PayLoad
I don't do spirals
We are over-thinking this. A zipper of that magnitude is way too much speed at ejection. Delay way wrong, the rocket was different from the others, or if they were all the same the others got lucky.
trying to understand how the rules work:)
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Tell us more about your team and their prior experience with rocketry, please. The term "team" makes me think of a college group. We've seen many college teams going for their L1 in October with no real previous experience. "But the sim said..." is a frequent refrain.
L1 one week and L2 the next sounds like a case of GO fever. If you're serious about being in the hobby long-term, take the advice given and learn. If you're padding your CV, RC plane and quadcopters are a great way to go.
L1 one week and L2 the next sounds like a case of GO fever. If you're serious about being in the hobby long-term, take the advice given and learn. If you're padding your CV, RC plane and quadcopters are a great way to go.
You don't have to count, but y'all should be watching your flights carefully enough to give a reasonable estimate of such things. But if it were for an engineering class of mine, I'd be recording these flights and analyzing them carefully. Two years later, I can still tell you that my L1 re-cert flight had a little bonus delay, ejecting about 2½ seconds after apogee. That was just from watching anxiously, and the 25 year old cardboard airframe is still in fine condition, not a sign of zipper.
Was 14 seconds shown as the "Optimum delay" by OR? That's what you should adjust the delay for, assuming all of the details are entered correctly.
i think it is location settings that caused this. I dont think he adjusted for that. nor did any of us in OR. He was the only naked rough rocket too, so im guessing alot of drag.
chanigng the settings in OR to 6400 feet elevation and unfinished yields 9.3s delay and 10.8 to apogee. But yet the other rockets were fine with 14 seconds... hmmmmmm
cavecentral
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Motor testing committee allows up to 20% slop factor in the delay on commercial motors, so it could have been a second or two longer.
Did the rocket go straight up? If it took off on an angle, they can be going pretty fast at apogee. If the delay is late, it would be going much faster than if the rocket went straight up.
I'm assuming this was same kit, chute, and harness as the other flights without damage. Lots of variables involved.
Did the rocket go straight up? If it took off on an angle, they can be going pretty fast at apogee. If the delay is late, it would be going much faster than if the rocket went straight up.
I'm assuming this was same kit, chute, and harness as the other flights without damage. Lots of variables involved.
Yeah it was after apogee but very short after. Thats what confused him. After entering the location data and making it a naked rocket, it says 10.8 to apogee and a 9.3 delay.
however, with all the other rockets passing just fine, something is off in OR.
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I don’t think there is anything wrong with OpenRocket, I think it is a learning curve with the software on the operators end. As for the other rockets being fine with a 14 second delay, I think the ones that had no issues got lucky.
What tool was used to make delay adjustments, if any?
MClark
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I also say it is not a cert.
With recovery there are many things besides delay times. How the chute was folded, and how tight, can effect opening shock.
With recovery there are many things besides delay times. How the chute was folded, and how tight, can effect opening shock.
it is a college team. i have experience with rockets and was building my own in the summer, but did not test it yet. We are all aerospace engineers and our capstone project is to build a lvl 2 or 3 rocket to hit 10,000 feet by may 2023
i do not go off of sims all to much, but i was asked to post what OR said on this thread. the other rockets passed so soemthing was a miss but we can fix it and try again. we are not worried at all, just wondering what happened and why it was considered a failure since it was recovered safely. We thought a zipper like this would not fail it perse and at least give us a lvl 1 cert as long as we repaired it. but it did not pass so we are ok with that. he is going to fly again in 2 weeks once it is fixed.
it is GO fever for us because we have deadlines. so far 4 of the 5 rockets are lvl 1. in 2 weeks is our level 2, then we start the 7 month journey for either the L2 or L3 project in may In the last 2 weeks we all have learned alot from the math, design, testing, and some sims. today, his rocket just had an odd situation.
you know what, you might be right with luck. Since mine did not fly today since my kit came in late, 2 days after the rest. im going to try using some numbers close to OR.
as for operator error, yes i can see that. math is not wrong, its just outputs what we give it.
ill post for OR help this week and really nail this done. i WOULD LOVE the forums input with OR
ohhh, i wonder if he folded it wrong??? thank you for stating that. How should it be folded and rolled?
MClark
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That is the LOC IV and we all used hte exact kit and motors
This rocket just happened to expiernce some stress that was unforeseen. Not a failure at all. May not have passed, which he found frustrating since he was able to recover it safely and we were told from others in various meetings that if it is recovered safely, then you pass. He is kind of upset at those who told us wrong.
all 5 kits are the LOC IV, all motors were the same, H550-14. His rocket was hte only one flown naked and not painted, which i think was the problem. It had more drag and the delay that worked for us did not for him
PayLoad
I don't do spirals
Right on NAR Website for level 1...
"...The Level 1 High Power Certification Candidate will fly their model. The flight must be witnessed directly by the Certification Team. Stability, deployment of the recovery system, and safe recovery will be considered when evaluating safety of the flight. Models experiencing a catastrophic failure of the airframe, rocket motor, and/or recovery system (e.g., shock cord separation) will not be considered as having a safe flight....
And right on Tripoli website.....
"...Post-Flight Inspection – The rocket must be presented to the certifying member for inspection. If the rocket cannot be recovered, but can be inspected in place (power lines, tree, etc...) this is acceptable. The certifying member shall inspect the rocket for excessive damage. Excessive damage shall be considered damage to the point that if the flyer were handed another motor, the rocket could not be put on the pad and flown again safely. Damage caused by wind dragging will not cause a disqualification.
"...The Level 1 High Power Certification Candidate will fly their model. The flight must be witnessed directly by the Certification Team. Stability, deployment of the recovery system, and safe recovery will be considered when evaluating safety of the flight. Models experiencing a catastrophic failure of the airframe, rocket motor, and/or recovery system (e.g., shock cord separation) will not be considered as having a safe flight....
And right on Tripoli website.....
"...Post-Flight Inspection – The rocket must be presented to the certifying member for inspection. If the rocket cannot be recovered, but can be inspected in place (power lines, tree, etc...) this is acceptable. The certifying member shall inspect the rocket for excessive damage. Excessive damage shall be considered damage to the point that if the flyer were handed another motor, the rocket could not be put on the pad and flown again safely. Damage caused by wind dragging will not cause a disqualification.
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This is not a wise idea, and in my mind, that is a huge red flag. For starters, it has been suggested several times in past threads to get a mentor. I recall you stating at one time that you tried contacting UROC, but didn’t get a response. Have you obtained a mentor to advise your group? Knowing all the math, and understanding it is one thing. But understanding it with practical experience is a completely different animal. Things might work out perfectly on paper, but in practical application, it might not work for one reason or another. Things get missed with GO FEVER, and it is not a good thing. You can still easily make the goals of your capstone project with a mentor.
Get a mentor who is L3, keep them informed of all your plans and ideas. Let them oversee your design and build. And if motor combination that puts the project into L3 territory is required for the flight next year, they can be the flier of record for the flight.
PayLoad
I don't do spirals
500 posts on this forum, all the replies you have been getting, 5000 more posts & replies in the future.....will not equal the quality of 10 minutes spent in the presence of a mentor. Book smarts are great. Experience trumps book smarts every time. Get a mentor.
exactly, and i dont call this catastrophic failure at all. Its a slight tear. catastrophic failure would be an explosion, fins coming off, a zipper more than half of the rocket, or a fire, but this i dont see as catastrophic failure. Thats where the disconnect is for us. We are aerospace engineers (students) and we have seen catastrophic failures in lab, machine shop etc and we dont see this as catastrophic. a slight tear and a few hours repair time yes, but not catastrophic.
Please help us understand why it is catastrophic? is it because if we stuck a new h550 in it, it wouldnt fly?
im not trying to argue either. We are truly trying to understand everyone and how this works haha. so much stuff to learn
we have a L2 mentor but not a l3 yet. We followed all the advice of the mentor and 4 out of 5 rockets for lvl 1 is not bad. We are doing the best we can at the moment. I have talked with a couple of L3's and they have helped us out and we followed their ideas. they are not our official mentors, but we have been talking with them
MClark
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If you and your group members need to be level 3 before May to launch your project you need to be in contact with the TAP/L3CC now.
we have spent about 3 or 4 hours with a few Lv2 and a couple of lvl 3 rocketeers. They are not our official mentors but they have let us talk with them on some calls. 4 out of 5 rockets is not bad
MClark
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You need to understand what is catastrophic and failure is not your opinion, it is the opinion of the person signing
we are working on this as we speak. i started this process 2 weeks ago. We are going with tripoli. We do not have a mentor yet but we have talked to lvl 2s and 3s.
interesting. Thats odd. so there is no standard or standard definition? its up to someone's interpretation?
thanks for letting me know this. it helps alot
PayLoad
I don't do spirals
waltr
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I agree that the damage is too much to safely fly again.
As to the OR Sims. The LOC IV with an H550 gives optional delay as 10.1 sec. The Default delay for this motor is 14second so possible this is where the student got this delay time from. With a 14sec delay OR says the rocket will be descending at 70f/s when the Main chute deploys. I am not surprised it zippered but the other flights got very lucky. Same as sometimes NASA gets unlucky.
Beside properly pack chute there is the length material of the cord. Kevlar has almost NO stretch, Nylon does have some but not much.
On any of my rockets weighting over a pound (400 gram) I either braid the cord or do 2-3 taped bundles. This is an Engineering problem --- Why would this decrease the recovery system shock???
Other question that should be asked is: What is the Force and over how much time is there on the recovery system with a piece of Kevlar verse Kevlar with 3 taped bundles????
These questions need to be known when your team designs and builds the 10k rocket. That will be what 50 pounds not the 3 pounds of the L1 rocket...
It is catastrophic since if you did try to fly it again, the ejection charge would just blow out the side where the rip is and NOT Eject the Chute leading to the rocket coming down Ballistic.
Actually Failing is hopefully a good thing as it will make the team think and hopefully evaluate why it happened.
As to the OR Sims. The LOC IV with an H550 gives optional delay as 10.1 sec. The Default delay for this motor is 14second so possible this is where the student got this delay time from. With a 14sec delay OR says the rocket will be descending at 70f/s when the Main chute deploys. I am not surprised it zippered but the other flights got very lucky. Same as sometimes NASA gets unlucky.
Beside properly pack chute there is the length material of the cord. Kevlar has almost NO stretch, Nylon does have some but not much.
On any of my rockets weighting over a pound (400 gram) I either braid the cord or do 2-3 taped bundles. This is an Engineering problem --- Why would this decrease the recovery system shock???
Other question that should be asked is: What is the Force and over how much time is there on the recovery system with a piece of Kevlar verse Kevlar with 3 taped bundles????
These questions need to be known when your team designs and builds the 10k rocket. That will be what 50 pounds not the 3 pounds of the L1 rocket...
It is catastrophic since if you did try to fly it again, the ejection charge would just blow out the side where the rip is and NOT Eject the Chute leading to the rocket coming down Ballistic.
Actually Failing is hopefully a good thing as it will make the team think and hopefully evaluate why it happened.
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Because the rocket is not safe to fly unless a MAJOR repair is made to it.
Having to shorten the airframe by several inches is a major repair.
MClark
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Post #45 gives the guidelines.
The rocket in the picture with the zipper could not be launched without repair.
boatgeek
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There isn't a standard definition--it's up to the individual certification team. The standard is something like "can be flown again with minimal repairs" (someone can correct that with exact wording if needed). I wouldn't exactly call that catastrophic damage because it could be repaired in an afternoon with a coupler and a piece of body tube, but it's definitely failing a cert damage.
[edit] I forgot that the NAR guidelines say catastrophic damage. I remembered them being more like the Tripoli guidelines. Same final answer, though.
If I had to guess, I'd say that the 4 that passed packed their chutes differently from the 5th. If they wrapped the shroud lines around the chute, that might have given just enough time for the rocket to slow down before the chute opened.
MClark
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The rocket could have been repaired in the amount of time spent on this thread.
or repaired in field and flow again for cert the same day.
or repaired in field and flow again for cert the same day.
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