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I am going to design a supersonic RC plane. You can build it...

Old 03-23-2015, 04:32 AM
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theapplepi3.14
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Default I am going to design a supersonic RC plane. You can build it...

The plan is to Design it in Autodesk inventor so that you can 3d print/CNC the parts or use the model as a plan for a scratch build. Warning! Use only quality metal, carbon fibre or other high quality parts! Balsa won't due!

My approach is to first to try to get it to fly supersonic using only a jet engine currently available, an afterburner, and a supersonic intake. This probably won't get me supersonic so I will probably end up adding a slot to put a rocket motor.

I do not plan to build the plane to take off so it might not have that ability, I do not know. All I know is I will need to learn a lot about flight between now and then.

This project will probably fail, but I will give it my best. The inlet design will probably be the hardest to do. Wish me luck!
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Old 03-23-2015, 05:13 AM
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Going to be hard to keep it in sight to fly it....
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Old 03-23-2015, 05:34 AM
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One word.. acronym actually: FPV

A backup pilot with a separate radio and FPV will be REQUIRED since the thing will have the same energy of a Ford Focus traveling at 44mph! Plus it will need to be done in a desert or over water.

Lift is basically nil at mach speeds so it is not like you could fly mile wide loops so you could keep LOS. Even if you could pull that kind of turn, which you cannot, the g forces would be ridiculous! 71+ g's! There is no way even metal wings could cope (without more work on my part that is)

Planing to use a flying wing with a symmetrical supersonic airfoil to keep things simple. HAHAHAHAHA... simple. If anyone has any interest helping me I would gladly accept it!
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Old 03-23-2015, 06:51 AM
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Not trying to be funny here but do you think that for your first attempt at designing an RC model, and not even having built any sort of RC plane before, and not even being able to competently fly one yet....... Would something a little less 'ambitious' not be a more realistic first attempt?
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Old 03-23-2015, 06:58 AM
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I'm not sure what G-force calculator you are using, but mine showed;
speed---------800 mph ----- I just picked a supersonic speed
turn radius---2640 feet --- 1/2 mile
G-force-------16.2963

A pylon racer at 180 mph turning a 100 foot radius generates 21.78 G's. I believe they turn sharper than that, I used to flag for pylon.

So I don't think G-force will be your biggest problem
Good luck
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Old 03-23-2015, 05:47 PM
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Originally Posted by theapplepi3.14 View Post
One word.. acronym actually: FPV

A backup pilot with a separate radio and FPV will be REQUIRED since the thing will have the same energy of a Ford Focus traveling at 44mph! Plus it will need to be done in a desert or over water.

Lift is basically nil at mach speeds so it is not like you could fly mile wide loops so you could keep LOS. Even if you could pull that kind of turn, which you cannot, the g forces would be ridiculous! 71+ g's! There is no way even metal wings could cope (without more work on my part that is)

Planing to use a flying wing with a symmetrical supersonic airfoil to keep things simple. HAHAHAHAHA... simple. If anyone has any interest helping me I would gladly accept it!
And when you wake-up from this "dream" post some scale schematics and calc's.........that may get nerd interests stimulated.........
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Old 03-23-2015, 06:11 PM
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Oh, sorry. I was calculating acceleration in m/s^2, not in g's. It would actually be something like 9gs! hahahaha! Sorry guys.

Im not building it, just designing it, as I said in my first post
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Old 03-23-2015, 09:17 PM
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Only took a few million dollars and several years to make the X-1 break the sound barrier...

Thrust needed is related to speed squared. More power means more weight which means a larger minimal size aircraft which means heavier structure.... vicious circle.

And that's before you get into Mach effects. generally starting appx .80 to .85 Mach you're building up the leading pressure wave that you have to break through. (in a way it really is a barrier)
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Old 03-23-2015, 09:38 PM
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True, but he's not attempting to design a full sized manned aircraft, he designing a model. I'm sure that most of us are aware that the physics for one are not necessarily applicable to the other. Bullets have been breaking the sound barrier for decades before planes were, and bullwhips for centuries before bullets. And they didn't cost millions to develop, nor do they require vast amounts of energy to attain Mach speeds.

I'm not saying he will succeed, but I do encourage him. Go for it; the hobby needs dreamers!
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Old 03-23-2015, 09:48 PM
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I'm sorry, but this is a bad idea in my opinion. Wrong on many levels.

As has already been stated, (the Ford Focus at 44 mph example) this is not a thing to be taken lightly. Your proposed project would produce a barely controllable RPG minus the explosive charge. Fatalities could easily result, and for what? So some guy can have his 15 minutes of fame, regardless of the consequences?

I realize this is just a speculative brainstorming session, but please, consider the implications. Even if it doesn't get past the drawing board stage, the discussion will encourage some dimwit to pick up the idea and try to cobble up a missile to impress his friends, creating another reason for society to fear and loathe us poor old harmless hobbyists.

It's unfair to the rest of us for you whacky guys to keep coming up with dangerous ideas. It's not a game.

I appeal to the moderators here to close this thread, and please be vigilant for any discussion which indicates that an individual is soliciting help in doing something dangerous, or even just opening a discussion on non-mainstream modeling that could be harmful.


Sorry for the diatribe, but we have to regulate our hobby, or else lose it.

Tom
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Old 03-23-2015, 09:57 PM
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Originally Posted by theapplepi3.14 View Post
Im not building it, just designing it, as I said in my first post
Yes but if you havent built then it's very hard to design, because you don't know how to build, and someone has to build whatever you design. I'm afraid this sort of challenge is beyond even very expert RC model designers and builders. Plus of course that no hobbyist would ever be likely to be able to fly it legally.

If you actually want to design something that has a hope of being built and flying you will have to aim much lower. Dont try to run before you can walk as the old saying goes.
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Old 03-23-2015, 10:02 PM
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Originally Posted by tr4252 View Post
I'm sorry, but this is a bad idea in my opinion. Wrong on many levels.
I appreciate where you are coming from but this is just a fantasy, nothing more. If it was being proposed by someone who actually had the wherewithal to make it happen then there might be something to worry about, but that's obviously not the case here. As it is this is about as 'real' and threatening as the local children running around the garden with sticks pretending they have bazookas and machine guns.
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Old 03-23-2015, 10:07 PM
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You'll poke your eye out.
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Old 03-23-2015, 10:21 PM
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good one!!
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Old 03-23-2015, 10:25 PM
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Obviously this is not something to be used in residential areas. planes are not allowed to go supersonic over these areas either!

As for the dangers of it? Well first of all it is going to take lots of CFD, calculations, and time, so I would be damned if there was someone less responsible than me who could design this themselves since usually responsibility comes with knowledge, so talking about it isn't dangerous. I understand that A, it should never be built, and B, if it is, it should be flown only over the ocean, or on a salt flat. If anyone else thinks any differently they are mad!

Second, If I do succeed, it would require THOUSANDS of dollars to get it to work. It will need to be made of high quality materials so there is at least $100 right there. If it is CNC milled or Carbon Fibre formed it will cost in the region of thousands of dollars. Then there is the jet engine. I will probably end up using something like the P200-SX Turbine, which costs $5,500 alone, not to mention the fact that there will need to be an afterburner.

Finally, To get into the mach reason will likely require (although it is too early to tell) a rocket engine which costs $100 per use and $200 for startup.

Of course that is if you don't care about controlling it. If you want control of it you will need two long range transmitters and two long range FPV systems. Not cheap.

I don't want to sound like I am ranting but there is a youtube video of a rocket that was launched by an enthusiast that reached 121,000ft and it hit mach 3+. It had the energy of a "small" Gulfstream jet traveling at around cruise speed! It was all totally safe though because he launched it in the middle of a salt flat.

How heavy is the pylon racer? A 180 lb pylon racer at 180mph also has the energy of a ford focus at 44mph. I am guessing a pylon racer is not that heavy though!

I understand your concern, but I think you are overestimating the budget of irresponsible hobbyists. Also, I think you are overestimating my ability to design such a plane. I really don't have any idea if it is possible. I am still in HS after all.

If you guys are concerned I will no longer post about it though. I don't want to ruin the hobby just to break a speed record. Someday it will happen, and I want to be a part of it, but not if that part leads to more regulations
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Old 03-23-2015, 10:34 PM
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Search Results
very very very fast Turbine powered RC Jet 440 MPH Speed ...
Video for smallest fastest fpv jet supersonic speed▶ 5:29
www.youtube.com/watch?v=sa-TSNeTK-A
Sep 18, 2013 - Uploaded by bunterfisch
very very very fast Turbine powered RC Jet 440 MPH Speed Guinness World Record 2013. bunterfisch ...


this is just a teaser to build something like what you want to design...very good pilot is at the sticks since a second of going straight would make this jet disappear very quickly.
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Old 03-23-2015, 10:42 PM
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Perhaps Bunterfisch would be interested in my design. lol.

I have seen that video. How much do you think it weighs?
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Old 03-23-2015, 10:57 PM
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very little judging the guy carrying it under his arm like that,plus they use a bungie to launch it. the 121,000ft rocket launch was also a cool video.

apple,you'v been honest about being in high school,no plans to actually build your design...ect..ect..... there are a few here who love tossing calculations in the mix. just not sure how much interest you'll get from them if they are focusing more on the realtime flying rc. have fun and keep on asking questions in this world. there's so much to learn.
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Old 03-23-2015, 11:30 PM
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Thanks tobydogs! I really appreciate it!

Okay. So my approach is to try to create a really high thrust system first, then design the plane around it. I think I will want to use a P200-SX Turbine engine because of it's high power/area ratio, and its high thrust. Now to design the inlet and afterburners...

the inlet will need to create a protective shockwave in front of the engine to prevent supersonic air form entering the engine. I will need to use cot(oblique shockwave)=tan(wedge angle*((specific heat ratio + 1)(Mach)^2/(2*(Mach)^2*(sin(wedge angle))^2 - 1) - 1)) I think. From that I can figure out approximately the intake I will need. I will be back in a few days with the design...
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Old 03-23-2015, 11:49 PM
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Originally Posted by theapplepi3.14 View Post
Obviously this is not something to be used in residential areas. planes are not allowed to go supersonic over these areas either!

As for the dangers of it? Well first of all it is going to take lots of CFD, calculations, and time, so I would be damned if there was someone less responsible than me who could design this themselves since usually responsibility comes with knowledge, so talking about it isn't dangerous. I understand that A, it should never be built, and B, if it is, it should be flown only over the ocean, or on a salt flat. If anyone else thinks any differently they are mad!

Second, If I do succeed, it would require THOUSANDS of dollars to get it to work. It will need to be made of high quality materials so there is at least $100 right there. If it is CNC milled or Carbon Fibre formed it will cost in the region of thousands of dollars. Then there is the jet engine. I will probably end up using something like the P200-SX Turbine, which costs $5,500 alone, not to mention the fact that there will need to be an afterburner.

Finally, To get into the mach reason will likely require (although it is too early to tell) a rocket engine which costs $100 per use and $200 for startup.

Of course that is if you don't care about controlling it. If you want control of it you will need two long range transmitters and two long range FPV systems. Not cheap.

I don't want to sound like I am ranting but there is a youtube video of a rocket that was launched by an enthusiast that reached 121,000ft and it hit mach 3+. It had the energy of a "small" Gulfstream jet traveling at around cruise speed! It was all totally safe though because he launched it in the middle of a salt flat.

How heavy is the pylon racer? A 180 lb pylon racer at 180mph also has the energy of a ford focus at 44mph. I am guessing a pylon racer is not that heavy though!

I understand your concern, but I think you are overestimating the budget of irresponsible hobbyists. Also, I think you are overestimating my ability to design such a plane. I really don't have any idea if it is possible. I am still in HS after all.

If you guys are concerned I will no longer post about it though. I don't want to ruin the hobby just to break a speed record. Someday it will happen, and I want to be a part of it, but not if that part leads to more regulations
I appreciate your response, and respect your evident good intentions. You present yourself well and your project is intriguing.

As you probably know, the hobby is presently having issues with public image and political involvement. We're also seeing an increase in publicized irresponsibility among some RC enthusiasts.

All I'm saying is that it makes what you're doing a matter of interest in a broader sense than just this forum. Your last post (above) has gone a long way to aid your credibility, so I'm confident that you will be circumspect in how you'll go about this.

Tom
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Old 03-23-2015, 11:54 PM
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Originally Posted by tobydogs View Post
Search Results
very very very fast Turbine powered RC Jet 440 MPH Speed ...
Video for smallest fastest fpv jet supersonic speed▶ 5:29
www.youtube.com/watch?v=sa-TSNeTK-A
Sep 18, 2013 - Uploaded by bunterfisch
very very very fast Turbine powered RC Jet 440 MPH Speed Guinness World Record 2013. bunterfisch ...
Supersonic is on a different technical planet to 440mph. Look at the full size airplane world to see the difference in aircraft design required. It's literally the difference between a P-51 Mustang and a Bell X-1... They are just totally different animals.

A ballistic rocket is one thing, a controllable aircraft capable of taking off completing it's mission and returning to complete a controlled landing is something totally different.

On course a supersonic RC plane is perfectly possible, it's been done many times for military purposes for target drones and cruise missiles and the like. But to try to emulate these multi million dollar projects as a hobbyist with virtually zero RC experience, zero qualifications, and near enough zero budget truly is cloud cuckoo land.... Sorry.
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Old 03-24-2015, 02:47 AM
  #22  
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Take the engine out of the plane. What is the current DS record? I think just north of 500mph....
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Old 03-24-2015, 03:47 AM
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It is true that I can probably get quite close to Mach 1 if I used one of those planes and I had perfect 100 mph wind conditions and I handed the controls to an experienced pilot, but the planes cannot go supersonic, or at least they shouldn't be able to because at supersonic speeds lift is very minimal which is one reason why propellers dot work at those speeds. So basically you wouldn't be able to pull a tight turn like try do.

Thanks for the tip though. It would work if I wasn't planning on going supersonic. And if I had a free pass up Mt Washington

You poor DS pilots! Mt Washington has perfect wind a huge number of the days of the year! It used to hold the straight wind record! I wonder if anyone has ever tried it...
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Old 03-24-2015, 05:03 AM
  #24  
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I wouldn't rule out a balsa built model, but i don't see getting those speeds while staying under the 55lb limit by the ama.
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Old 03-24-2015, 08:15 PM
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True. I wonder if the friction heating is high enough to ignite the wood though...
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