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This might be my next build...

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Mugs914

"Use enough dynamite there Butch?"
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Inspired by a balsa BT-60 balsa Gemini capsule I found in my stash-o-stuff, the Estes DOM Orbital Transport Lab and the 4" x .75" switch band tube that I got with a LOC av bay set, I started messin' around in OR and came up with this. Not terribly original or anything, but I think it's kinda cool lookin' and should be pretty fun to build.

I guess ring-fins give OR a headache, so the numbers are funny as far as flight sims go, I threw half an ounce of lead in the nose just to shut it up about stability, I don't think it'll need anything like that much in reality.

This is a quick workup of the design (and I'm no OR expert), so the real thing will be different in a few details, but this is the basic idea. OR screenshots (OR file below):

1595714912690.png

1595714994966.png
 

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Funkworks

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I'd be concerned that the 2 solar panel-looking details cause asymmetric drag.
 

BABAR

Builds Rockets for NASA
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Bumping up the length of the ring fin will give you a ton of tailward CP shift. I love ring fins, because since they are so far from the central axis they have much more effect than standard fins relative to surface area.
 

jqavins

Joseph Avins
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As I understand it, the current official release of OR doesn't support ringtails or tube fins. @neil_w uses a beta version which does, and he'd probably be happy to help. (I can't speak for him, of course, but he usually is.)

RockSim does support ringtails, so if OR will let you save as an RS file (.rkt) I'll see what I can do with it. (I know OR can read .rkt files, but I don't know about writing them.)
 

neil_w

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It is true that OR can't do ringtails, not even in the forthcoming version (insert super-sad-face here). If you save as an RKT file, you can let RockSim take a crack... *but* don't expect the ring in the original OR file to transfer properly. Joe, you'd need to delete it if it's there and add a proper ringtail in Rocksim.

Ringtails (or is it tail rings?) are wonderful for stability; I would *think* that design is stable without any more nose weight, but hard to say for sure.

Here's an old POF article from Bruce Levison describing treatment of ringtails: https://www.apogeerockets.com/education/downloads/Newsletter27.pdf. Using this approach, you could do the calculations yourself and put equivalent finnage onto your OR model to get a proper CP. For many of my designs, I keep (at least) two OR files: one for appearance and parts/construction, and one for flight sim. The latter includes whatever modifications I think are necessary to yield a design that includes only components that OR can simulate properly. It's more art than science if the design is complex.
 
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