ramjet rocket

So I finally started my own blogg my very own place to bitch about whatever I want.

I mean, every other ashole on the planet has their own bitching place. So why not me. I plan to log some of the experiments and activities i intend to carry out. I will remain anonymous, because from what I’ve seen happening to people experimenting in similar fields, and i think there are regulations that aim to limit such exploration and activities.
Of course, I seriously disagree with such regulations since I can’t understand why the fuck scientific endeavours. In certain areas should be exclusively government-controlled? actually across the planet government seems to forget that they are our employees who we have tasked to provide a few basic things such as roads basic education. Healthcare and security for people and property. government-controlled activities are inherently wasteful, ineffective and costly. So I don’t want them to do anything other than what we asked them to do.

My first experiment is actually inspired by a web page by Glenn Ohlson that has done some research into using a ramjet rocket as a launchplatform. This is an intriguing idea, and he has certainly has certainly put thought and effort into this idea but nothing I can find has ever been produced that could be considered flightworthy. One of the main problems faced by such an approach is that a ramjet isnt very effective at low speeds. In fact, it’s not very efficient until you reach speeds of about mach 3. So before you can actually use the ramjet stage. We have to accelerate the device up to a spoeed where the ramjet can start to produce useful thrust. i have seen quite a few different approaches to this problem everything from guns. To rubber band launchers seems to have been explored.

My approach will test. if It is possible to operate a rocket with different flight moudes it will start as a rocket and accelerate to about twice the speed of sound, were it will switch to ramjet mode for the remaining duration of the fight.

Luckily, I am not bound by financial time restrictions, and I expect to spend four years to complete the device.


29 Responses to ramjet rocket

  1. Asses your situation and if safe and their escape route is the route you and your family prepared in case there is a fire.

    As one of the most commonly used distance learning studies equipments.

  2. Doug says:

    Posting my ducted rocket on the PulseJet forum.
    Ramjet forum
    Flight SFRJParafin Development


  3. Cliff says:

    I tried to track down a copy of the ramjet inlet book you acquired. I found one at Amazon, but it was $48. Think I’ll pass, though you are in the right era for the good information days on them.
    Also checked out the Rocketry Forum, but for some reason I can’t post, and I can’t get any explanation from them as to why. However, I can log on. So I’ll just listen.


  4. Doug says:

    Thanks for the resource tips Cliff I hope to go over them in more detail soon. I’ve been immersed in this book. Still taking it in. Excellent resource on diffusers got mine used for less than $10.

    “Supersonic Inlet Diffuser An Introduction to Internal Aerodynamics”
    Rudolf Herman 1956

  5. Cliff says:

    Again you might try the NACA files, “FLIGHT TEST OF A RADIAL BURNING SOLID FUEL RAM JET NACA RM L52K03 Walter A. Bartlett, H. Rudolph Dettwyler Dec. 10, 1952.
    If I recall correctly, the fuel mixture is very clearly explained. It burned through the combustion chamber. With your thoughts applied to the matter, it may not burn through if the burn isn’t to extended.
    Also you might take a look at U.S. Patent number 5320692, SOLID FUEL RAMJET. As I recall it had several formula mixtures in its patent.


  6. Cliff says:

    Those of you interested in sub-sonic ramjets might try;

    NACA RM L53D02 Paul J. Carpenter, Edward J. Radin June 3, 1953


  7. Subsonic variants are really ineffective so i havent wasted my time on them.

    Trust me designing a working supersonic ramjet is f…. hard i have spent thousands of dollars already and i am nowhere near an effective design. since my design is a ram-rocket variant i don’t have to worry about flame holders ignition etc.

    Still achieving efficient combustion is extremely hard, i get trust but the streak of black smoke from the last test launch is glaring testimony to poorly combusted fuel.

    I will need a lot more tweeks and tests “and probably a lot more money” to get near to an efficient design.

  8. Doug says:

    Great information and advice Cliff. I agree the real performance lies above M1.5. However I’m curious to find out just how low into the subsonic range I can get positive thrust = to twice the ram rocket weight. My design is based on a 4″ combustion tube. The tube is a thin wall 6061 alloy with TIN ID coating, a phenolic liner acts as insulator between the solid fuel core and alloy tube. The forward diffuser section will be a basalt/CF composite. I want to utilize “G-80″ size composite motor(s) for the forward inlet center spike mounted ejector motor. This avoids BATFE ACPC LEUP storage permits and hazmat shipping fees. A 4″ OD diameter combustion duct with up to a 1″ thick solid fuel core (2″ ID) would provide quite a long burn at 1MM to 3MM polymetric regression rate. Ideally I would like to find a solid fuel with higher burn rates. I’ve herd poly/paraffin is a good quick burn mix. Just not sure what the best mix ratio would be or just how to mix and cast a combo like that. Diffuser design is my main concern right now I’m not sure how much compression will be needed. I’m searching for a book “Diffuser Design Technology” hoping to get some insights from it. I assume at subsonic M.5 or above will require some type of flame holder perhaps a flare like solid mix at the combustion chamber entrance. Using RocSIM software to compute ejector motor performance. That way I will know how fast and high the ram rocket will be when ejector motor burns out and the SFRJ phase has to start. I also plan to try and utilize fanno flow thrust augmentation during boosting ejector phase. Got a great thread going here on similar topic.


  9. Cliff says:

    I think a below the speed of sound ramjet design is a wasted effort. Sure it is easier to design, easier(?) to make, but the power just isn’t there to do anything much with. If your after something that will show a flame coming out the back, a subsonic ramjet might well do that. But a pulse jet of the same inlet area will out perform it without a doubt.
    Take a look at the basics, ignoring what you want them to say, but what they say. Notice that in the ramjet design flight area, they don’t start “coming on” until Mach 1.5. For example, and engine designed for M 1.5 will produce about 600 lbs of thrust. BUT take the same size “inlet area” and run it M 2.5 and suddenly you have 5,700 lbs of thrust!!
    Nothing is free. The hidden downside is DRAG, and at supersonic speeds it is “tremendous”. As you go up in speed, the “Wave Drag”, (shocks off the inlet spike and cowling) almost balance out the thrust of the engine.
    Also it should be kept in mind that ramjets work best at one speed, known as the design speed, if you don’t have variable inlets and outlets. So as the design speed is exceeded the thrust drops off. If the engine is below its design speed, the thrust really drops off. Think of a ramjet as a whistle. A ramjet works at one tone. Below that tone there isn’t enough air pressure to make it work. Above it, the engine chokes on the air flow.
    The WHOLE secret to ramjet design is in the diffuser, the rest is bolt on practically in my book. Without a good diffuser, the air is not slowed down and brought up to pressure. Shocks will develop in the inlet that will literally shutdown the air flow. Without the correct airflow, you can throw the rest of the engine away because it won’t function.
    My “suggestion” is you guys go to the NACA website and take a look at the early 1950 ramjet engines. Don’t Poo-Poo them as being old designs. Fact is they worked.
    maybe not as efficiently as todays designs, but they worked very well. And NACA spent millions in developing them. Millions we don’t have, or I don’t anyway, so don’t waste time reinventing the wheel. Take advantage of the drawings and measurements. You won’t find measurements on “today’s drawings” of ramjets! There is a reason. Someone could build one.
    With those measurements you can get “a feel” for proportion of each element of the engine. In other words, an idea of where to start on your own design, and what it will take in area of that section. Then start plugging in your numbers into the software packages listed above and see what you get for performance.
    I talked years ago to one of the guys that designed the RJSC program and asked him if I could really design an engine that worked by using it. He told me yes I could, but that ramjet design was made up of two things. A balance of diffuser, combustor , and nozzle proportions, to engine speed and altitude. The 2nd thing was, “Art”. Getting the engine design proportions of the engine to actually work. He said, “They paid the artist guys more than the book guys because the artist guys have learned from experience what really does work, though nobody really understood why.”
    ” However they would have killed for this program in the late 40’s and 50’s. It was strictly slide rule back then, stepping through all the calculations.”
    I’m not a math type, but I would highly recommend that if your serious about making one, and not just playing, you do some basic number crunching, especially if your thinking of subsonic speeds. You don’t see any subsonic ramjets around today for a reason. Air compression, air compression, air compression.

    I wish you guys luck, it needs to be done; Cliff

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