nozzle, then one of the BP + flash, then another half increment of the fuel, then a half increment of a slow delay with 10% Titanium capped off with half an increment of clay. My headers were small, just a short tube (5cm again) which fits snugly over the motor tube and is slipped a centimetre or so on to the top of the motor and taped in place before being filled with small stars, and the gaps between the stars filled with BP grain and a little bit of flash. This is a very small header for a 19mm rocket, but they are very quick to make, very reliable, and considering the effort needed to make them they give a pretty good effect. You could do this using plain BP. The point of my ramble is not to promote this fuel, but to give another example of the many possibilities you can choose from in deciding where to start.

[dangerousamateur]

I think the best fuel one can use is whistlemix.

It's much more powerful than Blackpowder and as long as you don't use the sodium salts it stores very good.

 

 

 

Not the cheapest, but the question was about the best

[dagabu]

My experience with both sodium and potassium is that neither store worth a darn. 1 year old and dozens Cato'd, sad day!

[dangerousamateur]

Is this just your problem or is a common issue?

I only have experience with smaller ones, 14mm for example, and they all worked well after 6 months.

 

Do you have any clue what the problem is?

 

Is this really a whistle specific thing?

[dagabu]

No, not just me, SLD even had chimed in about what he calls "The Relaxation Theory" with whistle motors. It seems likely that the increments allow microscopic fissures to occur causing the whole fuel grain to take fire at once. Dave F even worked to get wax into the fuel and lining the tubes to fight this from happening. I don't know if he licked it or not but at least the Benzo rockets should really be fired as soon as possible.

[dangerousamateur]

 

and lining the tubes

You mean he waxed his tubes, right?

 

 

 

 

at least the Benzo rockets should really be fired as soon as possible

Does that mean that sodium salycilate rockets have less problems?

[dagabu]

Good question, I rarely use it.

[OldMarine]

I've read conflicting recommendations from the same people. I would have to assume no whistle rockets will store long-term without the chance of a Cato going up over time. I'd hate to press a gaggle of rockets and then have to wonder if they'll launch or pop.

[dangerousamateur]

I thought that theese problems have finally been adressed by waxing the tubes?

So this is not the ultimate cure I was hoping for or what?

 

 

 

I'd hate to press a gaggle of rockets and then have to wonder if they'll launch or pop.

Yes! In this case I would forget about rockets and use mortars.

[OldMarine]

Waxing the tubes definitely helps stop CATOs right after pressing but I think it's the relaxation of the tube and fuel over time that causes CATOs after storage for a while.

[ddewees]

There's no reason to have to store rockets for that long...

[OldMarine]

There's no reason to have to store rockets for that long...

 

That's the consensus among most of the whistle builders. I haven't heard much on BP rockets. Are they more "storeable"?

[dagabu]

Yes, I have ESTES motors (just black powder endburners in an NEPT case) from the 1970's that still work just like the day I bought them. The grandbaby will light her first of them in a few years, I am sure they will work fine.

 

At PGI, the unspoken word is to press a whistle and light it the same day. That said, if you use a 50:50 mix of hot BP and hot whistle, both granulated, mixed together and press a *Hybrid, they seem to store well for weeks if not months.

 

My magazine gets down to -25°F and up to 120°F, a 145°F swing!!!!! Think like the pizza guy, "Make and Take"... to the rack.

[dangerousamateur]

Do you have any idea HOW long one could usually store them?

Is there some rule of thumb based on the professional guys experiences?

 

I mean, I would hate to start pressing my rockets 3 days before new years eve and than get into an hurry.

[OldMarine]

I have a bud who wholesales consumer fireworks and he has BP rockets that are several years old. Of course, Chinese rockets are pretty wimpy to begin with and probably wouldn't CATO even if the fuel grain cracked into gravel. I'm going to press some this weekend and put them back til NYE and see for myself!

[dagabu]

BOS

 

Bomb On a Stick

[ddewees]

I've stored fifty various motors for three months with no noticeable issues. Bp, whistle, ibp, ap, etc. All worked great. I was out of work, and spent my free time making rockets for Winterblast one year.

 

Of course, I ended up putting one of those rockets through an RV with a salute header... but that's a different story.

 

I think you should be fine for the most part... just make them to the best of your ability, ie use small consistent increments and press them.

[DavidF]

If you don't want rocket motors to relax, just eliminate the things they need to relax from. Using a compressible, flexible tube support such as PVC will certainly give the finished motor something to relax from later. Not allowing proper clearance between the drift and tube wall encourages the tube to 'pull down'. Again, something to relax from. Lubricating the inner tube wall (waxing) also reduces the friction that causes the tube walls to 'pull down'. In an ideal world where there is no pulling down of the tube, it doesn't re-expand (relax). Shimizu explains this in F.A.S.T. Relaxation might be more correctly called re-expansion. This might help folks understand it better. Just my .02.

 

Another thing I like to do to prevent initial compression of the tube: take your NEPT tube and sand the base end of it on a perfectly square disc sander. Push it really hard onto the disc slowly and steadily until the disc actually stops turning. This will carbonize the tube end and make it shiny, smooth, and hard. It will not compress like it would have otherwise during the early part of pressing.

 

Estes motors are made in a completely different way than 'our' black powder motors. Their reliability comes from the differences, and the motor type. To say that an Estes motor is still good after 20 or 30 years is a true statement that I have verified too. But to think that has anything to do with what we amateur BP rocket makers do is a bit of a stretch, IMHO.

 

If I wanted the best longevity of a rocket motor using amateur methods, I would use wax in the propellant. I'd also wax at least most of the tube. And, as has already been mentioned- small increments! I have flown probably 50 hot BP nozzleless motors that were 2-4 years old without CATO. I would use a solid tight incompressible tube support.