Insanity Plea: A sub minimum diameter M2245 project.

[ChrisAttebery]

I received my M2245 reload on Friday around 3PM. I spent the next 6 hours epoxying the grains into the motor, assembling the motor and the rest of the rocket.

I crawled out of bed at 5:30AM on Saturday and ate breakfast while I watched the sun come up.



I hauled the rocket out the 1000' pads and loaded the rocket into my tower.





The winds were calm and the waiver opened up at 7AM. We waited until about 7:30 to let everyone else wake up. I fired up the electronics and we attempted to launch the rocket. Apparently I got a little distracted and forgot to hook the igniter to the launch system. I ran out to the tower and hooked it up. We tried again and it lit after about 2 seconds.



The rocket screamed out of the tower and headed up at about a 3 degree angle to the West. Around 4 seconds into the flight, right around MaxQ, there was an event and the rocket made a hard turn to the North. Parts could be seen floating down.

Jim Green was able to track the rocket down to the ground so I headed out to collect the remains. The first thing I found was *most* of the aluminum airframe adapter. The threaded section was torn clean off the bottom. Next I found the drogue chute and shock cords tangled up in a ball of carbon fiber from the coupler. I found a fin another 100 or so yards away. The motor casing was roughly 3500' North of the tower.



On the way back I found the nose cone.



Here's everything that I recovered.


I'm not really sure what happened. All of the fins were stripped off the motor. The epoxy was still bonded to the motor. One of the fins I found had about 80% of the leading edge curled over about 3/16". The other fin had obvious impact damage. The nose cone has obvious ablation damage, but it was still solid. The coupler seems to have disappeared other than a small section that is still epoxied to the nose cone. The nose cone has impact damage and the CPU on the TeleMega had most of its pins broken right at the package so there won't be any way to recover data from it. The last packet I got from the TeleMega said it reached 5980 feet and 3960fps or 2700mph. RASaero II predicted it would reach 3981fps. Nice job Mr. Rogers. To give you an idea of just how fast that is a .30-06 bullet travels at around 2700fps.


I always knew that there was a good chance that the rocket wouldn't come back in one piece. It was an awesome launch anyway.

Now to get some rest...

 

[tim cubbedge]

Sorry to hear. Still an awesome build!

 

[Andrew_ASC]

Mach 3.5 is no slouch of an environment for materials and design. There are many failure modes at those extremes.

 

[Andrew_ASC]

Sorry to hear. Still an awesome build!

If he learns anything from the broken pieces it will be worthwhile to help his next build or anybody else attempting this.

 

[Cl(VII)]

Sorry to hear off the loss, but I wholeheartedly applaud the effort. I look forward to reading any insights you glean from the remains, and subsequent thought.

 

[grouch]

Sorry to hear but if you are gonna go, may as well go huge! I have been following this build and was pulling for you.

 

[Steve Shannon]

I know he’ll be back with the issues addressed.
As they say at the rodeo, “How about a hand for this cowboy; he’s not getting anything else!”

 

[ColumbiaNX01]

What epoxy was used for the fins??? Was there tip to tip?? How healthy were the fillets?

 

[ChrisAttebery]

Steve, I like that. I may have to borrow it. ;^)

I know he’ll be back with the issues addressed.
As they say at the rodeo, “How about a hand for this cowboy; he’s not getting anything else!”

 

[A-N-D-R-E-W]

Noooo! I’ve been following this build, sorry to see that it didn’t go as planned. Those fins look pretty chewed up.. are you thinking it failed at the top and folded back on itself?

That looks like a beautiful area, enjoy the scenery and the rest of the trip! Take care.

 

[UhClem]

Aluminum is a good conductor of heat and loses strength rapidly as it gets hot. I looked in MIL-HDBK-5 and didn't see any curves for stiffness which is the more important parameter for flutter.

I wonder what the staff thermodynamicist had to say about hanging bare aluminum out in the breeze without an ablative coating.

As for the Telemega, sheared off the pins on which package? So long as the 8 pin serial memory chip is in decent shape you can get data out of it.

 

[plugger]

Sorry to read about your non-nominal flight Chris. Great attempt though. Fingers crossed you find the root cause of the failure. I'm sure you'd like that information moving forward.

 

[Chuck Rogers]

The last packet I got from the TeleMega said it reached 5980 feet and 3960fps or 2700mph. RASaero II predicted it would reach 3981fps. Nice job Mr. Rogers.

Although technically there might have been a little propellant left when it broke-up.

We'll work on that last 21 ft/sec.


Charles E. (Chuck) Rogers
Rogers Aeroscience

 

[boatgeek]

Sorry to hear about the breakup on such a cool project. Looking at the pictures, I have a quick question: it looks like the fins and fillets sheared cleanly off the casing. You mentioned there was epoxy on the casing, but it looks really clean. Do you know if the failure was through the epoxy or at the glue join?

 

[ColumbiaNX01]

What epoxy was used for the fins??? Was there tip to tip?? How healthy were the fillets?

 

[pendrin2020]

Making it to that speed, even without getting the bird back is a monumental accomplishment. Dude, I can't wait to go to black rock someday!

Do you have any pics of the fin roots?

 

[tim cubbedge]

What epoxy was used for the fins??? Was there tip to tip?? How healthy were the fillets?

Start reading from this point: https://www.rocketryforum.com/threa...eter-m2245-project.143884/page-4#post-1806688

 

[ColumbiaNX01]

Start reading from this point: https://www.rocketryforum.com/threa...eter-m2245-project.143884/page-4#post-1806688

Cant see the fillets. I thought the fins were machined with a wide base to be attached. I have always used hysol e-120 hp.

 

[mpitfield]

Chris awesome attempt and I looking forward to reviewing your thoughts on what you need to change for your next attempt.

 

[Dipstick]

As they say in my field...nice try. Now try again

Thanks for the update, been following this for a while and very impressed with the design. Guess the real world wins this round

 

[ChrisAttebery]

Yes, the fins sheared off cleanly. The epoxy stuck to the motor case. I used lye to remove the anodizing on the case. Otherwise I prepped the fins and case in the same way. There was impact damage on at least two of the fins. One fin had 3/16" of its leading edge curled back 180 degrees. I don't think we'll ever know what happened but I think that the fins held on until the rocket tumbled. At that point the loads on the fins went off the charts.

I used 3M DP460-NS epoxy. I don't think the epoxy was the cause of the failure. My leading causes in no particular order are fin root prep, fin thickness, a coupler failure, nose cone tip coming off...

Sorry to hear about the breakup on such a cool project. Looking at the pictures, I have a quick question: it looks like the fins and fillets sheared cleanly off the casing. You mentioned there was epoxy on the casing, but it looks really clean. Do you know if the failure was through the epoxy or at the glue join?

 

[rfjustin]

Chris,

What held the tip in place? Was it removable?

 

[ChrisAttebery]

Tony Alcocer sent me his video of the launch. It doesn't show the breakup, but it captured the launch and the aftermath pretty well.

 

[ChrisAttebery]

It was a removable tip with a shoulder. In hindsight I probably should have epoxied it in place.

What held the tip in place? Was it removable?

 

[3stoogesrocketry]

What do the threads on the forward end of the case look like ? I'm thinking a high sideways torque was applied . This caused the threaded section of the case to oval out , the rocket then simply layed over due to the aero forces and the rest is history.

 

[Nick@JET]

Nice attempt Chris, followed from the start and was hoping for great success. Here is to you for going for the extreme

 

[ChrisAttebery]

I was able to download the onboard video. Unfortunately it doesn't really show anything.

 

[Steve Shannon]

I was able to download the onboard video. Unfortunately it doesn't really show anything.

That may be a clue though. As fast as it started spinning at low velocity right after launch, just think of the angular velocity when it was at 3961 FPS. It’s possible the epoxy simply could not provide the centripetal force needed to keep the fins on. If one flew off conservation of angular momentum would have torn everything else apart causing the pieces to strike each other in the air.

 

[pendrin2020]

Steve makes a really good point. That high rate of spin would have created some really massive force. Especially when you factor in the higher mass of the aluminum in those fins.

 

[ChrisAttebery]

I've been thinking about that. The fins had ~9.5 square inches of mounting surface. The epoxy was rated for 4500psi. 9.5 x 4,500 = 42,750 lbs of total holding force. The fins weren't that heavy. They weighed ~3.5 oz or .218 pounds each. 42,750 / .218 = 195,428 gees. I'm pretty sure it wasn't spinning enough to produce those kind of G forces.