I'm thinking how utterly cool it would be to build a working ramjet and fly a rocket using it. Even cooler would be if it could go supersonic, but I doubt I have the knowledge to play around in that area. Does anyone know any people that have tried this? Were they succesful? Just how much work would be involved in designing an amatur ramjet?

If this idea's realistic, I'd plan to get some people in my aerospace department together and start working on a practical design. Could make a sweet undergrad research project...

Guy, you are aware, are you not, that there is a LOT of prior art here, and at the hobbyist level? Please look it up and gain a perspective so that you will have a better idea what you want this project to do and where to go with it.

Ramjets need to be moving at a certain minimum speed to work at all, so a working model is going to have to go on a vehicle that can accelerate it to its operating speed. You are not only going to have to build a ramjet, you are going to have to build a vehicle and engines to take it up to speed.

The whole point of the exercise is to acquire knowledge, so have fun.

A working ramjet? Not really something you can easily build since to test it you'll need to get air moving past it faster than 0.5 Mach. Not a realistic undergrad project unless you just model the thing using computational fluid dynamics - that could be an interesting project.

They are said to be very,very loud. Maybe not an ideal garage project. Unless you live in Montana.

A quick google finds this;

http://www.cottrillcyclodyne.com/Maggie_Muggs/Maggie.html#TOP

looks like fun, ....!

They are said to be very,very loud. Maybe not an ideal garage project. Unless you live in Montana.

Hell, wear earplugs and call it techno.

after looking on various websites I figured putting the thing on a rocket (to give it the initial boost) would be the way to go. and flunch, now that I think about it, that would be pretty cool way to do it, do the design with fluid dynamics in account and consider construction later. I was wondering if just making a rough design and building that would be more realistic, even if it's not as efficient. but spending the time to make a high-quality ramjet design does seem to make more sense as a "research" project.

loud, I'll bet, probably sound exactly like a jet engine WOULD sound if you put it in your garage, lol. but launched a mile or so into the air... probably not too bad. thanks for the link

after looking on various websites I figured putting the thing on a rocket (to give it the initial boost) would be the way to go.

Ah, problems here are;

Ramjets are typically made out of a metal tube, to withstand the combustion temperatures. Metal tubes are fairly heavy.

Model Rockets tend to use high impulse, short burn engines (10-100 Newton seconds of impulse, ten second burn, for a hobby rocket engine) and are made of of lightweight cardboard tubes.

So you'd need to cluster lots and lots of high power solid rocket motors to accelerate that large ish mass of metal tube, get your ramjet up to speed, and them ignite it while it's in the air.

Getting the timing right will be quite tricky.

You'll have a solid rocket burn time of maybe ten seconds, in which time you'll have to get up to speed, and then start pumping fuel into your engine, and ignite it, before the solid propellant burns out (model rockets reach apogee in a coast phase, you need to get your ramjet lit well before that).

I'd suggest as a starting platform, to use a 'ramrocket' configuration, ie, a duct around your engine, that sucks in cool air, which is mixed with the rocket exhaust, and which expands, extracting heat from your exhaust, and providing more thrust;

http://www.ukrocketman.com/images/ramrocket.gif

(from http://www.ukrocketman.com/digital/pulsejets.shtml)

This is very simple, basically a thin metal tube that is larger than your rocket body, and extends beyond the end of your engine for six inches or more.

You could then try using a timer, and a valve, to release pre-pressurised fuel into the exhaust, to ignite that, and provide more thrust. Only issue here, is that ramjets use a diffuser, to mix the fuel and air, and keep the combustion from blowing out. Not quite sure how this would work with a ramrocket config, as you need a straight exit for your rocket thrust, that can't pass through a diffuser. I guess you could make a fairly long duct compared to it's width, and inject the fuel a fair way away from the solid engine, so the combustion does't set the tail of yoru rocket alight (or just use aluminium tube for your rocket body I guess!).

Without a diffuser you may suffer flame out once the solid engine has burned out though, as there will be too much airflow in the duct to hold a flame (the diffuser slows the air enough so it has time to mix the fuel and combust, and ignite the incoming fuel).

You could perhaps use the forward charge of a shorter burn time engine (you know this this works right? A typical hobby solid rocket engine burns for say 10 seconds,, then a fuse burns away inside the rocket from between zero (instantaneous) to five seconds, before igniting a _forward_ charge which is enough to blow off the nosecone of your rocket to release the 'chute'. You could perhaps use this forward charge to engage a diffuser or sorts (and operate your fuel valve), anything that can be made to slow the airflow in the duct once the other solid engines are nearly spent. Some perforated flap arrangement, sections springing down, released by a latch.

It sounds like so much fun I want to make one myself!

Building a crude ramjet itself is not a problem, but it has to be moving >600km/h before it can be efficient. When stationary it's as good as a heater.

heres plans for a $60 ramjet made from coffee cups.

enjoy.

http://www.cottrillcyclodyne.com/Maggie_Muggs/Maggie.html

heres plans for a $60 ramjet made from coffee cups.

enjoy.

http://www.cottrillcyclodyne.com/Maggie_Muggs/Maggie.html

DUH! I linked that a few posts up you MORON! Nice on your planet, is it?

Building a crude ramjet itself is not a problem, but it has to be moving >600km/h before it can be efficient. When stationary it's as good as a heater.

Efficiency does't matter a damn, this is about a hobby experiment.

You don't need to move the ramjet at >0.5 Mach. You DO have to figure out how to make the air move through it at several hundred miles per hour.....

Hard-mount it to something, and attach strain gauges to determine if it is making any thrust.

Efficiency does't matter a damn, this is about a hobby experiment.How do you plan to test it? Perhaps a motor driven rotating arm with it at the end?

not that I know what I'm doing or anything... but here's where the posts have lead me to think so far...

I was planning to test it in flight. either that or I could figure out who's ass I need to kiss for a test in the school's windtunnel. I havn't seriously looked into either of these, but I'm looking at the ramrocket idea phlogistician put up as candidate for a live launch, since it would essentially be a rocket up untill it's velocity is high enough. the configuration of the rocket nozzle - slash - ramjet fuel injector could at least be an interesting topic for a design study...

a forward charge setting off a diffuser, brilliant! either that or designing a very clever solid-state system involving no spring-loading or moving parts, but i havn't the slightest how such a diffuser would even look, which is why I thought it'd make a cool research project! still love the idea, might be a backup if we're not clever enough to make a breakthrough component, lol

The ramrocket could be in the form of a liquid-liquid engine (maybe NOS for an oxidizer) where oxygen injection is electronically/mechanically regulated such that initially, it's open-throttling the oxidizer to operate the ramrocket as a rocket, but once speed picks up it slowly thins out the amount of oxidizer being injected as it can now use external air as a ramjet. The testing would consist of repeated test launches (or burns in a wind tunnel) where the goal would be to tweak the rocket to the point where there is no internal oxidizer being used to supplement the ramrocket at higher speeds.

Such a rocket would be pretty freaking big, and would cost a lot to make and maintain since it'd probably be mostly metal and composites. That, plus whatever exotic fuel we decided to use might make high enough prices that it would never happen. Not to mention that such a rocket would be large enough as to go outside the designation of an amatur rocket, and thus alot more red tape and fees (so i understand). I'm starting to think more and more such a project would be a research project only, with no actual rocket construction, because no one in the school would be crazy enough to poor money on it :D.

For many decades a successful model aircraft engine has been produced and used, and a number of its clones. It is a pulse jet or flutter valve engine. It might be useful as a basis for adapting a ramjet head onto it.

Having just Googled "dynajet pulsejet", I know that you may be able to see a good amount of perhaps useful information.

You might think of adapting parts, techniques, and fuel cells from the model airplane shops and catalogs. They have some serious engines and fuels. A lot of the things you might need come pre-manufactured and tested.

Maybe you can use a charge of compressed air to start the engine. Think about making it a very small one, a couple of inches wide and a few inches high.

Dynajets and their clones, in their original flutter valve form, have usually been started by using compressed air, often coming from an ordinary tire pump. However, a ramjet transmutation is a no-mans-land of knowing how to start it.

And, no kidding, they are LOUD!

Such a rocket would be pretty freaking big, and would cost a lot to make and maintain.

I'd start small, for many and various reasons. First, cost, you'll be able to find lots of widths of pipe in diameters in the scale of inches to play with, and solid fuel hobby rockets will provide enough thrust to get that sort of weight moving. So that part is off the shelf, and easily aquired.

Secondly, the jet part requires a rocket carrying a payload of pressurised fuel, so carrying the least possible during proving flights is safest. You have to think what would happen if all the fuel somehow caught light at the same time, and with rocketry, weird stuff does happen (say for instance your rocket 'groundsharks' and ploughs into a wall, kaboom!)

Oxidiser, ... oh dear, now we really are talking about a bomb! Sounds like an added complication, to deliver a short burst of oxidiser into your fuel mix.

Start simple, and get clever later. I think a minor triumph would be just seeing the ramjet fuel ignite, let alone providing any thrust!

there is alot of paperwork and burocracy that goes into flying your own airplane, you will need a lawyer. ever if you build it which I find hard to believe, you will have to get clearence from the government and an inspection to deam it safe to fly.

DUH! I linked that a few posts up you MORON! Nice on your planet, is it?

well fuck you ball sack.

just a thought.

if you live near the ocean, you could get prototype ramjets up to speed by shooting them, with a rocket engine, straight down from a airplane. you would lose your prototype, but you might be able to save some money on early tests.

I would do it just to see how big the splash would be. =]

there is alot of paperwork and burocracy that goes into flying your own airplane, you will need a lawyer. ever if you build it which I find hard to believe, you will have to get clearence from the government and an inspection to deam it safe to fly.

Er, and here was me thinking that this thread was about a smallish hobby rocket experiment, but now Weed-eater is going to pilot the thing?

I don't think he mentioned being Dan Dare, did he?

well fuck you ball sack.

Is that what you Moronian Martians say to apologise for your own stupidity in not following a thread correctly?

The phonetic reply in my Martian dialect is 'S'OK, Dweeb'

posting a repeat link doesnt warrent an insult.

i stand by my statement,and fuck you too ass wad.

its pricks like you that make forums a crappy place.

next you should critize my spelling and harp on every little typo like a bitch.

posting a repeat link doesnt warrent an insult.

i stand by my statement,and fuck you too ass wad.

its pricks like you that make forums a crappy place.

next you should critize my spelling and harp on every little typo like a bitch.

Well, now you mention it, your spelling and punctuation do suck.

Why did I pick you up on the repeat link? Well, because it shows a lack of concentration and comprehension. Forums require a little concentration, and it would appear more than the little you put in.

Now, you could have taken the correction like a man, but instead, chose to whine like a child. Well, your ego has been bruised, and all you are doing is prolonging the agony, and drawing attention to your slip up.

its pricks like you that make forums a crappy place.

Yeah, people who read threads, post relevant links, and understand the subject matter are such party poopers aren't they? It would be so much better if everybody reposted spurious bullshit that was badly spelled and broke grammatical rules. You might not think grammar and spelling are important, but not everybody who uses these forums has English a a first language. Now, if they can make the effort to communicate in English, you could at least have a stab at it!

Phlogistician, if you're so great, why are you trolling and starting all these fights?

Phlogistician, if you're so great, why are you trolling and starting all these fights?

A few things;

I didn't say I am great, so you must think I am?

This guy could have taken me calling him a moron in good humour. He chose not to, his ego getting in the way. It's only a fight if the guy chooses to fight, he did.

I'm not trolling. Even if I were, you know that trolls die if you don't feed them, yes?

Don't you think he was a bit stupid for posting a link that had already been posted? I mean, come on, how slow is he?

Why are you suddenly interested? I mean, you just made a non-ramjet related post on a thread that is starting to lose it's way. At least I contributed something to this thread, what's your purpose here?

Interesting you choose to pick a fight on this thread, rather than address my points from the Orgone one too, ... got nothing further to say in Reichs defense?

A few things;

I didn't say I am great, so you must think I am?

This guy could have taken me calling him a moron in good humour. He chose not to, his ego getting in the way. It's only a fight if the guy chooses to fight, he did.

I'm not trolling. Even if I were, you know that trolls die if you don't feed them, yes?

Don't you think he was a bit stupid for posting a link that had already been posted? I mean, come on, how slow is he?

Why are you suddenly interested? I mean, you just made a non-ramjet related post on a thread that is starting to lose it's way. At least I contributed something to this thread, what's your purpose here?

Interesting you choose to pick a fight on this thread, rather than address my points from the Orgone one too, ... got nothing further to say in Reichs defense?

Shut the hell up, you cheap bastard.

Shut the hell up, you cheap bastard.

What a meticulously well thought out comeback! What wit!

Why am I 'cheap' by the way? What causes you to claim that?

And still no further input on the Orgone thread! You're just pissed off because you know you've been beaten!

A few things;


This guy could have taken me calling him a moron in good humour. He chose not to, his ego getting in the way. It's only a fight if the guy chooses to fight, he did.



Don't you think he was a bit stupid for posting a link that had already been posted? I mean, come on, how slow is he?



Interesting you choose to pick a fight on this thread, rather than address my points from the Orgone one too, ... got nothing further to say in Reichs defense?



so why didnt you take my comments in ''good humor''?

because your a prick.

a double link post DOES NOT require your stupidity and intolerance.

you ruin the world with your dumbassery .

I certainly wish I didn't have so much trouble dealing with people like Phlogistician. They have taken a hell of a lot of the pleasure out of my life, and most of the quiet order. They have replaced with both drivel and dribble.

It's just incredible how pervasive this garbage is, and some of it does come from people with the Piled Higher and Deeper degrees. Where do they even get the idea? Is the buying of term papers and theses by rich people this pervasive? I only know the background of one of these trolls well enough to know that his father makes megabucks, and I've got to ask you, even if he didn't buy his degree with his father's money, why does he feel like he has to get online and troll these forums and disrupt them by being an ass? I can think of some metaphors for going out and getting some illicit pieces of tail that would still, if he acted them out, leave him morally cleaner and feeling a hell of a lot better. The stuff they do here is dirtier and sicker than anything short of pedophilia. It is a lot more damaging than you might think at first glance.

putting all your egos aside... can someone properly describe the workings and function of the shutter valve....?? (valve shutter at end of rocket?)

i.e.. what makes it open?? and how do we time it?

-MT

so why didnt you take my comments in ''good humor''?

Because you have no wit.

because your a prick.

That should be "you're", short for "you are", not "your" which indicates possession.

a double link post DOES NOT require your stupidity and intolerance.

I think it does. It shows you weren't following the thread.

you ruin the world with your dumbassery .

Wow! And I thought I just made a few posts on a forum! I didn't realise just how wide reaching the ramafications were! I'm ruining the world! Oh, the guilt!

Got anything to actually add to the thread, that's on topic? Or you just going to keep polishing your ego?

I certainly wish I didn't have so much trouble dealing with people like Phlogistician. They have taken a hell of a lot of the pleasure out of my life, and most of the quiet order. They have replaced with both drivel and dribble.

Oh boo-hoo for you. Maybe you should take a step back, and stop taking things so much to heart? This is debate, it's not personal. We attack each others words, not each others character. If you cannot keep some emotional detachment from the debates, and are too mentally frail to deal with people who disagree with you, maybe you should go and post somewhere less contentious?

Is the buying of term papers and theses by rich people this pervasive? I only know the background of one of these trolls well enough to know that his father makes megabucks, and I've got to ask you, even if he didn't buy his degree with his father's money, why does he feel like he has to get online and troll these forums and disrupt them by being an ass?

Ah, can't be me you refer to 'cos I'm 'cheap'.


The stuff they do here is dirtier and sicker than anything short of pedophilia. It is a lot more damaging than you might think at first glance.

Oh, please, cut out the drama. If you can't handle the heat, get out of the kitchen, child.

putting all your egos aside... can someone properly describe the workings and function of the shutter valve....?? (valve shutter at end of rocket?)

i.e.. what makes it open?? and how do we time it?

-MT

Timing, there is some resonance in the exhaust tube, and timing the flap valve to this helps efficiency. It will run at tens of hertz, depending on the diameter and length of the exhaust.

It's purpose it to close and allow combustion in the chamber, forcing the thrust out of the exhaust, and then to open, and allow more air in, to mix with fuel in the combustion chamber. There's a nice diagram here;

http://www.answers.com/topic/pulse-jet-engine

Incoming air flow makes it open, and the pressue from the combustion makes it shut again, so it's quite simple, and timing isn't really an issue therefore, as it will dictate it's own frequency.

excellent.. thankyou...
i have often thought of attaching 20 or more side by side, and mounting them vertically... thus.. they might be used for lift...
and by tilting.. forward thrust.....

but as the effiecency is low, and the noise so high.. propellars still seem like a better option for my homemade flying machine,....
but pulse jets would be awesome, since such would allow the craft to take on any shape... with 100 tiny engines... rather than a couple big ones.

-MT

Here is a link that can help with the basic calculations: http://members.aol.com/engware.

Thanks,

Gordan