Can propellant types be mixed?

Could propellant types be mixed, ie, (aerotech) black jack and redline, to create interesting smoke/flame pattern or thrust curves?

BuiltFromTrash

I believe that CTI has some Blue grains and some Red Lightning grains in the same motor to make pink. The motors still need to be individually certified. If a person did this his / her self, the motor would not be a certified motor. I am not sure if it could be launched as research, but certainly could not be launched under normal NAR or TRA rules, particularly in California.

looking forward to see the reply to this.

The Loki Cocktail motors (only one certified at the moment) have blue and red grains that make purple.

The flame patterns don't really change, just the color.

If you mix the colors you can get different color flames mentioned above, or different types of grains to modify the thrust curve. Check out the CTI dual thrust motors. They are a combination of classic and a Vmax grain for a spike of thrust at ignition. So yes it is possible.

What about a 6 grain motor, with half Skidmark and half color?

If you are serious you should check out the web site for Rocket Motor Components (RCS) https://www.rocketmotorparts.com/ You have to be very careful and take a lot of precautions but it looks like some people are doing it.

Thanks for replying!

BuiltFromTrash

SCrocketfan said:

What about a 6 grain motor, with half Skidmark and half color?

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Mixing all the colors plus Skid, would you get a brown skidmark?

Salvage-1 said:

Mixing all the colors plus Skid, would you get a brown skidmark?

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Oh, I meant a combo like half skid and half green3, or half skid and half red lightning…

My guess is the crud of the skid would win out.


Mark Koelsch
Sent from my iPhone using Rocketry Forum

You are likely to get the: Choo-Choo effect.
as in: Chuff-chuff-CHUFF.
Different propellants operate at different pressures.
Mixing them will cause an instability at ignition.

I mix my own and have dabbled a little with this.
White and red mix quite well.
I've done 3 red with one white for a nice looking motor.
I call it Pink Carnation


JD

SCrocketfan said:

What about a 6 grain motor, with half Skidmark and half color?

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No, probably not.
It's not the same as your color wheel charts from HS.

It have more to due with flame temperature
You would probably get a grey smoke with a little to no flame.

JD

Salvage-1 said:

Mixing all the colors plus Skid, would you get a brown skidmark?

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You can but it is not commercial and would have to be flown research.

Salvage-1 said:

Mixing all the colors plus Skid, would you get a brown skidmark?

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I got it, Salvage-1. Thanks for the laugh.

Salvage-1 said:

Mixing all the colors plus Skid, would you get a brown skidmark?

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Knowing this guy, I'd say Rob is just joking around...

JDcluster said:

You are likely to get the: Choo-Choo effect.
as in: Chuff-chuff-CHUFF.
Different propellants operate at different pressures.
Mixing them will cause an instability at ignition.

I mix my own and have dabbled a little with this.
White and red mix quite well.
I've done 3 red with one white for a nice looking motor.
I call it Pink Carnation
View attachment 247018

JD

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I thought that might be a problem, especially if you mixed propellant types like black jack and warp-9.
I would probably be better off trying to build my own engine.

What if you made an engine that mixed propellants, but instead of stacking different grain types, actually embed them in the grain? For instance, with a core burning engine, you could have a ring of high pressure propellant, than a thin ring of medium pressure propellant, and finally a ring of low pressure propellant to get the thrust modulation or color transition that you desired.

BuiltFromTrash

A color changing engine would be cool

BuiltFromTrash said:

I thought that might be a problem, especially if you mixed propellant types like black jack and warp-9.
I would probably be better off trying to build my own engine.

What if you made an engine that mixed propellants, but instead of stacking different grain types, actually embed them in the grain? For instance, with a core burning engine, you could have a ring of high pressure propellant, than a thin ring of medium pressure propellant, and finally a ring of low pressure propellant to get the thrust modulation or color transition that you desired.

BuiltFromTrash

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I feel like I saw someone on here try that at some point. No idea if it worked

Both mixed grains and embedded grains have been done.

With mixed grains, you get a blend effect of the two. Blue + Red = Pink or purple.

With embedded, you get a bit of a mix, but a much more obvious transition. The core is propellant #1, but the grain faces are half and half.

Mixing grains is a bit tricky. I have a dual thrust 4 grain 38mm motor I've made a few times. It has only been static burned. It drops thrust about 50%, perhaps 60% thorugh the burn, going by memory. It is three EX grains of a very forgiving slow, with one EX grain of a fairly fast propellant. They are different colors, and the flame color difference is very obvious. I think I've done it three times now and it works very smoothly.

Now, take the same grains, and do 6+2 instead of 3+1. Keep the same Kn. The motor depressurizes when the 2 burn out. It takes a moment or two to come back to pressure afterwards, and doesn't do well.

I'll make a blunt suggestion here. If a person is asking the question about whether different propellant types can be mixed, and seriously intends to do it, the person should already know how and why. If the person doesn't, then the person isn't ready to do the experiment!

There are the following possible outcomes:

(1) Fails to pressurize, burning up the hardware.
(2) Chuffs, resulting in an unsafe flight.
(3) Burns steady thrust.
(4) Burns dual thrust.
(5) Burns first part of dual thrust but depressurizes.
(6) Overpressurizes damaging the hardware.
(7) Overpressurizes and CATOs.

Without knowing the characteristics of each propellant in the combination, plus possibly something about intermixed combustion from the two, and doing a proper motor design, the odds of (3) or (4) are not that great, for random choices without additional information.

Gerald

Or you could cluster different motors. I recently did one that had three Skidmarks surrounding a Red longburn in the center. All fired off the pad, and then as the skids burn out, the red motor keeps burning. It's pretty cool.

I've seen others do this with different combos of motors. Of course, getting clusters to all ignite together is tricky in itself, and having different propellants makes it even more challenging. But you like a challenge, don't you?

Liftoff shot:

s6

Ive seen people mix BlackJack and White Lightening, which made for an interesting effect, however lets say you mixed a I-211WL and a I154BJ (2 from each alternating), they used the I211 nozzle and opened the other to the appropriate size. Obviously this wouldn't be a commercial motor and would have to be launched at a research launch.

stealth6 said:

Or you could cluster different motors. I recently did one that had three Skidmarks surrounding a Red longburn in the center. All fired off the pad, and then as the skids burn out, the red motor keeps burning. It's pretty cool.

I've seen others do this with different combos of motors. Of course, getting clusters to all ignite together is tricky in itself, and having different propellants makes it even more challenging. But you like a challenge, don't you?

Liftoff shot:View attachment 247052

s6

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This is what I was going to suggest too. I think you could get some very cool-looking mixed flame and smoke effects with different motor combos. I've never done it or seen it done personally, but it's something I've had in mind to try in the future. Thanks for posting the picture --- it looks very cool!

That is just cool upon cool.

So if you mix Black Jack with Redline do you get Black and Red Flame? Otherwise known as BaRF.

If the different propellant grains are the same physical size but one type burns much faster; what happens internally when the faster burning grains are gone leaving a great big empty space in the casing while the slower burning grains are still burning?

The internal pressure will drop after the first grain(s) burnout.
In some cases it might even extinguish the flame.
A sudden and severe drop in pressure, believe it or not could shut down the motor prematurely.

Which in this instance would be welcomed because it would save the casing from melt down!
Without propellant to insulate the casing; it is exposed to the other burning grains....
burning through whatever is left of the casting tubes and liner.
In most hobby instances; the web thickness isn't that large to begin with so; exposure is small.

JD

boomtube-mk2 said:

That is just cool upon cool.

So if you mix Black Jack with Redline do you get Black and Red Flame? Otherwise known as BaRF.

If the different propellant grains are the same physical size but one type burns much faster; what happens internally when the faster burning grains are gone leaving a great big empty space in the casing while the slower burning grains are still burning?

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It can be done but, very time consuming when casting the motor.
You have to mix 2 different propellants ( longer turnaround time)
More chances to screw things up, as you have to be extra careful when mixing / casting.


JD

BuiltFromTrash said:

I thought that might be a problem, especially if you mixed propellant types like black jack and warp-9.
I would probably be better off trying to build my own engine.

What if you made an engine that mixed propellants, but instead of stacking different grain types, actually embed them in the grain? For instance, with a core burning engine, you could have a ring of high pressure propellant, than a thin ring of medium pressure propellant, and finally a ring of low pressure propellant to get the thrust modulation or color transition that you desired.

BuiltFromTrash

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Thank you for all the information! Got that straight... Another question, could I make a sugar propellant grain and use it in an AT motor? Or do I need to buy an experimental motor or make my own motor?

BuiltFromTrash

Rick M. and I built a truly color-changing motor. It is made not simply by mixing different grains, but by casting each propellant in layers. The inside layer is the last to burn. It's tricky to get the propellant web geometry right and is quite labor intensive. This is a video of the prototype motor static test. I'm planning on burning on a red-white-blue O motor in a big patriot in 2015.

[video=youtube;oH6xE_Ej0QY]https://www.youtube.com/watch?v=oH6xE_Ej0QY&list=UUgE9yxooDx1UwelAT7Xu7gQ[/video]

BuiltFromTrash said:

Thank you for all the information! Got that straight... Another question, could I make a sugar propellant grain and use it in an AT motor? Or do I need to buy an experimental motor or make my own motor?

BuiltFromTrash

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I don't know your location or cert level, so some of this may not apply. If you are not L2 at least, get L2 certified - it is a requirement to fly EX. You might get someone else to static burn a motor for you without the L2, but get the L2.

Then, see about getting into some propellant class or getting a mentor. Many of the "can I" questions have the answer "yes". Many of the associated "should I" have the answer "no", or "no without a lot of research, experimentation, and working up to it".

Gerald