Cable Cutter Dual Deploy using Drogue to Pull Out Main for LOC 3.90 V2

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WoShuGui

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The Archetype cable cutter with a small drogue on the shock cord to keep the nose cone above the booster during descent has worked great for my LOC 3.90 V2 with nose cone AV bay with one exception... the main deployment times are long. In two flights, it took 8 and 15 seconds for the burrito to open. This is the setup at apogee drogue deployment.

View attachment 156741

In the flight with the 15 s deployment, the main opened at 100 feet. Better late than never, but :y: !

View attachment 156744

This is a known issue with this type of recovery because it takes time for the burrito (bundle holding the main chute) to catch air and unfold after the cable is cut. Using a drogue on the shock cord likely makes this worse by slowing the descent.

Some good feedback from other forum members led me to the conclusion that some means of attaching the drogue to help open the bundle was needed for this recovery system to be reliable. First 8 seconds, then 15 seconds means the deployment time is not predictable. Sooner or later, the main chute is not going to open on time.
 
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The problem is managing to do that without overloading the burrito and having it open at apogee.
 
The problem is how to attach a drogue to help deployment while keeping the burrito intact during descent before the cable is cut.

This is the solution I came up with. The drogue is attached to the top of the main. A small piece of closed cell foam (3/4" - 1" diameter) is threaded through the drogue cord, tied in with a butterfly knot above the main and covered with duct tape. This foam ball is wrapped inside the burrito just BELOW the cable. The drogue cord exits at the top of the bundle such that it pulls against the foam ball that is wedged inside against the cable tie. Mechanically this is pretty strong and it does not add a whole lot of dynamic stress to the bundle during the typically violent descent. Once the cable is cut, the foam ball is released and the drogue pulls out the main.
View attachment 156746View attachment 156747View attachment 156748

This setup preserves a nice feature whereby the shock cord is connected to the nose cone and does not transfer separation force to the bundle. To protect the drogue and have it deploy cleanly at apogee, it is wrapped in a nomex blanket tied into the shock cord. This must be a loose wrap so no appreciable shock cord force pulls on the drogue.
 
Gotta love the straight man... thanks CarVac! Who do I make the check out to?:cool:

???

I am seriously interested in this, but the issue is it grows more challenging as the burrito gets larger and the load from the drogue gets stronger.

I think the issues that I had (without a drogue) may have been caused by an undersized chute protector relative to parachute size.

I have to note to myself: cable cutters may make adding dual-deploy easy, but they don't necessarily make it much more compact.
 
Sorry, your 1st response posted before I had uploaded the foam ball pics... thought it was kinda funny how that worked out.

I think the issues that I had (without a drogue) may have been caused by an undersized chute protector relative to parachute size.
Good point. An alternative way to mitigate slow main deployment is to reduce protector size, but then this trade-off.

I am seriously interested in this, but the issue is it grows more challenging as the burrito gets larger and the load from the drogue gets stronger.

I have to note to myself: cable cutters may make adding dual-deploy easy, but they don't necessarily make it much more compact.
Yes, I am in agreement. Cable cutters seem to fill a niche for smaller slower rockets like the LOC 3.90 V2 that don't really have the room for a descender. I think the size and speed ranges for descenders and cable cutters overlap somewhat, but at some point trying to make the cable cutter work may be counter productive.
 
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I'm not so sure the cutters are a niche, and would work in any instance no matter the size. The zip ties can be doubled up to get around a bigger chute.



TA
 
I'm not so sure the cutters are a niche, and would work in any instance no matter the size. The zip ties can be doubled up to get around a bigger chute.



TA

The forces grow larger the bigger the chute; eventually you'd have to upscale the cable ties and cable cutters in order to keep things under control.
 
The forces grow larger the bigger the chute; eventually you'd have to upscale the cable ties and cable cutters in order to keep things under control.
Was thinking the same thing. A minimum cable size needed for a given chute size. It got me thinking though, with a stopper above and below the cable tie; one below to the drogue and a second one above to the nose cone anchor why not increase the effective strength of the cable tie with multiple wraps?
 
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Was thinking the same thing. A minimum cable size needed for a given chute size. It got me thinking though, with a stopper above and below the cable tie; one below to the drogue and a second one above to the nose cone anchor why not increase the effective strength of the cable tie with multiple wraps?

Then you need two cable cutters--and the chance of failure is doubled unless you use two redundant pairs.

Edit: I see what you mean now.
 
This is similar to the method I use except my main is fully contained in the coupler between the payload bay and booster, the drogue polls the deployment bag out when the cutter goes off.
I will try to post pic of the system later.
 
WoShuGui:

I am building dual deploy in nosecone of Mega der Red Max!
I bought cable cutter as well.

How has your drogue pulling setup been working???
Thanks!
Jeff
 
Mixed results arringtj, but it has worked well as long as I pay attention to the details. A couple lessons learned.

1) Use a large enough drogue to pull out the main. I tried to go a little smaller once and the main stayed inside the bundle after the cable was cut.
View attachment 260937

2) It is very important to clip the nomex securely into the nose cone quick link as shown is post #3. You may even want to reinforce the button hole. This will keep the bundle from pulling away and stretching out the cable cutter wires. I did not do this once and a late apogee deploy broke the wires.
View attachment 260938View attachment 260939
 
I use this method on my 3" PML bullpup.

I used Archetype cable cutter to hold a Fruity Chute DP closed with the main packed in the DP including the shroud lines and harness. The bundle is kept within a few inches of the nosecone/alt bay, with the of the e-match coiled up, using a thick sharpie, to allow for about an additional 6" slack. The drogue/pilot (12" Fruity Chute Elliptical) is connected to the cable cutter and the top loop of the DP, on a 5' small harness. The 36" Fruity Chute Iris is connected to the DP via it's top loop and the harness that is built into the DP.

I have had mixed results and I believe worked out most of the issues, more launches are required for me to stand behind so I will have a better idea at the end end of the season. The issues I have had have all been with the DP, where I tried different modifications. I also sourced and used the highest rated cable tie I could find which fit into the cable cutter, and tested it. I am not sure if the standard ones have the same rating but I wanted to make sure I did not have a failure of the cable cutter tie strap, due to the additional load, and I haven't...yet!
 
Ouch. Sorry to see the rocket laying there with the burrito still intact. It has happened to me several times, and it is a sickening feeling!

The Cable Cutter, burrito, Tether Descender method - whatever you call it - is very clever, but surprisingly complex. There are lots of connections and loads to worry about, and some of your electronics are flapping in the breeze. I have about 50% success rate with this set up, whereas traditional two-tube DD is 97% for me.
 
I like the idea of cable cutters and tender descenders and the like, but they do not seem to be as reliable as a more traditional dual-deployment setup. I'd definitely consider a system that's easy to retrofit into existing rockets that uses one of these strategies, but I'd need to be sure it would work as intended.


Later!

--Coop
 
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