"Finless" Rocket Design - Ram Air Intake Stabilization?

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Dick,

It was about 10.98" long and about 5.38" in diameter and weighed about 16.79 oz. without motor. It flew on a E15-4. I will see if I can attach the Rocksim file here. I looked at the file today. It needed to be moving about 40 fps leaving the rail and according to the simulation it was about half of that.

Years ago I documented this build on Rocketry Planet.

View attachment Xmas ornament 2010.rkt

View attachment Xmas ornament 2010_small.rkt
 
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Both appear to have been well underpowered. Need a CTI 1G G75. With that loaded it looks stable and you haven't considered base drag.
 
In my haste I forgot one important thing....even if they did not fly so well, they look awesome!
 
I admire you for approaching these designs so scientifically. I neither have the launch site availability, or the patience, to try multiple iterations. If I don't get something going in 2 tries, it seems to get on the permanent back burner.

I like KenEC's work on the finless design. It looks like the RAIStone has long slots in the side and flies well.

I also tried an Apollo capsule design about 6 years ago for a Club Christmas oddroc contest. It had clear base fins, but did not do as well as KenC's model. It had AA batteries in the nose cone to light up Rudolph's nose. The large model went up only about 10 feet and did cartwheels. The smaller model did a little better. Rocksim said that it was stable, but it was not. I did not check the Rocksim simulation to see if there was a minimum velocity for leaving the rail.

Thanks guys! :)

Dick - For me, I wish I could give it a few tries and then shelve it, but all too often I'm OCD (my wife would say stubborn) and once I'm on it, I want to get it right. Unfortunately something like this is very difficult to get right. Still, sometimes I feel like a kid who just launched his first rocket when one of my wacky designs works...and that makes all those test flights worthwhile. :smile:

Aerostadt - that capsule looks great! Also great holiday theme! I think you were on the right path with the big fins and they disappear against the snow too, which is awesome. However I think Dick is right that more thrust/speed off the rod is needed...the short & squat rockets are so draggy with the CP so forward that it's hard to overcome. Plus adding more motor doesn't necessarily solve things since the bigger motor brings the CG back, hence more nose weight & lower speed, therefore more motor...uh oh. :wink:
 
20161126_112448.jpg

It's coming along. Psuccess estimated at around 15%.
 
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I have been following this in the shadows and have been intrigued by the idea. The problem is that, as I was catching up on your progress, the wheels started turning and I started inventorying my spare tubes in my mind. I have some T20, T50 and T60 tubes downstairs that don't have pointy ends yet. It will be near spring before I can begin in earnest but I may have to try my hand at this:bang:

My question is, have you done anything to alter the geometry of the air channel inside the rocket to utilize changes in internal air pressure/velocity to help stability?
 
My question is, have you done anything to alter the geometry of the air channel inside the rocket to utilize changes in internal air pressure/velocity to help stability?
All I've thought about doing is smoothing the joint between the inner BT-60 and the lower plate. So far, I haven't addressed even that.
 
My question is, have you done anything to alter the geometry of the air channel inside the rocket to utilize changes in internal air pressure/velocity to help stability?

I actually did a LOT of things to alter the internal air pressure/velocity...however none of it was calculated or programmed..it was mostly trial, error, success and fine tune. For my RAIS rockets, I started testing with Area Rule/1:1; however each rocket seemed to need something different depending upon so, so many factors (speed, intake shape, length, weight, vent shape, etc.).
 
Here's a bit more eye candy for those of you who are dedicated enough to read through 10 pages of this stuff... :pop:

One of the test designs I was most proud of was this one which I thought up and made myself...helical vanes! :grin:

2016-03-16%2023.28.59.jpg


2016-03-18%2023.26.48.jpg


2016-03-22%2007.35.44.jpg


[video=youtube;SQPdK8mjr1I]https://www.youtube.com/watch?v=SQPdK8mjr1I&feature=youtu.be[/video]

It was really cool to build and spun the rocket up like mad. I only got a few tests on it and on it's first A10 launch, it went up straight, but there was an extended/faulty delay and it lawn darted before it ejected, causing major damage to the forward tube, to which the vanes were glued to the bottom of. :facepalm: It seemed to be a bad batch of A10s since two other motors from the same lot also exhibited very long delays. I did repair it (as well as I could) and also made another less "helical" version since it seems that the first spins the rocket almost too much. Both worked well (even did some tests without nose weight) and I am hoping to one day kit this design as the second & higher level "finless" kit after the RAIStone. Maybe one day. :)
 
Laying out those helical vanes makes my brain hurt. The idea I understand but getting them to fit would drive me up a wall.
 
Here's a bit more eye candy for those of you who are dedicated enough to read through 10 pages of this stuff... :pop:

One of the test designs I was most proud of was this one which I thought up and made myself...helical vanes! :grin:

2016-03-16%2023.28.59.jpg


2016-03-18%2023.26.48.jpg


2016-03-22%2007.35.44.jpg


[video=youtube;SQPdK8mjr1I]https://www.youtube.com/watch?v=SQPdK8mjr1I&feature=youtu.be[/video]

It was really cool to build and spun the rocket up like mad. I only got a few tests on it and on it's first A10 launch, it went up straight, but there was an extended/faulty delay and it lawn darted before it ejected, causing major damage to the forward tube, to which the vanes were glued to the bottom of. :facepalm: It seemed to be a bad batch of A10s since two other motors from the same lot also exhibited very long delays. I did repair it (as well as I could) and also made another less "helical" version since it seems that the first spins the rocket almost too much. Both worked well (even did some tests without nose weight) and I am hoping to one day kit this design as the second & higher level "finless" kit after the RAIStone. Maybe one day. :)

That's awesome for sure. I don't know whether I'm more impressed with the concept or you ability to build it.
 
That's awesome for sure. I don't know whether I'm more impressed with the concept or you ability to build it.

Thanks Dick! I'm flattered! :blush: Once you get the arc correct, it's not that hard. I actually tried some calculations, but they didn't work right and in the end it was simpler to try trial and error...guess the arc...too big, try less...too small, try more, etc. I work on the computer all day and likely for most of my time now, but I usually prefer to just work with my hands when building things.

Building this gave me the idea of the spiral rotating fins on the summer build-off. If I do start making kits, I would likely have the modular can rockets as the first kit since they aren't difficult to build, they fly so well and are just plain fun.

If I get this helical finless version done up as a test kit I'll send the first one to you to try - it shouldn't be hard...biggest problem is finding the time & templates and making the instructions. Just don't wait on me or hold me to any specific timing since work gets obscenely crazy for me this time of year all the way through January - once it was really busy through March...ugh.
 
If I get this helical finless version done up as a test kit I'll send the first one to you to try - it shouldn't be hard...biggest problem is finding the time & templates and making the instructions. Just don't wait on me or hold me to any specific timing since work gets obscenely crazy for me this time of year all the way through January - once it was really busy through March...ugh.

Or, you could kit up a finless SSC:wink:. I know, lots more challenges to iron out on that but it would certainly be a departure from the 3FNC pattern.
 
Or, you could kit up a finless SSC:wink:. I know, lots more challenges to iron out on that but it would certainly be a departure from the 3FNC pattern.

Actually I was just thinking of something like that this afternoon...my current 29mm mmt SSC is modular and can accommodate the ball bearing 38mm fin can (which I really, really want to finish) and therefore, I believe I can try a spinning vented finless can (54mm?) as a test after that...hmmm....:confused:
 
I hate when I think I'm on to something just to find its been done :). I've enjoyed reading this thread and understand where you're going while curious about something too. On your earlier rockets, what if you left the base open, forego the slots, and extend the outer tube and internal vanes two or three inches below the lip of the motor (taper the fins to the external wall)? You have the helical fin directing air along the airframe already. The heated air from the motor mixing with the air along the lower part of the helical will increase the flow through the outer can thereby increasing the pressure somewhat, of the air being pulled in. Plus it should keep the heat from the motor from coming in to contact with the outer casing (boundary layer air). In my novice mind, the endplate is also a drag inducer internally, adds weight, and also creates a cavitation wave behind the rocket. Cool concepts, great learning experience for me, and enjoyed the vids. Hope your neighbors are understanding :)
 
On your earlier rockets, what if you left the base open, forego the slots, and extend the outer tube and internal vanes two or three inches below the lip of the motor (taper the fins to the external wall)?

You sir, sound like you would enjoy something called Gas Dynamic Stabilization!

Guaranteed to get you some sideeye at every launch!
 
Thanks Nytrunner, I am, finless and GDS combined. Boyles' laws, boat tails, laminar airflow, drag vortices, CG/CP, divergent surfaces, and airfoilless designs dance through the vast void of my noggin daily. I keep a notebook of ideas that I sketch out when the thought or possibilities hit me. Last night, I came across the info on here and saw that others are chasing that rabbit too. I read your link and bookmarked it for reading later tonight. Thank you. What happens if the lower tube is a couple of millimeters larger than the upper and the upper is boat tailed? Over thinking this or unnecessary weight? As for an internal fire retardant in the lower tube, has anyone used crushed perlite adhered to the inner tube as an insulator from the nozzle exhaust heat? A slurry would introduce the adhesive to the heat and conduct it. I was wondering if the tube was coated with a thin coat of glue and perlite dust was poured and shaken inside that tube, the insulative property somewhat protect the adhesive. Will have to raid the wife's gardening supplies and introduce it to a blowtorch! Just a hair brain thought.
 
I've been applying Minwax wood hardener to the back end of my GBIs. Its helped the delamination although my first few launches were without it. The first two barely had scorch specks, but it started bubbling slightly on the 3rd. That's with BP motors, I haven't tried Composites yet (although I've got an extra D10 in my box!)

Forward tailcone and enlarged rear tube inlet? The tailcone sounds cool, I'm worried the larger tube would become a giant rearwards ring fin with the associated drag.

There are only a couple ways to find out though: Build or Compute! (either way, please return the results to us :D )
 
I've been applying Minwax wood hardener to the back end of my GBIs. Its helped the delamination although my first few launches were without it. The first two barely had scorch specks, but it started bubbling slightly on the 3rd. That's with BP motors, I haven't tried Composites yet (although I've got an extra D10 in my box!)

Forward tailcone and enlarged rear tube inlet? The tailcone sounds cool, I'm worried the larger tube would become a giant rearwards ring fin with the associated drag.

There are only a couple ways to find out though: Build or Compute! (either way, please return the results to us :D )

The best way to do this would be to get a baseline design then make copies with variations. Various inlet sizes, varying GDS tube diameters or whatever. I am too impatient for that, unfortunately.

Basically unrelated, but the water rocket folks commonly use a ring fin that is the same diameter as the body but is offset below the nozzle with spars. Always wanted to try that on a small Estes class rocket.
 
from-nazi-germany-to-argentina-a-proposal-for-the-worlds-first-small-supersonic-cruise-missile

I find that as I think I have a great idea, like pyramids in Egypt and Latin America, someone did it already! But then again, the V-22 Osprey and B-2 aren't new designs...
Images aren't attaching for some reason, computer or web, but here is the link https://warisboring.com/from-nazi-g...worlds-first-small-supersonic-cruise-missile/
Minus the wing, with a convergent inner tube and the motor being farther aft for CG purposes, is it a ring fin or passive expansion nozzle? Will have to do my homework on Ring Fin concepts.

If you're replying, you're teaching, and I thank you.
 
The page would not fully load on my phone ...will look at the site later. There are multiple things that tend to creep in together. Ring fins provide stabilty, air intakes help to defeat Mr. Krushnik, thrust augmenters do nothing with our short burn motors and at low speed, GDS tubes add stability but have a limited range of designs on which they work, RAIS (ram air induction stabilization) works but is also limited in what it can do.
 
The best way to do this would be to get a baseline design then make copies with variations. Various inlet sizes, varying GDS tube diameters or whatever. I am too impatient for that, unfortunately.


And then there's me, who chooses a target geometry and stubbornly insists on trying to make it work.
 
And then there's me, who chooses a target geometry and stubbornly insists on trying to make it work.

That's more me too ;)

Umm...mee three? ;)

Sorry I've been away guys...life happens. Looking forward to getting back to this, but for now it seems to be at the limits of stability and fairly inefficient, so it would take a LOT more testing (which I'm not at the luxury of doing at this time). The recent discussion does make things interesting though. I'd love to really test the limits by combining some of the things mentioned recently, but that just muddies things up as to what is really working to help with stability.

Still, this has been an extremely interesting and cool endeavor for me so far and I hope to continue it when I have more time. Thanks for everyone's attention, feedback, input and patience. :)
 
Hey Everyone!

This hasn't been forgotten...life just got waaaay more complicated for me (and in many ways still is). However I've always wanted to revisit this and definitely will one day since it was quite a blast!

Another recent thread mentioned an "upside-down" rocket design, so I added my experience with "Whatside Down" and added the video. This lead to a few replies wondering about the design and what "trickery" I have going on (I noted that "there is a lot of hidden engineering going on, so it normally wouldn't work if built conventionally"). I didn't want to hijack that thread, so I figured I'd just update this one with what I had hidden up my sleeve on WSD...the "fins" themselves were ram air ducts!

I REALLY enjoyed brainstorming and building this one and I felt it came out beautifully; however it was really at the limits of what an A10-T motor could do and the weighted "nozzle" at the top was heavier than I would've liked (I don't think I got to test lighter versions). This one is also somewhat modular just like my other builds of this type; however the end "nosecone" with ducts is glued to the inner motor tube/body tube to ensure air doesn't leak out of gaps.



Here's some reveal pics!

One day I'll try to upscale...mini engines are too limiting; however up-scaling means I need to test in a bigger area which is harder to do nowadays. Still, I think it'd be awesome and so worth it! :D
 
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