N5800 min diameter attempt at Aeronaut

On Friday, August 3, 2012, Jackson and I launched a minimum diameter rocket on an N5800 under the new Tripoli Mentoring Program. The rocket failed at max Q.

Before we give out the details, this quote says it all. Thanks to Sather Ranum for introducing us to this quote.


For us, the project was not about the record, although we would have loved to have achieved it. We built this rocket and drove all the way to the Black Rock because others had tried and failed at the task. Keeping the fins on a minimum diameter N5800 is a very difficult thing to do, if not impossible. We had to try.

Aluminum fin can:
3/16 inch heat treated 6061 fins
Fins were beveled on the leading and trailing edges
Fins were welded onto a 1/8 inch fin can that fit directly over the motor case
High heat epoxy was used to smooth fillets for aerodynamic purposes

Nose cone:
Performance Rocketry spiral wound fiberglass/graphite
Titanium tip with shoulder, made by Eric Foster at BadAzz Rocketry, and seated tightly and correctly in the nosecone

Body:
Performance Rocketry carbon

Recovery:
Same end dual deploy. The area above the motor case reserved for recovery material was about 6 inches, plus the inside of the nosecone. Nosecone shoulder was carbon, 6 inches long, tightly fit.

Electronics:
Jackson created a very innovative av bay. Because space was at a premium in the rocket, he used the unused space above the motor case and below the internal motor retainer. Jackson fit a block of wood over the smoke grain holder, and mounted the 2 ravens on that. The wood insulated the ravens from the heat of the motor. We tested the set up to make sure that the motor did not overheat the electronics. It is too bad that we never got the chance to verify that this innovative av bay works. The design should have also protected the batteries from the cold air at 60,000 feet had we gotten there.

The first part of the flight was a sight to behold. The N5800 is an incredibly powerful motor. That’s why we like it. It was spectacular to see 40 pounds lift off weight scream into the blue sky overhead in the blink of eye. Tom Rouse took the attached picture. Notice how the flame beneath the rocket is larger than the rocket itself. Truly awe inspiring.

The full motor burned. No motor issues. Just at or after burnout, there was a slight wiggle. We all knew something was up. But, the rocket continued up for a few more seconds. Then, it arced over and began coming down – in pieces.

JLRockets said:

On Friday, August 3, 2012, Jackson and I launched a minimum diameter rocket on an N5800 under the new Tripoli Mentoring Program. The rocket failed at max Q.

Before we give out the details, this quote says it all. Thanks to Sather Ranum for introducing us to this quote.

THE MAN IN THE ARENA by Teddy Roosevelt
It is not the critic who counts; not the man who points out how the strong man stumbles, or where the doer of deeds could have done them better. The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood; who strives valiantly; who errs, who comes short again and again, because there is no effort without error and shortcoming; but who does actually strive to do the deeds; who knows great enthusiasms, the great devotions; who spends himself in a worthy cause; who at the best knows in the end the triumph of high achievement, and who at the worst, if he fails, at least fails while daring greatly, so that his place shall never be with those cold and timid souls who neither know victory nor defeat. ​

For us, the project was not about the record, although we would have loved to have achieved it. We built this rocket and drove all the way to the Black Rock because others had tried and failed at the task. Keeping the fins on a minimum diameter N5800 is a very difficult thing to do, if not impossible. We had to try.

Click to expand...

Wow good job guys. My mom, an artist once said to me, 'Ted, never be afraid to fail'. I think she was right.
I say, try again and learn from your mistakes! Also, great quote from Teddy Roosevelt, he's one of my favorite people in history (not just because he shares my name).

btw, any pictures of the rocket, launch, or aftermath?
Can you provide any details on how the fins were attached?EDIT: nevermind, you put them up while I was typing!

-Ted

There are two concerns that have plagued all minimum diameter N5800 projects: excessive heat from high mach speeds, and excessive vibration from high mach speeds and 20,000 Ns of total impulse unleashed in 3.5 seconds. One of the two did us in. Either the nose cone delaminated first, and caused a bad angle of attack, which caused the fins to detach. Or, the fins shredded first, which caused a bad angle of attack, which caused the nosecone to shred. We believe it was the vibration, although we may never know for sure. In the next two posts, we will review the condition of hte parts upon landing and discuss the merits of the vibration versus heat theories.

JLRockets said:

On Friday, August 3, 2012, Jackson and I launched a minimum diameter rocket on an N5800 under the new Tripoli Mentoring Program. The rocket failed at max Q.

Before we give out the details, this quote says it all. Thanks to Sather Ranum for introducing us to this quote.

THE MAN IN THE ARENA by Teddy Roosevelt
It is not the critic who counts; not the man who points out how the strong man stumbles, or where the doer of deeds could have done them better. The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood; who strives valiantly; who errs, who comes short again and again, because there is no effort without error and shortcoming; but who does actually strive to do the deeds; who knows great enthusiasms, the great devotions; who spends himself in a worthy cause; who at the best knows in the end the triumph of high achievement, and who at the worst, if he fails, at least fails while daring greatly, so that his place shall never be with those cold and timid souls who neither know victory nor defeat. ​

For us, the project was not about the record, although we would have loved to have achieved it. We built this rocket and drove all the way to the Black Rock because others had tried and failed at the task. Keeping the fins on a minimum diameter N5800 is a very difficult thing to do, if not impossible. We had to try.

Click to expand...

GOOD job....

what did you learn, and what will you do differently.

"Make the best use of what is in your power, and take the rest as it happens. "
Epictetus
or more famously...
“If you want to improve, be content to be thought foolish and stupid.”

The motor case and fin can hit the ground without any fins attached. We found two of the three fins. They both showed signs of being ripped off. It looks as though the ripping started at the top of the leading edge. In most cases, the tear was at the weld, but there were also places where the weld held for at least a little while, bending and tearing either the fin or the can. The aluminum fin itself tore at the top of the leading edge of all three fins.

The fin can we used was, unfortunately, not the original design. The original design was to have a fin can with aerodynamic fins. David Reese designed an airfoil and a radial taper for our fins, and put it into a cad/cam file. Originally, Eric Foster from BadAzz Rocketry was going to machine the fins and the fin can. Unfortunately, Eric was unable to complete the project. He informed us of this about 3 weeks before we were due to leave for the Black Rock. The problem with his late departure from the project is that machinists have queues. Waiting in someone else’s queue does not give you any credit towards the new queue. Although it would not have taken three weeks to do the actual work, the queue time for a small custom project like this is much longer. We pulled in big favors to jump to the front of a queue, but still, the best we could do with short notice was a flat fin with bevel on leading and trailing edges.

We honestly believed that the replacement of the airfoil/radial taper with a bevel would only bring about a loss of altitude. We did not believe that it would increase the chance of fin failure. At 3/16 inch, the fin was thicker than what had been tried before, and would hold up better to the flutter. Aluminum has a very high shear modulus, and back-of-the-envelope calculations on the velocity needed to induce problematic flutter were sufficiently high so as to not induce additional analysis. We also cross checked with what other teams had done or were doing. We believed the fins would stay on and that the only penalty for using the back-up design would be loss of altitude.

Perhaps the real problem was go-fever, but we stand by our decisions. We had planned our whole summer around the August trip to the Black Rock, and this was the only time that Jackson could go. The trip itself took a full two weeks, and therefore can’t be done during the school year. If we didn’t make Aeronaut, our next launch opportunity was next summer at LDRS 32, well past the time at which we expect this motor to be tamed by someone. But mostly, we’re not the sort of team that gives up just because everything doesn’t go exactly as planned. So, we made the choice to give the back-up design a try.

After the fact, we believe that the lack of aerodynamics on the fin itself was the primary contributor to the failure. We could be wrong about that, but that’s what our gut tells us. Our original design relied on this understanding. We also brought our Wildman Space Cowboy to the Black Rock. This rocket influenced our original design. The Space Cowboy fiberglass fin is attached only with external fillets – no carbon layup. Crazy Jim’s theory was that an aerodynamic fin would keep vibration at bay and therefore hold up on a minimum diameter rocket without tip to tip re-enforcement. David Reese designed the airfoil on the Space Cowboy, and Eric Foster did the machining. Our original design had us using the same team of experts. The day after we launched our N5800 project, we sent our Space Cowboy to mach 2.6 with no problems whatsoever. As far as we know, a Space Cowboy has never exceeded mach 3, but it has gone very fast with a less-than-usual fin attachment approach.

The nose cone was broken in several places, and the fiberglass fibers were shredded. The titanium tip survived just fine. At the launch, we heard opinions from those that thought that delamination was the problem, and from those who believed that the fibers, although shredded, did not show signs of heat based delamination.

While in the Black Rock, we had the opportunity to see what heat based delamination looks like. On Sunday, we launched a Wild Child that Jackson had modified to make into a minimum diameter 38mm. He left out the 29mm motor tube that comes stock with the kit, and did tip-to-tip layups with carbon. We put the Wild Child (a 12 oz rocket) up on a J350. We don’t know how fast it went, but we got whiplash following it up during the burn. When we recovered it, the leading edges had delaminated, although the fins stayed on. (Jackson had vacuum bagged, and created something of a radial taper with a 1/3, 2/3, 1 layup method.) The overheated Wild Child fins and the N5800 nose cone had distinctly different appearances, and not just because the of the difference between lay-up and filament wound.

The N5800 nose cone showed signs of ripping apart due to stress. On the rocket as a whole, the fibers were shredded everywhere that was not double protected by either the coupler, the motor case or the internal motor retainer. The carbon body tube also ripped apart below the internal motor retainer. The pull at this point was so great, that the retention screw stripped the threads of the retainer. The double protected areas would have been experiencing just as much heat on the outside as the other areas, but the fibers only pulled loose in areas that were not double protected and where the rocket tore apart.

Therefore, we tend to think that the nose cone did not delaminate and instead was pulled apart when the rocket went unstable after losing fins. However, the points that Chris LaPanse and others have made are valid. The N5800 does put unusual heat and pressure demands on the nose. The one piece of evidence that makes us question this interpretation is that the top of the nose cone just below the titanium tip does show small signs of the fibers pulling loose. This area was double protected by the shoulder of the titanium tip, but was also the area most directly exposed to the airflow itself. The amount of distressed fibers here is very small.

The CD3 charges and the tether charges were in tact, and the main parachute was still tethered upon landing. The failure was NOT caused by early deployment of the recovery system.

Whatever caused the failure, be it the fins or the nose cone, chaos was definitely the result. Both of Ravens were literally ripped in two. We did not find the part with the stored data for either one, so we have no chance of ever knowing how fast we went. The Big Red Bee hit the ground hard and is not currently functioning. We were able to salvage the titanium tip, the tether, the CD3 system, the parachute, and not much else.

You knew the lesson part coming, and it was laready requested in the very short time it took to upload the pictures in the previous posts.

We are glad we did the project. Keeping the fins on an N5800 powered rocket is a very difficult task. We failed where every other contender failed, and we believe we can hold our heads high on this one.

Although it is a worthy goal to attempt to tame the N5800, if we were more interested in the N record, we would use a long burn. If someone can keep the fins on with an N5800, they can likely best 45,000. But, after this attempt, we believe that the way to get maximum altitude is to use the tried and true method of the long burn. If we were to make another attempt at the record, this would be our approach.

However, as I said before, the record was not our goal. Taming the N5800 was our goal. We may try that again, but not until next summer when we can spend another two weeks travelling. By then, we’re guessing someone will have already beat us to the goal. If we do try again, we will strengthen the design in both the nose cone and the fin can.

We owe a great deal of thanks to a great many people.

Thanks to:
Aeropac – you guys put on a great launch. We will be back! Thanks especially to Tony for working with us to allow this to be flown under the Tripoli Mentoring Program, and for running a safe and well organized launch. Thanks to Ken Biba for advising us on GPS technology before the launch and fin resonance after the launch. Thanks to Tom Rouse for getting a great picture. Thanks to Larry for driving us out to the pad, and sweeping the debris field with us. Thanks to Becky for helping us search for our Wild Child on Sunday.

Thanks to David Reese – even though we didn’t use your airfoil, we appreciate the effort you put into it.

And a special thanks to Tim Lehr. Throughout the project, Tim made sure that we had what we needed when we needed it. Once we moved into the backup design mode, the project was moving quickly enough that we were hitting mission critical emergencies. Each and every time we hit a panic moment, Tim was there with his make-it-happen attitude. He rose above and beyond the call of duty multiple times on this project. He even helped us fix problems with parts he didn’t sell us. He drove out or sent a family member all the way to our neck of the woods (3 hours away) to facilitate exchange or to get various parts where they needed to be to get fixed. And the best part is, he does this for all of his customers. This is part and parcel of typical Wildman customer service. Tim, we’re proud to be loyal Wildman customers.

And a very, very special thanks to my husband Tom and daughter Emily for being supportive of this exhausting project. We got a big surprise when we arrived in Gerlach. Jackson and I drove the 30 long hours by ourselves, because a Black Rock trip was too much to ask even from our most loyal supporters. About 10 minutes after we checked into Brunos, we heard a knock on the door. Tom and Emily surprised us by flying out to witness our flight! It was great to have them with us.

Thats cool and devastating and awesome and sad and awe inspiring and just downright terrifying all at the same time!! I love it but I hate it!! AHHH!!!! :grin: :cry: :kill:

An admirable attempt, Congrats on your success thus far.

The avionics bay is genius! Thanks for posting your efforts.

Judy, Jackson... Great job. Love to see projects like this especially being spawned from a close family relationship. And good to see a nice showing from fellow Midwesterner's!!!

Just suppose someone could get a big enough chunk of material...would a solid, one piece fincan work? :confused2:

I am in no way expert, or even basically qualified, enough to put forth a theory as to the cause of the failure - but I'm going to do it anyway!

I was struck by the fact that the fin welds were not full length; in fact they seem almost like tack welds. I'm not sure why they were done this way.

With that noted, it also looks as if the high temp epoxy used for aerodynamics in the fillets did not adhere well and/or simply burned away.

Is it possible, that first that epoxy burned away, which exposed the very rough and broken surface of the welds? This then caused flutter/vibration and/or overheating enough to throw off the angle of attack, leading to the rocket shredding.

So, the real culprit would be either poor adhesion, or not sufficient high heat rating, of the epoxy fillets.
If so, the solution seems to be either:
A) full length welds along the fin root, that are then ground down smooth for aerodynamics.
B) a better epoxy with either higher temp rating, or better adhesion.

??? Maybe ????


All that said -
An awesome attempt by a pretty cool team in my book. Would have loved to seen or been part of it.
s6

I would say that vibration caused by inefficient fin design would be the culprit for failure. Full length welds wouldn't help if the fin cracked or was otherwise bent prior to being torn off.

I just want to say to all on this forum, Judy and Jackson are two of the brightest and talented individuals in this hobby. Even though they have not been in the hobby very long (the Lubin's and I flew our first high power motors on the same day!), they are a couple of VERY expirienced people. I was so surprised to hear of this failure, after looking at their rocket, I thought for sure it was going to work. Judy and Jackson, that was an AWESOME attempt, and I'm sure you guys will come back harder next time! I'm glad that I have had the priviledge of fly ing with the Lubin's throughout my rocketry expirience. I can't wait to talk to you guys about this project this weekend at Bong.

Manny

Yes + 1 for the full length welds. Look to the slightly larger, high performance projects that have worked over the years. They all had full length welds. One cant be 100% certain that it would have saved the rocket, but it is a good bet.

stealth6 said:

I am in no way expert, or even basically qualified, enough to put forth a theory as to the cause of the failure - but I'm going to do it anyway!

I was struck by the fact that the fin welds were not full length; in fact they seem almost like tack welds. I'm not sure why they were done this way.

With that noted, it also looks as if the high temp epoxy used for aerodynamics in the fillets did not adhere well and/or simply burned away.

Is it possible, that first that epoxy burned away, which exposed the very rough and broken surface of the welds? This then caused flutter/vibration and/or overheating enough to throw off the angle of attack, leading to the rocket shredding.

So, the real culprit would be either poor adhesion, or not sufficient high heat rating, of the epoxy fillets.
If so, the solution seems to be either:
A) full length welds along the fin root, that are then ground down smooth for aerodynamics.
B) a better epoxy with either higher temp rating, or better adhesion.

??? Maybe ????


All that said -
An awesome attempt by a pretty cool team in my book. Would have loved to seen or been part of it.
s6

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That sounds like some decent analysis.
Bonding epoxy to aluminum is very tricky and to do it properly requires a lot of prep work. Proper procedure may or may not have been followed.
I was looking into it and I found this highly informative thread:
https://www.boatdesign.net/forums/materials/bonding-aluminum-epoxy-2629.html
I wonder if the epoxy ripped off, then exposed the welds, which caused significant heating. It would have weakened the welds and metal significantly when it got above ~500 deg and ripped the fins off.

edwinshap1 said:

I would say that vibration caused by inefficient fin design would be the culprit for failure. Full length welds wouldn't help if the fin cracked or was otherwise bent prior to being torn off.

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I wasn't thinking so much about the strength of the full length welds - more about aerodynamics. What I'm thinking is that once the epoxy fillets burned away (IF that is what happened), that would have left a VERY rough surface area along the fin roots, with those big weld-blobs. That could have caused the vibration/flutter/heat problems that eventually led to the fins ripping off.

If those welds were full length and ground down smooth for aerodynamics (eliminating the epoxy filler), the vibration/flutter may not have occured. And yes, the actual fin to airframe bond would have been stronger as well, but that's not the real issue.

Again - I'm absolutely not experienced or qualified enough to really know any of this. It's just a guess/intuition on my part.

s6

edwinshap1 said:

I would say that vibration caused by inefficient fin design would be the culprit for failure. Full length welds wouldn't help if the fin cracked or was otherwise bent prior to being torn off.

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I can speak a small amount to the fin design -- though the JJL team ran out of time to do a 3D airfoil taper on the fin, the shape is very similar to that which I helped Jackson design. My role was quite small; I performed a sensitivity analysis on various fin planform control variables (root, tip, sweep, span) using my second-generation DATCOM optimizer (see here for a basic description of the previous generation); Jackson took the information generated by this analysis and worked it into a series of RASAero simulations to narrow down the final shape, balancing altitude with "constructability". I then took the final shape from Jackson and ran the code again to generate the airfoil. So I can guarantee that the fin design was anything but inefficient, at least from an aerodynamic perspective.

Would you mind explaining your fin design? I see a lot of people using swept fin designs where the back of the back of the tip chord in behind the fin root. Ive seen this in several high altitude rockets, such as yours and Ken Biba's N altitude record rocket. It occurs to me that the design my not be as efficient strength-wise as one where the entire tip chord is in front of the back of the root chord. It seems like fin designs like the one shown would be more susceptible to fin flutter.(but what do I know? I'm not even a L1) To you think a different fin design would have resulted in a different outcome?

Alex

{edit} You guys wouldnt happen to have any video, would you?

Judy and Jackson,

You guys ROCK! I think it was a very admirable attempt at taming the dragon!

Thanks for the inspiration :clap:

I wonder about something. At the speeds this rocket was likely traveling, the surface heating of the fins would have been substantial... Can the surface temperature have gotten high enough for loss of stiffness of the fins? The outer layer would lose its temper by the time the surface reaches 450F. Stiffness would start decreasing rapidly. The core would maintain properties longer than the surface. The fin would get progressively weaker while losing stiffness rapidly.

You can probably test whether this happened with the recovered fins. Take one of the fins, in an area away from the leading edge, and cut out a test strip. Do the same from a sample of the original aluminum that didn't get flown. Perform a bending test. If the sample which flew is substantially less stiff or less strong, then this could have been a contribution. Essentially, the fins would have the mass of that size fin but not the stiffness, under the aero heating they experienced.

BTW, the stiffness when the aluminum is hot should be less than it will be once it is cooled back to room temperature. So if you measure a loss of mechanical properties of the aluminum in the fins, then in flight it was worse.

One possible contribution, anyway...

Gerald

PS - COOL PROJECT!

I have serious doubts about the fins ever getting that hot in thickness. It is 3/16ths aluminum, a great heatsink, and was exposed to mach 2+ airstream for 2 or 3 seconds at the most at the time of failure. If it did shred at max q, that points towards aerodynamic failure. The most likely culprit is the fins, but a nosecone or airframe implosion or crimp is not out of the question either.

Next time, will you consider full length welds and an all-metal airframe and nosecone?

New Ocean said:

Next time, will you consider full length welds and an all-metal airframe and nosecone?

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Do you suppose adding a coupler to the area above the retainer but below the nc shoulder would do any good to achieve the same effect?

Dear Judy and Jackson,
I am proud to have been a small part of this effort.
I hoped my schedule would have allowed for me to complete what I had planned for you but it was not to be.
None the Less, You have done a Great work in this attempt and you Both should be Very Proud!
I wish you all the best!!

Aksrockets said:

Would you mind explaining your fin design? I see a lot of people using swept fin designs where the back of the back of the tip chord in behind the fin root. Ive seen this in several high altitude rockets, such as yours and Ken Biba's N altitude record rocket. It occurs to me that the design my not be as efficient strength-wise as one where the entire tip chord is in front of the back of the root chord. It seems like fin designs like the one shown would be more susceptible to fin flutter.(but what do I know? I'm not even a L1) To you think a different fin design would have resulted in a different outcome?

Alex

{edit} You guys wouldnt happen to have any video, would you?

Click to expand...

According to David Reese’s DATCOM statistics, sweeping the fins back increases altitude, ceteris paribus. But, sweeping back too much will increase the chance of flutter. The sweep that gives the most altitude actually goes well past the bottom of the rocket. We actually comprised and swept back only slightly.

We discussed fin design with Ken Biba, who does hold the current N record. His planform is almost identical to ours. However, the planform is not the biggest determinant of fin performance. The airfoil and radial taper are much more important. Thanks again to David. Too bad we couldn’t use the full force of his work.

We tried to get video with a go-pro set up on a tripod at the pad. The camera mysteriously shut off just minutes before launch. We had enough chip and we had enough battery. Someone thought that the battery may have gotten too hot sitting on the desert floor for over a half hour. Whatever the reason, our sole photographic memento is Tom Rouse’s picture. Thanks, Tom. We are so happy to have it.