anyone have info on Nozzle-Less rockets?

[Zippiot]

Having a hard time finding info over the web, does anyone have a general uderstanding or, even better, some plans?

[Zippiot]

It cant be as simple as a fast hot burning propellant in a cored endburner configuration...can it?

[Najm]

No nozzle, low pressure, so small thrust.(I think so)

[Zippiot]

Actually most of the videos and pics I have seen would say otherwise. One website said progressive thrust too!
Search the aerotech theater for nozzleless vids, quite impressive.

[larry cottrill]

Though I am no rocket expert, I HAVE in fact seen a "nozzle-less" engine, and a mighty impressive one - one engine mounted on a Titan rocket on display at the Strategic Air Command Museum (the old location just outside Omaha) many years back. The rocket was mounted vertically oriented and the bottom of the engines were boarded over with plywood - but on ONE of them, the plywood cover had become detached and had fallen on the ground, leaving about a foot of clearance where I could crawl under and look up into the engine shell.

Once my eyes were accustomed to the relative darkness, I could clearly see a couple of things that amazed me: First, the top plate of the combustion chamber was covered with a precise matrix of HUNDREDS of little holes to let the fuel and LOX into the chamber. Second, there was NO nozzling into the expansion bell - the engine was just a straight-sided can followed by a huge metal bell. Unbelievably simple geometry.

Now, before you get too excited about the possibilities, consider the fact that this engine's chamber was over a foot in diameter and undoubtedly was fed fuel and oxidizer at the rate of hundreds of kg/second!!! The reason this design works is that you already have supersonic flow at the bottom end of the cylindrical chamber without having to "nozzle down" to get it - this gives it basically the same outlet configuration as a supersonic ramjet. If you can't achieve well over supersonic flow in a cylindrical engine shell, you can't really use this kind of design - and doing that will take a LOT of chamber pressure (which you have to achieve without the choking effect of a definite nozzle zone)!

What I'm saying is that it is a lot easier to get the velocity and pressure needed with a huge engine than with a small or even moderate sized one. To achieve this in a hobby size engine shell will require extremely fast-burning fuel grains. But, maybe a grain material like this can be safely made and used - I'm not up on this stuff, so I have no idea.

L Cottrill

[Najm]

After running some numbers on SRM(see Richard Nakka's website) for nozzle less motors all it gives is error in the output whereas pressure rises and thrust also is is very high but all at zero seconds progressively as you mention, so it might work or work with crappy results, it all comes down to practical testing in the end.

OK so nozzles are used to get the exhaust to supersonic speed?

[larry cottrill]

OK so nozzles are used to get the exhaust to supersonic speed?

Nozzles actually accomplish two things: They increase gas flow speed, and they create a pressure difference. In a pulsejet (which is what I'm familiar with), we don't get supersonic flow, just an increase in velocity when the chamber pressure comes up. In even a small rocket motor, you can achieve much higher pressure, so it is possible to go sonic at the nozzle throat. If you provide a deLaval cone after the throat, you can then get speeds even higher (as long as you don't make the expansion cone too long!) - so in other words, the tail cone of a deLaval nozzle really IS part of the nozzle: as flow travels down the cone, pressure drops and flow velocity increases!

The opposite of a nozzle is a diffuser (like the front end of a ramjet) - in a diffuser, the flow gradually slows down as pressure increases.

L Cottrill

[Zippiot]

Sugar rocket fuel burns very slowly int he absence of pressure, but once it gets up to pressure it burns like crazy! Composite fuel "chuffing" is when the fuel and nozzle are mismatched so that the correct pressure is not achieved, the fuel chokes itself out/down. I have found much info on nozzleless rockets (solid fuel) except!!! the type of fuel used. It must be fast burning and very hot, I assume bp is the standard but to my surprize many ata missles are nozzleless composite fuel. This may be b/c of what Larry said about already having supersonic flow...

[Greg O'Bryant]

Zip I don't know why you shouldn't be able to calculate the KN ratio based off of the core diameter instead of the nozzle diameter. The drawback would be that you would have a relatively long engine. This may not be so bad, but I am concerned with if the rocket candy will be structurally able to withstand the duel function of being the propellant and the nozzle at the same time. How do the other nozzle less engines work? Do you have any burn profiles for them? Let me know how it goes.

[Zippiot]

Well I seriosuly doubt that sugar fuel will work...and I hate working with bp...
Maybe composite might work I'll give it a try. The cut-away drawings I have seen of nozzleless motors just looks like a cored endburner, some dont even have bulkheads!

hard to find info but here is a decent site:
http://www.creagan.net/fireworks/rockets.html

[Greg O'Bryant]

Well that web page answers my question. Just about any thing you can do with BP you can do it better with rocket candy, other than an end burner. Like I said before you are going to have a long engine, but should work.

[Zippiot]

Yeah it would definitely need to build up pressure for the sugar ful to work. Well I'll play around with the idea for a while, maybe this will work inside my ram-rocket project...

http://www.bayernchemie-protac.com/meteor.htm

nozzleless rocket with throttleable ram air induction

[Greg O'Bryant]

Zip

I may have good news if you are looking for a faster propellant. I just made a batch of sucrose rocket candy with glycerin and it looks like it has tons of potential! I made a standard batch of recrystalized 65/35 sucrose propellant. The propellant was left in the frying pan at 250 until it was bone dry. I then mixed in a little glycerin until it had the consistency of sticky cookie dough. When I tested a piece it started right up and had a good strong burn. I then added a little brown iron oxide. Now the propellant had the same texture and color as brownie dough. When I tested this propellant it started even easier and had a stronger burn. In fact it is probably the fastest burning sugar propellant that I have ever made! The smoke had a gray tint to it indicating that it is fuel rich so next time I will take into account the fuel that the glycerin is adding, and it should have an even better burn rate. Last I noticed that the more you worked the propellant the more liquid it became. This will prove to be very helpful when making engines. The biggest draw back to this propellant is that glycerin is extremely hydroscopic and may make the propellant even more prone to absorb moisture.

[Zippiot]

That sounds great, but I do have a question.
If it is always liquidy, then can I expect it to hold shape inside of a rocket? Would be great for casting but can it be hardened?

[Greg O'Bryant]

Sorry zip I should have made myself more clear. It is like brownie dough at 250 degrees. When it cools down it is hard like any other rocket candy.