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  #1  
Old 11-04-2011, 08:47 PM
DGLand DGLand is offline
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Default High Apogee Low Opening

I kind of raised this qstn previously on another forum but it didn’t get much (any?) discussion there. Plus, I have been thinking some more about the details and I think I have a product idea that would sell……what do you think?

High flying model rockets pose the same recovery problem as high flying highpower rockets. Especially around north Texas, the wind is blowing ALL THE TIME and I am sure we’re not the only ones with this problem. I like to launch ‘em high but I also kinda like to get them back. I don’t like to pack $50 or $100 worth of electronics onto a $15 rocket and still have a pretty good chance of losing the whole thing.

I am looking for a way to accomplish a low-power (inexpensive) version of dual-deploy. I don’t like messing with electronics (cost, complexity, fresh batteries, etc) and I don’t like how you step across the line into a legal quagmire when you have to start storing/using e-matches and loose black powder ejection charges. (And yes, all the ‘substitutes’ still require all the PITA paperwork, licenses, lockers, inspections, and all the other nonsense.) Seems that issue gets all wrapped up over whether the black powder comes prepackaged inside a manufacturer’s motor or if it (the exact same &^$# stuff) comes separately in a can and you use it for something other than a firearm. I am not holding my breath on getting that changed, no matter how cosmically stupid it is.

What if there was a way to do this using a new product with existing paper casing materials for expendable ‘black powder’-style motors? Probably using existing tooling? And existing processes? And existing pyrogens? And (the best part) cheap enough to use once and throw away? (No heartbreak if it drifts out of sight on the breeze!)

(OK, thinking out loud here….) If a manufacturer (like......Estes?) would offer a motor without propellant, including only a delay and ejection charge (don’t know if you would need/want the nozzle), such a ‘HALO’ could be used the same way we currently install an upper stage black powder motor. You could use monster first stage motors (like the new E12), still choose the ejection delay for the main motor as you normally would, and still use that motor-based ejection charge to separate the model rocket into two tethered sections at apogee. The rocket would then use break-up recovery for the initial descent, like many of us already use for high fliers. The ejection charge would also ignite the HALO during separation at apogee.

The HALO would burn and exhaust (feebly?) from the bottom end of the upper portion of the rocket in similar fashion to a discharging second stage motor. The HALO would be selected from a couple of available burn times (maybe 3, 5, or 7 seconds?) and it would make more tracking smoke on the way back down.

When the HALO finished its delay (at a lower altitude) it would ignite a second ejection charge for the main recovery system deployment. You would get significantly reduced drift in the breeze and you would have a much improved chance of recovering your bird. I don’t know about you, but if I had good confidence that I would get my rocket back I would launch more and burn/buy more motors. (Big launch fields are getting harder to find.)

The HALO could probably be packaged into an Estes-style 13 x 45mm “T” paper case. You might not want any ceramic nozzle stamped in the rear, to improve ignition from the first stage motor. You would simply stamp in the delay material (same stuff as currently used) which should fit nicely inside that case if there is no propellant load. The delay materials could even be stamped against the same tooling already used to form the ceramic nozzle---this would provide more exposed surface area for a better chance of ignition. Top it off with an ejection charge (maybe a little extra big load to successfully pressurize a BT50-60-70 rocket?) and retainer cap and you’re done.

If there is an ignition problem with getting delay-pyro material to burn when exposed to an ejection charge, perhaps a small layer of normal propellant could be dropped in first to enhance the reliability of start-up. Without a nozzle to make effective use of the combustion products, the primer propellant would produce negligible thrust, the small charge would flash quickly, and it should be able to transfer the flame to the delay pyrogen (same as in motors now).

If there is a problem with ejection gases venting out the back end and not forward, you could help direct the gas path by stamping in a nozzle-like ring (same ceramic materials?) between the delay and ejection charges. (Possible special production-line tool?)

The 13mm case size would nestle quite nicely against (or into) the front end of an 18mm case and could still be used with 24mm or other 13mm motors. The 13mm size would present only a small weight penalty for the overall rocket design.

Model rockets designed to use this system would look exactly like BT50-60 two-stage birds already do. There would be a set of parts just like a normal MMT to hold the HALO. There would be a stage coupler to hold the rocket sections together just as for two-stage designs. There would be a tether system to attach the two sections, probably using Kevlar cord or something heat resistant, maybe with a length of shock cord in there somewhere. The biggest difference would be that the upper section would not need ‘second stage’ fins….unless you just like lots of fins.

Cost numbers could be funky due to small-batch-economics but at least the manufacturer could use most (or all) of their existing motor production setup and materials----no extra parts or supplies inventory. Cost could/should be in the same ballpark as existing 13mm motors? Packaging could certainly be the same as existing 13mm. Labeling might take a little work but that should not be difficult (not rocket science?) Marketing wouldn’t be a problem because the guys who would want something like this would latch onto it immediately with only a few announcements, and you wouldn’t need to tell the whole world about it because it would just confuse all those first-timer rocketeers (who already cannot figure out the motor codes). No handling of loose black powder, no LEUPS, no permits, no electrical/pyro igniters, everything manufactured and safely/legally packaged just like current low power motors. Nothin’ but net. Since this is not a thrust-producing ‘motor,’ would this even have to be certified by the NAR S&T bunch? (I guess we’d want them to verify that the delay charges burn for the proper time intervals.)

And if you don’t like HALO (too many loyal game players out there?), how about High Apogee Delayed Ejection System?

Do you think this might be a go-er?
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  #2  
Old 11-04-2011, 11:44 PM
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bernomatic bernomatic is offline
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To me, it just seems too complicated, too much additional cost, too...

I am a firm believer in K.I.S.S. If you start adding seperate delay charges (in LPR, which is what we're talking about), there is now additional weight to consider, which means a stronger, heavier parachute and so on and so on.

On top of this, you better have all the launch factors figured out because you don't leave much room for: slow deploying parachutes; weathercocking and other issues which if given the extra height might correct themselves.

Personally, I think it's more simple and a lot easier just to switch out the model's parachute for a chute with a spillhole or streamer.
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  #3  
Old 11-05-2011, 12:36 AM
DGLand DGLand is offline
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Yeah, I understand simple, that's part of why I don't want to use electronics and separate ejection charges, etc

If you want simple, why not go all the way to just leave off the chute (or streamer) completely. Use break-up recovery and let the whole thing fall all the way to the ground. Only problem there is that the rocket then hits the ground harder. In my yard, it's gonna land on rocks (unless I let the weeds grow).

This comes right back around to the question of how to perform dual-deploy on a low power rocket using inexpensive gear. Dual-deployment is not too hard for high power guys, the only difference is one of scale. It would be worth the little extra cost ($1? $2?) to me so I would be better able to launch on the days around here when it is windy. What's an E12 going to cost? I'll bet those will be upwards of $3-4 each, plus the cost of a kit, plus all the time you spend building and finishing it. (And we all finish our rockets nicely, don't we?)

I still think that the weight of a 13mm casing (and probably only partly filled, at that) is not going to be much of a weight penalty. Sure, for competition, you would not want even a little extra weight, but I think this idea is slanted more toward sport fliers and slightly larger low power modrocs. The added weight of the HALO would be less than the epoxy root fillets everyone seems so anxious to add on.
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Old 11-05-2011, 02:38 AM
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I like your out-of-the-box thinking here. My biggest problem when launching small model rockets to great height is simply tracking them and seeing where they go (and end up). Here in the northeast (as is true in many parts of the country, especially the East), launches are on soft, grass- (or hay-) covered fields and the breezes aren't too bad most of the time. Simply keeping a bead on the rocket, and keeping it within the often-tight confines of the launch field are the big issues. Fliers in the East get pretty good at trajectory-planning and making adjustments to get the rocket down in a specific drop zone, simply by necessity and through steady practice. The manageable atmospheric conditions also make this possible. The big issue is being able to see high-flying rockets well enough to discern where and when they are arcing over and deploying so that one can fine-tune the adjustments.

Out in the southern plains you seem to have a different set of conditions and challenges. You mention that your enemies are the continually gusty conditions (and ever-present thermals, I assume) and the hard-packed or rocky ground. Presumably then you are able to maintain visual contact with high-flying model rockets? If so, I would love to know your secret. Being able to follow a 21" long by 1.33" diameter rocket to 1800 feet well enough to see the recovery system deployment, and only having to worry that it will drift too far away has got to be a pretty neat trick. I lose sight of such rockets after around 900 feet. Even if I subsequently hear the ejection charge go off, I have no idea by then where in the sky the rocket is anymore. In order to make adjustments and to know where it recovers, you have to be able to see the flight. That imposes an upper limit to how high model rockets can be flown, and it is often much lower than they are capable of going on available motors, especially 18mm and 20mm Ds.

My biggest concern then is if you intend to launch a model rocket into the 2000 foot neighborhood and then have it simply separate and fall until it reaches a low altitude, how are you planning on tracking it as it comes down without the added visibility of a deployed recovery device?
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Old 11-05-2011, 09:06 PM
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bernomatic bernomatic is offline
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I think the idea would be tracking smoke and/or a drouge chute or streamer.
What you have to remember DG is that scale, especially at the lower ends, doesn't always equate to workability. In other words, yes the scale weight of just the casing may be neglible when compared to a HPR rocket, but the real world addition of said weight may take it out of the high altitude club. I don't have any numbers as I haven't run any that I can recall, which doesn't mean much right now as I am PWI (posting while intoxicated), but try running some RockSim or other altitude program to see what affect the weight has on a LPR. I'm not trying to kill the idea, just see some pre-lim feasibility numbers.

In other words, before we argue over wether we should, can we?
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Old 11-05-2011, 09:16 PM
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and not to brag (as if it's something to brag about ) But Cleveland,Ohio is like the second windiest city in the nation (windier even then Chicago, which I hear tell when talking about Chicago as the "windy city" they are talking about the politicians and they're yapping, not necessarily mother nature)

Either way, I have seen wat toooooooooooooo many rockets float off on a "gentle" breeze and get stuck in a tree.
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Old 11-06-2011, 12:17 AM
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Don't get me wrong, I like the approach to addressing a major limiting factor in low power launches. I am not against the idea; I just see some issues that need to be worked out. Low power tracking smoke isn't all that visible at high altitude; on the few occasions when I have been able to follow an LPR to 1000+ feet, the tracking smoke from the delay was a tiny whisker that was only just barely perceptible at the very limits of my (well-corrected) visual acuity, and all but lost in a vast sea of sky. These aren't big motors and the small delay grains in them don't emit profuse clouds of smoke. Even talcum used for deployment detection doesn't help all that much at extreme (for LPR) altitudes.
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Old 11-06-2011, 12:28 AM
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GregGleason GregGleason is offline
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My question is that would NAR see this as a motor modification. If so, then, pardon the pun, it wouldn't fly. But if not, then there would likely be interest. The question at that point is would it be economically viable.

Have you performed at proof-of-concept test?

Greg
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Old 11-06-2011, 12:57 AM
DGLand DGLand is offline
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Quote:
Originally Posted by GregGleason
My question is that would NAR see this as a motor modification.


This would not modify any motor. It would be used just like a second stage motor but would involve absolutely no changes to any first stage motors.

Quote:
Originally Posted by GregGleason
Have you performed at proof-of-concept test?


Nooooooo........... That would seem to require me to pack pyrogens into a motor case, which IIRC would be a violation of the NAR safety code....and would be completely counter to the whole point of having a motor manufacturer do this. Obtaining loose BP for the ejection charge, even for a single 'proof of concept' test, would also require me to go get all the paperwork and storage lockers. Last but not least, I do not happen to have a handy supply of unused 13mm motor cases, or the secret Estes receipe for delay charge either.

I think if a manufacturer thinks this is worth looking into, they would be far better equipped to run a test or two.
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Old 11-06-2011, 01:25 AM
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Quote:
Originally Posted by DGLand
This would not modify any motor. It would be used just like a second stage motor but would involve absolutely no changes to any first stage motors.



Nooooooo........... That would seem to require me to pack pyrogens into a motor case, which IIRC would be a violation of the NAR safety code....and would be completely counter to the whole point of having a motor manufacturer do this. Obtaining loose BP for the ejection charge, even for a single 'proof of concept' test, would also require me to go get all the paperwork and storage lockers. Last but not least, I do not happen to have a handy supply of unused 13mm motor cases, or the secret Estes receipe for delay charge either.

I think if a manufacturer thinks this is worth looking into, they would be far better equipped to run a test or two.
Use an AeroTech RMS delay module and a prepackaged AeroTech EFC ejection charge. You would just need to find the right-sized container to hold them. One that wouldn't catch fire during the test. Do a ground test first. You aren't modifying a motor, you aren't attempting to make a motor, and in a ground test, you aren't launching anything.
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