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- Jul 23, 2023
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I was looking into different dual-deploy concepts and am wondering if anyone has thoughts. I noticed on single-sep dual deploy concepts (the avionics stay in the same airframe/ only one separation event) that I haven't seen anyone keep their main parachute inside the rocket after drogue deploy. Why not keep the main inside and use a second ejection charge to get the main out and have the apogee ejection charge vertically above the main parachute?
The essential design I guess I am proposing is to have drogue deployment at apogee with an ejection charge on top of the Main parachute. The main parachute would be protected by a thin CF or metal bulkhead. Drilled above the bulkhead (not into the bulkhead) are shear pins to make sure you do have an early deployment due to drag on the line connecting the main to the nosecone/drogue line. The nosecone/drogue line would connect to the airframe and main chute where the line to the main chute would be longer so no load goes through it. The drogue/nosecone line would be tied to a small bolt or ring at the top of the airframe which would then be tied to the bulkhead or bolt connected to the motor so that the load of the drogue and nosecone line could be transferred radially down the side airframe as to not mess with the main parachute still in the center airframe. Main deployment would then be as simple as firing an ejection charge at the bottom of the airframe to force the protecting bulkhead to brake the shear pins and deploy the main parachute. (realizing now it's a lot more complicated out loud than in my head.) This would be compared to a Lummineer style single sep dual deploy using tether defenders or a similar design using a jolly logic chute release.
Cons: The component that holds the drogue/nosecone line radially against the airframe is likely not going to be able to withstand large forces or non-nominal situations so the drogue would have to be small, just enough to point the booster up for main deployment (in my opinion this is not really an issue as drogue-less dual deploy recovery is decently-ish common) (the whole epoxy something to the side of the airframe for feed a line radially down is a technique I haven't seen anywhere else and is kinda sketchy)
Pros: Tether descenders are riskier and harder than a simple ejection charge and your main could easily come loose (both are solved for the most part by a jolly logic chute release) as compared to other single sep dual deploy systems. If your drogue parachute rips or the ejection charges fail at apogee the main can still be deployed (rip Lumineer). It's theoretically cheaper and possibly lighter than normal single sep dual-deploy concepts. Multiple radial bolts/rings at the top of the airframe could also be directly tied through the same method as the nosecone/drogue line to secure the motor to the airframe without the need for epoxying anything in.
PLEASE share all of your thoughts. I am looking into using a design along these lines for my L3 next year.
The essential design I guess I am proposing is to have drogue deployment at apogee with an ejection charge on top of the Main parachute. The main parachute would be protected by a thin CF or metal bulkhead. Drilled above the bulkhead (not into the bulkhead) are shear pins to make sure you do have an early deployment due to drag on the line connecting the main to the nosecone/drogue line. The nosecone/drogue line would connect to the airframe and main chute where the line to the main chute would be longer so no load goes through it. The drogue/nosecone line would be tied to a small bolt or ring at the top of the airframe which would then be tied to the bulkhead or bolt connected to the motor so that the load of the drogue and nosecone line could be transferred radially down the side airframe as to not mess with the main parachute still in the center airframe. Main deployment would then be as simple as firing an ejection charge at the bottom of the airframe to force the protecting bulkhead to brake the shear pins and deploy the main parachute. (realizing now it's a lot more complicated out loud than in my head.) This would be compared to a Lummineer style single sep dual deploy using tether defenders or a similar design using a jolly logic chute release.
Cons: The component that holds the drogue/nosecone line radially against the airframe is likely not going to be able to withstand large forces or non-nominal situations so the drogue would have to be small, just enough to point the booster up for main deployment (in my opinion this is not really an issue as drogue-less dual deploy recovery is decently-ish common) (the whole epoxy something to the side of the airframe for feed a line radially down is a technique I haven't seen anywhere else and is kinda sketchy)
Pros: Tether descenders are riskier and harder than a simple ejection charge and your main could easily come loose (both are solved for the most part by a jolly logic chute release) as compared to other single sep dual deploy systems. If your drogue parachute rips or the ejection charges fail at apogee the main can still be deployed (rip Lumineer). It's theoretically cheaper and possibly lighter than normal single sep dual-deploy concepts. Multiple radial bolts/rings at the top of the airframe could also be directly tied through the same method as the nosecone/drogue line to secure the motor to the airframe without the need for epoxying anything in.
PLEASE share all of your thoughts. I am looking into using a design along these lines for my L3 next year.