Single-sep dual deploy concept

[Jacob Jackson]

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.

 

[Voyager1]

Have you considered using a tether/release device such as the Tender Descender from Tinder Rocketry? You have both drogue and main in the same compartment behind the nosecone, but you hold the main in with the tether/release device. At the main altitude you release the main tether by firing the small charge in the device.

Tender Descender

 

[Hobie1dog]

to the forum

 

[David Schwantz]

That is almost how I deploy the main on the 12" V2. 4 6-32 shear pins hold the main in place after drogue deployment. Then a charge fires to deploy main out of NC. Only difference is a small 6" avbay is also discharged out of NC at the same time. It is kind of semi HED.

 

[cls]

Jolly Logic Chute Release

https://jollylogic.com/products/chuterelease/

 

[Jacob Jackson]

Have you considered using a tether/release device such as the Tender Descender from Tinder Rocketry? You have both drogue and main in the same compartment behind the nosecone, but you hold the main in with the tether/release device. At the main altitude you release the main tether by firing the small charge in the device.

Tender Descender

Sorta. I think Lumineer used a similar Tender descenders design to that but instead had the main bag flop around in the wind. My worry for a design like that is because you don’t have a physical bulkhead preventing the main from coming out early some of it will unravel from the high vibrations or shift around in a way that part if it to get into the wind stream and that could best case scenario lead to a little more drag on the way down and worst either an early main or a ripped main. It also costs a lot more. But maybe I am thinking about this wrong and that design doesn’t have any risk of an early main. I think the difference is that I am replacing the tender descenders with a BP charge, shear pins and a bulkhead. Thank you for the comment btw. Still very helpful

 

[jmasterj]

What about a chute cannon? That seems to fit pretty well with what you're describing. There were several good pictures I found via search here in the past.

 

[robopup]

That's very similar to how I do dual deploy, here and latest version here. In general, I've been quite pleased with the method - it packs tight and simple. I have failed to get my main out twice (charge gases leaked around sides of parachute), and the parachute was at the end of the recovery tube just flopping around on recovery. Very loose, but apparently not loose enough. Accordingly, I've moved to a piston to help push things out, shown in my second link.

 

[user 30299]

Have you considered using a tether/release device such as the Tender Descender from Tinder Rocketry? You have both drogue and main in the same compartment behind the nosecone, but you hold the main in with the tether/release device. At the main altitude you release the main tether by firing the small charge in the device.

Tender Descender

Here's a picture of the Tender Descender setup you describe :

 

[Jacob Jackson]

Ahh. That makes much more sense now. And I was totally wrong about a possible early deployment. Thank you!

 

[Art Upton]

Have you considered using a tether/release device such as the Tender Descender from Tinder Rocketry? You have both drogue and main in the same compartment behind the nosecone, but you hold the main in with the tether/release device. At the main altitude you release the main tether by firing the small charge in the device.

Tender Descender

That technique I used on my L3 with a device just called Tether.

 

[Cameron Tinder]

Ahh. That makes much more sense now. And I was totally wrong about a possible early deployment. Thank you!

The Tender Descender has been used to restrain the main(s) until the altimeter(s) determine it's time for the drogue to pull the main(s) out by releasing the tethered (Still inside the airframe) deployment bag(s) that contain(s) the main(s). The Tender Descender is a very good and very strong device that has largely been replaced by the TD-2. The TD-2, unlike any other tether and release device, does not have parts blowing apart to release, as do both the Tender Descenders and the old "Tether" from Defy Gravity.

Link to the TD-2: https://www.tinderrocketry.com/td-2

In addition, the device is completely sealed so that it cannot be set off at apogee because of flame from the ejection charge reaching the small pyro charge in the DG "Tether" and the Tender Descenders. At the same time, when the device is actuated, it does not eject a bunch of burning particles like the DG "Tether" and the Tender Descenders do.

And lastly, the TD-2 is considerably stronger than the original DG "Tether" and even the L2 Tender Descender when you consider the weak link is the quick link in the Tender Descender. Oh and not that it may matter to you for your application, but the TD-2 can still release with a VERY large load still attached. The TD-2 has been tested to release with about 1500# attached, the L2 Tender Descender was tested with about 500# and the DG "Tether" as I recall could release up to 100#.

FWIW, I am just finishing a new test vehicle (A rocket) that will be used to demonstrate a new and very simple method of dual deployment from a single compartment. I will be introducing this rocket along with the TD-1 and will be discussing, demonstrating and testing all of this in the coming days and weeks.

I will post all of this here under "Recovery".

 

[waltr]

I use a small Cable cutter to do the same thing the Descender in above diagrams do on the sustainer of a 2-stage.

 

[Cameron Tinder]

I use a small Cable cutter to do the same thing the Descender in above diagrams do on the sustainer of a 2-stage.

A line cutter is an excellent way to release a burrito wrapped parachute and is favored by many.