Maximum Parachute Deployment Speed

What is the recommended maximum speed at which you want your parachute
to deploy?

I'm running some OpenRocket test simulations on a Dual-Deployment
design I'm looking to scratch-build and with using a 12" Drogue chute and
a 52" Main chute, I have the drogue deploying at apogee (1300/meters)
and the main chute deploying at 500/meters.

This arrangement is giving me a main chute speed deployment warning
of 22.7 m/s. As such, I'm wondering what is really the danger range, assuming
you have a normal rocket built from cardboard tubing and epoxy'd together?

Alby said:

This arrangement is giving me a main chute speed deployment warning
of 22.7 m/s. As such, I'm wondering what is really the danger range, assuming
you have a normal rocket built from cardboard tubing and epoxy'd together?

Click to expand...

Depends more on the chute than the rocket, I'd say.

I've done drogueless dual deploy around 80 fps (24 m/s) without any problems. I'd say 100 fps/30 m/s isn't a bad upper bound. Things like sliders and deployment bags may limit the speed of the chute opening and make higher speeds possible.

Sky divers in the old days used to deploy round parachutes at 176 feet per second. It just depends on how you deploy the chute and how your recovery harness is rigged. I will say that a tightly rolled chute will open slower especialy if the lines are rolled arround it. As was previously said deployment bags and sliders help and are much more profesional.

For the sake of argument it is POSSIBLE to build a recovery system that can survive a mach one deployment. It is possible but not neccesary, but with the right drogue and sequencing it can be done.

Cool... So with a quality parachute, you can get away with a higher speed.
Thanks.. I was eyeballing the SkyAngle Parachutes for this mission.. Hopefully
it can take the stress.

This chute:

https://www.rocketryforum.com/showthread.php?t=27000

deployed fine with 136 feet/second. No damage. Strangely it took awhile to inflate, though, about 4 seconds. It lost 500 feet in that amount of time. :eyepop: Good thing I set the main at 1200 feet.

Adrian A said:

This chute:

https://www.rocketryforum.com/showthread.php?t=27000

deployed fine with 136 feet/second. No damage. Strangely it took awhile to inflate, though, about 4 seconds. It lost 500 feet in that amount of time. :eyepop: Good thing I set the main at 1200 feet.

Click to expand...

That'll work..

Remember, a fast deployment, unless you control the parachute opening speed (and thus opening shock) puts a lot more load on the rest of the recovery system, as well as the airframe.

-Kevin

jazzviper1 said:

Sky divers in the old days used to deploy round parachutes at 176 feet per second. It just depends on how you deploy the chute and how your recovery harness is rigged. I will say that a tightly rolled chute will open slower especialy if the lines are rolled arround it. As was previously said deployment bags and sliders help and are much more profesional.

For the sake of argument it is POSSIBLE to build a recovery system that can survive a mach one deployment. It is possible but not neccesary, but with the right drogue and sequencing it can be done.

Click to expand...

I don't know if others will agree with me, but I think recovery deployment is one of the most challenging aspects of the hobby (consistent AP motor ignition seems to be a close second, at least for me). There are SO many opportunities to get it wrong.

Since you know way more about this than I do, how do you set up your recovery system? Any help would be appreciated.

Greg

GregGleason said:

I don't know if others will agree with me, but I think recovery deployment is one of the most challenging aspects of the hobbies (consistent AP motor ignition seems to be a close second, at least for me). There are SO many opportunities to get it wrong.

Since you know way more about this than I do, how do you set up your recovery system? Any help would be appreciated.

Greg

Click to expand...

I would agree, recovery is a seriously challenging aspect of rocketry.
There is no margin for error and failure is often catastrophic.

GregGleason said:

I don't know if others will agree with me, but I think recovery deployment is one of the most challenging aspects of the hobby (consistent AP motor ignition seems to be a close second, at least for me). There are SO many opportunities to get it wrong.

Since you know way more about this than I do, how do you set up your recovery system? Any help would be appreciated.

Greg

Click to expand...

I have not needed to use such a system, but if I did I would set it up the same way our high speed ejection seat systems work. Most specificaly the old Martin/Baker out of the F-4 Phantom. After the seat cleared the aircraft a small controller drouge 22" in dia. was fired in to the air stream (this could be well above MACH) It would pull out the stabilizer drogue 5' in dia. This would stabilize and decelerate the seat/man combo. At a pre selected altitude, or after a time delay if the ejection took place below the pre selected altitude, the drogue would be released and it would pull the main chute out of its container and this would seperate the man from the seat.
The only changes I would make would be in the drogue construction. The F-4 drogue chutes were made out of a highly porous cotton. I would make mine out of ribbon like most modern drogues. The delay between the time the controller is deployed to the time the stabilizer opens will allow some deceleration and being made of ribbon with lots of gaps it will not produce the rapid deceleration of a solid canopy. If I can ever afford to cert level 3 you can bet I will use this system. If its good enough for our air crew its good enough for our rockets.

While that system is good for people deploying at high speeds, it might not be the best for a rocket system. There is generally no one size fits all solution to recovery. I generally size my main parachute to produce a 10-15 fps descent rate. Then for a drogue (if I use dual deploy, 90% of the time I do single deploy) I use a simple circular parachute with six lines and 50% of the area cut out as a spill hole. That way it doesn't tangle and slows things down. I'll also use streamers and no-see-um net for a drogue.

Edward

AlphaHybrids said:

While that system is good for people deploying at high speeds, it might not be the best for a rocket system. There is generally no one size fits all solution to recovery. I generally size my main parachute to produce a 10-15 fps descent rate. Then for a drogue (if I use dual deploy, 90% of the time I do single deploy) I use a simple circular parachute with six lines and 50% of the area cut out as a spill hole. That way it doesn't tangle and slows things down. I'll also use streamers and no-see-um net for a drogue.

Edward

Click to expand...

Did you mean to say that if you use dual deploy, 90% of the time you go drogueless?

If I use dual deploy at all. I generally don't because GPS let's you find a rocket easily and I don't mind a walk.

I go drogue-less a lot though because you don't get the tangles. The times I don't are when the back end of the rocket is stable on it's own and can keep going in a ballistic path. My L3 was like this. Fin can with motor was 2.5" diameter and 72" long. It was definitely stable after separating them so I used a small drogue.

Edward

AlphaHybrids said:

While that system is good for people deploying at high speeds, it might not be the best for a rocket system. There is generally no one size fits all solution to recovery. I generally size my main parachute to produce a 10-15 fps descent rate. Then for a drogue (if I use dual deploy, 90% of the time I do single deploy) I use a simple circular parachute with six lines and 50% of the area cut out as a spill hole. That way it doesn't tangle and slows things down. I'll also use streamers and no-see-um net for a drogue.

Edward

Click to expand...

I agree there is no "one size fits all" but we are not talking about size. This system could be used on most rockets of 3 inches diamiter and up. The size of the chute is not what I was talking about. The canopy sizes could be "any size". What we are talking about is a system that can recover delicate cargo (human, rocket. ect.) from worst case scinarios.

Tangeling by the way is not related to the number of suspension lines. And cutting the large hole weakens the canopy. A ribbon canopy is very strong and lets lots of air flow through.

Repeat reliability is what I am trying to show here, and is a system is reliable enough for people then it should be reliable enough for rockets.

I have been a parachute rigger for 26 years and a rocketeer for over 30. I have worked with, repaired, repacked and designed many parachute systems.
I just want to share my knowledge and experiance with the rest of the rocket comunity.
People should not have to accept recovery system failures as "part of the hobby".

@ Mike J:

Pardon my ignorance, but could you explain what, exactly, a ribbon canopy is? I'm still relatively new to the hobby and find the discussion enlightening.

spiff95 said:

@ Mike J:

Pardon my ignorance, but could you explain what, exactly, a ribbon canopy is? I'm still relatively new to the hobby and find the discussion enlightening.

Click to expand...

Go to p. 32 of the link below:

https://www.mrc.uidaho.edu/~atkinson/IPPW-3/Parachute%20Course%20Material/02%20Definitions%20Nomenclature%20and%20Types%20Lingard.pdf

Greg

Thanks Greg!

Alby said:

Cool... So with a quality parachute, you can get away with a higher speed.
Thanks.. I was eyeballing the SkyAngle Parachutes for this mission.. Hopefully
it can take the stress.

Click to expand...

My data from most recent flight with a Skyangle X large was: 70lb 6in diam rocket

55lbs after fuel is burned, descent from apogee with a 24in Cert 3 drogue was 85 -110 ft/sec. until main opened.

The difference between 85 and 110 due to fincan stabilizing and "floating'' on & off during the drop.

As a retired skydiver I can tell you that a staged (reefed) deployment of any recovery system is the key to the proper operation and survival of said system.