Drogue Parachute Sizing

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Rocketclar

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I've done a fair bit of searching and talking about sizing drogue chutes for deployment at apogee and still haven't found a good estimator or 'rule of thumb.' I know for example that Rocketman has a drogue sizing chart. However, I've been told my drogues are either too large or others say too small on a particular flight. I've also been told that you want an 'inverted v' coming down and many of mine had this. While most of my >20 dual deployments have been successful, most of them have been deployed under 4000 ft for rockets varying from 6 to 50 lbs. I'm sure really high altitudes call for different characteristics. So, what do you all recommend for sizing drogues? Any simulation programs out there? Rules of thumb? Etc?
 

Onebadhawk

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Check out this sequence of shots..

https://onebadhawk.com/uploads/3/4/7/5/34752854/6160586_orig.jpg

And just in case that link doesn't work,, here's a link to the pic gallery that the pic comes from....

https://onebadhawk.com/mars-8222015.html

This is a flight of my scratch build "SteamPunk"...
Without a drogue the 2 falling sections of rocket flail around uncontrolled..
With a small drogue the 2 sections won't flail around like that..
The larger the drogue,, the more "closed" the "legs" of the inverted "V" are...
With too large of a drogue the 2 sections hang straight down from the oversized drogue,,
ensuring the nosecone will fire pointed straight down into the path of the rest of the falling rocket parts..
With the correct size drogue the nose will point out away from all of the other parts of the rocket..
If you'll go through the pics on my site you'll find other examples of this with my other rockets...

Teddy
 
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mpitfield

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I've done a fair bit of searching and talking about sizing drogue chutes for deployment at apogee and still haven't found a good estimator or 'rule of thumb.' I know for example that Rocketman has a drogue sizing chart. However, I've been told my drogues are either too large or others say too small on a particular flight. I've also been told that you want an 'inverted v' coming down and many of mine had this. While most of my >20 dual deployments have been successful, most of them have been deployed under 4000 ft for rockets varying from 6 to 50 lbs. I'm sure really high altitudes call for different characteristics. So, what do you all recommend for sizing drogues? Any simulation programs out there? Rules of thumb? Etc?
Keep in mind that not all chutes are created equally when it comes to size vs decent rates. My protocol has been to make an estimate based on simulation data, and experience at this stage, then do a couple of low and slow 3-4K flights and then follow them up with post flight analysis on the decent rates to ensure it is withing my targets.

This past URRF4 I sent my 3" Darkstar up on a Loki L1040 to 14K, it was 7419g (16+lbs) on the pad and I used a 15" Fruity Chute classic elliptical chute. After reviewing the on-board video I can see that in my packing hast I left a couple of pieces of tape on the drogue shroud lines, one right where the chute closes and one half way down. What was interesting was to watch the decent stability of the rocket with just the, now streamer, taped shut chute deployed.

To me it behaved much more like the on-board and ground based videos I have reviewed with a drogueless decent, and I have watched many in an effort to remain open on the ongoing drogueless vs. drogue debate. The decent was much more unstable with the harness getting all wrapped up.

The interesting part to me, which just reaffirmed my belief in a properly sized drogue is the best way to do this, was that after 50 seconds of decent, the tape on the drogue shroud lines let lose and the rocket immediately settled down and descended in a much more controlled inverted V manner.

Good luck in your sizing efforts.
 

DavidMcCann

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Drougeless is how I fly. Reviewing tons of my own and others photos and videos, it's effective at bringing rockets down fast and close...... but some pretty scary stuff happens. Impacts, cords wrapping up boosters, harnessing tying in knots, etc. I've never seen the dreaded booster flying into the main chute, but it's not impossible.

I should probably look into some drouges, but I do get a nice flat fall with most rockets. It's just ...exciting video some days.
 

markkoelsch

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Drougeless is how I fly. Reviewing tons of my own and others photos and videos, it's effective at bringing rockets down fast and close...... but some pretty scary stuff happens. Impacts, cords wrapping up boosters, harnessing tying in knots, etc. I've never seen the dreaded booster flying into the main chute, but it's not impossible.

I should probably look into some drouges, but I do get a nice flat fall with most rockets. It's just ...exciting video some days.
David, I used to fly that way until the upper airframe and nosecone managed to be facing the booster when the main fired. The rocket survived, but was horribly tangled. The rocket was a Wildman Junior- it now uses a 9" TFR as a drogue. Did my L3 a little over a month ago with a Wildman Extreme- used an 18" drogue- works beautifully.
 

Onebadhawk

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David, I used to fly that way until the upper airframe and nosecone managed to be facing the booster when the main fired. The rocket survived, but was horribly tangled. The rocket was a Wildman Junior- it now uses a 9" TFR as a drogue. Did my L3 a little over a month ago with a Wildman Extreme- used an 18" drogue- works beautifully.
Perfect Mark.....
What was the weight,,, either on the pad or at apogee ???

( I kinda get the feeling I should know the answer to this question,, lol... )

Teddy
 

cwbullet

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I fly all level 3 rockets with a drogue. Large level 2 rockets, I fly with a drogue.

I have never seen anything that sizes a drogue. My level 3 flight had an 18-foot parachute, and the drogue was 4 foot. It keeps the rocket facing correctly as the main deployed.
 

markkoelsch

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Perfect Mark.....
What was the weight,,, either on the pad or at apogee ???

( I kinda get the feeling I should know the answer to this question,, lol... )

Teddy
Teddy, my Extreme sans motor is 16.4 pounds. The 18" is a flare chute from Aerocon.
 

Bobfly

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This is a very interesting discussion. It's hard to believe that there isn't weight / sizing charts for drouge chutes. I have been using a 15" Fruity Chute as a drouge chute on 4" 16 pound rockets with good results. This size was found by trial and error.

Now I'm working on a 45 pound Level 3 project. It will use a 96" Fruity Chute for the main. I am looking for advice on the drouge Chute size. I am concerned that too small of a Chute might rip and become a streamer. The larger chutes use heavier shroud lines. Any advice?
 

markkoelsch

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This is a very interesting discussion. It's hard to believe that there isn't weight / sizing charts for drouge chutes. I have been using a 15" Fruity Chute as a drouge chute on 4" 16 pound rockets with good results. This size was found by trial and error.

Now I'm working on a 45 pound Level 3 project. It will use a 96" Fruity Chute for the main. I am looking for advice on the drouge Chute size. I am concerned that too small of a Chute might rip and become a streamer. The larger chutes use heavier shroud lines. Any advice?
A 24" B2 Skyangle Cert 3 drogue or equivalent. Not much larger
 

Bobfly

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Thanks Mark. Are the shroud lines on the Skyangle you recommend, and the general construction, heavier duty than you would see on a standard 24" Chute? I've seen others online were using 30" drouge chutes for these 45 pound Pikes. They didn't specify the Chute manufacture. I will be flying this up at Penn Yann. There are a lot of trees up there. A smaller 24 inch Chute should keep the rocket closer to the launch point if it can handle the weight.
 

Onebadhawk

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I use 2 chutes for drogues..
Don't forget that a drogue will be dragged through the air at around 90 fps or better ( we hope )...
Cato chutes are the most robust small chutes made..
I use them on most builds..
But if the build is big and heavy enough,,
( I always like big chutes for their presence in the air ),,
Top Flight makes their X form chute in an "Ultra"..
The Ultra X starts at 24" and goes up from there...
These are both really heavy, robust chutes.....
Perfect for drogues...

Teddy
 

markkoelsch

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Thanks Mark. Are the shroud lines on the Skyangle you recommend, and the general construction, heavier duty than you would see on a standard 24" Chute? I've seen others online were using 30" drouge chutes for these 45 pound Pikes. They didn't specify the Chute manufacture. I will be flying this up at Penn Yann. There are a lot of trees up there. A smaller 24 inch Chute should keep the rocket closer to the launch point if it can handle the weight.
The Skyangle cert 3 stuff is very sturdy. I would not hesitate there.

You could go with a Rocketman Pro XP or Ballistic Mach II chute. Good stuff too.

The Top Flight Ultra X or Crossfire chutes are good options too.
 

Bobfly

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Thanks Mark and Teddy. I'm going to order the Rocketman Ballistic Mach II Chute. It seems to be the strongest out of the lot. Rocketman has a drouge Chute weight vs descent speed chart. It has their three foot Chute descending at 80 feet per second and the twenty four inch Chute descending at 120 feet per second.

It it seems like one is a little too fast and the other a little slow. Maybe Rocketman will custom make a thirty inch Chute. Do you guys have recommended drouge descent speeds that you like to work with?
 

markkoelsch

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How high are you flying, and how much space do you have for recovery? I try to stay in the 100'/second. I have gone as low as 75 or so.

You could call Ky and ask.
 

Onebadhawk

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I can't get 100 fps...
I like the presence of big chutes in the air,,
on main I like very slow descents..
I also like to fly high..
I like as fast of a decent on drogue as I can get...
With the correct size drogue that's usually around 85 or 90 fps...

Teddy
 

Bobfly

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Hi Mark & Teddy,

In answer to Mark's question, I am only flying up to 6,300 feet on a Cesaroni M 2250. Future flights will be up to about 10,000 feet. Teddy was at last month's URRG Event. There were about 350 launches in three days. I was told 15 rockets landed in trees. One of them was mine.

Teddy may know how large the property is, I do not. The problem is that there are isolated clumps of trees throughout the property which are magnetic to rockets. The trees are up to 70 feet tall. The one tree climber that the club has would be busy for days. It took him 5 hours to get my rocket down.

Some people were flying drougeless to avoid the drift. I think this is too dangerous with 50pound rockets.
 

DavidMcCann

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Thanks Mark and Teddy. I'm going to order the Rocketman Ballistic Mach II Chute. It seems to be the strongest out of the lot. Rocketman has a drouge Chute weight vs descent speed chart. It has their three foot Chute descending at 80 feet per second and the twenty four inch Chute descending at 120 feet per second.

It it seems like one is a little too fast and the other a little slow. Maybe Rocketman will custom make a thirty inch Chute. Do you guys have recommended drouge descent speeds that you like to work with?
the trouble with those rates are they're based on weights. a rocket with fins, falling flat could fall slower...or the wind could trip it wrong and it could streamline back down even under chute. I've had rockets come back in so fast that looking at the GPS packets and altitude rates I thought I had one coming in ballistic....but was wrong.

Sadly, drogue sizing is more art than science....and I don't think there will ever be a "weight X go for Chute Y" formula.
 

DavidMcCann

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Teddy may know how large the property is, I do not. The problem is that there are isolated clumps of trees throughout the property which are magnetic to rockets. The trees are up to 70 feet tall. The one tree climber that the club has would be busy for days. It took him 5 hours to get my rocket down.
It's a decent sized field....but there are trees around. Most times, drifting helps keep you out of them....

 

mpitfield

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It's a decent sized field....but there are trees around. Most times, drifting helps keep you out of them....

Don't let Dave's god like recoveries fool you, this is what mine look like. This is my last flight of URRF4 on the Sunday. It was recovered 1.6 miles from the pad, sadly after spending 3 days hanging from the top of a really, really tall tree. This was using a 12" drogue on a 7.5lb rocket (net after burning 3lbs of propellant). Decent rates were all over the place from 105 to average 90ish f/s. My longest recovery from the same site was 3.46 miles, that is what happens when your main shear pins fail @ apogee.

 

Onebadhawk

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the trouble with those rates are they're based on weights. a rocket with fins, falling flat could fall slower...or the wind could trip it wrong and it could streamline back down even under chute. I've had rockets come back in so fast that looking at the GPS packets and altitude rates I thought I had one coming in ballistic....but was wrong.

Sadly, drogue sizing is more art than science....and I don't think there will ever be a "weight X go for Chute Y" formula.
Yes,,
+1 for sure..
But I still think most use too big of a drogue..
Just my humble opinion...
For about 26 lbs at apogee,, I find a 16" drogue is the perfect size..
I will add in though that the rocket has relatively large fins...

Teddy
 

markkoelsch

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the trouble with those rates are they're based on weights. a rocket with fins, falling flat could fall slower...or the wind could trip it wrong and it could streamline back down even under chute. I've had rockets come back in so fast that looking at the GPS packets and altitude rates I thought I had one coming in ballistic....but was wrong.

Sadly, drogue sizing is more art than science....and I don't think there will ever be a "weight X go for Chute Y" formula.
I do not disagree- it can be a bit of trial and error for sure.

I think Teddy is right too- most folks use too large a drogue- it is to stabilize the rocket as it falls- not to really slow it significantly.
 

Onebadhawk

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I do not disagree- it can be a bit of trial and error for sure.

I think Teddy is right too- most folks use too large a drogue- it is to stabilize the rocket as it falls- not to really slow it significantly.
+1 big..........

I'm looking for a fast decent on drogue...
I like to fly high....
I don't want the drogue to slow the decent,,,
I just want it to hold the nose cone pointed out away from the other falling parts
so it fires out of the way of everything else falling...

Teddy
 

Handeman

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I do not disagree- it can be a bit of trial and error for sure.

I think Teddy is right too- most folks use too large a drogue- it is to stabilize the rocket as it falls- not to really slow it significantly.
+1 big..........

I'm looking for a fast decent on drogue...
I like to fly high....
I don't want the drogue to slow the decent,,,
I just want it to hold the nose cone pointed out away from the other falling parts
so it fires out of the way of everything else falling...

Teddy
I agree with the idea of using the drogue to get the rocket down fast, but I don't think you will ever see a chart or list of drogue sizes that will work for many rockets. There might be a list for a specific rocket or two, but rockets are way too different, especially when apart and falling to every be able to put a list together for all rockets.

You might be able to put a weight, fin area, dia. and drogue size list together that might be a good starting point .

I really think you need to make several flights in the 3000- 4000 ft range with various size drogues to be able to zero in on what is the right size and performs the way you want.
 

markkoelsch

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I agree. There are a bunch of variables involved. A case in point would be my Wildman Extreme. It weighs 16.4 pounds sans motor. I can fly it on high thrust J motors through 75 mm M motors. What works really well as a drogue for the M motor might be a little large for a 54mm K motor. I have some data from the last flight on an M1297- hoping to fly it on a K motor later this month or in August to compare descent rates.
 

Nytrunner

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Yes,,
+1 for sure..
But I still think most use too big of a drogue..
Just my humble opinion...
For about 26 lbs at apogee,, I find a 16" drogue is the perfect size..
I will add in though that the rocket has relatively large fins...

Teddy
I agree with the idea of using the drogue to get the rocket down fast, but I don't think you will ever see a chart or list of drogue sizes that will work for many rockets. There might be a list for a specific rocket or two, but rockets are way too different, especially when apart and falling to every be able to put a list together for all rockets.

You might be able to put a weight, fin area, dia. and drogue size list together that might be a good starting point .

I really think you need to make several flights in the 3000- 4000 ft range with various size drogues to be able to zero in on what is the right size and performs the way you want.

The tumbling velocity of the booster seems to be a big factor in trying to hit that inverted-V sweet spot with the drogue.

I'm just happy if the vendor lists Effective Area and Drag Coefficient on their products. From there I can do some envelope calcs to pick one.
 

Maxitout

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Interesting conversation. I try to size my drogue based on my simulation results. I usually try for about 50-60 fps descent rate on the drogue, not only to bring it down a little quicker, but also to reduce the load on the main when it deploys. I also keep in mind that it's possible the rocket will land on drogue only.
On some of my smaller rockets, I'll use a streamer for the drogue to avoid drifting. That also helps to keep the parts from banging together.

Phil L.
 
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