SHOWTIME: Level 2 Re-Attempt After Epic Fail. MAC Performance Firestick XL With Redundant Dual-Deploy. Project Hurricane is Go For Launch.

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tsmith1315

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I've had cardboard wrinkle in the same place- just ahead of the forward CR, with similar pattern when landing hard on sod. Booster about the same angle as the pic above on contact.

Fortunately, you got everything back and in good shape otherwise!
 

Tractionengines

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Yep, Looks like just bad luck. As you said 3-4feet earlier touchdown and different story.
(I have cracked a fin off a rocket by landing directly on the only road through a couple hundred acre field.)
Think a coupler tube, some glue, and paint will get her back in the air?
 

NateB

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That looks like really bad luck to land on the road. I bet that was the culprit.
 

Tractionengines

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Just went thru your build thread. 24FPS under main seemed really fast and I (and others) would have questioned main chute. Found this:

Project Hurricane is go for launch.
Date: 11/20/2021
Motor: CTI J355 Redline
Projected Altitude: 5822'
Max. Velocity: 494 mph
Max. Acceleration: 8.8 G's
Touchdown Velocity: 15.8 mph.
Any idea why speed under main was so high? ( torn lines, tangled lines, wrong size or CD value in sim compared to real...) What type and size main is it? (I don't see chute info in build thread.)
 

Mach_Seven

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Just went thru your build thread. 24FPS under main seemed really fast and I (and others) would have questioned main chute. Found this:



Any idea why speed under main was so high? ( torn lines, tangled lines, wrong size or CD value in sim compared to real...) What type and size main is it? (I don't see chute info in build thread.)
It was a Loc Precision 50 inch parachute with spill hole. There is a preset for that parachute in open rocket which is what I used. The weight of the actual rocket and the open rocket Sim were almost identical. So I’m not sure why the impact speed was higher. The main was laid out nicely on the side of the road. No tangles. Rocketry is hard.
 
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mikec

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Did you compute the actual descent rate under main from altimeter data or is that predicted?

I agree with others, you'd have been fine if you had missed the road.
 

Mach_Seven

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Did you compute the actual descent rate under main from altimeter data or is that predicted?

I agree with others, you'd have been fine if you had missed the road.
Altimeter data. The two RRC2L's were remarkably close in their data points. Main and drogue decent rates were identical. 50 fps under drogue, 24 fps under main.
 

bobbyg23

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It was a Loc Precision 50 inch parachute with spill hole. There is a preset for that parachute in open rocket which is what I used. The weight of the actual rocket and the open rocket Sim we’re almost identical. So I’m not sure why the impact speed was a little higher. The main was laid out nicely on the side of the road. No tangles. Rocketry is hard.
Just an fyi, that is way to small of a loc chute. On a 9.5lb rocket they recommend a 60" chute.
 

Sandy H.

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Hate that the road caught you. It might have been dinged up a little on the grass, but I bet you would have been able to re-fly.

My 1st L2 landed in a creek, but that was a godsend, as the trees on either side of the creek were tall. When the main popped, it drifted right for the forest, but there was a clearing due to the water and it had a soft 'ground-level' splashdown.

Sandy.
 

Mach_Seven

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Just an fyi, that is way to small of a loc chute. On a 9.5lb rocket they recommend a 60" chute.
It was 7 lbs 5 oz. without the motor. So a 3 grain CTI case and the residue left inside added to that. Borderline, but I went with the 50" due to the tight 3" airframe and just figured, "What's a few more miles per hour?"
 

Tractionengines

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SORRY I didn't catch this. You decent rate was given in MPH not FPS in your build thread. 15.8FPS would be fine, but 15.8MPH is 24+FPS which is very high for normal rockets.
I try to stay under 17FPS for a main on Dual deploy or chute release.
 

mikec

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I don't think the RRC2's record that.
You can figure it out from the video timing by assuming the deployment altitude was where you set it. You were on the main for about 26 seconds, so if your deployment was set at 500 feet, that's 500/26 = 19.2 FPS.
 

rocketgeek101

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Dang, sorry to see that. That is about as close as you can get and not be successful. I had a rocket CATO back in September that was built from 3” canvas phenolic. The airframe above the fincan just shattered. I know paper based phenolic tube is quite brittle and based on my recent experience I’ve been wondering if the same is true to some extent with canvas phenolic.
 
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Theory

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RM had some great chutes. Just bought a “ultralight parabolic” for my WM Drago 4.
 

Buckeye

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You can figure it out from the video timing by assuming the deployment altitude was where you set it. You were on the main for about 26 seconds, so if your deployment was set at 500 feet, that's 500/26 = 19.2 FPS.
The question was about acceleration, which the RRC2 does not do. This video method gets you close, but the slope of the baro altitude is better. Too bad the RRC2 does not download the data vs time. Single number reporting is tainted by extrema.

Both altimeters logged 24 fps under main.
For what it is worth, my Firestick XL weighs in at 2770g (6.1 lbs) dry, and I use a Wildman Recon 40" chute. My flights on 38 and 54 reloads have main rates under 20 fps. Here is how I determine the descent rates with least squares fitting. In this case, drogue ~57 ft/s and main ~18 ft/s.

1638719490292.png
 

Zbench

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Steve I get it, but the picture shown does not seem to indicate that the rocket was moving that far off vertical. And the drogue is relatively small compared to the tremendous stress that would have been placed on the airframe from a high speed main deployment.

Seems that the cause of the cracked airframe is now an undersized chute anyway.
 

Chris_H

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You can figure it out from the video timing by assuming the deployment altitude was where you set it. You were on the main for about 26 seconds, so if your deployment was set at 500 feet, that's 500/26 = 19.2 FPS.

That method of figuring is assuming that at deployment, the descent rate is immediately at 19.2 FPS, which it is not. Also, that deployment happened exactly at 500', not accounting for any time needed for full deployment. Any seconds 'lost' to 'slippage' in the first seconds of deployment, as the descent rate slows, the remaining descent rate / time, the rate is higher.

Still, your method is a good reference to keep in the bag of tricks.
 

mikec

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Still, your method is a good reference to keep in the bag of tricks.
Obviously if you have a recording altimeter you can linear-fit the altitude readings once under main and get a better value. As it happens, the RRC2L reports the average descent rate under main and I presume it's doing something like this internally. At any rate, any approximation from real data, even with assumptions, has got to be better than predictions from a very simple parachute model.
 

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