Amateur Solid Fuel Ramjet rocket?

Hello everyone,

The other day I was researching about the Talos ramjet missile. Fueled by kerosene, this mainly sea to air missile cruised to its target at mach 2.5.
I found a website that goes into great detail. From the ramjet used to the operating system. Check it out.
https://www.okieboat.com/Talos missile.html

I stumbled upon another website. They used to pretty normal techniques to boost a slightly supersonic ramjet sustainer. It was under ramjet power for a couple of seconds and accelerated an extra 4g's at that time. The eventual goal of the team is to test hypersonic vehicles.
https://www.appliedthermalsciences.com/pages/hypersonics.html

So, my question to all of you is why hasn't someone from the hobby attempted something like this?? I think that given the technology that we have. Someone could do it. Liquid fueled ramjets on a small scale would be hard to do. No doubt about that. But I was thinking more on the lines of a solid fuel one. Using magnesium and some sort of binder, one could eliminate the complexity of a fuel delivery system.

Im posting this to generate discussion and see what others think.

Tominator 2 said:

Hello everyone,

The other day I was researching about the Talos ramjet missile. Fueled by kerosene, this mainly sea to air missile cruised to its target at mach 2.5.
I found a website that goes into great detail. From the ramjet used to the operating system. Check it out.
https://www.okieboat.com/Talos missile.html

I stumbled upon another website. They used to pretty normal techniques to boost a slightly supersonic ramjet sustainer. It was under ramjet power for a couple of seconds and accelerated an extra 4g's at that time. The eventual goal of the team is to test hypersonic vehicles.
https://www.appliedthermalsciences.com/pages/hypersonics.html

So, my question to all of you is why hasn't someone from the hobby attempted something like this?? I think that given the technology that we have. Someone could do it. Liquid fueled ramjets on a small scale would be hard to do. No doubt about that. But I was thinking more on the lines of a solid fuel one. Using magnesium and some sort of binder, one could eliminate the complexity of a fuel delivery system.

Im posting this to generate discussion and see what others think.

Click to expand...

My idea... now that i am going bald, my be rather hair brained.....

I did some 3D modeling of nozzles after the case. whereas one could inject alchol and 15%water, and create thrust from the exaust of the rocket motor.... Think of it as a seudo stage booster, that would be attached only for the flight duration...

My final closure on the subject was that it would be like turning a J58 turbojet into a turbofan..............

I'm not totally sure what a solid-fueled scramjet would look like. The key feature of a scramjet is that the fluid flow through the combustion is supersonic. If the fuel you're imagining is a magnesium powder or the like, I guess it would ablate from the high temperature high-speed air flow though the core-the ablation would mix the magnesium powder with the air, and the pre-existing high temperature air (from oblique shocks in the inlet) would spontaneously ignite the Mg powder? I don't have the experience to know if that's really possible. The geometry of the combustion would change as the fuel-laden walls ablated away, which would change the flow properties...it'd be highly difficult to keep the flow in a condition to burn properly, I would guess.

That applied thermal rocket looks pretty cool. I wonder if Mainer / Darren Marriner was there for any of those launches at Cherryfield. He might have some tales to tell.

CCotner said:

I'm not totally sure what a solid-fueled scramjet would look like. The key feature of a scramjet is that the fluid flow through the combustion is supersonic. If the fuel you're imagining is a magnesium powder or the like, I guess it would ablate from the high temperature high-speed air flow though the core-the ablation would mix the magnesium powder with the air, and the pre-existing high temperature air (from oblique shocks in the inlet) would spontaneously ignite the Mg powder? I don't have the experience to know if that's really possible. The geometry of the combustion would change as the fuel-laden walls ablated away, which would change the flow properties...it'd be highly difficult to keep the flow in a condition to burn properly, I would guess.

Click to expand...

I was talking about a ramjet. A ramjet slows down air down to subsonic velocity. Simultaneously raising pressure for combustion. You have a point about ablation of the fuel grain.
Here is a simple diagram of a solid fuel ramjet.

https://settlement.arc.nasa.gov/Nowicki/SPBI1043.GIF

jsargevt-Yeah, i would love to hear info on how they did it.

Tominator 2 said:

I was talking about a ramjet.

Click to expand...

And that is why I shouldn't be allowed to use the internet when I just got out of bed.

In this case, I guess the point is that the combustion chamber is at high pressure and temperature to start out with? That will improve ISP by burning more efficiently, but not by as much as it could unless you carefully tweaked the amount of oxidizer. The real potential for improvement over conventional designs lies in the fact that your oxidizer is free if you can figure out how to use the air; ISP goes way up and you get more energy out of the same volume and mass of motor. If you made the propellant to ablate into the airstream upstream of the combustion, it might work.

IIRC Korey Kline did it back in the early 80's.
There was one at LDRS 10 at Black Rock that used a fuel rich propellant to feed the ramjet
Mark

Here's the basics on how the RIM-8 Talos works. The solid rocket booster brings the rocket up to speed to engage the ramjet engine, then the booster drops off and the flight is sustained by the ramjet. To duplicate this design would require sophisticated avionics in the realm of a professional hobbyist. Commercially available flying model jet motors are only capable of speeds around 200 mph, I think. Where are you going to pack the laundry? Missiles were never designed to be recovered.

MClark said:

IIRC Korey Kline did it back in the early 80's.
There was one at LDRS 10 at Black Rock that used a fuel rich propellant to feed the ramjet
Mark

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Wow, thats awesome. any idea on where to get more info on that?

And phantasmo, yes recovery would be tricky. it would have to be single deploy through the diffuser section.

There are several solid fuel ramjet rockets, mostly military. I've got several papers on them. The first one I've found is a little over 1Meg in size; too big to post as an attachment. PM me your emain address and I'll send you this paper, plus the others I find.

It's way outside the range of 99% of hobbyists, I would imagine. I could see a niche for it in multi-stage altitude attempts, but ramjets work well at high mach numbers where the materials used in most hobby projects simply don't hold up for more than a few seconds.

GQM-163A Coyote

View attachment 100388

Bob

Nerull said:

It's way outside the range of 99% of hobbyists, I would imagine. I could see a niche for it in multi-stage altitude attempts, but ramjets work well at high mach numbers where the materials used in most hobby projects simply don't hold up for more than a few seconds.

Click to expand...

Yes, You have a point. I don't think it is impossible though. And I am sure a 75mm or 98mm booster can get it up to sufficient speeds to light it. The biggest trouble would be lighting the fuel and sustaining the burn at those speeds.

Here's a couple of thoughts on this, and give feedback, because I might be way off base here:

1. Some of the research that I've done on ramjets says that they dont necessarily have to be moving at supersonic speeds to function, but rather, give usable thrust at +/- mach 0.5 and increase in efficiency through transonic speeds (assuming a correct design), with maximum efficiency somewhere in the supersonic range. If this is true, this would bring the project into the possible range since 400 mph+ would be a totally reasonable speed for ramjet ignition (i.e. smaller booster, etc).

2. I realize a lot of the issues with liquid fuel rockets. However, in this case, why would a turbopump be needed for a SMALL liquid fuel ramjet? If it's going more or less straight up, why not just have a LiPo battery and a brushless motor, and possibly a pressurized fuel tank? NOTE: this is probably my weakest area of expertise, so I'm probably missing something huge here, but really, why not?

3. To avoid problems with ignition of the ramjet (solid or liquid), why not have a rocket motor ( probably a small, long burning one) feeding directly into the combustion chamber? Due to nozzle effects, this motor would probably not generate significant thrust on it's own (i.e. without the ramjet/from zero velocity), but it would:
a) Serve as a simple and effective means of ignition.
b) Provide supplementary heat and pressure if the ramjet were not moving at a speed fast enough to be fully self-sustaining (and possibly further lowering the possible ignition velocity).
c) Eliminate the need to have a nozzle custom sized to handle both a solid fuel rocket burn and a ramjet burn (like in the diagram provided by Tormentor above), since, unlike in that design, air is supplied to the combustion chamber throughout the ignition sequence.
d) Provide usable thrust if the ramjet were in ignition sequence.

4. Where would the laundry go? I can think of a lot of answers to that, namely that if this thing looks like a giant flying SR-71 nacelle with fins, the parachute would eject from the shock in the front. But that's just one idea.

5. What about flame holders? These can still be used with solid fuel ramjets, right? That would probably deal with the solid fuel ablation problem and it wouldn't create a drag issue that doesn't already exist in liquid fuel ramjets.

I think, assuming that these are actually good ideas, the problem really becomes one of finding a guy with a machine shop, and not really one of complex avionics and crazy aptitudes in ridiculous things. You should probably understand how to create an efficient nozzle geometry, have some understanding of ramjets, have experience mixing your own propellants, and staging high power rockets, all of which are somewhat higher level skills, but also things a lot of people on here, including myself, can do. And I would add that, when thinking about the mixture of APCP, removing the oxidizer from the equation might just give you some crazy ass performance per unit of propellant mass. Who knows till we try right?

NPS published papers on the orifice sizing in solid fuel ramjets. The NAVY CATO'd a few in a lab in 70's trying to do research the math equations to size the components. Studies in Virginia say the polystyrene beads are in the Coyote fuel by Aerojet. They did some wicked arse CFD on grad student engineering level.