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BABAR

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I feel rather hypocritical urging @Senior Space Cadet not to launch his dirt dive recovery rocket, even on a deserted soccer field miles from anyone, while saying this looks like a cool experiment and eagerly waiting for the results. I assume you've got a 'chute or streamer in there, but that's not the point. It looks potentially dangerous, to a significantly greater (if not very large) degree than most of the rockets any of us launch.

You're certain that tension in the strings keep them rigid enough to transfer force to the body, but I confess I'm skeptical (not that I'm anywhere near sure they won't). You're not so sure it will work that way after burnout, and I have very little doubt on that part; it won't. (You aptly point out that at that point it's a hazard only to the rocket, assuming a 'chute or streamer deploys.)

Still, because of the substantially larger than normal chance of totally unpredictable behavior immediately upon leaving the launch rod, please don't launch this anywhere near other people.

Do you plan to prop the drive section up on the rod so that the ring is dangling, i.e. the strings start out straight?
My doubts are a bit different. And I am with Drew that likely if this goes unstable, it will STAY unstable. Interestingly I think the most dangerous rockets in terms of instability are those that are temporarily unstable. Scary flight at NSL 2020 where a high power rocket did a near complete loop about 50-100 feet off the pad, fortunately the trajectory on the final segment was at least 45 degrees vertical and perhaps more importantly (and frighteningly likely purely fortuitously) AWAY from the flight line and parking lot. It’s these rockets that start unstable, get a no vertical trajectory, and then get up enough speed to BECOME stable and therefore pick up kinetic energy that are scary. Rockets that become and STAY unstable tend to sky write, they just spin and twist randomly, main risk is that they fall on someone or something and cause injury because of their mass rather than their velocity, or they are fire risk because they come to earth with motors, delays, or ejection charges still active.

I am curious about your concern after burn out, I am thinking the drag of the tail will be greater than the drag on the nose and tube section, so I expect that it won’t become significantly MORE unstable than it may be during active boost, but often the intuitive answer isn‘t correct. And if it DOES become unstable during the delay/coast phase, unless the delay is really long it is unlikely to re-orient node down and pick up enough speed to “go ballistic” before ejection charge fires.

so risks from this rocket are significantly different, if fecal turbine interaction occurs, I expect it will be immediately as it leaves the pad, it will sky write and flop to the ground possibly still under thrust, and be a fire danger (this is one rocket where I would keep an extinguisher handy unless you are launch on playa. The “other” rocket discussed is a “missile”, I don’t care if it spins a bit and has a blunt nose cone, the EXPECTATION is a ballistic return. That takes it out of the “model rocket” category. At that point it is either a weapon or a dangerous experiment.

this pushes the envelope, but at least has some science behind it. Still a FAR pad bird (or better, fired with no spectators in a remote location with a very low fire/brush danger.
 

jqavins

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I probably shouldn't have mentioned the post burnout behavior, since it's not the real concern. Coming down before burnout is a possibility if it never gains stability. Since the rigidity of the strings depends on the speed (because it depends on drag) there is the possibility of being one of those scary temporary instability cases and a landshark, a.k.a. cruise missile.

As I said, it felt hypocritical not to say something. The similarity is that they both, in my mindsim, create a higher than normal probability of dung getting into the air mover. The other is worse, in that it's intended to break both the rules and the ground, yet it too has a very low (non-zero) probability of causing injury given the simple precaution of solitude. And all I'm asking here is that same precaution.

Incidentally, if it had rigidish rods instead of threads I'd have no such concern. I've been mentally designing such a variant for a couple of days now. 3 mm CF rods, and 3D printed connectors (like Tinker Toys) where they meet. In a larger one, with more truss members, there could be more connectors to accommodate members that would otherwise cross.

(Another major difference, Drew, is that you're taking my concern seriously.)
 
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DrewW

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I am curious about your concern after burn out, I am thinking the drag of the tail will be greater than the drag on the nose and tube section, so I expect that it won’t become significantly MORE unstable than it may be during active boost, but often the intuitive answer isn‘t correct. And if it DOES become unstable during the delay/coast phase, unless the delay is really long it is unlikely to re-orient node down and pick up enough speed to “go ballistic” before ejection charge fires.
Under thrust their will be hot high velocity gas filling the space inside the ring, after burnout the inside of the ring will likely transition to a low pressure zone via base drag of the body. My gut feel was that a 5 caliber separation would allow the low pressure zone to collapse and the ring would be operating in an ideal gas flow zone, but I’m just making an educated guess. If I’m wrong the ring is likely to push forward; this was why I added the six fins to the ring, to increase drag. If the ring does push forward the second version of this will have a ring more like an inverted transition section or maybe like the “twin factor” rings.

Honestly just looking to build things that arent following the standard 3/4 FNC model. Nothing wrong with them, I have about a dozen sitting in the build pile, but want to try some “different” things as long as they have a reasonable chance of success and a low enough risk posture to be acceptable without needing a military ordnance range.
 

DrewW

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Incidentally, if it had rigidish rods instead of threads I'd have no such concern. I've been mentally designing such a variant for a couple of days now. 3 mm CF rods, and 3D printed connectors (like tinker tows) where they meet. In a larger one, with more truss members, there could be more connectors to accommodate members that would otherwise cross.
CF is a great choice for rigid rods. I worry about someone else coming along and making them out of balsa or something that doesn’t have the tensile strength to withstand the launch conditions. Most of the construction techniques I’ve seen in the hobby assume compressive loads not tensile loads “wacky wiggler” is a great example of taking advantage of the compressive loads.

I’ll mention I’m trying to not overestimate my abilities; I’ve only been building rockets since May, and using OR since October. So I’m still building a broad intuition across the spectrum of what to expect. I needed an outlet when COVID made other hobbies difficult to enjoy.
 
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Funkworks

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I'm concerned about oscillations or spiralling. Seems to me like oscillations would either increase with time ("catastrophic" path), or remain stable (typical spiral). Not sure the CP would behave as with a rigid rocket.

Unless there is zero wind and you have some special launch rod system to keep everything perfectly symmetrial, I can't imaging this making a straight flight. A spiral at best, but who knows how perfect launch conditions must be to even get that.
 

DrewW

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I'm concerned about oscillations or spiralling. Seems to me like oscillations would either increase with time ("catastrophic" path), or remain stable (typical spiral). Not sure the CP would behave as with a rigid rocket.

Unless there is zero wind and you have some special launch rod system to keep everything perfectly symmetrial, I can't imaging this making a straight flight. A spiral at best, but who knows how perfect launch conditions must be to even get that.
I’ll make sure to take video for posterity sake, and will even try to measure wind speed at launch 🚀 🌪 💥 success or failure, I plan to learn some things here.

Considering I know there is a ~2 degree alignment offset, body longitudinal axis to ring axis, in the ring fin (best I could manage by eye) I anticipate some spiraling as well. But to that point most spin stabilized rockets have a natural precession rate and are not inherently unstable.
 

Daddyisabar

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Dragging things up with the motor pointed straight down. MADNESS! I feel the dark side of the force flowing through this one. Look at the thrust curve on your motor, as long as conditions are good and you have lots of lovely thrust you should be OK, Lord willing. On the down side of the power curve and during the coast you will get to know Flutterina, she is not your friend. By that time you should have enough enertia to keep going up. All the while you must play Johnny Cash Ring of Fire to appease the pagan rocket gods. The next step down the Dark path will be to telescope your ring fins off the pad, relying solely on drag separation for deployment.

IMG_20160612_122452789.jpg
 

David Schwantz

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Could you put a motor in each section???
the one above just must have more thrust and longer burn time than the one below.
 

Daddyisabar

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Heaverly Rider meets up with Flutterina on the coast phase and she distracts him from his primary task of opening the Pearly Gates every time! But the kids and the big kids in the crowd love the flutter before ejection pops.

IMG_20170520_112921672.jpg
 

Daddyisabar

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What is your lauch set up going to be? Taunt or baggy on the strings? Definitely tape the lead cord or clip whip to the rod so it doesn't interfere on launch. Use good clustering techniques and Q2G2s! A 6foot 1/4 inch stainless steel rod? No rod whip on this 3 x18mm cluster.
 
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Daddyisabar

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So is the name going to like Mob Rules, or Flash Mob or Mob Mentality. Maried to the Mob, Mob Boss, Towing the Ring of Fire, or Mobbing for Dollars!
 

Daddyisabar

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A lot of problems solved with minimal loss of power by canting motors and moving them forward.

NO NO. You are wrong Daddy! Motors pointed down at the back of the rocket! THIS IS THE WAY!
 

neil_w

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My mindsim received an update recently and now is more doubtful about this design. Still curious to see you try it, but agree to give it plenty of room.
 

Daddyisabar

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My mindsim received an update recently and now is more doubtful about this design. Still curious to see you try it, but agree to give it plenty of room.
Wow! You must be getting those on air, real time updates and upgrades from mindsim Tesla! I still have to wait for floppy disks and punch cards in the mail!

I always have to review with the RSO and if I brought this one up to the table chances are I would be sobbing back to my car without a pad assignment. Then off to Mustafar I would go to hang out at the separatists launch. My money is that it will fly without grievous bodily harm bit with a good amount of burn and some string repair. Love to bet on those pod races, very dangerous. Those Huts are mobsters, long live the Techno Union!
 

Stemmy

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I’m thinking this will act like a kite tail and add stability with enough velocity. I’m hoping we get to see a short launch video of this one day!
 

Daddyisabar

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I’m thinking this will act like a kite tail and add stability with enough velocity. I’m hoping we get to see a short launch video of this one day!
Streamers or tails do work but they do tend to get burned and ripped. Like a flag in a hurricane. So cool when the atmosphere burns the paint off your high power rocket.
IMG_20141018_135440852.jpg
 

DrewW

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Any progress or other updates?
Sitting on the rack with 6 other virgin rockets from last month unfortunately. I had to bail on my local club launch at the last minute, might get around to launching this weekend or next...but far away from people and things. Thankfully the Arizona desert is large.
 

DrewW

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Could you put a motor in each section???
the one above just must have more thrust and longer burn time than the one below.
just to check, did you mean rocket motors in the body tube and the ring tail when you said each section? If so that would end badly as currently designed. It would totally work if the stringers were rigid.
 

David Schwantz

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Hi Drew, I had first mentioned about having rigid Stringers, and just thought this might be an option. Good luck with however you go. Love to see pics when you are done though. Dave
 

Sooner Boomer

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Looks like this is something along the lines of;
and

If you made the "strings" that hold the tail tube on into "T" shaped stringers, the shape has very little flex.
 

DrewW

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So my RSO was feeling good today and let me get the Mob Missile out on the rod with 3xB6-2 cluster. Set up went pretty smoothly, I had a small stand off for the rod I brought just for this launch and remembered most everything else. Hit go on the launcher and....one of the alligator clips snagged the ring tail on the way up the rod and cause a hang-fire. No damage to people, property, or even pride on that. C'est la vie.

Need to fix the Kevlar lines for the next launch, and will be looking into some long ignitors for my motors to get those alligator clips under the rocket.
 

jqavins

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As an alternative to long igniter leads, you can solder extensions onto onto an igniter. The leads on Estes igniters are plated, I think with nickel. You more or less can't solder to nickel (it takes acit flux and the right solder, which is a PITA) but you can scrape or sand the nickel off, then solder on the extensions. I've done it.
 

DrewW

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As an alternative to long igniter leads, you can solder extensions onto onto an igniter. The leads on Estes igniters are plated, I think with nickel. You more or less can't solder to nickel (it takes acit flux and the right solder, which is a PITA) but you can scrape or sand the nickel off, then solder on the extensions. I've done it.
Lord knows I have enough extra Estes igniters to give it a try. 🤷‍♂️
 
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