Deployment Bag Question - First Time User

[jhill9693]

Hi all, I'm planning to use a deployment bag for the first time, and I have a question about the deployment sequence.

Deployment plan:

1. Launch to apogee.
2. Deploy drogue at apogee.
3. Descend under drogue to 1,000 ft (orange - Sky Angle Cert-3 Drogue).
4. Deploy main at 1,000 ft (blue - Sky Angle Cert-3 L chute in a Sky Angle Cert-3 XL deployment bag). Shroud lines extend under gravity plus the reaction force of the downward-facing main ejection charge.
5. Main inflates, and the whole assembly remains connected together by a safety harness (green).
6. Main reorients to the top.

Based on what I've seen, this is nearly identical to SkyAngle's recommended "free bag" configuration, with the addition of a safety harness connecting the booster to the avionics bay (frames 5-6, green):

The FreeBag is designed to be attached directly to your nose cone and deployed separately. A separate chute in addition to the main (and a drogue, if used) will be necessary for the safe recovery of your nose and bag assembly independently of your main airframe. Deployment in this manner will virtually insure main chute inflation without entanglement. It also reduces main airframe recovery weight, allowing use of a smaller chute that normal. [NOTE: While the nose/bag combo can be secured to the airframe via shock cord, doing so may increase the likelihood of entanglement and/or possible failure to deploy the main chute. We do include a loop sewn inside the bag, however, for custom applications of this nature.]

Notes:

• The nose cone tip will contain 2.5 lbs of weight for stability. Total combined empty weight is 25 lbs.
• This safety harness (green) would be longer than the deployment bag, main shroud lines, and main canopy, fully extended, so that it does not prevent the main from fully deploying from the bag.
• The nose will be held on by 3x 2-56 shear pins, and the booster will be held on by 6x 2-56 shear pins.
• In case it isn't obvious in the above frames, the drogue is in the nose and the main deployment bag is in the booster. (Not enough room in the nose for the main.)

Scenario A: Inflation of the drogue produces a jerk against the booster, which is the heaviest part of the rocket, breaking the booster shear pins. The booster descends under gravity until the main fully deploys from the deployment bag near apogee. In this event, the safety harness would prevent potentially losing the booster (the avionics bay will have GPS tracking).

Scenario B: The booster shear pins hold at apogee, and the main deployment happens as planned at just below 1000 ft. In this event, the safety harness would provide no added benefit.

Scenario C: The booster shear pins hold at apogee, and the main deployment happens at just below 1000 ft, but the main chute rises into the nose cone tip or avionics bay, fouling the main chute. In this event, the safety harness may be a contributing factor by limiting the amount of travel that the booster can have from the drogue before the main fully inflates.

Potential Mitigations for C in order of preference:

1. Use a true "free bag" configuration and ditch the safety harness. Add a GPS unit to the booster in case of premature deployment.
2. Add a pilot chute larger than the drogue chute to the top of the main deployment bag, to encourage safe reorientation of the assembly while the main shroud lines descend.
3. In addition to (2), place both the drogue and the main in the booster compartment, and reef the main chute and pilot chute with the Tinder Rocketry Tender Descender.

Here's my question: which scenario do you think is most likely, and how much more likely do you think it would be than the other scenarios? If (C), which mitigation would be most likely to be effective?

I'm especially interested in feedback from people who have actually flown deployment bags. Thanks in advance!

 

[Art Upton]

The Freebag method #1 you post does work, but I did something different.

I first used the Sky Angle chutes and bag in my L3 build and tested it in Med K, Full K, Big L, and then the 98mm M motor in my Bruiser EXP 4. Then flew another big L, and later the infamous N.

I had the drogue pull on the Main's Chute at the top ring that was on my Cert 3 Sky Angle Chute. I had a device called a tether that kept the drogue line attached to a U-clamp at the top of the AV-bay.

When the charge released it, the drogue line pulled the chute out of the bag, and pulled all the shroud lines out of the loops in the bag.

The the drogue cord was long enough that it went over one side of the chute and the nose cone and drogue were off to one side.

This Forced the Drogue to pull the chute out, not rely on ejection charge to push the big heavy chute out of the 7.5" payload bay.

 

[tfish]

I've never flown a "true" deployment bag but...I'd switch the location of each of the chutes.. get the drogue attached to the 'fin can' and get it under control..spinning and flying around...those fins like to grab on to shock cords and twist them all up..

Tony

 

[Art Upton]

To answer your question, I 'Sorta' used #3 above, except the main and drogue were in the payload section, and the bag was attached and not come out to the AV bulkhead.

The booster was not shear pinned to the payload/AV-bay.

Sometimes it separated and sometimes it stayed together till the main deployed.
It came down faster when it stayed together.

I was fatter back then

 

[Art Upton]

Stay tuned, I found the picture of it coming down...Scanning

 

[Art Upton]

This was one of the 2 K tests at LDRS23. I had just found the two prints , take off and deploy just this past summer cleaning up a book shelf downstairs.

The bag is still in the Chute Cannon/Payload tube attached to a U bolt in the top bulk head. That is a nomex blanket between the nose and drogue

If I did it again, I might want to keep the booster and payload section together. On a small J motor a Jr. Bruiser booster got too light and flat spun on me once instead of coming down like in the picture. Think of a light Warlock with Bruiser shaped fins I put that Chute Cannon setup on once. [Since the EXP 4 version was gone by that time]

 

[rharshberger]

This was one of the 2 K tests at LDRS23. I had just found the two prints , take off and deploy just this past summer cleaning up a book shelf downstairs.

The bag is still in the Chute Cannon/Payload tube attached to a U bolt in the top bulk head. That is a nomex blanket between the nose and drogue

If I did it again, I might want to keep the booster and payload section together. On a small J motor a Jr. Bruiser booster got too light and flat spun on me once instead of coming down like in the picture. Think of a light Warlock with Bruiser shaped fins I put that Chute Cannon setup on once. [Since the EXP 4 version was gone by that time]

View attachment 671448

This is what I did on my L3 flight as well, a traditional drogue in the aft deployment bay, then the nose cone had a pilot chute attached to it and the top of the D-Bag with a long light shock cord (attached to the nose cone only NOT the D-bag) going back to the forward deployment bay main anchor point. The Main is also anchored to the main anchor point using a short shock cord long enough to get the shroud line connection point outside the airframe. Putting the main in the rear deployment bay as the OP is describing MIGHT allow the upper sections to fall onto the main as it deploys causing it to deflate, I always try and get my main out into open space with none of the rest of the rocket above it as it deploys.

 

[311stylie]

Watching this thread, I have several bags on hand but have not used them yet. I need to practice before my L3. Seems like there are so many different ways to configure it.

 

[rharshberger]

Wathing this thread, I have several bags on hand but have not used them yet. I need to practice before my L3. Seems like there are so many different ways to configure it.

There are indeed a number of ways they can be configured, there is even a thread about them somewhere here on TRF.

 

[cwbullet]

Hi all, I'm planning to use a deployment bag for the first time, and I have a question about the deployment sequence.

Each brand is slightly different.

 

[tfish]

@JimJarvis50 If you have some time...



https://www.rocketryforum.com/threads/drogue-chute-in-main-compartment.160139/post-2014204

Tony

 

[Handeman]

Since you can't fit the main in the payload tube above the av-bay, this may not be relevant.
I separate below the av-bay and use a drogue. When the main deploys, there is a pilot chute attached to the nose cone that pulls the d-bag out of the payload section. If you watch to the end, you will see the pilot and nose cone lifting above the main chute. There is about 100 ft. of 150 lbs. dacron attaching the inside of the d-bag to the top of the main. The pilot drops at a much slower rate then the main and the rest of the rocket so it stays above the main chute and can't tangle it. The dacron keeps everything together so they all land in the same place.

Here's the recovery part of a L motor flight. Ignore Kenny Allen, he couldn't figure out what motor it was until it was on the ground.

Towards the end you will see the pilot chute, nose cone, and d-bag following the main chute down.

 

[rharshberger]

Since you can't fit the main in the payload tube above the av-bay, this may not be relevant.
I separate below the av-bay and use a drogue. When the main deploys, there is a pilot chute attached to the nose cone that pulls the d-bag out of the payload section. If you watch to the end, you will see the pilot and nose cone lifting above the main chute. There is about 100 ft. of 150 lbs. dacron attaching the inside of the d-bag to the top of the main. The pilot drops at a much slower rate then the main and the rest of the rocket so it stays above the main chute and can't tangle it. The dacron keeps everything together so they all land in the same place.

Here's the recovery part of a L motor flight. Ignore Kenny Allen, he couldn't figure out what motor it was until it was on the ground.

Towards the end you will see the pilot chute, nose cone, and d-bag following the main chute down.

This is the same method I use...usually, though the Nuclear Sledgehammer used a true free bag setup for the main on its first flight and a Tinder TD-2 on its second flight.

 

[jhill9693]

I used phantom stage in OpenRocket to simulate separate descent rates of the nose/payload section separately from the booster:

• Add a phantom stage.
• Put the payload, nose cone, and drogue in the upper stage.
• Put everything else in the lower stage.
• Set the lower stage separation to Launch + [seconds]. Determine the appropriate value by plotting a simulation and taking the time-since-launch reading of when the altitude-based ejection event happens.
• To get the weights of each section, you can toggle on/off both stages alternately.

Here's what I found:

1. The nose+payload is heavier than realized and comes in at 10lbs, and the booster section comes in around 15-20lbs, factoring in the empty motor.
2. Using the freebag configuration, the SkyAngle Drogue chute alone will not provide a safe descent rate for the nose+payload section. If I use the freebag configuration, a pilot chute will be required. The Rocketman R4C or R6C (I have both) should be about right.
3. If I try to keep everything together, I would be at the upper limit of the safe operating weight of the Sky Angle CERT-3 L chute that I'm planning to use. But in the freebag configuration, the booster weight is very comfortably within the operating weight range for the CERT-3 L chute.
4. Using the freebag configuration with these modifications, both the payload section and the booster section will descend at approximately the same rate.

 

[rharshberger]

I used phantom stage in OpenRocket to simulate separate descent rates of the nose/payload section separately from the booster:

• Add a phantom stage.
• Put the payload, nose cone, and drogue in the upper stage.
• Put everything else in the lower stage.
• Set the lower stage separation to Launch + [seconds]. Determine the appropriate value by plotting a simulation and taking the time-since-launch reading of when the altitude-based ejection event happens.
• To get the weights of each section, you can toggle on/off both stages alternately.

Here's what I found:

1. The nose+payload is heavier than realized and comes in at 10lbs, and the booster section comes in around 15-20lbs, factoring in the empty motor.
2. Using the freebag configuration, the SkyAngle Drogue chute alone will not provide a safe descent rate for the nose+payload section. If I use the freebag configuration, a pilot chute will be required. The Rocketman R4C or R6C (I have both) should be about right.
3. If I try to keep everything together, I would be at the upper limit of the safe operating weight of the Sky Angle CERT-3 L chute that I'm planning to use. But in the freebag configuration, the booster weight is very comfortably within the operating weight range for the CERT-3 L chute.
4. Using the freebag configuration with these modifications, both the payload section and the booster section will descend at approximately the same rate.

View attachment 671611

It should work, and a true free bag setup is very reliable, watch out for shearing your pins in the booster section at apogee since its the heaviest part of the rocket and the stress will concentrate on the shear pins as the drogue opens.

 

[jhill9693]

Thanks @rharshberger, that was my original concern. I’ll start with lower altitude flights and observe what happens. If it becomes an issue, I can add shear pins or upgrade to 4-40s.

 

[Buster]

You may want to check my

“Deployment Bag Test”

Used the Sky Angle DB for my first successful Dual Deployment

 

[jhill9693]

You may want to check my

“Deployment Bag Test”

Used the Sky Angle DB for my first successful Dual Deployment

link please

 

[Buster]

We stand on the shoulders of Giants. I used mpitfeld “Demystifying Deployment Bags” for my setup and it worked well.

 

[Buster]

Search “Deployment Bag Test”

 

[jhill9693]

Search “Deployment Bag Test”

You mean this? https://www.rocketryforum.com/threads/deployment-bag-test.182234/

Thanks

 

[jhill9693]

We stand on the shoulders of Giants. I used mpitfeld “Demystifying Deployment Bags” for my setup and it worked well.

Thanks, link for reference: https://www.rocketryforum.com/threads/demystifying-deployment-bags.144212/

 

[Buster]

You mean this? https://www.rocketryforum.com/threads/deployment-bag-test.182234/

Thanks

Yes that’s the one

 

[troj]

Two important things to keep in mind when using a deployment bag....

1) There should always be something that actively pulls the bag off the chute. This isn't just inertia and hoping - the drogue as shown in the initial post along with a tether, the tethered approach Art suggested, or even a small pilot chute on top of the bag - these are all good. Relying on inertia is a bad idea. Yes, yes, there will be people who say "But it's always worked when I've done it!" Until it doesn't. You don't want to hope inertia works, you want a smaller chute to make it work.

2) A parachute should be placed in the bag in a neat and orderly fashion. Don't just shove it in.

There are old timers in the hobby who have nothing but bad things to say about deployment bags. This is often because of a failure to follow the two items above.

Everything about your recovery system deployment should be planned and organized, not just hoping stuff pops out.

-Kevin

 

[Art Upton]

2) A parachute should be placed in the bag in a neat and orderly fashion. Don't just shove it in.


-Kevin

I had actually watched teams of parachute packers at a small airfield we launched at once in lower Michigan off of Route 50.

They spent some time and double checks on packing a neat and orderly packing job. I remembered that when I got my Deployment bag for my L3 cert setup.

I did testing like at the NASA USLI safety checks. Remember us having the students pull the rocket apart slowly and making them watch the recovery harnesses and parachutes come out and work correctly, or fail or tangle.

Interestingly, you may remember Scott Miller the Hybrid guy from our JMRC gang. He flew a low wing plane he used for instruction to that launch field in Michigan.

 

[troj]

I had actually watched teams of parachute packers at a small airfield we launched at once in lower Michigan off of Route 50.

They spent some time and double checks on packing a neat and orderly packing job. I remembered that when I got my Deployment bag for my L3 cert setup.

I did testing like at the NASA USLI safety checks. Remember us having the students pull the rocket apart slowly and making them watch the recovery harnesses and parachutes come out and work correctly, or fail or tangle.

Interestingly, you may remember Scott Miller the Hybrid guy from our JMRC gang. He flew a low wing plane he used for instruction to that launch field in Michigan.

A lot of my parachute information comes from talking to riggers.

We still do that at SLI. I still spend a lot of time on the floor helping teams learn to properly pack parachutes.

-Kevin