Would this work - 2 stage rocket with booster having a rear ejection recovery system?

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rcode

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I was thinking a building a 2-stage rocket with Estes C6-0 motor lighting the core motor at the same time push a piston i.e. the motor mount assembly like a rear ejection system that would deploy a parachute. I would like to use another centering ring to keep the motor mount assemble from being able to separate from the booster so the complete booster in recovered as one unit. I was wondering if an Estes C6-0 motor had enough ejection force to push the piston, separate the booster from the core and light the core motor before attempting to build it. So, would it be a waste of time and material or a workable concept?2 stage plans.ork..jpg2 stage plan.jpg
 
Yes, it can be done.
https://www.rocketryforum.com/showthread.php?143132-Designs-I-m-proud-of

What I did was to have the forward part of the tube fixed and the aft part coupled into it. You need to vent the stuffer/motor mount to the outside in some way to avoid misfires from the stage detaching too early, but the exhaust from the second stage should be plenty to kick out the booster. When in doubt, make the centering rings looser. I wouldn't even include the middle CR- just run some Kevlar between the two halves.

Does that make some amount of sense?
 
Do-able yes. Reliable, so-so.
You are trying to get two thing out of the burn through of the sustainer propellant (there is no thin clay cap nor ejection charge in 0 delay booster black powder motor.) First and most important is igniting the upper stage. You want a quick separation once upper stage ignites, otherwise the upper motor plume will roast the forward end of the sustainer.

The second is deployment of your rear eject system. Before separation, there will be a TRANSIENT pressure buildup in the “chamber “ between the stages, first from the burn through of propellant from sustainer motor and then (if THAT pressure hasn’t already resulted in separation of stages) from the propellant of the newly lit sustainer. As soon as the stages separate, that pressure is vented out the forward end of sustainer.

If your rear ejection “piston” mechanism is really “loose” it will successfully get forced out the back. Emphasize REALLY loose.
In my experience with rear ejection mainly with boost gliders, the really “tight” part is the recovery system. Trying to pack a chute or streamer between the outer body tube and the motor mount I found really challenging, and resulted in considerable friction that sometimes prevented deployment (and remember that is with a “closed “ forward system with a bulkhead or nose cone upfront and using a standard non-0 engine with a cap and delay charge which I think produces more force than just a sustainer engine burn through). Your system by definition has a much shorter duration of pressurization (terminates abruptly with stage separation) and has what I think is a lower initial force of propellant burn through compared with ejection charge igniting and “blowing” through a clay cap. While sustainer will definitely generate a whole lot more force, sustainer ignition should be followed by almost immediate separation, so if normal will be quite transient and IF ABNORMALLY prolonged will barbecue the booster.

That said, try it and see how it works for you. Maybe add some sort of rubber band or elastic pusher system with burn through activation that actively shoves the central core out the back at separation?

Best of luck!

Tom
 
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