MIRV Gryphon inspired

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GlenP

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I have been wanting to build a MIRV Gryphon but wanted to avoid the cluster ignition, so I came up with an alternative similar to the Estes MIRV where you have a single booster engine but gap staged like the Gryphon version.

I made a manifold of sorts and hope that it will be vented sufficiently to gap stage the four sustainers. I also added a boat tail, shifted the engine back a little and added more booster fin area to help it tumble better. I might have a very small volume where I could stuff a streamer between the sustainer tubes for the booster, but will probably keep it tumble. I may add a dowel to the booster and lugs to the sustainers to keep their noses together, like the Estes MIRV.

I am still undecided if I should stick with the four nose cones on each sustainer, or try to make them piece together to form the shape of a single large cone. Experimenting with both ideas still. This model is basically made from cardstock, except for the balsa fins.
 

Lawndart

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Very nice. I've something similar on my workbench.
 

Zeus-cat

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I have seen the title of this thread for over a month; the light bulb finally turned on tonight. MIRV Gryphon. Ha!

On a related note: at our weekly rocket club metering tonight I came up with a cool name for a rocket - The Slauson Cutoff. You have to be of a certain age to get the joke on these names.
 

GlenP

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they still show re-runs of the show on getTV www.get.tv I get this channel over rabbit ears from a local broadcast station.

I have some new cardstock parts for building the big nose cone from 4 segments that will fit together, using the standard 13mm nose cone template from the Project Paper thread here scaled up to the diameter of the 4x13mm sustainer tubes (and booster tube diameter) still a work in progress. I am cutting up that big blue nose cone in the above picture into quarters cross-section-wise, like pickle spears.

M.I.R.V. Gryphon model rocket plans:
https://www.oldrocketplans.com/srw/srwMG/srwMG.htm

EDIT -
Answer: Founder of two popular hit TV game shows still running today: Jeopardy and Wheel of Fortune.
Question: Who is Merv Griffin?
 
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GlenP

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I really like the look of the 4 individual nose cones, very realistic appearance of multiple warheads. But, I am still experimenting with making them fit together to appear like a larger cone. My mock up made from cardstock is a little larger than I wanted. With the cardstock you have to be very accurate, which is hard to do for me at least, so I think I will end up cutting this up from balsa so I can sand it down to custom fit the parts with each other. I noticed that the size cone I need is roughly the same size as the Cub Scout Space Derby kit, so I might get a couple of those to cut up and try to attach them to coupler tubes to fit the top of the sustainer tubes. It helps that the Space Derby shape is already hollowed out, so that the launch lugs that I will put on in the middle of the sustainers (see the Estes MIRV kit instructions) won't hit the nose cones if they come together in the middle corner, like my cardstock mock-ups.

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EDIT - That particular Space Derby rocket (rubber-band and propeller removed for clarity) was the 1st place winner in our Pack derby a couple of years ago, it went undefeated in all heats.
 
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GlenP

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I tried another nose cone concept made from balsa to be covered with cardstock. This allowed me to make the profile shape I was looking for fairly accurately without having to cut up 4 quartered "pickle spears" from a larger block. I think this is getting closer to the shape I was looking for. Here are some shots of the balsa frame partially covered with cardstock paper. Crazy enough, it just might work.

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Nytrunner

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That's looking really good. Have you tried some simulations with CG and best guess of CP to see how it does?
 

GlenP

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Many thanks! I haven't built a sim for this one, I do have Open Rocket and have some worked out some other multi-stage designs, but not exactly sure how to do a MIRV cluster-sustainer stage, maybe someone has already done that and there is one out there, I just have not looked. With this concept I have just made some minor tweaks to the existing Seattle Rocket Works design that I think should match or improve on the static margin. A C6-0 (~0.8 oz) should weigh a little less than 4 A10-0T engines (~1.0 oz), my single booster tube should weigh less than the original 4 booster tubes, so I have decreased the aft-most located weights of the booster. I added a boat-tail, which will increase some aft weight, but I also added some extra fin area aft of the original booster fin planform, you can see the seam in my balsa on the booster fins, the top portion is the original fin pattern. The sustainers should be roughly the same as the original design, I have not really changed them much with the cardstock nose cones. I was thinking about adding variable amounts of nose weight to each of the four sustainers to give each one a unique bias to their trajectory when they ignite. Once I cover the cone forms with cardstock I can sand them to match up a little better. The one part that is remaining is to add a dowel that protrudes up from the booster in between the sustainers, and to add staggered lugs to each of the sustainers to hold them together during the boost stage, borrowing from the Estes MIRV design.
 

Nytrunner

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My question wasn't clarified, sorry. I was honestly just thinking of the boost phase prior to separation. As far as I know, OR can't do a split sustainer. Or even the four parallel.tubes. (Unless you made a 0 thickness tube with four tube fins. Hmmmm).

Caution adding different nose weight. That could cause an off-center CG that will make an even more entertaining flight.

This design is really cool. Best success to you!
 

GlenP

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I understand, I think since the original total vehicle was a proven stable design, the changes that I am making will not detract from the stability, it may actually be overstable with the larger fins and tend to weathervane. I don't plan on adding too much off-center weight to the sustainers, it should be fine with those larger fins on the booster. I like how this kit-bash is turning out, should look cool when I get around to painting it.

Thanks! This is not really an original idea, but a combination of the designs from the Seattle Rocket Works and Estes MIRV kits, so you could say that the design of this kit-bash rocket is itself a Gryphon of MIRVs. :)
 

neil_w

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That is looking great. I've never seen one fly (either the Estes or any other variant) but they seem like a lot of fun.
 

Lowpuller

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I have an Estes MIRV, fun to fly works great, but you need all eyes watching to help you find the parts. It is also a pain to paint because some parts are made of styrofoam. It had to be painted with Liquatex.
 

soopirV

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I cloned the original MIRV gryphon several years ago, but stopped short of painting it when I realized that 13mm booster engines were no longer available. I heard more recently that Estes was (planning?) bringing back the A10-0T, but haven't started looking for them...may have to resurrect this!
 

GlenP

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I cloned the original MIRV gryphon several years ago, but stopped short of painting it when I realized that 13mm booster engines were no longer available. I heard more recently that Estes was (planning?) bringing back the A10-0T, but haven't started looking for them...may have to resurrect this!
I got some mini boosters here recently
https://www.acsupplyco.com/estes/engines.htm
I have a mini cardstock Groove Tube and Excalibur that I launch two stage with a Booster 5, downscale of the Booster 8
 

GlenP

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That is really cool, I like the box fins. With the three coupler tubes it looks like you have plenty of venting, when you pack four tubes together that space gets smaller, so I thought I needed to add some vents holes to the coupler tubes and the outer body tube, might be overkill. Using a Harry Potter theme, you could also call that one "Fluffy."
 

lcorinth

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I have seen the title of this thread for over a month; the light bulb finally turned on tonight. MIRV Gryphon. Ha!

On a related note: at our weekly rocket club metering tonight I came up with a cool name for a rocket - The Slauson Cutoff. You have to be of a certain age to get the joke on these names.
It took me about a year to notice the pun in the name "Cluster Duck."
 

BABAR

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Hmmm, like your idea of the nose cone pickle spear wedgies.
What if we used a polygonal diamond cross section body tune wth matching nose cone, box fins, we can fit the whole thing together. All combined would have hexagonal cross section f you go with 3' octagon if 4 sides?
This has potential!
 

GlenP

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Very cool,I can see you have put some thought into the MIRV concept.

After papering my nose cones it is starting to look like what I envisioned. I can do some sanding to fine tune the fit. I kind of like the faceted appearance, with a polygon shape also, it helps to hide the seam between the segments.

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GlenP

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Hmmm, like your idea of the nose cone pickle spear wedgies.
What if we used a polygonal diamond cross section body tune wth matching nose cone, box fins, we can fit the whole thing together. All combined would have hexagonal cross section f you go with 3' octagon if 4 sides?
This has potential!
Your Cerberus and Three Dog Night MIRVs are inspiring me and now you have me thinking of some more MIRVs ideas. You have created a monster...

MIRV means multiple independent Re-entry Vehicles, right? so why not make the interlocking sustainers look like re-entry vehicles? I am thinking of a variation on the venerable Centuri X-24 Bug, but stretched out lengthwise. You could modify the cross section so that 3 of them fit together. Maybe make them rear-eject and have them actually glide back...getting the balance for both boost and glide recovery might be a challenge. Not sure when I can get around to solving that one, but feel free to take the idea and run with it.
 

BABAR

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Yeah, I'm thinking I have one of my next projects starting to form up in my head.
Love to do gliders, just having a tough time figuring out how to get the CG far back on a two stage launch vehicle for stability, with wing/surface area fare enough forward to successful glide.
Gonna be interesting! Thanks for stimulating this line of thought.
Tom
 

GlenP

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I just built an Estes SkyDart II (from the recent estesrockets sale) and they use a through tube with weight on the front end that gets rear-ejected with the engine. So, why not make your c.g nose weight rear-eject, with both the booster and sustainers? Also, they have a trim flap that gets deployed by elastic for the glide when the engine tube ejects. You CAN haz c.g shift and glider trim!

The shape I am thinking of is more like an elongated Wave Rider/NASP than the stubby HighLifting body entry vehicles that inspired the X-24 Bug. They could be built in 3 tapered spears that fit together to make a larger cone shape, who says it has to be a straight tube on the outside? I need to sketch this out.
 

GlenP

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Final construction update: added a central dowel to the booster up through the middle of the sustainers, and lugs to the sustainers, staggered to hold them together. I now realize that I could have made th nose cone fit much more accurate if I did this first, inserted the couplers and then glued the nose cone tops into their couplers all in position, but the gaps here are fairly small and I still have some wiggle room with sanding. I just might remake nose cones for this one later.

Just need one more lug for the outside of the booster and then some primering, sanding, and finishing. Will try to make the SRW decals on my home ink jet with decal paper.
 
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BABAR

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I concur with the central dowel "launch rod" on the boosters to keep sustainers aligned (you can see the splayed look on the Cerberus, although surprisingly it worked"

What is the plan for recovery of the sustainer?
 

GlenP

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https://www.homedepot.com/p/Bird-B-Gone-Deterrent-Flash-Tape-MMFT050X/202347479
I will use this bird deterrent tape as a streamer, I might even be able to wrap some around the bottom of the dowel on the booster in the small space available. I used this on a three stage Excalibur 3 mod for the top sustainer and it really reflects the sunlight to help you find it on the ground if you lost sight of it in the air. Packing a chute into those BT-5s would be a challenge and probably drift too far.
 

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