X-type Drag Coefficient?

Any one know what the drag coefficient of an X-type parachute? I thought I read once that it was .9, but that seems kind of high to me.


TA

it is approx 0.64 (or about 80% of a ordinary chute) hth.
rex

Thanks.

TA

I am resurrecting this topic because I came across actual test data for X-type chutes. In 1971 the Naval Ordinance Lab. conducted drag tests on several X-Type parachute configurations - Report Link.

The report shows that the answer to the OP's question is not straightforward. An X-Type chute's Cd is a function of several factors (1) Arm length-width ratio; (2) Shroud line length to chute diameter ratio; (3) Material permeability; (4) # of shroud lines, (5) Deployment velocity...

The report generally finds the Cd for the X-Type chute configurations tested falls into the range of 0.54 to 0.75 where deployment velocities exceed 40 FPS. Below that speed, the Cd increases sharply - approaching 1.0, and slightly higher (Fig 44). Also know that low cloth permeability contributes to canopy rotational instability.

Another link was found where the REXUS project performed X-Type chute testing and found their chute design (no specs provided) provided a 0.9 Cd - the chute deployment velocity was below 40 FPS.

As such, the Cd could be as high as 0.9 if the deployment velocity is below 40 FPS....

Feel free to add your thoughts or addition test data results... :smile:

Anybody seen a rotafoil x-type? Seems with non-parallel shroud edges a spin could be induced without spillholes, possibly alleviating some of the instability. RotaX?

Our XT chutes have a CD of .98

crossfire said:

Our XT chutes have a CD of .98

Click to expand...

I have two of these chutes and I'm curious how that value was obtained - performance testing or calculation? I ask because the Naval testing suggests that high a Cd was only seen with deployment velocities below 40 FPS.

The CD tests for all our chutes were tested by a guy who worked at the Space Shuttle assembly building. He run tests when the Shuttle was out of the building. So it performance testing I guess.

The measured Cd highly depends on the surface you count. For example Skyangle counts only the top of the canopy, so the Cd is huge.

Btw why don't you have the Cd values on the homepage, I always though skyangle was the only company who have measured them.

You are right we should put them on the home page. Up until 5-6 years year's ago no one ever asked for the CDs. I guess its because a lot of flyers are using Roc Sim or another program to help them with their designs.

crossfire said:

... I guess its because a lot of flyers are using RocSim or another program to help them with their designs.

Click to expand...

Yes, and the chute Cd is one of the parameters that has an impact on my chute choice to optimize a rocket's descent rate and down-field landing distance for a given motor and packing volume. Which is why I asked for that info in 2015 - you replied..." :wink:

Hello,
The XT CD.98
The standard chutes CD 1.34
Crossfire chutes 1.55

Hope this helps.
Thanks
Gary

Yes you are right on the CDs.

Gary

Gary those are some really good Cd numbers and much higher than I expected or ever modeled with your chutes. I know my Ultra-X drogues have always performed well, but now I know why. You should definitely post those numbers on your site.

More information is always good. If it's not too much burden, please post!

Bat-mite said:

More information is always good. If it's not too much burden, please post!

Click to expand...

Who post what numbers? If it's the TRF chute Cds they're in post #11...

wighty44 said:

Who post what numbers? If it's the TRF chute Cds they're in post #11...

Click to expand...

Woops. Missed that. Thanks. But I also meant that Gary should put that info on his site.