Horizontal Spin Recovery - with Magnus Effect?

[Dotini]

Superb!

sorry if I missed the build on this (maybe gimme a thread number if it is here, we are on page TWENTY-ONE!)

I mentally pooh-poohed the retrojet idea purely due to “tunnel vision” on my part. Now of course it seems brilliant.

if I understand it right, delay is targeted for pre-apogee (so rocket is up vertical or near up vertical prior to event) and since evenly distributed (also something I initially misunderstood) post event somewhere between up vertical and horizontal, definitely shouldn’t be able to have any nose down vector at all.

questions.

are fins through the wall?

can this carry an altimeter and if so, where?

can the retrojets be built into a minimum diameter? And in any case how do you get the angled “pipes” or “nozzles” ?

is that a standard or extra light balsa or vacu-form nose cone?

in any case, congrats!

Thanks for your excellent questions!

- There is no thread on this build as I had taken a two month hiatus from this forum.

- The delay must not come too soon nor too late - like on all model rockets. But there is a comfy, broad latitude. The key is the CG, which you forgot to ask me about.

- The fins on the model depicted as well as the 3 fin version are not conventionally "through the wall", but are effectively so. On the six fin version there is a significant layer of epoxy applied to the exterior of the fin can between the fins after they have been tacked and filleted. On the 3 fin version an Apogee BT-50 tube sleeve has been modified to provide the outer "beef" structure.

- This model carries an altimeter in a vented cavity immediately ahead of the ejection nozzles.

- Nozzles can indeed be built into a smaller BT-20 diameter model. The diameter of the nozzles themselves must be large enough so as not to be occluded by proliferous large, solid ejection particles common with our Estes motors. We frequently examine and clean them if necessary.

- The nozzles are drilled on a drill press with an adjusted table. The balsa "plug" is subsequently internally sculpted with Dremel tools, and finally protectively coated internally with wood glue.

- The nose cone is standard commercial balsa offering, albeit a very particular one. This is subject to change. The nose cone is key to fine tuning the CG.

 

[BABAR]

. The key is the CG, which you forgot to ask me about.

Lol,

FINE, what’s the CG, and is it dependent on body tube diameter?

 

[Dotini]

Lol,

FINE, what’s the CG, and is it dependent on body tube diameter?

We discovered the "magic" ratio with the pink and black BT-20 beauty called X-8, featured somewhere in the previous 20 pages of this voluminous thread. This bird never failed to achieve HSR over dozens of flights. Uniquely, we measure the CG from the back of the installed but expended motor. The motor must be installed and expended to make this measurement. Since we sometimes trim the CG with a longer or shorter nose cone, we measure from the back end. The magic number is 28%, plus or minus about 1/2" to allow for the difference between 18mm and 24mm motors and/or altimeter installations, different fin cans, etc. This figure works for BT-20 and BT-50 sizes, and should work for others.

 

[Rktman]

The development that makes success almost a certainty is the "retro-jet" ejection plan combined with a very particular CG and correct motor delay.

View attachment 593106

Four 5/32" ejection ports angled as seen above are formed in a 1.2" balsa plug in the section immediately above the fin can. A six fin can has been mainly employed on the premise that the model will land on two fins and spread out the landing load. However, the model operates even better on 3 fins.

I personally think this research and its results are groundbreaking. There's been no new recovery method developed in decades (save maybe the horizontal flop recovery documented by someone else in another thread) but I feel the amount of research that went into this project is worth documenting and sharing with the rest of the sport.

Is there any way I can again convince you to summarize your experiments and results into a NAR research paper or at least a Sport Rocketry article? I'll be glad to help you put together an SR article. You will of course receive credit as its author and researcher.

 

[BABAR]

I personally think this research and its results are groundbreaking. There's been no new recovery method developed in decades (save maybe the horizontal flop recovery documented by someone else in another thread) but I feel the amount of research that went into this project is worth documenting and sharing with the rest of the sport.

Is there any way I can again convince you to summarize your experiments and results into a NAR research paper or at least a Sport Rocketry article? I'll be glad to help you put together an SR article. You will of course receive credit as its author and researcher.

Concur.

Also think this would make a great new NAR duration competition category.

 

[Dotini]

I personally think this research and its results are groundbreaking. There's been no new recovery method developed in decades (save maybe the horizontal flop recovery documented by someone else in another thread) but I feel the amount of research that went into this project is worth documenting and sharing with the rest of the sport.

Is there any way I can again convince you to summarize your experiments and results into a NAR research paper or at least a Sport Rocketry article? I'll be glad to help you put together an SR article. You will of course receive credit as its author and researcher.

I'm very grateful, appreciative and humbled by your expression of approval for the research that I and my part-time collaborator are doing. And that gratitude also applies to all the other rocketeers who follow and like this thread. But it is a highly unexpected, even shocking honor to be asked to submit a paper or article to such institutions as NAR or Sport Rocketry. For this I don't feel particularly worthy or qualified. I feel like we are the only persons on Earth building and launching HSR models - isolated! But I will talk it over with my collaborator, a retired Boeing engineer, and listen to what he says. With your guidance, maybe we can work something out?

 

[BABAR]

I'm very grateful, appreciative and humbled by your expression of approval for the research that I and my part-time collaborator are doing. And that gratitude also applies to all the other rocketeers who follow and like this thread. But it is a highly unexpected, even shocking honor to be asked to submit a paper or article to such institutions as NAR or Sport Rocketry. For this I don't feel particularly worthy or qualified. I feel like we are the only persons on Earth building and launching HSR models - isolated! But I will talk it over with my collaborator, a retired Boeing engineer, and listen to what he says. With your guidance, maybe we can work something out?

Let's see, what's needed to submit a paper or article:

1. Original Idea. Check.
2. Good Idea. Check
3. Ability to write complete and coherent sentences. Check
4. Ability to build rockets. Check.

I don't see any requirement for any degrees or other work experience, although putting a Boeing Engineer on the byline certainly doesn't hurt.

I think you have more than enough in the pot to make this a slam dunk. I am guessing you are probably up to over 1000 flights counting all your versions. Just out of curiosity, have you even kept count of how many versions of this you have flown?

 

[Dotini]

Let's see, what's needed to submit a paper or article:

1. Original Idea. Check.
2. Good Idea. Check
3. Ability to write complete and coherent sentences. Check
4. Ability to build rockets. Check.

I don't see any requirement for any degrees or other work experience, although putting a Boeing Engineer on the byline certainly doesn't hurt.

I think you have more than enough in the pot to make this a slam dunk. I am guessing you are probably up to over 1000 flights counting all your versions. Just out of curiosity, have you even kept count of how many versions of this you have flown?

I've communicated with Blair, and he likes the ideas, including the duration competition. We've kept all the models, but smushed tubes we throw away. We have written records and video of most all flights. Since we can only post very short videos on this forum, we are looking into getting a YouTube account.

 

[Rktman]

I've communicated with Blair, and he likes the ideas, including the duration competition. We've kept all the models, but smushed tubes we throw away. We have written records and video of most all flights. Since we can only post very short videos on this forum, we are looking into getting a YouTube account.

EDIT: Decided this sounded too unnecessarily and absurdly much like a resume so I deleted everything other than too say:

Before retiring I was a graphic designer with a lot of print experience.

If you and Blair could use any assistance along those lines to put together a NAR research report or Sport Rocketry article I'd be happy to volunteer my time.

 

[thecapotc]

I've just spent three days reading all 22 pages of this thread ... and all I can say is WOW.

The experimentation, craftsmanship, and discoveries are simply mind blowing. I used to be an engineer until I cut half my brain out and became a manager, but I don't recall ever learning about the Magnus Effect (I was a mechanics/FEA guy not a fluids guy) and I certainly haven't devoted the time to the science of model rocketry that has been on display in this thread.

Just going through this inspired two builds to add to my list, two new techniques to try, the push to really get into OR, and hopefully a super handy and free tool for making builds less aggravating.

My hats are off to you good sirs, and I sincerely thank you for the work you put in and the inspiration you have given me.

 

[BABAR]

I've just spent three days reading all 22 pages of this thread ... and all I can say is WOW.

The experimentation, craftsmanship, and discoveries are simply mind blowing. I used to be an engineer until I cut half my brain out and became a manager, but I don't recall ever learning about the Magnus Effect (I was a mechanics/FEA guy not a fluids guy) and I certainly haven't devoted the time to the science of model rocketry that has been on display in this thread.

Just going through this inspired two builds to add to my list, two new techniques to try, the push to really get into OR, and hopefully a super handy and free tool for making builds less aggravating.

My hats are off to you good sirs, and I sincerely thank you for the work you put in and the inspiration you have given me.

If you can come up with a way to get those curved plastic fins accurately modeled in open rocket, that would be very helpful!

 

[BABAR]

Pics to follow, but HSR has now been successfully flown at NARAM Sport Range.

2 separate rockets, using the tubing you gave me. Painted.

Both BT-5, perfectly stable, immediate transition (forward three puff ports), fully horizontal recovery, no damage.

 

[Rktman]

Pics to follow, but HSR has now been successfully flown at NARAM Sport Range.

2 separate rockets, using the tubing you gave me. Painted.

Both BT-5, perfectly stable, immediate transition (forward three puff ports), fully horizontal recovery, no damage.

Whoo Hoo! Hope you're having a ton of fun. How was the crowd/announcer reaction? Looking forward to those pics!

 

[BABAR]

Whoo Hoo! Hope you're having a ton of fun. How was the crowd/announcer reaction? Looking forward to those pics!

Awesome time.

Very small crowd. I doubt there were more than 10 people in the Sport flight area at any one time. Competition area seemed far more crowded.

First Blue Horizon

Original fin can flown is alongside, these are @Dotini plastic . The one attached is one I am gonna try tomorrow.

Close ups vent holes and fins cans

 

[BABAR]

Next is Back Spin

I wanted to use @Dotini idea of a retrograde puff, but rocket was mostly built. So I trimmed off the tip of nose cone .

It was BT-5. And I waaay overdid the fin can. So only practical motor was A10-3T. Couldn’t do much about delay. I think this is viable for larger tube sizes. I am sure it is less aerodynamic than standard nose cone, but I think easier to implement than other solutions (and drag May not be that different from others. ). I also like blunting the cone, in case it goes ballistic, I think it is a bit safer.

 

[BABAR]

In our experience, the retro puff technique at least doubles the reliability of achieving HSR with a side puffer, but potentially with the loss of a bit of hang time. But isn't the act of a backslider blowing off its nosecone tantamount to a retro puff? The delay time is a critical element of success, as is the CG.

Thank you for chiming in. since you are the acknowledged master of HSR, is “retro-puff” the correct term? I like it. I am guessing the loss of hang time is simply due to increased drag on boost?

also, IMO a ”pure” backslider does not blow it’s nose cone.

people can and should build rockets however they want. However, one of the characteristics which makes now three forms of recovery relatively unique is transition from boost to recovery WITHOUT any physical change in structural shape (the experienced rocketeers will say this is also true for featherweight and saucer rockets, but those both return ballistically so I’d argue they never really “transition.”). The three forms now being played with more extensively are

Horizontal Spin Recovery (HSR)

Back Slide Recovery (BSR)

and Belly Flop Recovery (BFR) (which to the best of my knowledge is actually invented although not yet patented by @sr205347d )

of these, HSR and BSR require some sort of perturbation of the angle of attach initiated by the ejection charge to alter angle of attack. Per @sr205347d , his don’t need it. I don’t claim to understand that yet, but I haven’t tried it WITHOUT the side port puff.

I know the first two and likely BFR as well CAN be done by blowing the nose cone (This was my first successful method of HSR in 2018
https://www.rocketryforum.com/threads/bail-out-bill-and-the-horizontal-spin-recovery-rocket.147210/
and I have also used it successfully for booster recovery.)

I kind of think of this as ”cheating”, but as I said, people can do what they want.

in discussion with @BEC , he tells me anyone CAN submit a NAR contest rules change, and I plan on submitting one for two new categories for competition, HSR and BSR (@sr205347d , if you want to go for BFR, go for it. I leave that in your court.)

as a minimum IMO rules would state

the rocket must ascend and descend in a single piece with (aside from propellant burn) no shape or other change in configuration of the rocket.

sorry Ron for derailing the thread.

edit, I am going to ask the Moderators to move this post to the
https://www.rocketryforum.com/threads/horizontal-spin-recovery-with-magnus-effect.165378/thread

 

[BABAR]

Updates on my experience at NARAM.

First, the The Cotton City Rocketry Club hosts were superb, can't thank them enough.

As to my HSR rockets, the ones where I used @Dotini 's plastic fins WORKED. they were all BT-5 models, and VERY heavy for the A10-3T motor. They did obtain suprising altitude, I don't have an altimeter but easily over 100 feet. Descents were all horizontal, although no significant "hang time", they came down quickly but with no damage.

My designs with the cardboard tube fins were too tail heavy, I think I overbuilt the fins and the cans were so heavy that they all came in tail first, at best a 45 degree angle. I think I can build lighter and still have durability.

Since I don't think anyone else has laid out any groundwork, I propose that you @Dotini should at this time be approving authority for the lingo. I will make proposals but I think it is your call. I do think lingo needs to be standardized, especially if this is to become a competition category for NARAM.

I propose

Abbreviations for Horizontal Spin Recovery (HSR) and Back Spin Recovery (BSR). Also, @sr205347d consenting, for Belly Flop Recovery (BFR.)

"side-puff" be the official term for any Lateral port puff that throws off angle of attack. the ports would be "side-puff ports"

(Note from the Alway patent on Back Slider the following quote: " The side thrust may be generated by the ejection charge being vented through a hole or port in the body tube near the nose cone.")

"retro-puff" be official term for any forward directed puff which is meant to slow, stop, or reverse the forward rocket trajectory, and such ports would be "retro-puff ports."

I also propose that "true" HSR recovery be defined as that which has no structural change in rocket configuration between launch and recovery and the model recovers as a single piece. Aside from burned propellant and ejected gas and potential clay cap debris, nothing is ejected from the rocket. Means no nose blow, no chute, no streamer. Other than singed nozzle, the rocket should be picked up off the bround looking exactly like it looked on the pad, 'cept for maybe some grass stains, dust, or mud.

Okay, back to my experience.

The cut off nose hole for the "retro-puff port" worked fine. It has some pluses and minuses compared to to yours version.

Pluses.
It's just darn easy for PLASTIC cones. For a Vacu-Formed cone you can do it with a hobby knife, for a plastic cone a Dremel or equivalent would be easier.

You can size it however you like, if needed easy to make bigger, but can't make it smaller once you made it bigger.

It takes weight off the forward end of the rocket, in this case since you are mainly using the LENGTH of the rocket to shift the CG, the weight loss doesn't hurt although likely negligible.

Negatives

Likely a real DRAG, although I don't know how to calculate it. Not sure however how the drag from this compares to that from your "retro-puff ports"

If used with a VacuForm nose cone, the force of ejection might rupture the cone, since you won't/can't have a protecting bulkhead. I don't think this will be a problem for non-VacuForm regular plastic cones, but the weight of these cones might be a problem. My plastic cone above I got about a decade ago at an Apogee Garage sale, got 50 or 100 for about $10. I still have a pretty good stash. I didn't have my dremel at NARAM, so that was a rough tough cut with a hobby knife (fortunately bloodless, but close!)

Okay, some theory here.

Sounds like with SIDE PORTS you are not having 100% success with HSR (I'm not either, but I do better than with BSR.) If I think of a roulette wheel with equal numbers of red and black slots and ONE green slot, and I am getting on BOTH red and black, for HSR the wheel has 10 slots, for BSR 5 slots. Meaning the house wins and the rocket comes in ballistic 10% with HSR and 20% with BSR.

The problem is the transient rocket orientation after whichever puff you use (and possibly the rocket's velocity vector.)

If I understand it right, at least for HSR and BSR (not sure about Belly Flop Recovery [BSR], @sr205347d gets it to work with NO puff but I don't get how), the TRANSITION depends on a significant deviation from near zero angle of attack (the world where Barrowman Equations work), to well OFF zero angle of attack (no, I don't have a number) where Center of Lateral Area (CLA, or cardboard cutout) works.

the big "No-No" for HSR and BSR is a Transient Post Ejection Orientation which is at or near NOSE DOWN when vertical velocity falls to zero (or worse, after the stable rocket arcs over and begins descending if ejection even occurs post apogee.) At this point, Gravity and Drag are the main forces on the rocket (I think Wind can be disregarded at this time.) If the rocket is NOSE DOWN, gravity pulls the rocket down nose first, the fins' drag keeps it tail up, and the rocket returns to STABLE linear (and in this case unfortunately BALLISTIC re-entry.) Note that for MOST rockets with failed ejection of the nose cone, the rocket is stable by BOTH Barrowman AND CLA calcs, so they will go "ballistic" regardless of orientation.

HSR and BSR rely on the rocket being far enough off "Nose Down" attitude that something ELSE happens.

For HSR, I think even with minimal "off nose down" attitude, the falling rocket causes the angled or curled fins with a little sideways force, enough to start the rocket rotating. I THEEENK the principle of conservation of angular momentum is what forces the FALLING rocket to turn toward the horizontal position (perpendicular to the vector of fall, so parallel to the horizon). The more it turns horizontal, the more fin surface the rocket "offers" to the airstream and the faster the rocket rotates. It's a positive vicious cycle, maximized when rocket is perfectly horizontal. Because of this, I think HSR tolerates more "near nose down vertical" position than BSR.


So with "side port-puff", the problem is that the post-puff orientation is completely random. So once in a while the roulette wheel lands on green, and rocket comes in ballistic.

Now, with your innovation of retro-puff, maybe it's a new ball game. Assuming at least a slightly short delay (yeah, that's gonna cost a bit of altitude), the puff occurs with the rocket presumably at or near vertical (there may be some weathercocking.) Next question is "how strong is the puff?" If it is enough to either STOP or REVERSE the upward trajectory, seems like the probability of the rocket starting to "fall" in a "nose-down vertical" (i.e., BAD) orientation is near zero, I think certainly far less than the completely random side port puff.

So am I correct that your success rate of transition to HSR has greatly improved with retro-puff? And if not 100%, do you have a good explanation for the failures?

Me thinks the retro-puff technique pre-apogee would be a GREAT technique for Back Sliders, as pausing mid-air at or nearly at perfectly nose UP should be the PERFECT orientation for transition to Back Slide (? @Rktman what do you think?)

Okay, got to get to work on submitting the rules change to make Horizontal Spin Recovery a competition event. I'm leaning toward Duration rather than altitude for a couple of reasons.

1. Adding altimeter weight certainly doesn't IMPROVE reliability of transition.

2. The real challenge/cool part is the transition and hang time, rather than how high you can get it to go (and altitude is gonna help your duration anyway).

I will run my submission by you and @BEC and @Rktman before I submit it.

 

[Dotini]

Updates on my experience at NARAM.

First, the The Cotton City Rocketry Club hosts were superb, can't thank them enough.

As to my HSR rockets, the ones where I used @Dotini 's plastic fins WORKED. they were all BT-5 models, and VERY heavy for the A10-3T motor. They did obtain suprising altitude, I don't have an altimeter but easily over 100 feet. Descents were all horizontal, although no significant "hang time", they came down quickly but with no damage.

My designs with the cardboard tube fins were too tail heavy, I think I overbuilt the fins and the cans were so heavy that they all came in tail first, at best a 45 degree angle. I think I can build lighter and still have durability.

Since I don't think anyone else has laid out any groundwork, I propose that you @Dotini should at this time be approving authority for the lingo. I will make proposals but I think it is your call. I do think lingo needs to be standardized, especially if this is to become a competition category for NARAM.

I propose

Abbreviations for Horizontal Spin Recovery (HSR) and Back Spin Recovery (BSR). Also, @sr205347d consenting, for Belly Flop Recovery (BFR.)

"side-puff" be the official term for any Lateral port puff that throws off angle of attack. the ports would be "side-puff ports"

(Note from the Alway patent on Back Slider the following quote: " The side thrust may be generated by the ejection charge being vented through a hole or port in the body tube near the nose cone.")

"retro-puff" be official term for any forward directed puff which is meant to slow, stop, or reverse the forward rocket trajectory, and such ports would be "retro-puff ports."

I also propose that "true" HSR recovery be defined as that which has no structural change in rocket configuration between launch and recovery and the model recovers as a single piece. Aside from burned propellant and ejected gas and potential clay cap debris, nothing is ejected from the rocket. Means no nose blow, no chute, no streamer. Other than singed nozzle, the rocket should be picked up off the bround looking exactly like it looked on the pad, 'cept for maybe some grass stains, dust, or mud.

Okay, back to my experience.

The cut off nose hole for the "retro-puff port" worked fine. It has some pluses and minuses compared to to yours version.

Pluses.
It's just darn easy for PLASTIC cones. For a Vacu-Formed cone you can do it with a hobby knife, for a plastic cone a Dremel or equivalent would be easier.

You can size it however you like, if needed easy to make bigger, but can't make it smaller once you made it bigger.

It takes weight off the forward end of the rocket, in this case since you are mainly using the LENGTH of the rocket to shift the CG, the weight loss doesn't hurt although likely negligible.

Negatives

Likely a real DRAG, although I don't know how to calculate it. Not sure however how the drag from this compares to that from your "retro-puff ports"

If used with a VacuForm nose cone, the force of ejection might rupture the cone, since you won't/can't have a protecting bulkhead. I don't think this will be a problem for non-VacuForm regular plastic cones, but the weight of these cones might be a problem. My plastic cone above I got about a decade ago at an Apogee Garage sale, got 50 or 100 for about $10. I still have a pretty good stash. I didn't have my dremel at NARAM, so that was a rough tough cut with a hobby knife (fortunately bloodless, but close!)

Okay, some theory here.

Sounds like with SIDE PORTS you are not having 100% success with HSR (I'm not either, but I do better than with BSR.) If I think of a roulette wheel with equal numbers of red and black slots and ONE green slot, and I am getting on BOTH red and black, for HSR the wheel has 10 slots, for BSR 5 slots. Meaning the house wins and the rocket comes in ballistic 10% with HSR and 20% with BSR.

The problem is the transient rocket orientation after whichever puff you use (and possibly the rocket's velocity vector.)

If I understand it right, at least for HSR and BSR (not sure about Belly Flop Recovery [BSR], @sr205347d gets it to work with NO puff but I don't get how), the TRANSITION depends on a significant deviation from near zero angle of attack (the world where Barrowman Equations work), to well OFF zero angle of attack (no, I don't have a number) where Center of Lateral Area (CLA, or cardboard cutout) works.

the big "No-No" for HSR and BSR is a Transient Post Ejection Orientation which is at or near NOSE DOWN when vertical velocity falls to zero (or worse, after the stable rocket arcs over and begins descending if ejection even occurs post apogee.) At this point, Gravity and Drag are the main forces on the rocket (I think Wind can be disregarded at this time.) If the rocket is NOSE DOWN, gravity pulls the rocket down nose first, the fins' drag keeps it tail up, and the rocket returns to STABLE linear (and in this case unfortunately BALLISTIC re-entry.) Note that for MOST rockets with failed ejection of the nose cone, the rocket is stable by BOTH Barrowman AND CLA calcs, so they will go "ballistic" regardless of orientation.

HSR and BSR rely on the rocket being far enough off "Nose Down" attitude that something ELSE happens.

For HSR, I think even with minimal "off nose down" attitude, the falling rocket causes the angled or curled fins with a little sideways force, enough to start the rocket rotating. I THEEENK the principle of conservation of angular momentum is what forces the FALLING rocket to turn toward the horizontal position (perpendicular to the vector of fall, so parallel to the horizon). The more it turns horizontal, the more fin surface the rocket "offers" to the airstream and the faster the rocket rotates. It's a positive vicious cycle, maximized when rocket is perfectly horizontal. Because of this, I think HSR tolerates more "near nose down vertical" position than BSR.


So with "side port-puff", the problem is that the post-puff orientation is completely random. So once in a while the roulette wheel lands on green, and rocket comes in ballistic.

Now, with your innovation of retro-puff, maybe it's a new ball game. Assuming at least a slightly short delay (yeah, that's gonna cost a bit of altitude), the puff occurs with the rocket presumably at or near vertical (there may be some weathercocking.) Next question is "how strong is the puff?" If it is enough to either STOP or REVERSE the upward trajectory, seems like the probability of the rocket starting to "fall" in a "nose-down vertical" (i.e., BAD) orientation is near zero, I think certainly far less than the completely random side port puff.

So am I correct that your success rate of transition to HSR has greatly improved with retro-puff? And if not 100%, do you have a good explanation for the failures?

Me thinks the retro-puff technique pre-apogee would be a GREAT technique for Back Sliders, as pausing mid-air at or nearly at perfectly nose UP should be the PERFECT orientation for transition to Back Slide (? @Rktman what do you think?)

Okay, got to get to work on submitting the rules change to make Horizontal Spin Recovery a competition event. I'm leaning toward Duration rather than altitude for a couple of reasons.

1. Adding altimeter weight certainly doesn't IMPROVE reliability of transition.

2. The real challenge/cool part is the transition and hang time, rather than how high you can get it to go (and altitude is gonna help your duration anyway).

I will run my submission by you and @BEC and @Rktman before I submit it.

Approved!

My one and only failure with the new retro-puff came when we tried a C11-3 when we already knew C11-5 was the correct delay. Sure enough, the rocket was still going at high speed and the premature puff was insufficient to make it stop and slide back tail first. It was on a slightly sloping trajectory, and when it finally hit apogee, it carried on and gracefully swan dived into the ground, crumpling only the foremost tube. We recommend a 72/28 location (plus or minus ~1/2") for the CG for both side port and retro-puff port configurations. The CG must be measured with an expended motor. Rate of descent as well as sheer hang time is a good criterion for performance. A BT-20 model on B4 might not go as high as a BT-50 with C11 power, but might have a better rate of descent. We currently like to build with BT-50 because of better visibility and data collection. In this model, we put the Alt2 at the CG, just ahead of the retro-puff ports.

Below, our first attempts at retro-puffing:


New and different HSR models are on the way.

 

[Rktman]

Me thinks the retro-puff technique pre-apogee would be a GREAT technique for Back Sliders, as pausing mid-air at or nearly at perfectly nose UP should be the PERFECT orientation for transition to Back Slide (? @Rktman what do you think?)

Agreed. Tests seem to verify it would be far more effective.

 

[BABAR]

Approved!

My one and only failure with the new retro-puff came when we tried a C11-3 when we already knew C11-5 was the correct delay. Sure enough, the rocket was still going at high speed and the premature puff was insufficient to make it stop and slide back tail first. It was on a slightly sloping trajectory, and when it finally hit apogee, it carried on and gracefully swan dived into the ground, crumpling only the foremost tube. We recommend a 72/28 location (plus or minus ~1/2") for the CG for both side port and retro-puff port configurations. The CG must be measured with an expended motor. Rate of descent as well as sheer hang time is a good criterion for performance. A BT-20 model on B4 might not go as high as a BT-50 with C11 power, but might have a better rate of descent. We currently like to build with BT-50 because of better visibility and data collection. In this model, we put the Alt2 at the CG, just ahead of the retro-puff ports.

Below, our first attempts at retro-puffing:

View attachment 597661
New and different HSR models are on the way.

Hadn’t thought about TOO EARLY an ejection/puff port event, where the ”puff” is insufficient to adequately slow, stop, or reverse the rocket.

by the way, there another term that I struggle with coming up with a good word, “ejection.” This isn’t restricted to just our club of initials (HSR, BSR, BFR), also true for helicopter and likely some other bird, where there is no physical ejection (nose blow, chute, streamer, or even tumble with posterior ly displaced motor like the classic Scout.). Do we stay with “ejection” to describe event? Seems misleading/inaccurate. I am open to other terms, thus far best I can come up with is ”Ejection Charge Activation” which is kind of awkward, but supports this from the Estes 2015 catalog which is clipped from this site

http://rocketn00b.blogspot.com/2015/01/rocket-motor-basics-and-not-so-basics.html
anyway, open for ideas, maybe some think I am making a big deal out of nothing.


@Dotini , what do you think of the nose cone tip cut-off hole? Not sure it adapts well to your models for at least three reasons.

1. Need hollow nose cone (drilling out a balsa nose would be do-able by wood masters like @lakeroadster , but challenging for the rest of us mortals.). So need plastic.

2. You like transitions (I believe you said they spiral better so are less likely to depart the field). These would need to be hollowed.

3. Makes altimeter placement challenging.

4. You like BT-50s for good reasons listed above. I theeeeeeenk that a 24 mm motor ejection charge would adequately pressurize that volume to get enough force out the nose hole, but not sure. Putting in a stuffer chimney to reduce the volume was my first thought, but that adds a good bit of weight exactly where you don’t want it.

questions:

have you tried SHORTER rockets (maybe with tail weights to achieve your magic 72/28 ratio? I am thinking sport rockets, not a lot of hang time but would have to come in slow enough for both personnel safety and undamaged rockets.

how is 3 fins working out? I am pretty sure that six plastic fins on my BT-5 birds was overkill. The fins obviously have two purposes, first is boost stability, second is induction of horizontal spin. A third EFFECT, which may or may not be helpful, is they add tail weight, so they may contribute to your 72/28 ratio.

Any experience with shorter span, longer cord fins? I was thinking these would be more durable. They may also need a smaller (tighter) radius of curvature.

 

[BABAR]

Okaaaaay, here's my proposed submission to National Association of Rocketry to make this a competition category. Feedback welcome. @Dotini , this is basically your ballpark, so if you want to quash it that's okay with me. I have to get this in by September 1, 2023 to get it considered for the next cycle. I do think DURATION is a better category than Altitude. It simplifies things as altimeters are not needed, and I think the real challenge is achieving long hang time.

Basically I just used the Parachute Duration rules as a template, changed the numbers, and changed material to cover Horizontal Spin Recovery.

I am posting this in both the Scratch Section and the Contest Section.

Brief Summary of the Proposed Change:
New Competition Category: Horizontal Spin Recovery Duration

State Logic and Intent of Change:
Something relatively new and fun to interest current members and possibly entice new members.

Effect, if any, on current competition and NAR records:
None.

Exact wording for the rule revision as it should appear (include section#):

41 (next unused number under Duration) Horizontal Spin Recovery Duration

41.2 Scope
Horizontal Spin Recovery (HSR) comprises seven events open to single-stage entries using rockets with no moving parts. The rocket uses a fin configuration that functions under Barrowman equations for boost stability, uses the ejection charge vented through one or more ports to redirect the rocket from stable boost near zero angle of attack, to significantly off-zero angle of attack. Once well off zero angle of attack, the applicable stability equation of Barrowman doesn't apply and Center of Lateral Area (aka Cardboard Cut-Out) rules apply. Falling off vertical axis induces rotation of the rocket around its long axis as the rocket falls. The induced spin causes the rocket to orient perpencular to the fall vector (parallel to the horizon, i.e., Horizontal, hence the name.) This is a positive feedback mechanism, as the rocket becomes gradually more horizontal, the spin effect is amplified and the rocket becomes even more horizontal. Eventually the rocket achieves a perfect horizontal position. This causes the rocket to fall in the orientation of maximum drag.
The purpose of this competition is to achieve the longest flight duration time.

41.2 Qualification
With the exception of the burned motor contents and blown clay cap, the rocket must remain in one piece with no structural change of any kind. This includes no device or machination to change the center of gravity aside from the motor contents above. The rocket must be returned for inspection in one piece with no damage and capable of repeating a flight with only replacement of the motor.

For safety purposes the rocket must have a blunt tip, foam, or vacu-form nose cone. (Note: This is my own opinion. Not sure of the failure rate with lawn darts of other forms of competition but I am guessing it isn't rare. In this case, I think we can anticipate some lawn darts. I don't think anybody is likely to get hurt by a blunt tip, foam, or vacu-form nose cone flying on C and under motors.) @BEC , would it be a better sell to leave this out?

41.3 Classes
This event is divided into classes based on the permissible total impulse of the motor(s). The following classes of
Horizontal Spin Recovery Duration are established:
Motor
1/8A Class Multi-Round Maximum NRC Maximum 40 sec
1/4A Class Multi-Round Maximum 60 sec NRC Maximum 180 sec
1/2A Class Multi-Round Maximum 120 sec NRC Maximum 360 sec
A Class Multi-Round Maximum 180 sec NRC Maximum 540 sec
FAI A 300 sec
B 240 sec
C 300 sec

 

[Dotini]

@Dotini , what do you think of the nose cone tip cut-off hole? Not sure it adapts well to your models for at least three reasons.

1. Need hollow nose cone (drilling out a balsa nose would be do-able by wood masters like @lakeroadster , but challenging for the rest of us mortals.). So need plastic.

2. You like transitions (I believe you said they spiral better so are less likely to depart the field). These would need to be hollowed.

3. Makes altimeter placement challenging.

4. You like BT-50s for good reasons listed above. I theeeeeeenk that a 24 mm motor ejection charge would adequately pressurize that volume to get enough force out the nose hole, but not sure. Putting in a stuffer chimney to reduce the volume was my first thought, but that adds a good bit of weight exactly where you don’t want it.

questions:

have you tried SHORTER rockets (maybe with tail weights to achieve your magic 72/28 ratio? I am thinking sport rockets, not a lot of hang time but would have to come in slow enough for both personnel safety and undamaged rockets.

how is 3 fins working out? I am pretty sure that six plastic fins on my BT-5 birds was overkill. The fins obviously have two purposes, first is boost stability, second is induction of horizontal spin. A third EFFECT, which may or may not be helpful, is they add tail weight, so they may contribute to your 72/28 ratio.

Any experience with shorter span, longer cord fins? I was thinking these would be more durable. They may also need a smaller (tighter) radius of curvature.

- We think enough of the nose cone tip discharge hole to try it for ourselves.
- Transitions are being investigated with respect to spiraling, but may not be the real answer. Could be a kink in middle works better.
- After trying 40:1 for a time, we are back at 50:1 for the most reliability in achieving HSR.
- We are now vacillating between 3 and 4 fins. Having six doesn't help spin rate or landing reliability to be worth the trouble.
- Check out the X-8 somewhere above in this thread. We have several dozen flights with no failure, and it spins faster and spirals better than anything else so far. The fins are cut from the same 3" diameter tube I gave you.

Note: I had a pipe break in my home which flooded several rooms, including my basement work shop. I'll be out of commission in terms of rocketry until it's cleaned up and repaired.

 

[BABAR]

Note: I had a pipe break in my home which flooded several rooms, including my basement work shop. I'll be out of commission in terms of rocketry until it's cleaned up and repaired.

Bummer.

I'll keep playing with the tubing you gave me. I may try going a bit longer in the chord and shorter in the hemispan. I do think plastic is the answer, although I also keep playing with cardboard.

 

[Cape Byron]

I have to be honest, my admiration for you guys is off the scale.

 

[lakeroadster]

Note: I had a pipe break in my home which flooded several rooms, including my basement work shop. I'll be out of commission in terms of rocketry until it's cleaned up and repaired.

I feel your pain. We had a similar issue, broken supply line on toilet, caused $50,000 in materials and another $100,000 in labor. Took us 9 months to repair it all. We did most of all the labor ourselves, and insurance kicked in the $50,000.

 

[BABAR]

I feel your pain. We had a similar issue, broken supply line on toilet, caused $50,000 in materials and another $100,000 in labor. Took us 9 months to repair it all.

Would have been cheaper to replace it with a toilet from NASA.maybe.

 

[BABAR]

Updates on my experience at NARAM.

First, the The Cotton City Rocketry Club hosts were superb, can't thank them enough.

As to my HSR rockets, the ones where I used @Dotini 's plastic fins WORKED. they were all BT-5 models, and VERY heavy for the A10-3T motor. They did obtain suprising altitude, I don't have an altimeter but easily over 100 feet. Descents were all horizontal, although no significant "hang time", they came down quickly but with no damage.

My designs with the cardboard tube fins were too tail heavy, I think I overbuilt the fins and the cans were so heavy that they all came in tail first, at best a 45 degree angle. I think I can build lighter and still have durability.

Since I don't think anyone else has laid out any groundwork, I propose that you @Dotini should at this time be approving authority for the lingo. I will make proposals but I think it is your call. I do think lingo needs to be standardized, especially if this is to become a competition category for NARAM.

I propose

Abbreviations for Horizontal Spin Recovery (HSR) and Back Spin Recovery (BSR). Also, @sr205347d consenting, for Belly Flop Recovery (BFR.)

"side-puff" be the official term for any Lateral port puff that throws off angle of attack. the ports would be "side-puff ports"

(Note from the Alway patent on Back Slider the following quote: " The side thrust may be generated by the ejection charge being vented through a hole or port in the body tube near the nose cone.")

"retro-puff" be official term for any forward directed puff which is meant to slow, stop, or reverse the forward rocket trajectory, and such ports would be "retro-puff ports."

I also propose that "true" HSR recovery be defined as that which has no structural change in rocket configuration between launch and recovery and the model recovers as a single piece. Aside from burned propellant and ejected gas and potential clay cap debris, nothing is ejected from the rocket. Means no nose blow, no chute, no streamer. Other than singed nozzle, the rocket should be picked up off the bround looking exactly like it looked on the pad, 'cept for maybe some grass stains, dust, or mud.

Okay, back to my experience.

The cut off nose hole for the "retro-puff port" worked fine. It has some pluses and minuses compared to to yours version.

Pluses.
It's just darn easy for PLASTIC cones. For a Vacu-Formed cone you can do it with a hobby knife, for a plastic cone a Dremel or equivalent would be easier.

You can size it however you like, if needed easy to make bigger, but can't make it smaller once you made it bigger.

It takes weight off the forward end of the rocket, in this case since you are mainly using the LENGTH of the rocket to shift the CG, the weight loss doesn't hurt although likely negligible.

Negatives

Likely a real DRAG, although I don't know how to calculate it. Not sure however how the drag from this compares to that from your "retro-puff ports"

If used with a VacuForm nose cone, the force of ejection might rupture the cone, since you won't/can't have a protecting bulkhead. I don't think this will be a problem for non-VacuForm regular plastic cones, but the weight of these cones might be a problem. My plastic cone above I got about a decade ago at an Apogee Garage sale, got 50 or 100 for about $10. I still have a pretty good stash. I didn't have my dremel at NARAM, so that was a rough tough cut with a hobby knife (fortunately bloodless, but close!)

Okay, some theory here.

Sounds like with SIDE PORTS you are not having 100% success with HSR (I'm not either, but I do better than with BSR.) If I think of a roulette wheel with equal numbers of red and black slots and ONE green slot, and I am getting on BOTH red and black, for HSR the wheel has 10 slots, for BSR 5 slots. Meaning the house wins and the rocket comes in ballistic 10% with HSR and 20% with BSR.

The problem is the transient rocket orientation after whichever puff you use (and possibly the rocket's velocity vector.)

If I understand it right, at least for HSR and BSR (not sure about Belly Flop Recovery [BSR], @sr205347d gets it to work with NO puff but I don't get how), the TRANSITION depends on a significant deviation from near zero angle of attack (the world where Barrowman Equations work), to well OFF zero angle of attack (no, I don't have a number) where Center of Lateral Area (CLA, or cardboard cutout) works.

the big "No-No" for HSR and BSR is a Transient Post Ejection Orientation which is at or near NOSE DOWN when vertical velocity falls to zero (or worse, after the stable rocket arcs over and begins descending if ejection even occurs post apogee.) At this point, Gravity and Drag are the main forces on the rocket (I think Wind can be disregarded at this time.) If the rocket is NOSE DOWN, gravity pulls the rocket down nose first, the fins' drag keeps it tail up, and the rocket returns to STABLE linear (and in this case unfortunately BALLISTIC re-entry.) Note that for MOST rockets with failed ejection of the nose cone, the rocket is stable by BOTH Barrowman AND CLA calcs, so they will go "ballistic" regardless of orientation.

HSR and BSR rely on the rocket being far enough off "Nose Down" attitude that something ELSE happens.

For HSR, I think even with minimal "off nose down" attitude, the falling rocket causes the angled or curled fins with a little sideways force, enough to start the rocket rotating. I THEEENK the principle of conservation of angular momentum is what forces the FALLING rocket to turn toward the horizontal position (perpendicular to the vector of fall, so parallel to the horizon). The more it turns horizontal, the more fin surface the rocket "offers" to the airstream and the faster the rocket rotates. It's a positive vicious cycle, maximized when rocket is perfectly horizontal. Because of this, I think HSR tolerates more "near nose down vertical" position than BSR.


So with "side port-puff", the problem is that the post-puff orientation is completely random. So once in a while the roulette wheel lands on green, and rocket comes in ballistic.

Now, with your innovation of retro-puff, maybe it's a new ball game. Assuming at least a slightly short delay (yeah, that's gonna cost a bit of altitude), the puff occurs with the rocket presumably at or near vertical (there may be some weathercocking.) Next question is "how strong is the puff?" If it is enough to either STOP or REVERSE the upward trajectory, seems like the probability of the rocket starting to "fall" in a "nose-down vertical" (i.e., BAD) orientation is near zero, I think certainly far less than the completely random side port puff.

So am I correct that your success rate of transition to HSR has greatly improved with retro-puff? And if not 100%, do you have a good explanation for the failures?

Me thinks the retro-puff technique pre-apogee would be a GREAT technique for Back Sliders, as pausing mid-air at or nearly at perfectly nose UP should be the PERFECT orientation for transition to Back Slide (? @Rktman what do you think?)

Okay, got to get to work on submitting the rules change to make Horizontal Spin Recovery a competition event. I'm leaning toward Duration rather than altitude for a couple of reasons.

1. Adding altimeter weight certainly doesn't IMPROVE reliability of transition.

2. The real challenge/cool part is the transition and hang time, rather than how high you can get it to go (and altitude is gonna help your duration anyway).

I will run my submission by you and @BEC and @Rktman before I submit it.

Given no objections, I’ll run it up the flagpole and see if it makes a splash.

 

[Dotini]

After months of toil dealing with my home since last August, plus a miserable winter of cold and wet, I'm re-emerging into the model rocketry mode. My shop is fully back in commission, and both old and new projects are back in work. The past three days were above 60 F and below 60% humidity, so I spent them priming and painting new tubes. Spring has sprung!

Shortly, I hope to be producing new models, new tests, new photos and new video.

 

[Rktman]

Looking forward to it!

 

[lakeroadster]

@Dotini is back in the mix.... outstanding.