Plan 9 From Outer Space

[Dotini]

The purpose of this experiment is to build (at minimal time, cost and effort) a backslider with belt and suspenders, a model which predictably glides to a stop on its belly, and rarely sustains any but the most minor damage. It has a streamer, and a payload compartment for my new altimeter. It looks strange to me; bizarre even. Perhaps I've gone off the deep end?



Payload section accommodates Jolly Logic 2, bulky plastic nosecone from Estes E2X to be retained by black tape. Hole is for atmospheric equalization. Central section (E2X main tube) accommodates 6" streamer, Qualman crossover baffle/shock cord mount and plenty of line and wadding.


Fin unit from E2X, heavy duty tube from Semroc, winglets and canards from plastic shipping tube. Note 4th fin reduced to a skid.

Weight, ready to fly with B6-2, altimeter, and streamer is a bit over 3.0 oz. Painted plastic take up to a week to cure for best durability, so first flight will be next week.

I made use of some dubious adhesives in this experimental model. So I may have a canard come off at some point. But no worries; Plan 9 From Outer Space is with us now.

 

[BABAR]

The one thing I know about the flight, it will be entertaining, one way or another.

let’s hope in a good way!

my Screwball probably won’t fly until Saturday, due to winds.

 

[BABAR]

Hmmm, Houston, we may have a problem

couple concerns.

1. I see the hole, which you say is for atmospheric equalization presumably for your altimeter. { Ignore the rest of this section if it is a dual purpose vent for the altimeter AND for the “kick.” } Do you have a Forward vent hole (I have some to believe it may not matter what side it is on, right, left, ventral, or dorsal) to KICK this puppy out of stable Barrowman/OpenRocket flight mode Into what I am calling “stall” mode or ”free fall” mode? If not, I am afraid the most likely outcome is that, unless you achieve a perfect vertical flight (rare with LPR models, bigger models may have more inertia so they may be more likely to stay vertical), this will go up stable (hopefully)— all good, at apogee it will arc over STILL STABLE with some forward motion, and without that “kick” from an eccentric port, what went up nose first and stable is gonna come DOWN nose first and stable. This is sometimes referred to as “poor form.” Also if you don’t have a vent, you may either spit your motor or rupture the tube,

2. I suspect your altimeter is in the nose, that’s gonna add to your nose weight and MAY keep this Barrowman stable even WITH an ejection side port “kick.” My recommendations, for what they are worth, are that you fly first without the altimeter (less nose weight), second with a dummy weight altimeter (see if it recovers appropriately WITH the weight) and only THEN risk an altimeter flight.

my working theory is that BOTH horizontal spin AND backslide recovery REQUIRE ”stalling” or otherwise abruptly and sharply deviating from “normal” stable low angle of attack flight (what I call the ”Barrowman Zone”) into the extreme high angle of attack (ideally 90 degrees, but I suspect anything over 45 degrees works, maybe even less) “Stalled Freefall Zone.” That just sounds more erudite then the “Cardboard Cutout Zone.” The intention is that the BODY tube, which contribute little to aerodynamic forces at and near zero angle of attack, imparts SIGNIFICANT aerodynamic force during “stall” recovery. Most rockets NEVER reach the stall zone, either because they arc over and NEVER reach zero angle of attack OR because they deploy the recovery gear as intended. For rockets that fail to deploy the nose cone, assuming they are otherwise “normal” unless the BOTH go into a perfect vertical stall AND they are either SuperRocs (extremely long compared to wide, like 30 to 1), they behave exactly as expected, they Recover from the stall nose down and become (or resume) progressively more ”ballistic” stability and auger in.

I think you and I have proven that with a good “kick” to initiate stall, we can induce HORIZONTAL SPIN with considerably less than 30-1 length to caliber ratios. I am not so certain about BackSliding.

 

[Dotini]

Hmmm, Houston, we may have a problem

couple concerns.

1. I see the hole, which you say is for atmospheric equalization presumably for your altimeter. { Ignore the rest of this section if it is a dual purpose vent for the altimeter AND for the “kick.” } Do you have a Forward vent hole (I have some to believe it may not matter what side it is on, right, left, ventral, or dorsal) to KICK this puppy out of stable Barrowman/OpenRocket flight mode Into what I am calling “stall” mode or ”free fall” mode? If not, I am afraid the most likely outcome is that, unless you achieve a perfect vertical flight (rare with LPR models, bigger models may have more inertia so they may be more likely to stay vertical), this will go up stable (hopefully)— all good, at apogee it will arc over STILL STABLE with some forward motion, and without that “kick” from an eccentric port, what went up nose first and stable is gonna come DOWN nose first and stable. This is sometimes referred to as “poor form.” Also if you don’t have a vent, you may either spit your motor or rupture the tube,

2. I suspect your altimeter is in the nose, that’s gonna add to your nose weight and MAY keep this Barrowman stable even WITH an ejection side port “kick.” My recommendations, for what they are worth, are that you fly first without the altimeter (less nose weight), second with a dummy weight altimeter (see if it recovers appropriately WITH the weight) and only THEN risk an altimeter flight.

my working theory is that BOTH horizontal spin AND backslide recovery REQUIRE ”stalling” or otherwise abruptly and sharply deviating from “normal” stable low angle of attack flight (what I call the ”Barrowman Zone”) into the extreme high angle of attack (ideally 90 degrees, but I suspect anything over 45 degrees works, maybe even less) “Stalled Freefall Zone.” That just sounds more erudite then the “Cardboard Cutout Zone.” The intention is that the BODY tube, which contribute little to aerodynamic forces at and near zero angle of attack, imparts SIGNIFICANT aerodynamic force during “stall” recovery. Most rockets NEVER reach the stall zone, either because they arc over and NEVER reach zero angle of attack OR because they deploy the recovery gear as intended. For rockets that fail to deploy the nose cone, assuming they are otherwise “normal” unless the BOTH go into a perfect vertical stall AND they are either SuperRocs (extremely long compared to wide, like 30 to 1), they behave exactly as expected, they Recover from the stall nose down and become (or resume) progressively more ”ballistic” stability and auger in.

I think you and I have proven that with a good “kick” to initiate stall, we can induce HORIZONTAL SPIN with considerably less than 30-1 length to caliber ratios. I am not so certain about BackSliding.

Normally I launch these types of rockets with a 2 second delay. That seems to ensure it never goes over apogee without the ejection charge activating, stalling the rocket and in this case, deploying the streamer. The streamer is a permanent part of this design, and any backsliding is only an embellishment, not a necessity for safe recovery.

 

[BABAR]

Ah, my lights are on. Dim, but on.

I like this with a small streamer!

 

[DaHabes]

Hmmm, Houston, we may have a problem

couple concerns.

1. I see the hole, which you say is for atmospheric equalization presumably for your altimeter. { Ignore the rest of this section if it is a dual purpose vent for the altimeter AND for the “kick.” } Do you have a Forward vent hole (I have some to believe it may not matter what side it is on, right, left, ventral, or dorsal) to KICK this puppy out of stable Barrowman/OpenRocket flight mode Into what I am calling “stall” mode or ”free fall” mode? If not, I am afraid the most likely outcome is that, unless you achieve a perfect vertical flight (rare with LPR models, bigger models may have more inertia so they may be more likely to stay vertical), this will go up stable (hopefully)— all good, at apogee it will arc over STILL STABLE with some forward motion, and without that “kick” from an eccentric port, what went up nose first and stable is gonna come DOWN nose first and stable. This is sometimes referred to as “poor form.” Also if you don’t have a vent, you may either spit your motor or rupture the tube,

2. I suspect your altimeter is in the nose, that’s gonna add to your nose weight and MAY keep this Barrowman stable even WITH an ejection side port “kick.” My recommendations, for what they are worth, are that you fly first without the altimeter (less nose weight), second with a dummy weight altimeter (see if it recovers appropriately WITH the weight) and only THEN risk an altimeter flight.

my working theory is that BOTH horizontal spin AND backslide recovery REQUIRE ”stalling” or otherwise abruptly and sharply deviating from “normal” stable low angle of attack flight (what I call the ”Barrowman Zone”) into the extreme high angle of attack (ideally 90 degrees, but I suspect anything over 45 degrees works, maybe even less) “Stalled Freefall Zone.” That just sounds more erudite then the “Cardboard Cutout Zone.” The intention is that the BODY tube, which contribute little to aerodynamic forces at and near zero angle of attack, imparts SIGNIFICANT aerodynamic force during “stall” recovery. Most rockets NEVER reach the stall zone, either because they arc over and NEVER reach zero angle of attack OR because they deploy the recovery gear as intended. For rockets that fail to deploy the nose cone, assuming they are otherwise “normal” unless the BOTH go into a perfect vertical stall AND they are either SuperRocs (extremely long compared to wide, like 30 to 1), they behave exactly as expected, they Recover from the stall nose down and become (or resume) progressively more ”ballistic” stability and auger in.

I think you and I have proven that with a good “kick” to initiate stall, we can induce HORIZONTAL SPIN with considerably less than 30-1 length to caliber ratios. I am not so certain about Backsliding.

Attached is a good article on backsliding. Model built by Peter Alway's brother about 20 years ago. The location of the CG vs. the Barrowman CP vs. the CLA (Center of Lateral Area) is fairly precise. It took them trial and error to find the right location. I'm building this model, just primed it.

For the model above, you should find the CP per Barrowman and the CLA (via cardboard cutout method) and try to figure out where to put the CG, using weights as needed. In any event, the first flight should be a heads up flight. If you get it wrong it will come in ballistic.

 

[Ronz Rocketz]

 

[Dotini]

Attached is a good article on backsliding. Model built by Peter Alway's brother about 20 years ago. The location of the CG vs. the Barrowman CP vs. the CLA (Center of Lateral Area) is fairly precise. It took them trial and error to find the right location. I'm building this model, just primed it.

For the model above, you should find the CP per Barrowman and the CLA (via cardboard cutout method) and try to figure out where to put the CG, using weights as needed. In any event, the first flight should be a heads up flight. If you get it wrong it will come in ballistic.

Thanks for your post, and extra thanks for including Backslider:The Super Roc Rocket GliderBy: Peter Alway. That superb paper should be like a chapter of the Old Testament to all rocketeers of the maverick bent. I used it extensively in designing and building my Magnus X series of experimental rapidly spinning rockets. Tests with these rockets goes on at a glacial pace, slowed by damaged fins and tubes inflicted by landing horizontally at high rpm.

https://www.rocketryforum.com/threads/horizontal-spin-recovery-with-magnus-effect.165378/page-5

Magnus X-3. This rocket spins in a blur and glides far, far away in a 4mph wind.


For the thread model, Plan 9 From Outer Space, I don't see the need for a heads up first flight, as from the start it is designed around a big pleated streamer, so really only a pseudo super roc. This model is almost ready to test, but I am held by bad weather.
And I've started an exciting new pseudo super roc, a ringtail designed around a C11-3.

 

[BABAR]

Attached is a good article on backsliding. Model built by Peter Alway's brother about 20 years ago. The location of the CG vs. the Barrowman CP vs. the CLA (Center of Lateral Area) is fairly precise. It took them trial and error to find the right location. I'm building this model, just primed it.

For the model above, you should find the CP per Barrowman and the CLA (via cardboard cutout method) and try to figure out where to put the CG, using weights as needed. In any event, the first flight should be a heads up flight. If you get it wrong it will come in ballistic.

I have built this pretty much as presented here, and it definitely works. The problem being, like the prototypical horizontal spin recovery, it tends to break at least one fin on landing.

I am having some success with my asymmetric fin models, but not 100%. Devil's Triangle made 4 great flights, number 5 was an Asphalt Dart. Skrewball in the Slide Pocket made 2 out of 3. Both of those were just guestimations on fin area. BECAUSE they are asymmetric fin, I think they need a little more fin area for stable boost (they corkscrew, that's a gimme, but no really any problem, in fact I kind of like it.) I tried a Ring Fin (along the lines of the classic Corkscrew that Odd'l Rockets used to sell, original designed by Bruce Levison
http://modelrocketbuilding.blogspot.com/2011/03/corkscrew-2-build-backstory.html
unfortunately he passed recently
https://www.rocketryforum.com/threads/we-lost-one-of-our-own-bruce-levison.158724/#post-1987593
Anyway, the Skrewball was easy to make, worked 2 out of 3.

I am thinking the failures may be due to too much tail surface combined with "unlucky" port puff kick. Specifically the port puff knocks the rocket out of stable flight, but exactly HOW much is pretty much completely unpredictable (10 degrees? 20? 40? 90? 180?) My theory (@Mike Haberer , @Rktman , @Dotini
, and anyone else out there in the peanut gallery feel free to chime in) is that MOST of the time if the rocket is built with Barrowman Stability and Cardboard CutOut IN-stability, once it is kicked out it will backslide. However, ONCE IN A WHILE, the kick ends up with the rocket UNFORTUNATELY transiently paused in mid flight with tail fins up and nose down. This is sort of the reverse of what I have read about the High Power Guys describing a TRANSIENT backslide, which I understand to be a perfectly vertical flight, where the rocket runs out of kinetic energy and transiently pauses for a moment NOSE STRAIGHT UP, the rocket then falls BACKWARD tail first for a few moments before the electronics decide "hey, we ain't going up anymore so time to deploy the drogue or chute." (You may have guess I don't know much about electronics and you are correct.)
Not at all arguing with Peter Alway's report, just wondering if it worked EVERY time (I was going to say Always, but that might be redundant and confusing!)

Also wondering how many of Peter's rockets snapped fins on landing?

Also regarding PAINTING these rockets, the relative SuperRoc 30 to 1 ratio buys you more surface area for the Cardboard CutOut IN-stability you want, but you start losing that when you paint that big long forward tube. Eric, I think you said you actually added some tail weight to get it to balance, is that right?

Problem with the asymmetric fin design is that I am not sure it sims properly. I will play with it and maybe run it by @neil_w .
.
I was really bummed with the fifth flight of the Devil's Triangle, I really thought I had it down.

 

[BABAR]

@Dotini , throwing a small streamer out the front really helps with a backslider (although some people may say it's not REALLY backsliding), I have seen that with many rockets.

here's a nice flight of a two planar fin rocket (not supposed to work, but it does. People may correctly argue that this isn't two planar fins, it is one NON-planar fin, oh well.)

despite coming down on pavement, the fin configuration keeps the fins relatively "up" so no damage.


build here

https://www.rocketryforum.com/threads/2fnc-2-linear-fins-and-a-nose-cone-the-lucky-7.56426/

 

[Dotini]

I have built this pretty much as presented here, and it definitely works. The problem being, like the prototypical horizontal spin recovery, it tends to break at least one fin on landing.

I am having some success with my asymmetric fin models, but not 100%. Devil's Triangle made 4 great flights, number 5 was an Asphalt Dart. Skrewball in the Slide Pocket made 2 out of 3. Both of those were just guestimations on fin area. BECAUSE they are asymmetric fin, I think they need a little more fin area for stable boost (they corkscrew, that's a gimme, but no really any problem, in fact I kind of like it.) I tried a Ring Fin (along the lines of the classic Corkscrew that Odd'l Rockets used to sell, original designed by Bruce Levison
http://modelrocketbuilding.blogspot.com/2011/03/corkscrew-2-build-backstory.html
unfortunately he passed recently
https://www.rocketryforum.com/threads/we-lost-one-of-our-own-bruce-levison.158724/#post-1987593
Anyway, the Skrewball was easy to make, worked 2 out of 3.

I am thinking the failures may be due to too much tail surface combined with "unlucky" port puff kick. Specifically the port puff knocks the rocket out of stable flight, but exactly HOW much is pretty much completely unpredictable (10 degrees? 20? 40? 90? 180?) My theory (@Mike Haberer , @Rktman , @Dotini
, and anyone else out there in the peanut gallery feel free to chime in) is that MOST of the time if the rocket is built with Barrowman Stability and Cardboard CutOut IN-stability, once it is kicked out it will backslide. However, ONCE IN A WHILE, the kick ends up with the rocket UNFORTUNATELY transiently paused in mid flight with tail fins up and nose down. This is sort of the reverse of what I have read about the High Power Guys describing a TRANSIENT backslide, which I understand to be a perfectly vertical flight, where the rocket runs out of kinetic energy and transiently pauses for a moment NOSE STRAIGHT UP, the rocket then falls BACKWARD tail first for a few moments before the electronics decide "hey, we ain't going up anymore so time to deploy the drogue or chute." (You may have guess I don't know much about electronics and you are correct.)
Not at all arguing with Peter Alway's report, just wondering if it worked EVERY time (I was going to say Always, but that might be redundant and confusing!)

Also wondering how many of Peter's rockets snapped fins on landing?

Also regarding PAINTING these rockets, the relative SuperRoc 30 to 1 ratio buys you more surface area for the Cardboard CutOut IN-stability you want, but you start losing that when you paint that big long forward tube. Eric, I think you said you actually added some tail weight to get it to balance, is that right?

Problem with the asymmetric fin design is that I am not sure it sims properly. I will play with it and maybe run it by @neil_w .
.
I was really bummed with the fifth flight of the Devil's Triangle, I really thought I had it down.

Absolutely first rate post! There's a lot of information, a lot of emotions, and a lot of significantly interesting questions packed up in there.

I will say a few things.
- Both my Magnus X-2 and X-3 have alternate upper sections/nose cones for puffer and streamer deployment duties. I will continue to test both methods with the goal of determining which is a more reliable recovery system in the long run. These are ~50:1.
- Plan 9 From Outer Space is a 27:1 putative backslider with streamer, ready to test as early as tomorrow.
- My ringtail, Animist II, is 16:1 and shows signs of backsliding. But she's heavy with paint and full baffle.
- My current project is a relatively lightly built ringtail, another putative backslider with streamer but with a 24mm motor mount. I'm hoping to run this at under 6 oz on C11-3. I may run a ~25:1 ratio.
- I'm set in my way as far as paint goes. IMHO, it's required for visibility, durability, and a minimal pride in workmanship. It's my job as designer, builder and operator to achieve interesting experimental results, suffer some damage and setbacks, and at the end of the day solve the challenge of also delivering repeatability and reliability. It's a journey to savor.

 

[BABAR]

.
- I'm set in my way as far as paint goes. IMHO, it's required for visibility, durability, and a minimal pride in workmanship. It's my job as designer, builder and operator to achieve interesting experimental results, suffer some damage and setbacks, and at the end of the day solve the challenge of also delivering repeatability and reliability. It's a journey to savor.

This makes you an Engineer AND a Craftsman.

I'm happy if I can just get the Engineering right!

 

[Rktman]

Eric, I think you said you actually added some tail weight to get it to balance, is that right?
I was really bummed with the fifth flight of the Devil's Triangle, I really thought I had it down.

Affirmative, can't remember the exact amount anymore. Probably would've needed a tad less had I used the aft coupler that the Always used to swap out fin cans.

 

[Dotini]

Sneak preview of the 6th Observable:


Fin unit complete with 24mm motor mount and coupler, 0.67 oz. Still needs some glue and finish.

 

[BABAR]

Sneak preview of the 6th Observable:

View attachment 465894
Fin unit complete with 24mm motor mount and coupler, 0.67 oz. Still needs some glue and finish.

I like this. Interestingly I think this has potential as a horizontal spin rocket as well as a back slider.

if it backslides you still have issues with impact of the ring fin traveling longitudinally, parallel to the rocket axis. It has a bunch of short strong fins/struts, so it may take the impact without damage due to brute force structural integrity,

however, if you put “windows” in the rings right next to the fins, you basically have a horizontal spin rocket similar to but classier than Bail Out Bill. The rocket impact will be horizontal. You will still have the vertical kinetic energy to dissipate, but the rotary kinetic energy will dissipate much more slowly, it will “rub” on the ground until it stops, rather than a single jarring impact like you current fins.

nice work. Hoping for a good flight either way.

 

[Rktman]

Great looking, can't wait to see the rest of it. Sure would be cool if you left that ring fin clear.

 

[Ronz Rocketz]

Pick a glue that is plastic friendly. Don't want the acrylic to fog up.

 

[Dotini]

Great looking, can't wait to see the rest of it. Sure would be cool if you left that ring fin clear.

Yes, there's little reason to paint this kind of plastic, as experience indicates it's only going to chip off, although curing for a week or more helps. So I'm probably not going to paint it. However, I may adorn it with segment(s) of chrome mylar tape for visibility purposes, leaving 50% (or more) of the ring clear.

Pick a glue that is plastic friendly. Don't want the acrylic to fog up.

An apposite comment/observation. Keep them coming! My experience in the 21st Century with modern plastics adhesives is both limited and checkered. At the moment, I'm using Gorilla Superglue, which is very user friendly in application. Original Gorilla Glue however was a nightmare.

 

[BABAR]

Something I have used to attach rings to fins (or struts.) “Cheaters” or “balsa fillets.” Basically mark where each of the fins is going to join the ring. Use colored tape or ink to Mark them, as you want to make sure the same fins are aligned with the same marks later. Remove the ring. Place a long thin balsa strip (cut 1/16” balsa the length of the fin, 1/16” wide, so you get a piece 1/16x1/16xfin length) on the inside of the ring and attach it with glue of choice (I lean toward epoxy when bonding unlike materials, like wood and plastic.)

once these are glued in place and dry, re-attach the ring and glue in place. This allows more surface area for better adhesion, and should maintain alignment better as the glue dries (assuming you got the cheaters in the right place to begin with!). Adding a second cheater on the opposite side of each fin/ring joint once the above assembly dries is purely optional.

note: I frequently use this technique on fin/body tube joints. The cheater is easily lined up with the tube marking line and since it has almost no weight, it glues in place easily without slipping. It makes obtaining perfect fin alignment a snap. Using double wood glue joint technique, it tends to ”tack” faster (although lots of people do quick “tacks” with a small amount of CA at the front and rear edges), and provides a stronger joint. Remember to sand off the glassine layer from the tube before applying!