Cone Shaped Rockets

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evildave42

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Hi all,
Iv'e been tossing around an odd idea, I wanted to build a rocket-deployed radio controled glider. Thats part is easy enough, the ejection charge just spits out the nose weight instantly balancing it for gliding.

Here's the trick: I want to make it a scale model of Wernher Von Braun's 3-stage Ferry Rocket. Google it. It has the glider on top of a 3-stage cone shaped rocket. But for now, let's ignore the glider and just say its short tube with a cone on top.

The lower-most stage has large fins, so thats no problem.

But the second stage does not! It is still cone shaped though. I want to make the whole thing rather large and I dont want clear fins. I've only been able to find a tiny bit of info on finless, cone-shaped rockets.


So, what do I need to know to make a stable, finless, cone-shaped rocket?


Bare in mind I dont care about performance, I just want to see if I can do it, I dont mind adding lots of nose weight.

P.S.: The more dramatic it looks the better!

P.P.S.: Anyone have experiance with clustering AND staging in the same rocket?
 
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To answer your question about finless, cone-shaped rockets:

A simple cone is inherently stable. The CP is 2/3 of the cone's length behind the point. As long as you don't have a lot of tail weight, it will be stable. That's why kits like these are so easy to do.
Point-lg.jpg
 
2/3rds huh? That should be realy easy. The glider or dummy cone should add plenty of nose weight.

On another note, I've never built a rocket with fins close to the nose. Since the final stage is made up of a large wiged glider I can scaresly imagine what that will do to the CP with any stages attached. Are there any existing examples of this?
I suppose I could try it on the kit pictured above, they are less than $8 anyway.
 
I don't know for sure that it can handle your design, but a little time playing with Open Rocket might provide you both answers and solutions.
 
I don't know for sure that it can handle your design, but a little time playing with Open Rocket might provide you both answers and solutions.

Naw, I just mean sticking little fins to the nose cone to see how well it works in practice after running some sims.

I'm also going to have to run some sims on the Ferry glider, I'm concerned that that T-tail will cause asymmetrical drag while boosting. I was thinking I might add two long but low-profile fins on the otherside that double as landing skids.

With the ejecting nose weight it should lend itself to boosting and gliding quite well.
But I also thought I might test the Ferry in practice too by quickly building a semi-scale rocket using the same fin configuration around a BT-50 before moving up to a 2.5 or 4 inch tube. It won't glide though, it would only test the boost phase.
 
Okay this is what I'm talking about building:
4-Stage Ferry.jpg

I'm starting by building the Radio Controlled Ferry shuttle:
DSC02159.JPG

I got some rough details on the scale:
If I make the glider using a BT-80 for the body, it will be 16.2 inches long. With all of the boosters attached, it would be 5ft 6in tall. Bottom Dia.: 1ft 2in.
If I make the glider using a 4 inch tube for the body, it will be roughly 24 inches long. With all of the boosters attached, it would be 8ft 2in tall. Bottom Dia.: 1ft 9in. This would likely make a much better Radio Controlled glider though.

With all three boosters:
DSC02162.JPG

The idea is to:
A) build the RC rocket glider first and test (Uses a C11-D12)
B) assuming it is successful, built the 3rd stage and test (Uses a C11-E12)
C) assuming it is successful, build the 2nd stage and test (Uses an E12-F26) (*May require an Air-Start when used with 1st stage*)
D) assuming it is successful, build the 1st stage (Uses an F26-G40)

Sigh. I'd like to build the Glider out of a 4 inch tube, but once you add all of the boosters it seems to become unmanageably large. I'm also shooting for under $100 in engines per launch. At this rate it seems like would need a High-Power or a cluster of Mid-powers in the first stage.

If I built it around the smaller BT-80 glider, do you think I could get away with one G-40 in the first stage? What about with the 4 inch tube? (Remember, performance is not really an issue)

P.S.: no idea on the over-all weight yet.

Also: I am quite aware how insane this is. That's why I'm asking, the largest thing I've fired to date is an E9, though I'm designing a supersonic rocket for a G80.
 
Fins on the forward glider are going to move the CP forward a LOT in the boost config... the cone stability is correct that the CP is at the 2/3 length of the cone chord line, BUT putting fins in front of the CP is going to have the same effect as it would on a regular tube-n-nose cone rocket... like the sidewinder or whatever... it's going to move the CP forward...

The more fins you have up front, the greater their area, the more it's gonna move the CP forward...

Hope this helps! OL JR :)
 
Yeah, I'm a bit worried about using the 2nd stage (which has no fins) with it. Although, if I move away from the cluster idea and opt for higher power singles (thus lighter) I can keep the tail weight down, especially in the long 2nd stage. The Ferry on top will weigh significantly more than a normal rocket being radio controlled, it will also be carrying the ejectable nose-weight for boosting by itself. Still, those wings make for really big fins....
Perhaps a heavier ejectable nose-weight for use with the booster?
Or maybe, since Mr. Von Braun’s rocket never got past a few concepts anyway, I could make a non-scale version, with a longer/wider 2nd stage booster? That would move the cone’s CP farther back.
I'm thinking I just might try it on one of those tiny Semroc kits first…. With a 1/2A….and stand far away.
 
For "unconventional" rocket designs, I'm of the mindset that you start with small "boilerplate" models with "A" or "B" impulse. Fly them. Make adjustments where necessary. Then scale up and repeat the process. I understand at the smaller scales you can't "RC" the ferry craft, but you will quickly learn if the stack will fly well.

I think it's less risky than an "all up" test.

Then you will have confidence (and so will your RSO) that your project will have a reasonable chance of success.

Greg
 
For "unconventional" rocket designs, I'm of the mindset that you start with small "boilerplate" models with "A" or "B" impulse. Fly them. Make adjustments where necessary. Then scale up and repeat the process. I understand at the smaller scales you can't "RC" the ferry craft, but you will quickly learn if the stack will fly well.

I think it's less risky than an "all up" test.

Then you will have confidence (and so will your RSO) that your project will have a reasonable chance of success.

Greg

Hmmm... a good point. I was already going to make a small version of the Ferry as a test of the tail design, proly around 9-10 inches long, streamer recovery (no gliding). Using a BT-50 as the body, it should not be difficult to multy stage it on As and Bs. Might make a nice model itself.
Guess I'd better sim the small version of the ferry tonight.
 
By staging it you will have to deal with variable CP for each stage and that is only the beginning of the complexity on this hot lookin' Kraut bird. This one will melt your computer simulation and will call for a Von Braun level mind simulation.
 
By staging it you will have to deal with variable CP for each stage and that is only the beginning of the complexity on this hot lookin' Kraut bird. This one will melt your computer simulation and will call for a Von Braun level mind simulation.

*Snort* Yeah I Know! I use the free Open Rocket too! That’s why I'm gonna make a small scale one.
I've gotten pretty good at RC planes, I have no doubt that I can make it work as a glider (on the scaled up version), and I think I can balance it for boosting, but Oh Man! with that finless cone stage added and giant wings on the front? That’s probably outside of most sims abilities. So, I build it, stick an A in it and wear safety goggles. Maybe a 1/2A.
 
This one looks to me as a top down job. Get a working glider - the heavier the better - the smaller the wings the better, use all those RC tricks I know nothing about. Then get real creative on the booster side. Make it a little longer and narrower with bigger fins but still looking good. Use some lead pipe for the booster-glider connection. Custom fabricate a booster glider rail up the backside of the glider (ataached to the booster) with a balancing tail made out of the heaviest - densest material you can find - metal (lead) and steel epoxy clay - but it still must look good. Put that high kick and powerful composite motor as far up the hind end as you can get with out the Krushnik effect. Still provide an area for minimum adequate recovery gear (rear ejection). Make the hind end and cone of the booster as light and strong as possible. Get a very long launch rod. Find a very kind RSO or rogue launch. Pray. Have a video of the perfect launch and recovery for everyone on the forum. In thrust we trust. In sickening amounts of nose weight on that booster we trust. In absolutely calm weather we trust.
 
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Tubular shapes have a lot less aerodynamic effect than fin ones for their size. So I think trying to fly that glider on the front end of a finless shape is going to be difficult at best. The CG could have to be as far forward as the rear of the glider, in front of the entire cone. Thes sizes you're talking of also will be heavy unless very weak.

I don't use a stability sim myself but I think it could be more right than wrong. I don't know if you can sim it as one rocket, maybe diff. rockets for each stage.

Consider using fewer stages. Not only is there stability and ignition issues, each staging tends to knock a model rocket off course. Four stages rarely produce an advantage. Look up "rack rockets" for some background.
 
Well, I sim-ed the small version, dont know how to do the T-tail in OpenRocket, but it balanced well with 0.5 oz nose weight. Gonna monkey with it some more before building the test unit
 
This is a fun and challenging project, indeed. Just making the WVB project without the second stage really staging is challenging. I tried it once and it didn't work. You can get plans for the basic boiler-plate model from NARTS, i.e., The Sentinel (newsletter of CMASS), collected plans 1989-1994. Perhaps, you already know this. There is also some mention in Hagerty's Spaceship Handbook. There is also the possibility of using clear plastic fins for the second stage or using fold-out plastic fins that Apogee has talked about in some of their newsletters.
 
This is a fun and challenging project, indeed. Just making the WVB project without the second stage really staging is challenging. I tried it once and it didn't work. You can get plans for the basic boiler-plate model from NARTS, i.e., The Sentinel (newsletter of CMASS), collected plans 1989-1994. Perhaps, you already know this. There is also some mention in Hagerty's Spaceship Handbook. There is also the possibility of using clear plastic fins for the second stage or using fold-out plastic fins that Apogee has talked about in some of their newsletters.

With my rockets, I try to do something different and a little challenging with each of my scratch builds, I'm working on a supersonic one and one with strapon boosters as well, But this is probobly my most ambitious. To me, the RC glider is the easy part, I have experiance with RC planes, making it to be ballanced and withstand boosting is the challenge, even with no bosters at all it would be fun!

I'm not familiar with NARTS is that an online resource? It would be nice to have some scale drawings, I've been basing mine on the Glencoe model kit, but its a bit tiny.

Maybe I'm just being stubborn, but I want to avoid clear plastic fins. However, since it was only a concept design, I could take some artistic license, i.e.: make the 2nd stage cone longer/wider allowing it to balance better or add tiny fins to it.

My biggest problem after testing the small scale will be settling on a size.
If I went with a BT-80 for the glider body, due to it's size, it would be more difficult to glide especialy in any kind of wind. Unless I went with the older Ferry design with the long wings instead of the delta, but that has a cone shape that would be hard to RC and would also cause more CP problems when stages are added.
If I went with the 4 inch tube, the glider would probobly work great, but If I built scale boosters, it's overall hight would be 8 feet 2 inches. Thats a bit dificult to manage.

Right now I'm thinking the BT-80 glider with some minor alterations to it and the boosters may be the best way to go. What do all of you think?
 
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The NARTS is found on the NAR website. You would need to order this particular item for a small cost. This particular issue of the Sentinel has a WVB with a glider based on a BT-50 tube and the model uses either a D12-3 or an E15-4 in the booster base. There is a conversion in the same issue to fly the plastic Glencoe model on an A10-3T.
 
Well, here's the miniature prototype:
DSC02164.JPG

It's built around a BT-50, OpenRocket simulates it as well balanced with 0.4oz of nose weight.
This one does not glide, it is just to test boosting.

I am a bit concerned about the asymmetrical drag from the T-tail. OpenRocket doesn't seem to simulate it. To counteract it I added two small 'landing skids' to the bottom that are actually small fins but I'm not sure how effective they will be. I've never built a rocket with asymmetrical fins before, what do you guys think?

P.S.: Wont have the chance to test it for another week. *sigh*
 
Well, here's the miniature prototype:
View attachment 124104

It's built around a BT-50, OpenRocket simulates it as well balanced with 0.4oz of nose weight.
This one does not glide, it is just to test boosting.

I am a bit concerned about the asymmetrical drag from the T-tail. OpenRocket doesn't seem to simulate it. To counteract it I added two small 'landing skids' to the bottom that are actually small fins but I'm not sure how effective they will be. I've never built a rocket with asymmetrical fins before, what do you guys think?

P.S.: Wont have the chance to test it for another week. *sigh*

Just a small critique, the wings will be stronger if the wood grain is parallel to the leading edge.
 
Here is an idea that might help for the original idea of this thread designing the WVB Ferry Rocket, which has large forward wings (or fins). The idea may or may not be practical. The design concept of making forward fins ineffective is found here:

https://archive.rocketreviews.com/reviews/all/python.shtml

Perhaps, a design could have the forward fins on a freely moving axle that during ascent would produce no moments or turning forces on the model. When the ejection charge fires on the lower stage some sort of moving piston would move forward to lock the wings in place. The Ferry rocket would then be able to have a glider recovery.
 
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Here is an idea that might help for the original idea of this thread designing the WVB Ferry Rocket, which has large forward wings (or fins). The idea may or may not be practical. The design concept of making forward fins ineffective is found here:

https://archive.rocketreviews.com/reviews/all/python.shtml

Perhaps, a design could have the forward fins on a freely moving axle that during ascent would produce no moments or turning forces on the model. When the ejection charge fires on the lower stage some sort of moving piston would move forward to lock the wings in place. The Ferry rocket would then be able to have a glider recovery.

I had been thinking of the very same thing for a design I had in mind!
 
A simple cone is inherently stable. The CP is 2/3 of the cone's length behind the point. As long as you don't have a lot of tail weight, it will be stable. That's why kits like these are so easy to do.

Point-lg.jpg

(Sorry to revive an old thread!) :bangpan:

So, theoretically, you can put an engine in the aft section and not at the top or mid-length like most kits, right? It just need more nose weight.

Is there a limit to the ratio of the base vs. length in terns of stability? I mean, I've seen pyramids and the kit above but what about a cone that has the same base diameter but is much longer?
 
I am a bit concerned about the asymmetrical drag from the T-tail. OpenRocket doesn't seem to simulate it. To counteract it I added two small 'landing skids' to the bottom that are actually small fins but I'm not sure how effective they will be. I've never built a rocket with asymmetrical fins before, what do you guys think?
Take a look at this:

230dfs346_small.jpg

That's my DFS 346. It's not a glider but it does have an asymmetrical upper fin, and it flies quite well considering that it's somewhat overweight for an A10-3T.

The wings are probably fine as they are; having the grain parallel to the trailing edge isn't too bad, it's having the grain parallel to the root which would seriously weaken them. However, you can strengthen them by laminating them with paper - that's the reason the wings and tail on the DFS 346 are white.

Then there's this:

View attachment 146395

That's my old model of the Feuerlilie F25. It flew very nicely on B6-4's until it was retired because I got better plans showing that the real thing did have a matching underside tail fin.

Bottom line: I wouldn't worry about the upper fin on your rocket. I didn't worry about it on mine. :)
 
I certainly would not worry too much about asymmetry---the big thing is to keep EVERYTHING, as straight to the airflow as possible.It is possible with a large surface to get a little bit of arcing in flight but it should be minimal. As it turns out ,I don't have a single symmetrical rocket in my collection--I need to do something about that!!--Check out my profile albums.
As far as this project goes, I've toyed with the idea of building this and put it on the backburner. If I did it---not likely in the near future--I'd build the top two stages stable together and get that part flying. After that---and that's gonna be a trick---adding the bottom stage should be easy enough given the cone shape and large fins. The cone shape works to your advantage but nose weight would be needed --pretty sure of that!! I also thought about downsizing the glider a tick --It just looked out of scale to me---you know what I mean --just not quite right. Anyway, good luck on this I'm sure you'll succeed-----H
 
Okay, wow I haven't updated this in a while!

Well the F-11 prototype above worked great. it was eventually retired last year and in it's place I built the Radio Controlled F-13 Thunderwing Mk. I:
12423128053_5cbcebf495_o.jpg

It is a radio controlled glider launched on an E9 motor. I have had plenty of flights on it now, there are several videos of it on my Youtube, here's one to start you on:
[video=youtube;2s5eOE17zc4]https://www.youtube.com/watch?v=2s5eOE17zc4"]https://www.youtube.com/watch?v=2s5eOE17zc4[/video]
I also have loads of pictures on my Flickr: https://www.flickr.com/photos/53996788@N07/sets/72157649059210920/

I have already designed the very similar but much improved F-15 Thunderwing Mk. II but it will be a while to completion.

BUT, that is not why I update!
Today I am working on the F-14! A cone shaped rocket that will have 4 fins on the back and run on an E-12 or E-9. It is just a simple single stage cone shaped rocket only much bigger.
Length: 32 inches
Bottom Diameter: 12 inches

It has a core tube made out of BT-55 ans a stock plastic Estes cone. The bottom 12in bulkhead is made of foam-core board (5mm foam laminated on both sides with glossy card-stock), two progressively smaller support bulkheads are made of 6mm sheet-foam, and the outside is wrapped in regular poster-board, all assembled with lightweight RC aircraft glue.

The plan is to add 4 fins and a bit of nose-weight. The Open Rocket simulations say it will be stable but I want to be sure, how big do you all think I should make the fins (I would prefer they slant back a bit, gives it that retro look).
DSC02993.jpg

P.S.: Anything else I should be looking out for?
 
12" diameter?!? You need more power. Long burn but way more power. E9's are great for 5.5", at 5 oz. makes about 400'. You'd need at least 4 of them to make that.

I wouldn't put fins on a cone rocket, kind of the whole point, but then you'll also need nose weight. The CP of a long cone should be at 2/3 the length back, although that one's squat enough you may get some saucer effect. It has been speculated this is due to "base drag" but for some reason it only occurs when the front shape is saucerlike.
 
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