Neil_W's half-baked design thread

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BABAR

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Here's a 2-stage version:
View attachment 468469
The required enlargement of the sustainer fins makes it look a little more traditional (albeit nice). And here's what the sustainer looks like on its own:
View attachment 468470
I don't think I would trust those fins to survive boost *or* landing.
First, as always, cool.

second, sustainer fin problem easily solved with rear eject. For flight purposes, stick a section of Nerf Dart or tape on the nose tip to reduce chance of breakage since this will be point of “First Contact” on landing (not the Star Trek kind, either!)

third, is BOOSTER stable post staging? If so, you are indeed looking at a true Core Sampler. If NOT, does the surface area of the fins provide enough drag for a safe tumble recovery? Options include deploying a small Nomex streamer tucked around the sustainer motor mount, or mounting accessory cluster pod or pods on the booster. Simplest would be a 1/2A3-2T BT-5 pod, just long enough for motor, wadding, streamer, and nose cone. The delay allows the sustainer to stage and separate before the auxilliary pod pops the streamer.

you would be fine IMO with a single pod, the asymmetric thrust assuming you put the pod right up against the main body tube is negligible. If you are a purist, or for aesthetic looks, use two, one on each side. Gives you more redundancy.

another advantage of the smaller pod motors, if the main doesn’t light, the auxiliaries are likely too weak do get the rocket off the pad. Mildly embarrassing but not a safety risk. If the main lights and the auxilliary does not, at worst you are looking at the same core sample you would have otherwise had. Not optimal, but a cone less rocket tube coming down open tube end first is unlikely to do much damage, except possibly to your relationship with the RSO…. Actually, if the auxilliary does NOT light, it increases the probability the booster will be UNSTABLE (good thing) as it will be a bit more tail heavy, so better chance of tumble.
 

BABAR

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If you go Auxilliary root, do NOT use a zero delay motor on the AUXILLIARY, obviously you need it for the main assuming BP gap staging. If you do you will deploy the streamer AT or near Staging. This sounds good, but it’s not. The booster will be at or near MaxV, this is the WORST time to deploy a streamer. I know, I tried something like this with a parachute. Came down with one shroud line intact….

you can argue that if you nest the streamer in the sustainer it is EXACTLY when you will deploy it, but in that case you HAVE no other option (except maybe to fold it up kind of tight, so it unravels slowly. Problem with this is it may not unravel at all….)
 
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BABAR

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A cool part of your design if you go two stage is it naturally vents into the small gap around the “plasma core.” You can not get a gap position better than than, gases will go straight forward up and around the sustainer motor. Perfect.
 

jqavins

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third, is BOOSTER stable post staging? If so, you are indeed looking at a true Core Sampler. If NOT, does the surface area of the fins provide enough drag for a safe tumble recovery? Options include deploying a small Nomex streamer tucked around the sustainer motor mount, or mounting accessory cluster pod or pods on the booster. Simplest would be a 1/2A3-2T BT-5 pod, just long enough for motor, wadding, streamer, and nose cone. The delay allows the sustainer to stage and separate before the auxilliary pod pops the streamer.
Another option is to rear eject a streamer from the booster.

Gap staging typically involves vent holes up near the sustainer motor. One can, instead, use an expanding volume to keep ejection gas moving upward; this is done by using a combination of vented and solid centering rings and coupler stock to light the sustainer motor and eject the booster motor pod and let a streamer out.

See my Quest Terrier-Orion two stage conversion build thread for details. There is a ground test which, despite it explosive climax, does provide evidence (if not proof) of concept. It's a slightly complex build, but a lot less so than many of Neil's previous builds. And it provides, in my opinion, a nice elegant solution.
 

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Another option is to rear eject a streamer from the booster.

Gap staging typically involves vent holes up near the sustainer motor. One can, instead, use an expanding volume to keep ejection gas moving upward; this is done by using a combination of vented and solid centering rings and coupler stock to light the sustainer motor and eject the booster motor pod and let a streamer out.

See my Quest Terrier-Orion two stage conversion build thread for details. There is a ground test which, despite it explosive climax, does provide evidence (if not proof) of concept. It's a slightly complex build, but a lot less so than many of Neil's previous builds. And it provides, in my opinion, a nice elegant solution.
I get nervous trying to reliably get one expanding gas cloud to do TWO things, light the sustainer AND blow the laundry.

with Neil's design, easy to run a motor mount chimney forward, stop about 3 to 5 mm below nested base of sustainer. Gases flow up chimney. Circumferentially bath the sustainer motor and continue up and around sustainer base out the gap around the narrow segment. Bob's your uncle.
 

neil_w

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I don't think about any of that stuff at this very early stage of design. To be sure, gap staging implementation considerations could render a design impractical, or force significant changes, or push the design back to a single-stage.

But that's all for later, if at all.
 

jqavins

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It's been a little while with no posts. You know we all wait eagerly for new half baked ideas.
 

neil_w

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I’m trying to revitalize this thread a bit, but right now I’m at the beach. 😀
 

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Aren't those beaches where the original Jaws was filmed? Da-da, da-da...

-Bob
 

jqavins

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From HGTV.com (the headline result from Googling (jaws filming location)
Though the film takes place in the fictional town of Amity Island in New York, it was actually filmed throughout Martha's Vineyard, Mass. (Long Island was considered "too busy" — the filmmakers wanted an island that would feel eerily empty to filmgoers.)
Why HGTV, I couldn't say; they were probably doing an episode of something out on Martha's Vineyard; "Jaws was filmed here."
 

Raptor 2

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I’m assuming you are using open rocket for your designs. Would open rocket be able to handle the Titan III C I’m working on? I don’t use open rocket myself yet but would like to try it on my Titan. I generally use a string test for stability on my rockets.
 

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I’m assuming you are using open rocket for your designs. Would open rocket be able to handle the Titan III C I’m working on? I don’t use open rocket myself yet but would like to try it on my Titan. I generally use a string test for stability on my rockets.
Yes, it will, it you use an alpha build of the forthcoming release. The standard 15.03 release won't do it.
 

Raptor 2

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Thanks for the info. Not sure what the alpha build means but I’ll down load the the new release when it becomes available. It will take me awhile yet to finish the Titan IIIC build. I’d like to model it in open rocket to check it’s stability. Do you know when the next version will be ready.... eta?
 

neil_w

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Thanks for the info. Not sure what the alpha build means but I’ll down load the the new release when it becomes available. It will take me awhile yet to finish the Titan IIIC build. I’d like to model it in open rocket to check it’s stability. Do you know when the next version will be ready.... eta?
Real Soon Now.

In the meantime, you can get it running but it might take a bit of effort. If you want to try, send me a PM.
 

jqavins

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Not sure what the alpha build means...
An alpha version, or alpha test version, is what comes before a beta test version. In beta testing, the basic functionality is already confirmed and there are (one hopes and expects) no major bugs. A long test by lots of people is called for to identify minor bugs and deficiencies.

An alpha version, on the other hand, is put out when the developers think the basic functionality is right and the major bugs are gone, but everyone know that some major problems of some sort are waiting to be found.

Both are "use at your own risk", but your risk is greater with the alpha version. (Actually, there are no guarantees with the full releases of OR either, but they are believed to be as stable, accurate, and compliant with the interface spec as possible.)

I rarely use OR myself. I won't mess with an alpha version, and I would recommend the same to a new user.
 

neil_w

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I rarely use OR myself. I won't mess with an alpha version, and I would recommend the same to a new user.
I've been very cautious about recommending it in the past, but it's progressed quite a bit and the current alpha is quite usable. I use it full-time with no problems.
 

jqavins

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Does the OR developer community use the beta designation? From what you've said, it sounds like you may have a beta there for all intents and purposes.
 

neil_w

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Does the OR developer community use the beta designation?
Yes, and right now our goal is to get to a public beta.
From what you've said, it sounds like you may have a beta there for all intents and purposes.
We're definitely close to beta, and it's not like there's a bright-line distinction between alpha and beta anyway. But we still have a small set of issues to resolve before going public beta. And then another set to resolve before official release.

The important thing is, we're at the point where I wouldn't try to dissuade someone from giving it a go. It's usable now.
 

Raptor 2

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Thanks Javan’s for your info. All helpful information for me to help me in making a decision on going forward. Neil I’ll be starting the procedure you outlined to get Java 11 And will let you know when I’ve got it set up. Thanks again guys.
 

BABAR

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Just don’t mess with the Delta version


(sorry, couldn’t resist)
 

smstachwick

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Here's one that's "half-baked", but more in the sense of "I didn't put a lot of thought into this and realized that it was probably a bad/impossible idea." It's a stock Estes Star Orbiter loaded with the most powerful motor (by total impulse) that will fit in the stock 29mm mount: the Ratt I90L hybrid motor.

not enough room.jpg


The first problem is pretty obvious: There's not enough room for that huge oxidizer tank. I ended up deciding it wasn't really a big deal, the main obstruction being the bottom of the nose. Removing the bottom edge creates enough room for it, and there might be room around the oxidizer tank for the shock cord and parachute (just work with me here, alright?)

Second problem: Obviously that long motor would put a lot of stress on the motor mount from not having a centering ring towards the front end. I just decided to ignore this for now. If I were to actually build this, I could slide a removable one in and have it rest on top of the tube coupler.

Third problem: The 2D flight profile indicated that the rocket would likely shake itself apart. I was initially puzzled by this, until I consulted Stine's book and realized that this configuration perfectly matched his description of a statically stable but dynamically unstable model. The fins are too small to produce sufficient restoring force for that heavy motor.

I set to work increasing the fin area. I didn't bother with making the through-the-wall tabs physically compatible with stock body tube and motor mount, I just wanted to see what external modifications it would take to bring about dynamic stability. After some assistance from @kuririn I was able to rapidly throw together some simulations with fins of increasing upscale factors over the original. I ended up discovering that the minimum upscale required to dynamically stabilize the rocket was a factor of 16 by area, 4 by linear dimensions. This was the result.

huge fins.jpg


That, of course, is just silly. It's probably also completely infeasible with 1/8th inch balsa, and it would be statically unstable on other I-type motors that don't have that oxidizer tank to push the CG forward. The Cesaroni I243, for example, would have the CG over an inch aft of CP.

So I drew the conclusion that I had at the start: this one will definitely remain a paper project. Fun to think about but entirely impractical to actually build and fly. I can probably think of about a dozen other things wrong with a design like this, but this was enough to convince me to abandon it.
 
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