Successful Launch and Staging Cerberus III

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BABAR

Builds Rockets for NASA
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Single booster to three sustainers (C6-0 to A10-3T)
Uses asymmetric diamond fins proven from prior design on the sustainers.

I know MicroMeister has something like this, 'cept I believe his was 3 booster motors to 3 sustainers.
Also seen this on the Estes MIRV and something called the MIRV Gryphon (Love the name!)

Hopefully first flight much later this morning (when sun comes up).IMG_2226.jpgIMG_2217.jpgIMG_2218.jpgIMG_2222.jpg
 

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Interesting....looking forward to more pics as you get done.
 
Successful launch and 1 to 3 gap staging. Despite the unconventional Tri-Headed appearance, had an arrow straight boost. Sustainers all ignited and deployed. Sustainers a little squirrelly (dropped length from 18 inches to 9 inches for the test model)

Fins on the sustainers are card stock. I think I will go with 1/32 balsa on next model. Will build better jig to keep that perfect 120 degree angle so the sustainers "mate" better when loaded on the booster. Will go back to 18" on the sustainer length.

Was pretty happy with the ducting of the ejection gas/particles to achieve 3/3 ignition on the sustainers. Now that I know the design works, I feel better about taking more "finishing" time, so next time the rocket(s) won't be nekkid.

Now that I've already built this, I have ordered the Estes MIRV to see how they do it. I know, mixed up the order. You know us Air Force guys, Teach One, Do One, See One.
 
Babar: have you got some more detail on the venting you used for the gap staging?
 
Not even sure if I did vent it. My experience with staging has been to put two regular hole punch size holes in the BOOSTER tube just below (caudal, aft, tailward) where the butt of the sustainer engine will be nested in the forward end of the booster TUBE. Rockets are used to one on each side just to balance it out to make sure that the puff going out one side doesn't veer the thing off course although I don't think it really matters.

Previous articles and at least one NAR very nice talk have shown that the booster engines do not emit particles but instead emit a plume of hot gas, and it is actually the radiant heat of the gas itself that ignites the upper stage engine. Therefore what you really need to do is make sure that this gas gets to and passes over nozzle of the upper stage engine it doesn't really go into it, but the photons/radiant heat do/does. Therefore if you place your vents just immediately below the butt end of the engine then that plume of gas will get up there before it starts to exit out the sides. The second function of the vents obviously is to act as a pressure relief to make sure that if you are gap staging and not taping the engines together that the upper stage doesn't blow off before it can ignite.

Using this technique the maximum I have successfully achieved in flight is a 36 inch gap stage. I have successfully gap staged up to 6 feet on a test stand but have yet to achieve that in-flight.

Aside from structural considerations or drag from the holes themselves I really don't think you can make the holes too big. The key again is not how big are the holes are it is where they are placed again it needs to guide the gas so it gets to expose the nozzle of the sustainer engine(s.)
 
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Not even sure if I did vent it...

Looks like the venting is through the open area between the sustainer couplers:

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No, look closely- there are holes in the tubes, going counterclockwise.

Dang! You are absolutely right. Good grief, I must be losing it, I built the thing and can't even remember it.

In any case, that would be my typical place for a vent hole, in the forward nesting tube(s) of the booster. Location would be just below (tailward) of where the sustainer engine(s) nest(s) within the booster tubes. I guess the correct term for that is the coupler section.

Thanks for reviving my memory!
 
By the way, for NON-minimum diameter standard staging, the rocket needs a vent hole in the coupler section, and another PATHWAY (not necessarily a HOLE) in the outer fuselage/body tube of the either the adjacent sustainer or IMO better the booster. This pathway does NOT have to be in the side of fuselage. Don't know how much drag a hole causes in the side of the rocket, but an alternative pathway is INTERNAL, punching some decent size holes in the centering rings to allow gases to vent out the back of the sustainer.
 
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