Open Rocket and Jolly Logic Chute Release

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I'm a novice with Open Rocket and have been running simulations for some of my builds and using the Jolly Logic Chute Release. I set the parachute option to deploy at a specific attitude during descent in Open Rocket and get the simulation warning of recovery device deployment at high speed. Should I just ignore this warning or is there another way to simulate using the CR in Open Rocket?

Thanks
 
I'm a novice with Open Rocket and have been running simulations for some of my builds and using the Jolly Logic Chute Release. I set the parachute option to deploy at a specific attitude during descent in Open Rocket and get the simulation warning of recovery device deployment at high speed. Should I just ignore this warning or is there another way to simulate using the CR in Open Rocket?

Thanks

That warning is probably because your drogue/drogueless decent rate is over 75 fps, when the main opens.
 
Ok, so how do I simulate the reefed parachute acting as the drogue pending it's release by the JL chute release? I've never done dual deployment so I'm not sure how to simulate it in OR.
 
What you need to do (in both OR and Rocksim) is to simulate two-stage deployment.

Assuming you do NOT use a drogue at ejection:

1. At apogee, model a zero-weight drogue of some very small size (start with 8", increase until you correctly model your rocket's tumble rate) to simulate tumble descent rate
2. At Chute Release altitude, deploy your main.

If you go to https://www.jollylogic.com/chute-release-for-rocketry-ready-for-testing/ you can see the screens from Rocksim that show this being done.

If you don't know your rocket's tumble rate, you can guess that it's between 30 fps (light rocket, like Estes Pro Series II Leviathan) or 75-95 fps for a heavier one. I'd strongly encourage you to fly something like AltimeterThree or another recording altimeter so that you can see what this rate really is. Once you know, you can model it. Hopefully folks will post their tumble rates for various size/weight rockets to contribute to general knowledge.

Your rocket may fall FASTER with a drogue that without (totally depends on drogue and rocket, but a drogue will hold your rocket vertical during descent), but you can more predictably model it ahead of time by using the drogue size.
 
If you haven't already, set a small streamer at apogee or at the engine delay then set your chute at the desired altitude during descent. This may help Open Rocket not have a ballistic return until the parachute ejects.

However, sometimes OpenRocket has a problem modeling drogueless returns
 
Thanks for the suggestions. I've added a streamer or small parachute at ejection charge and it dropped the deployment speed but OR is still not liking the speed at parachute deployment. I guess I'll have to wait and see how it actually flies.

Thanks again.
 
If you've got the descent rate (on imaginary chute) in the range of 30 (light)-90(heavy) fps, I guess you can ignore the warning.

I'd appreciate if everyone would report any descents after ejection that look sketchy, such as rockets that come down seemingly ballistic or totally tangled up. Hopefully we could associate those with the type of rocket, the length of the shock cord, the timing of the ejection, the bundling of the parachute, the use of a drogue/streamer, etc.
 
Apogee did a newsletter on how figure descent rate on drogueless dual deployment, which is close to what this is. It's actually relatively simple in concept, and goes something like this:

Set up like dual deployment, but the 'drogue' parachute should have the same area as the surface area of the side of your rocket's BODY TUBE, without taking the area of the fins into account.

The actual math for the diameter of your phantom parachute is Diameter = Square root of (4 x L of rocket x D of rocket / 3.14). With a Leviathan, which has a body of 3" x 31.5", that's going to come out with a chute of 10.97" which you'd round to 11.

Staying with the Levi example, in your OR model you would install a phantom zero mass drogue chute right in with your main parachute that's 11", but set it to deploy at apogee, and set up your main 24" parachute to open at the Jolly Logic preset altitude.

Likely the initial fall rate you'll get in the sims is a little higher than you'll actually see in the real world, because it's not a perfect simulation, and you're not taking into account the surface area of the fins or the effect of the flapping main (acting, until released by the JL unit, like a streamer).

OR has a preset velocity at which it issues a 'warning'. In this case, be aware that your parachute construction and materials need to be BULLET PROOF, because you're going to be opening at a higher velocity than the chute was designed likely designed for (which was probably little to zero velocity at apogee). I see a LOT of folks learning that they're going to need to switch to top flite ultra light nylon parachutes for the larger/heavier LP/MP rockets to ensure safety and longevity of recovery equipment.

That'll get you as close as you're going to get in the sims, at least until the sims get more sophisticated.


****************************************************************************************************************************
EDIT: https://www.apogeerockets.com/education/downloads/Newsletter361.pdf
 
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Just a note... Apogee assumption only works if your sections individually are not stable on descent.
 
Thanks for the suggestions. I've added a streamer or small parachute at ejection charge and it dropped the deployment speed but OR is still not liking the speed at parachute deployment. I guess I'll have to wait and see how it actually flies.

Thanks again.

OR might not be "liking" the deployment speed of your streamer/small parachute(phantom drogue). Even though you are using motor ejection charge, try selecting "Deploys at: Apogee". Otherwise of course you will need to enter the optimum delay figure for each motor selection. Once OR likes your drogue deploy timing, then, like others have mentioned....probably nothing to worry about.
 
I use Rocksim and I just ignore the rate of descent completely. Once you deploy the thing in real life a few times, you know it works and the chute doesn't get stripped, so you go on to more worrisome problems, like remembering to bring sunscreen even in winter.
 
What you need to do (in both OR and Rocksim) is to simulate two-stage deployment.

Assuming you do NOT use a drogue at ejection:

1. At apogee, model a zero-weight drogue of some very small size (start with 8", increase until you correctly model your rocket's tumble rate) to simulate tumble descent rate
2. At Chute Release altitude, deploy your main.

If you go to https://www.jollylogic.com/chute-release-for-rocketry-ready-for-testing/ you can see the screens from Rocksim that show this being done.
Hi everyone,

I know how to simulate two-stage deployment in RockSim, but not in OpenRocket.

Could someone please explain that process to me.

Thank you.

Stanley
 
Hi everyone,

I know how to simulate two-stage deployment in RockSim, but not in OpenRocket.

Could someone please explain that process to me.

Thank you.

Stanley
1: add a small drogue to open at your primary ejection event; this represents the bundled laundry
2: add your main chute to open at your JLCR altitude; this represents the open laundry
 
Hi everyone,

I have now definitely decided to do a dual deployment using the Jolly Logic Chute Release, without a drogue parachute. So I am going to pick up a thread that I haven't touched in a few months, if I may do so.

I need to ask how to simulate this in both RockSim and OpenRocket.

I thought I knew how to do it in RockSim, but now I realize that I don't. In Post #4, John Beans provides a link to a dialogue box in RockSim with two different stages. But I don't see how to show the second line, where it says "Sustainer -- Parachute Drogue -- No event."

As for OpenRocket, in Post #14 dhbarr explains how to add a small drogue and how to add the main chute. I just don't know the steps to do that. Could someone please explain that.

Thank you so much.

Stanley
 
OK. I figured out the RockSim portion. I needed to add a drogue parachute to the configuration. Silly me.

But I am still confused about how to do this in OpenRocket,
 
If you haven't already, set a small streamer at apogee or at the engine delay then set your chute at the desired altitude during descent. This may help Open Rocket not have a ballistic return until the parachute ejects.

However, sometimes OpenRocket has a problem modeling drogueless returns
I do the same thing in Rocksim, a dummy streamer at apogee, big enough that the descent rate is under 75mph. What I want to know is the descent rate of the parachute from the sim, so I can determine what size to use. Unless you have gail force winds aloft, a parachute reefed with a JLCR will act like a drogueless deployment, with one caveat. If you have a REALLY heavy nose cone such that it descends faster than the airframe, the parachute will be coming down canopy top first. When the JCLR releases there is no wind for the parachute to catch. How do I know? SHR Mercury Redstone with a resin capsule. Weighs a ton, even drilled out a bunch. Broke off three fins (repaired :clapping:).For heavy nose cones, attach or streamer to the NC so it stays above the main.
 
OK. I figured out the RockSim portion. I needed to add a drogue parachute to the configuration. Silly me.
But I am still confused about how to do this in OpenRocket.

Identical approach.
Configure two events under <Recovery> tab:
1). Drogue deployment at apogee (you can define drogue to be a tiny 10" chute, or a streamer)
2). Main chute deployment at JL-configured altitude (e.g.: 300 ft).
1621833474624.png

I do the same thing in Rocksim, a dummy streamer at apogee, big enough that the descent rate is under 75mph. What I want to know is the descent rate of the parachute from the sim, so I can determine what size to use.

I've found that SIM-defined chute descent rates are a rough approximation. There are far too many chute canopy designs, weights, and shapes, and the only reliable way to simulate actual chute descent rates are:
1). Check with the chute manufacturers, and hopefully, they have descent rate vs. rocket weight charts. Use those.
2). After the inaugural flight, compare SIM-projected vs. altimeter recorded descent rates, and update the SIM variables to better reflect reality.

Unless you have gail force winds aloft, a parachute reefed with a JLCR will act like a drogueless deployment, with one caveat. If you have a REALLY heavy nose cone such that it descends faster than the airframe, the parachute will be coming down canopy top first. When the JCLR releases there is no wind for the parachute to catch.

Perhaps I'm not following something in your description. If the nose is heavier than the booster (rare, but possible), it will be the leading element in the descent daisy chain.
Still, the chute and JLCR should be attached to the shock cord in a way that allows that package to act as a mini-streamer. Thus, the JLCR-constricted chute canopy bundle should be fluttering adjacent to the rocket daisy chain, and attached to it only at the swivel, one end of which is connected to the shroud lines.

Consequently, the vertical sequence of items in the shock cord daisy chain should have no effect on chute's orientation.

YMMV,
a
 
IMG_2419.JPG These two rockets come screaming in nose first all the time; 4" Madcow Super Batray and Phoenix. They are not dual deploy.
Both use the Jolly Logic Chute Release.

IMG_8379.JPGIMG_8381.JPGIMG_8387.JPGIMG_8394.JPGIMG_8406.JPG

IMG_8391.JPG This photo sequence shows how I rig the chute and Release to handle their fast nose-first descent.

Been rigging it this way for a couple years. There were some earlier variations. But it took a good numbers of flights, and closely watching the descent, to figure out what worked best for these two rockets. No failures of the Release, and chutes always open.
 
Consequently, the vertical sequence of items in the shock cord daisy chain should have no effect on chute's orientation.
In my case it did. You are assuming. I have real world evidence.

One factor you are not considering is the speed with which it was descending. It was falling much faster than with a normal NC such that the there was no fluttering, it was moving, much faster than if it was under a drouge. When the JLCR popped the canopy was oriented down and was going too fast for the unwrapped bundle to flop around and catch air. Thump. After repair I put a 12" chute on the NC, perfect flight.
 
In my case it did. You are assuming. I have real world evidence.

One factor you are not considering is the speed with which it was descending. It was falling much faster than with a normal NC such that the there was no fluttering, it was moving, much faster than if it was under a drouge. When the JLCR popped the canopy was oriented down and was going too fast for the unwrapped bundle to flop around and catch air. Thump. After repair I put a 12" chute on the NC, perfect flight.
Those nose-first descents can be exhilarating and stressful at the same time. I have considered putting a small chute/drogue on the nose cone to slow things down, get the fins coming down first, and take stress off the chute when it opens.
 
In my case it did. You are assuming. I have real world evidence.

One factor you are not considering is the speed with which it was descending. It was falling much faster than with a normal NC such that the there was no fluttering, it was moving, much faster than if it was under a drouge. When the JLCR popped the canopy was oriented down and was going too fast for the unwrapped bundle to flop around and catch air. Thump. After repair I put a 12" chute on the NC, perfect flight.
There has to be more to your rigging, that we aren't understanding. Simply having the nose cone coming down first won't cause the parachute canopy to be upside down. You must also be doing something like wrapping the shock cord in the JLCR (along with the chute) to hold it upside down. Likewise, simply going too fast isn't enough to keep a chute from opening. So help us understand what else is going on.
 
This photo sequence shows how I rig the chute and Release to handle their fast nose-first descent.
1621877739199.png
Been rigging it this way for a couple years. There were some earlier variations. But it took a good numbers of flights, and closely watching the descent, to figure out what worked best for these two rockets. No failures of the Release, and chutes always open.

It looks like you are attaching the JLCR tether to the shock cord in a way that prevents it from acting as a streamer, and also transmits the aerodynamic loads of folded chutes air resistance through the tether.
I'm glad it works well for you, but this appears to be contrary to the JLCR tethering recommendations:
1621878098564.png
https://jollylogic.com/wp-content/uploads/2015/12/JollyLogicChuteReleaseWeb.pdf
If you are happy with what you've got, and it's working well, don't change a thing.
Alternatively, I attach the tether to one of chute shroud lines (in slides down to the swivel once chute opens), allowing the folded chute to separate from the shock cord and act as a mini-streamer. This way it is always oriented perfectly for opening, regardless of which airframe element is leading the descent, or if the entire stack is coming in horizontal (happens with one long rocket).

In my case it did. You are assuming. I have real world evidence.
One factor you are not considering is the speed with which it was descending. It was falling much faster than with a normal NC such that the there was no fluttering, it was moving, much faster than if it was under a drouge.

You are not the only one flying JLCR, and your experience is inconsistent with mine.
Perhaps there is something unique to how you attach and tether your JLCR?
The speed of descent should have no effect on chute opening. Period. If the airframe is falling way too fast, the chute may open and shred, but it will still open.

By following JLCR chute packing and tether attachment instructions, I can't visualize a situation that you match your error condition.

YMMV,
a
 
It looks like you are attaching the JLCR tether to the shock cord in a way that prevents it from acting as a streamer, and also transmits the aerodynamic loads of folded chutes air resistance through the tether.
I'm glad it works well for you, but this appears to be contrary to the JLCR tethering recommendations:
View attachment 465730
https://jollylogic.com/wp-content/uploads/2015/12/JollyLogicChuteReleaseWeb.pdf
If you are happy with what you've got, and it's working well, don't change a thing.
Alternatively, I attach the tether to one of chute shroud lines (in slides down to the swivel once chute opens), allowing the folded chute to separate from the shock cord and act as a mini-streamer. This way it is always oriented perfectly for opening, regardless of which airframe element is leading the descent, or if the entire stack is coming in horizontal (happens with one long rocket).



You are not the only one flying JLCR, and your experience is inconsistent with mine.
Perhaps there is something unique to how you attach and tether your JLCR?
The speed of descent should have no effect on chute opening. Period. If the airframe is falling way too fast, the chute may open and shred, but it will still open.

By following JLCR chute packing and tether attachment instructions, I can't visualize a situation that you match your error condition.

YMMV,
a

In a nose cone descent you don't want that chute and Release acting as a streamer. You're increasing the odds of the chute being pushed/pulled out from under the band, along with it getting knocked around pretty good. Learned from experimenting. You would think the open end of the booster would offer up some sizeable drag on a nose cone descent - but it doesn't. It takes a good number of launches and watching the descent performance to figure this out. But of course this is for my two rockets.

And how large do you think the aerodynamic load is from the bundled chute on that tether? Take a good look at it how it's all aligned. If you look in the photos you will see the tether is a Kevlar cord, not the Kevlar string. I changed it out a long time ago because you will wear out the string if you use the Release enough. Again - experience.

I prefer not to have my Release ride along with the chute when it opens in a nose cone descent. I can't quantify it, but there's a lot going on load wise when the chute opens. I would prefer to have my electronics clear and separated from that action.

The Chute Release is an excellent piece of electronics. Glad I have it. Recommendations are a good starting point, but flight experience and constant review of flight performance can be just as important.
 
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