Drogue chute in main compartment

[Steven88]

Please see attached photo. I am thinking about attaching a drogue chute in the main compartment on my Big Nuke Loc 3E to help it deploy. I will have a 9’ Rocketman main chute. I am wondering how I go about attaching my drogue to the main chute? Do I attach it with a shock cord off the main and if so, how long of shock cord do I need coming off the loop on top of the main chute leading to the drogue? Also, how do I package all that into the rocket so it doesn’t get tangled? I suppose the drogue chute wouldn’t need a protective blanket around it since it will be on top of the main chute which is protected? Any help is appreciated. Thanks in advance

 

[Steven88]

Photo of main chute

 

[OverTheTop]

I suggest using a deployment bag. The drogue pulls the main out of the bag, or pulls the bag off the main. Until then everything is neat and tidy.

Make sure you size the deployment bag correctly for the airframe.

The way I usually fly is to have the drogue in the d-bag with the main, but just under the flap. Charges blow the bag out into the airstream where the flap lifts, exposing the drogue, which then pulls out the main. I suppose technically it is then really a pilot chute I think.

 

[Steven88]

And then where does the deployment bag end up? Just hanging from the shock cord like a protective blanket would? I’ve never used a d-bag before

 

[OverTheTop]

And then where does the deployment bag end up? Just hanging from the shock cord like a protective blanket would?

Yep. Just hanging off the harness somewhere, generally near the rocket for me.

 

[Steven88]

What size of a drogue do you recommend for my application, and should it have a spill hole in it?

 

[Steve Shannon]

And then where does the deployment bag end up? Just hanging from the shock cord like a protective blanket would? I’ve never used a d-bag before

Ideally the pilot chute and the d-bag come down completely separate, but that’s one more thing to find.

 

[Steven88]

Ok. Ya I’d like to keep it as simple as possible for now until I have a few more launches under my belt. But I want to have successful deployment too

 

[richP]

Not really understanding this. Your scenario would be best if using a deployment bag. In that case, a "pilot" chute helps pull the main out of a tightly packed bag. Otherwise, using a drogue attached to your main wouldn't really help, and could also cause tangles. In a traditional chute protector, the main would begin opening as soon as it is propelled into the airstream. Just make sure you get good separation when ground testing, and you will be fine.
As to your other question, ejection charge blow-by will singe your chute if it is not covered in the airframe; you can drop a few pieces of tissue in the airframe during ground tests to verify.
Also - That's an awfully big chute. What's the weight on your rocket?

 

[Steven88]

Ok. Thanks for the info. I’m just not really interested in a separate pilot chute that is separate from the rocket as it would be another thing I’d have to find after launch. I have a tracker on the rocket but the pilot chute could go anywhere and be hard to find since it would only be attached to the nose cone and not the rocket. Do most high altitude flyers use pilot chutes unattached from the rocket?

 

[Steve Shannon]

Ok. Thanks for the info. I’m just not really interested in a separate pilot chute that is separate from the rocket as it would be another thing I’d have to find after launch. I have a tracker on the rocket but the pilot chute could go anywhere and be hard to find since it would only be attached to the nose cone and not the rocket. Do most high altitude flyers use pilot chutes unattached from the rocket?

Most don’t use pilot chutes.

 

[afadeev]

Please see attached photo. I am thinking about attaching a drogue chute in the main compartment on my Big Nuke Loc 3E to help it deploy. I will have a 9’ Rocketman main chute. I am wondering how I go about attaching my drogue to the main chute?
[...]What size of a drogue do you recommend for my application, and should it have a spill hole in it?

What are you trying to accomplish with the smaller/drogue/pilot chute?
Are you sure you need it at all?
Single deploy or DD rocket (I assume the latter, but can't be certain)?

 

[Steven88]

It will be a DD with a main at 1000’. I was told that a drogue chute attached somehow to my 9’ RocketMan main chute or to the nose cone maybe? would help make sure that I got the main chute out and properly inflated. I’m just not sure how to go about putting two chutes into my main compartment successfully.

 

[richP]

It will be a DD with a main at 1000’. I was told that a drogue chute attached somehow to my 9’ RocketMan main chute or to the nose cone maybe? would help make sure that I got the main chute out and properly inflated. I’m just not sure how to go about putting two chutes into my main compartment successfully.

While it theoretically could provide a backup for the ejection charge not having enough umff to get the main out, I think that risk would be better mitigated with a dual-altimeter/ejection system. If it were me, I'd nix the pilot chute and thoroughly ground test the ejection.

 

[Steven88]

Yes thanks, I already did that the ground test and it spit the chute out several feet. Also, I do have a back up altimeter

 

[Steven88]

I think I’ll try your suggestion and keep it simple for now. Thanks!

QUOTE="richP, post: 2013606, member: 29591"]
While it theoretically could provide a backup for the ejection charge not having enough umff to get the main out, I think that risk would be better mitigated with a dual-altimeter/ejection system. If it were me, I'd nix the pilot chute and thoroughly ground test the ejection.
[/QUOTE]

 

[OverTheTop]

Ideally the pilot chute and the d-bag come down completely separate, but that’s one more thing to find.

I have never flown that way. D-bag is normally attached to the harness for me.

 

[Steve Shannon]

I have never flown that way. D-bag is normally attached to the harness for me.

Whatever works for you is great. There are many ways to skin a cat.

 

[Steven88]

I have never flown that way. D-bag is normally attached to the harness for me.

And then you use a small drogue attached to the harness to pull the d-bag off the main chute?

 

[OverTheTop]

As per my earlier post, the drogue is inside the D-bag, just under the flap. When the bag is blown into the airstream the drogue escapes from under the flap, catches the air and drags the main out of the bag. I attach the drogue to the main where the lines attach to the recovery harness.

 

[Speaknoevil]

As per my earlier post, the drogue is inside the D-bag, just under the flap. When the bag is blown into the airstream the drogue escapes from under the flap, catches the air and drags the main out of the bag. I attach the drogue to the main where the lines attach to the recovery harness.

The operation you describe is really not a drogue, it is a pilot chute. Your main will be deployed at high altitude if you are not using some sort of mechanism to retain the main, like a cable cutter or Defy Gravity tether.

 

[OverTheTop]

The operation you describe is really not a drogue, it is a pilot chute. Your main will be deployed at high altitude if you are not using some sort of mechanism to retain the main, like a cable cutter or Defy Gravity tether.

Both statements of fact. My earlier post even mentioned it was really a pilot chute.

I use single-ended dual deploy. I blow the nosecone off at apogee which is effectively the drogue deployment, but without a drogue typically. The main stays in the airframe till deployment altitude when it is blown out by charges.

 

[Speaknoevil]

Both statements of face. My earlier post even mentioned it was really a pilot chute.

I use single-ended dual deploy. I blow the nosecone off at apogee which is effectively the drogue deployment, but without a drogue typically. The main stays in the airframe till deployment altitude when it is blown out by charges.

So, just to understand, you don't have the drogue chute. Your first charge is sitting up by the nosecone so you can pop the nosecone off, yet in doing so you push the main down into the payload bay enough that the drag from the nosecone doesn't pull out the main/d-bag combination. Then your second charge is aft of the main/d-bag combination and it fires at a lower altitude to get the stuck main/d-bag combo out of the airframe?

BTW, I use single-ended dual deploy often, but have never done so successfully without main chute retention.

 

[OverTheTop]

So, just to understand, you don't have the drogue chute. Your first charge is sitting up by the nosecone so you can pop the nosecone off, yet in doing so you push the main down into the payload bay enough that the drag from the nosecone doesn't pull out the main/d-bag combination. Then your second charge is aft of the main/d-bag combination and it fires at a lower altitude to get the stuck main/d-bag combo out of the airframe?

Correct. The square of Nomex I use as a chute protector at the NC end provides enough drag, with the NC, to bring everything in flat normally. The main stays in the deployment bag in the airframe until requested.

 

[PatD]

Whatever works for you is great. There are many ways to skin a cat.

But they all anger the cat.

 

[Handeman]

I use standard DD. The payload separates from the booster at apogee and a drogue chute controls things as the rocket drops.

At the designated altitude, the main charge blows the nose cone off and that pulls the pilot chute out of the payload. The pilot, attached to the nose cone, is set to drop at about 13-15 ft/sec with the nose cone. The pilot pulls the d-bag with the main out of the payload and pull the d-bag off the main. The shroud lines are z folded under elastic on the d-bag so they pull out first, and stretch out before the d-bag comes off the main.

By the time that happens, the d-bag and shroud lines are well above the main rocket and the main opens into clean air. The main is designed to bring the rocket (-nose cone) down at 17-19 ft/sec. There is a 100 ft piece of 150 lb dacron line between the inside of the d-bag (attached to the pilot) and the top of the main chute. The difference in decent rates keeps the pilot and nose cone above the main, but the line keeps them together so I only have to find one thing not two.

The way the pilot lifts the d-bag while the shroud lines pull off first, it stretches everything nicely vertical before the main deploys. Because of the clean consistent deployments, I've lowered my main deploy from 1000 ft to 700 ft. The main is open by the time the booster get down to 600 ft.

 

[JimJarvis50]

The shroud lines are z folded under elastic on the d-bag so they pull out first, and stretch out before the d-bag comes off the main.

By the time that happens, the d-bag and shroud lines are well above the main rocket and the main opens into clean air.

I think this is a good way to employ a deployment bag. A concept that I think is important is to allow time for the d-bag to get above the other parts before the chute opens. Too many of the techniques that are used open the bag low. I also like the way you have the parts connected.

A few years ago, when I was developing my stabilization module, I had a lot of problems with deployment because the heavy top-end of the rocket (the stabilization module) tended to hang straight down under drogue. Upon deployement, the main would simply go straight up and tangle into the upper air frame. So, I developed something along the same lines as Handeman, but with a few differences so solve my particular issue. This technique works, and I now use it in all of my flights (heavy top-end or not). The technique is particularly well-suited to student rockets (SLI and SpacePort) with heavy payloads.

One pic below shows the overall configuration. The main thing is that the nose cone and pilot/bag/main are on different harnesses. The idea is for the cone to continue downward on its harness while the pilot/bag/main goes upward on its harness. Then, the pilot/bag/main can rise past the other parts of the rocket before the main opens. There is a piston (in green) because with this configuration, the cone doesn't serve as it normally would to pull out the chute. There is a picture of an L3 flight by David Abmayr where you can see how the cone has gone down while the pilot/bag/main has gone up and cleared the other parts before the main opens.

Also attached is a short video that shows the concept of how this works. You have to look closely at the video, but you can see the pilot chute rising before the main opens. There are some things I do to keep the twin lines from tangling and to keep the bag closed until I want it to open. However, it has proven to be a very reliable technique for me and others over dozens of flights.

Jim