Bigger chute, dual chute?

I've used two chutes before but not on HPR. It seems that they'll inflate but touch each other so neither are flat and presenting the maximum area. If one chute is below the other the upper one will definitely be less effective because it'll be travelling in turbulent air. As you say, the masses may act so the shock cord collapses one side of the lower chute too.

I think I'd try using two chutes attached at the same place but with maybe 3m of line to each from a single attachment point on the shock cord so they'll both be flatter to the incoming air. Failing that, have you considered bring the main body and the nosecone down separately? That has worked very well for us on the large vehicles.

Chris

Fold them together and they will deploy together side-by-side.

I have three 72' chutes on one of my birds. I have 10 feet of shock cord on each cord and they are all connected to the same point. I then have 30 feet of cord going to the rocket. They come down about 10 feet from each other.

-- Drake "Doc" Damerau

NEPRA President NAR Section 614 NAR 79986 L3 Remove "My Shorts" to reply

Chris suggested similar. I think I'll try that.

Thanks.

What are you recovering? A full scale Apollo capsule?

:-)

Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD" >>> To reply, remove the TRABoD!

I would have guessed a stress-strain testing machine to test materials at high altitude. ;)

Darren I've always been told that an odd number works better than an even number, for chutes. Doc's suggestion for three sounds perfect. I've seen numerous recoverys using three chutes and all have worked well. If I were going to try multiple chutes.....I'd use a setup like Doc suggests. Now all you need is a third chute:-)!

Lloyd Wood BRS Secretary LDRS LD/RSO Level lll

LOL :-) I Have them in my Prometheus.

Her is a pic of of it on the pad at a NEPRA launch.

Here is a pic looking up my nose as I wire the central K550 SU and the 4 air started J330's

-- Drake "Doc" Damerau

NEPRA President NAR Section 614 NAR 79986 L3 Remove "My Shorts" to reply

Hmmm, high alt testing sounds interesting. I would need bigger chutes though, My lightest force testing machine weighs around 3 tons.

I think I'll just leave it in the lab. ;-)

-- Drake "Doc" Damerau

NEPRA President NAR Section 614 NAR 79986 L3 Remove "My Shorts" to reply

...But don't forget to use 3 smaller chutes. Go to Info-Central on ROL and use the chute calculator there. It allows you to see the decent rate using multiple chutes.

-- Drake "Doc" Damerau

NEPRA President NAR Section 614 NAR 79986 L3 Remove "My Shorts" to reply

Here's a pic of one of my Little Joe-II models that used three chutes. Two are directly side by side:

Now, ideally I would have preferred to have those two (red) chutes using separate shock cords but the two shock cords still would have been attached at the very same point they were in that photo, where the chute shroud lines were directly attached. So it would have been like an "X" sort of arrangement - the upper two arms being the shock cords for the chute, the lower left line to the nose cone, and the lower right to the main body. The long shock cords would make the chutes operate somewhat better, with less air spillage.

Now on that Little Joe, the nose cone has a small chute for a reason. It's a "Semi-Drogue" arrangement. So if the nose comes off at all, it takes the tightly packed small chute with it, then that chute deploys, and can help to yank out the main chute (or chutes) inside the main body (The main is packed so it can slide out of the tube when pulled by he shock cord). I normally would only use two chutes that way, a small drogue, and then one large main, but that model wasn't practical to pack a big single main so I used the two somewhat smaller chutes for the main.

Anyway, GOOD CALL on not using totally separate recovery for the nose and main body. I started using the semi-drogue method due to a certain model with separate recovery systems coming down with the nose having a deployed chute and the main body streaming into the ground with no deployed chute (often the main was stuck inside the main body). Saw that more than once. The semi-drogue method has never failed since I switched to it over 20 years ago.

- George Gassaway

I have a third chute, but they're all 34" :-(

When seeing three chutes used, did you happen to see how they were packed? All together, as Jerry suggested, or separately?

Cheers

I usually use RockSim, but thanks for the tip.

Actually using three 34" chutes isn't that far from the mark according to that calculator. Descent rate of 13.5'/s.

Cheers

Remember my delivery to your lab? Remember seeing big firings on my site? Those were the SMALL ONES. Let's rock! :)

Jerry

Nice picture. As you say, it looks like the chutes wouldn't spill as much if attached to a common point via individual straps.

Three 72 foot chutes ought to handle 3 tons easy.... :-)

"Doc"

Doh!

72' means 72 inches, but only if your working on a Mars rover program. ;-)

I swear I didn't do any work on the Beagle 2!

-- Drake "Doc" Damerau

NEPRA President NAR Section 614 NAR 79986 L3 Remove "My Shorts" to reply

Remember? They brought it to me on a fork truck!

-- Drake "Doc" Damerau

NEPRA President NAR Section 614 NAR 79986 L3 Remove "My Shorts" to reply

Maybe that is the problem. :)