3/4ish semi-scale Redstone Missile

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kclo4

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Just wanted to post up a teaser for my university rocket teams flight this weekend.

48' tall. 48" body diameter. Sub 300lbs. CTI O8000 motor.

0520171740b.jpg

Instructor for scale.

I am pretty confident the motor will run because I built it, not sure the rest of the thing will hold together, but it will be exciting either way.

Changing pic for reasons. Will update later.
 
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jsdemar

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Wish I could be there. We have this thing called NSL happening in Southern NM this weekend.

Launch early. Winds will be 10mph+ by 10am. NWS forecast.
 

kclo4

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John, I am bummed that a lot of the club folks can't make it. Out schedule and communication of that schedule has been fairly appalling.

The launch pad will be setup today, and we will be starting setup of the rocket around 5:30AM tomorrow to try and make a 8AM launch. That should keep us in the 6-8mph range.

Coyote, the skin is made of Dacron aircraft fabric.
 

OverTheTop

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What's your dry mass on the rocket? Our 1:1 V2 which was of similar size came in at 400kg, and flew on an O25000
 

rstaff3

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I trust there will be plenty of documentation on the flight! It should be really cool or really, really cool :)
 

kclo4

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Things were pretty rough. Still collecting videos so we can try to get a better idea of what happened, but total airframe failure. Motor left the airframe and took up a career in skywriting, but we found it quickly. It is no longer round, expensive mistake.

From one of the cell phone videos that I did watch, it looks like the fins failed first, then airframe failure( caused by a new yaw moment maybe?). The other possibility is the fins failing was just a symptom of the lower airframe tube holding the motor failing. Dunno yet, waiting on video to get uploaded to our dropbox.
 

Cl(VII)

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:shock: 2000 lbs of thrust going rouge had to be a pucker factor moment. Hope you got enough info to diagnose the problem.
 

CoyoteNumber2

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:shock: 2000 lbs of thrust going rouge had to be a pucker factor moment. Hope you got enough info to diagnose the problem.
Agreed, a free-flying O motor sounds like an exciting day.
 

Nytrunner

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I am pretty confident the motor will run because I built it, not sure the rest of the thing will hold together, but it will be exciting either way.
This turned out unfortunately accurate.

What were your stringers and frame composed of?
 

rharshberger

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We like carnage too, video or it didnt happen....

Sorry to see such an impressive sized project fail. We understand the loss and the immense amount of time to design and build.
 

jsdemar

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[video=youtube;A94tUX_FlTI]https://www.youtube.com/watch?v=A94tUX_FlTI[/video]

Appears to fold due to aerodynamic forces after an off-center thrust and/or wind effect.

Same motion would happen if it were marginally stable and beginning an initial turn before correction. The flexible structure with relatively small fins isn't predictable with standard stability margin guidelines.
 

dhbarr

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Bird turned, motor kept going.

I'll be interested to hear how the o8000 was selected.
 

jsdemar

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I'm assuming the O8000 was chosen because it's the only full O commercial motor.
 

kclo4

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Here is some quad footage of the setup, erection (giggity), and the flight.

[video=youtube;sgCwPPeOetg]https://www.youtube.com/watch?v=sgCwPPeOetg[/video]


Another rando video:
[video=youtube;x_5eVafa42s]https://www.youtube.com/watch?v=x_5eVafa42s[/video]

Also saw some of the GoPro videos, and I am pretty confident that the whole thing failed because of the fins letting go. Will try to make those available soon.

They used the same gatorboard foam on the fins that the centering rings are made of without reinforcement. I tried to get them to do a single layer carbon laminate, we had both weight and money budget for it...

O8000 was selected because it was the only commercial motor that would give us a better than 6:1 thrust to weight that wasn't an O25000. We were trying to keep the acceleration and drag forces as low as possible while still providing a stable flight. Was trying to get Scott at Loki to roll us something, but the schedule ended up being too tight for him to design us something with the required thrust curve. Would have gone with a P but again, not enough schedule to make sure we had the FAA class 3 stuff worked out either.
 
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Nytrunner

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That is a beautiful motor spiral. I wonder what helped it keep to that axis.

Definitely post the on boards if you get a chance.
 

dhbarr

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Naked polystyrene foam board bonded between two layers of wood-fiber veneer?
 

kclo4

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Naked polystyrene foam board bonded between two layers of wood-fiber veneer?
I believe that is the makeup of the gatorboard, yes. The technique does in fact work on a 1/2 scale V2 that our instructor has flown on 75mm M motors, but does not scale to 300lb 48ft tall rocket apparently.
 

rstaff3

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I have to admit I don't think unreinforced gatorboard would have been my choice. That being said, the size of the rocket and motor aren't what kills fins (at least on the way up). It's the velocity. That looked plenty slow to me. It kinda looks like the rocket had a slight bend before launch but maybe that's an artifact of the video?

Correct me if I'm wrong.
 

cerving

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It sure looks from the second video that the airframe was bent, and it failed in the direction of the bend.
 

kclo4

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The whole rocket was kind of cocked to one side leaning off the tower, combined with the taper at the top makes it look like it was bent more than it really was. The first 2 seconds of video show the airframe pretty straight under boost. with no noticeable deformation in the outboard stringers until the fins let go and the yaw rotation starts. I think that because it started a little slanted when it went unstable that was the natural direction it was going to rotate and ultimately fail.
 

kclo4

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Here is a video containing the on-board footage. It is a lot more telling than the far shots regarding the order in which stuff failed.


[video=youtube;_dUk_z-M6gg]https://www.youtube.com/watch?v=_dUk_z-M6gg[/video]
 

dhbarr

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Yup, that's rough. Fin, fin, frame.
 

JohnCoker

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I appreciate the attempt to build light and with alternative materials, and I'm sorry it didn't work out.
 

Aksrockets

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Can we please move this to the "cardstock rocketry" subforum?
 
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