T10 35' parachute - anyone used one for big HPR?

[Crooksz_Rocketz]

Hi all,

I'm working on my L3 scratch build which is a 9" "Talon" style rocket. I've purchased a 35' military surplus T10 parachute which just arrived! Was wondering if anyone has any experience using a T10, or similiar, parachute for HPR!

My Talon 9 will end up being around 100 pounds or so, the tube this chute needs to fit inside is approximately 8.75" Inner Diameter with plenty of space lengthwise. Rocket will be around 16' tall!

Some photos attached, and thanks in advance for the feedback!

 

[mccordmw]

That's a pretty large parachute for a 100 lb rocket. Without knowing the exact Cd of the chute, here are rough estimates by a descent rate calculator.

Rocket mass: 1600 ounces
Parachute shape/type: SkyAngle
Parachute size: 420 inches measured by diameter

Calculation Results


Descent rate:
10.52 ft/sec
3.2 meters/sec
11.54 km/hr
7.17 mph
Estimated descent time, assuming ejection at 1000 feet: 95 seconds


Recommended parachute diameter for a landing @ 15 ft/sec: 280.0 inches

The recommended size would be closer to 24' diameter. Be careful about when you pop the main, or you could drift out of range and be disqualified. Maybe try reefing the chute or putting in a spill hole. But now you're getting into chute expertise that I don't have a clue about.

Also, for a 100 lb L3, you're looking at something in the M2700+ engine range for a safe 6:1 thrust-to-weight. That's a big L3! Good luck and post a build thread!

 

[Crooksz_Rocketz]

I think using "Parachute shape/type: SkyAngle" will drastically skew the calculations you did...The Cd (drag coefficient) of SkyAngle chutes is enormous in comparison to a typical "Spherical" type chute, which I believe the T10 to be...The Cd of this T10 is probably like 0.8, whereas the SkyAngle Cd's I'm familiar with are in the 1.5 range or so.

But it's a linear correlation, so the decent rate is probably more like 14 mph using a Cd of 0.8, still slow I agree, but IF I can fit this enormous chute into the tube and a nomex bag/chute bag I think it's a go for me

I've been documenting all of the build farely thoroughly but have not started a post, it's basically to the stage where I have a "kit" to build, so it should start to come along fairly quickly!

 

[Bat-mite]

I also find that calculator to usually come in a bit higher than my OR sims. I think it errs on the safe side.

 

[mccordmw]

This looks interesting. From the test data, it looks like the Cd of a cargo parachute is 1.0?

I would think it's greater than 0.8 since that's the estimate for a flat sheet parachute, and those cargo chutes seem more hemispherical.

https://www.dtic.mil/dtic/tr/fulltext/u2/690808.pdf

 

[Crooksz_Rocketz]

Since the T-10 is such a well known/used chute, I would think the Cd is also well known, just need to find it....But, my initial gut feeling is in agreement with the majority, this chute is probably TOO BIG!

I might look into cutting out some of the panels, as I've seen done on some photos of T-10s...

Still hoping somebody with actual experience using a T-10 will chime in! Thanks all for the references and your thoughts.

 

[The_Lone_Beagle]

Still hoping somebody with actual experience using a T-10 will chime in! Thanks all for the references and your thoughts.

Actual experience using it with a rocket, or actual (personal) experience using it to jump out of an airplane?

 

[Crooksz_Rocketz]

Either!! I'd really like to hear from a rigger who has packed these in a past or current life! I watched a video on packing a T-10 and the way they pack it is great for the backpack, not so great for my tube size (8.75")

Actual experience using it with a rocket, or actual (personal) experience using it to jump out of an airplane?

 

[ksaves2]

Since the T-10 is such a well known/used chute, I would think the Cd is also well known, just need to find it....But, my initial gut feeling is in agreement with the majority, this chute is probably TOO BIG!

I might look into cutting out some of the panels, as I've seen done on some photos of T-10s...

Still hoping somebody with actual experience using a T-10 will chime in! Thanks all for the references and your thoughts.

Not if you add weights to the rocket! But I think the suggestion it might be too large could be correct unless you make the attempt at a venue that has a wide radius. Also you may want to consider the deployment altitude
to be "up high" like 1000' or perhaps even higher to allow the canopy the time it needs to fill.

Technically, if the waiver is a 2 mile radius and you recover a perfectly fine rocket (especially with an extra soft landing with a 35' chute) the certifier's wouldn't be obligated to approve the flight. I suspect darned well
they wouldn't approve it if the rocket landed in someones backyard. If out in the wide open spaces perhaps they would look the other way but in the wide open spaces, 2.25 miles may be well within a waiver radius.

How high you expect this thing to fly? If it's not going so high it might not be an issue. With something this large, I think you would want to err on the side of "too large" a chute than "too small". Crack a fin on landing and
that is an oh shoot moment.

I've witnessed a 135 lb rocket come down on three 15 foot parachutes "Apollo style" very nicely. The over sized nosecone came down on three 5' chutes. Next flight on a larger motor the flier decided to use two 15 foot
chutes instead of three and one of the two streamered. Aft end of the rocket was damaged with one chute and one streamering. The L3 was already in the bag with the first flight though. Kurt

 

[ksaves2]

Either!! I'd really like to hear from a rigger who has packed these in a past or current life! I watched a video on packing a T-10 and the way they pack it is great for the backpack, not so great for my tube size (8.75")

There are riggers on this board and perhaps one or some will see and answer.

 

[The_Lone_Beagle]

Either!! I'd really like to hear from a rigger who has packed these in a past or current life! I watched a video on packing a T-10 and the way they pack it is great for the backpack, not so great for my tube size (8.75")

Well, bear in mind the T10 was made for somebody to jump out, not only their own body weight but their pack, rifle, + whatever. Wikipedia tells me the total suspended weight limitation is 360 pounds, so, it may be overkill for "just" a hundred pound rocket.

 

[crossfire]

Is a 100lb rocket going to fall fast enough to open a 35' chute?

 

[jazzviper1]

Is a 100lb rocket going to fall fast enough to open a 35' chute?

Yes it will. It will just have lots of hang time.

 

[Wayco]

I have packed thousands of T-10's for student static line jumps. We would use the smaller 28 ft. emergency chutes for lighter jumpers. The T-10's were packed into a deployment bag that was attached to the jump plane with a static line, and the falling weight of the student would pull it out of the bag. Lightweight students (less than 150 lbs.) would float for quite a while under a T-10. My wife Sharon has several jumps on them, weighing in around 110 lbs. She says it's not much fun hanging around til your legs go numb. Catching a thermal with one could extend the experience.

 

[Lowpuller]

I second Wayco's comment but would add that you hit the ground like a sack of potatoes. At 150 lbs. imagine jumping off the top of a six foot step ladder.

Frankly I would be concerned that you might not fully inflate a T10.