Mach 3.5 Loki L Altitude Record Attempt Build

[watheyak]

It was unsuccessful. It made it most or all of the way through the burn berfectly straight and beautiful, then bad things. So close.

But it was freaking spectacular nonetheless. The carnage is evidence of how brutal the N5800 is.

So what happened? Based on visual evidence from several people with binoculars, the nosecone failed, which removed the fins. But it's hard to say, really. Many projects like this end with a chicken or the egg problem. Did the nosecone failure remove the fins, or vice versa.

But the condition of the nosecone seems to support that it's failure that started the chain of events. I was one of a few failures of the Wildman high temperature nosecone at this Balls. Mine faired much worse than some previous N5800 flights with normal nosecones. That is, well, strange. But that aside, I don't think any off-the-shelf component is really up to the challenge. All the filament wound stuff has the wrong wind angle for the loads place on it. Too much hoop, not enough axial. It's probably too thin, temperature resistance aside. The thickness and temperature resistance are really only an issue fie crazy high impulse flights like this.

I was able to thoroughly obsess over the next attempt for the whole 17 hour drive home. I'm aiming for Balls 32. I have made a nosecone that survived a similar flight profile, and making a 4 inch version is step one. There are a few other improvements I'd like to make as well, and there's lots of CAD work to do. Luckily(?) Half my life is spent in a hotel and I'm excited to use that time buried in Fusion 360.

I welcome all questions, suggestions, opinions and snide remarks.

Here's some pictures of the carnage.

 

[robopup]

Great design, build and attempt! Looking forward to next year's. Sometimes I'm asked why I make so much of my own stuff and, apart from the enjoyment, usually the fundamental reason is that the commercial stuff just doesn't quite do what I want it to do - And fortunately we have guys like you on the forum to copy!

 

[kjhambrick]

I've really enjoyed your Build Thread and I have learned a lot from you.

Maybe a silly Q but not intended as a snide comment ...

Have you tried to power up the Blue Raven ?

Maybe it has some clues ?

-- kjh

 

[watheyak]

I've really enjoyed your Build Thread and I have learned a lot from you.

Maybe a silly Q but not intended as a snide comment ...

Have you tried to power up the Blue Raven ?

Maybe it has some clues ?

-- kjh

@Adrian A looked at it at the launch. It's missing a voltage regulator that will prevent it from powering up. I may explore a solution, for it certainly holds some clues.

 

[Adrian A]

@Adrian A looked at it at the launch. It's missing a voltage regulator that will prevent it from powering up. I may explore a solution, for it certainly holds some clues.

Awesome attempt and carnage!

I don't think I realized what it was you were showing me. If you email me some photos of both sides (featherweightaltimeters at gmail.com) I'll be able to tell better if it looks recoverable, at least for downloading the data.

 

[watheyak]

Awesome attempt and carnage!

I don't think I realized what it was you were showing me. If you email me some photos of both sides (featherweightaltimeters at gmail.com) I'll be able to tell better if it looks recoverable, at least for downloading the data.

Thanks! The carnage will definitely make a good trophy for the wall of the shop.

I'll send a pic this evening.

 

[robopup]

Thanks! The carnage will definitely make a good trophy for the wall of the shop.

My carnage trophy case is running out of room...

 

[MClark]

I saw another fried nose cone that appeared to be wound in only one direction
It to collapsed.

 

[watheyak]

I saw another fried nose cone that appeared to be wound in only one direction
It to collapsed.

I think that was Steve Jurvetson's. He's got some wild pics of the event in progress.

 

[StreuB1]

Nice work and nice designs. Though, it appears you have all your avionics mass, and the mass of the aluminum tip, hanging from the leading edge of the NC. That puts the entire NC transition in immense compression, on top of the aero loading on the exterior. Add to that the compression loading placed on the NC to compress the o-rings you have added to the 3D printed avionics chassis'. Even with ultra soft o-rings, there is a lot of force exerted by them.

If the rocket experiences any off-axis loads, this will put the region directly aft of the last mass object in bending, on top of all the compressive loads mentioned above.

Do you have all your models in 360 with their actual mass? Did you run any FEA on the stack to see what the axial stress was down the NC by chance?

The NC looks like it failed from embedded delamination due to compressive forces beyond its capability.

I would say with some relative certainty that the NC's that Tim sells are not designed for these levels of loads to be placed on them. They aren't designed to have mass hung from their tip.


For high G flights, I would replace the aluminum tip with a tip made from phenolic laminate, bonded in place and retained lightly with a threaded fastener and a backing washer. This will be lighter and put less stress on the leading edge of the NC; phenolic laminate is around half the density of aluminum so it will be half the mass. I would also move all mass objects to the point of main aero structure, the airframe or the top of the motor......or both.

The N5800 is an absolute monster for sure, but it can be tamed.

 

[MClark]

I think that was Steve Jurvetson's. He's got some wild pics of the event in progress.

Yes, it was Steve’s

 

[robopup]

Nice work and nice designs. Though, it appears you have all your avionics mass, and the mass of the aluminum tip, hanging from the leading edge of the NC. That puts the entire NC transition in immense compression, on top of the aero loading on the exterior. Add to that the compression loading placed on the NC to compress the o-rings you have added to the 3D printed avionics chassis'. Even with ultra soft o-rings, there is a lot of force exerted by them.

If the rocket experiences any off-axis loads, this will put the region directly aft of the last mass object in bending, on top of all the compressive loads mentioned above.

Do you have all your models in 360 with their actual mass? Did you run any FEA on the stack to see what the axial stress was down the NC by chance?

The NC looks like it failed from embedded delamination due to compressive forces beyond its capability.

I would say with some relative certainty that the NC's that Tim sells are not designed for these levels of loads to be placed on them. They aren't designed to have mass hung from their tip.


For high G flights, I would replace the aluminum tip with a tip made from phenolic laminate, bonded in place and retained lightly with a threaded fastener and a backing washer. This will be lighter and put less stress on the leading edge of the NC; phenolic laminate is around half the density of aluminum so it will be half the mass. I would also move all mass objects to the point of main aero structure, the airframe or the top of the motor......or both.

The N5800 is an absolute monster for sure, but it can be tamed.

Ehh, I'm not so sure I buy that. These ebays are pretty light - my 54mm version with a very similar design weighs 105 grams for example. I've hit them fairly hard - up to 80+ g's in 38mm, 35 g's in 54mm. So my max acceleration load on my 54mm version is putting 0.105kg*350m/s2 = 35 N on that edge. EDIT - with aluminum nose tip, the whole package is 125 g so load goes to 44 N. That's nothing; I bet I could stack the whole book case next to me on that NC edge and it wouldn't bat an eye. And I suspect that's worst case - at least in my design, the ebay is screwed into the nosetip and the oring is taking some of that load.

I'm not saying it's simply aero loads either, but continuing with my example, that 54mm flight above hit mach 2.5. So dynamic pressure on it was 0.5*1.225kg/m3*(2.5*340m/s)^2 ~= 442,000 Pa. So apprx load on the nosecone would be 442,000Pa*pi*(.054m/2)^2 ~= 1000 N. I'm obviously cheating here - with a proper cd, total drag is probably more like 300-400 N but you get my drift... In short, I'm a lot more worried about aero loads than the acceleration on my ebay.

And I'd be willing to bet the discrepancy between aero and ebay acceleration loads is quite a bit larger for @watheyak 's flight then mine - his frontal area is going up by the square, while the ebay probably isn't that much heavier.

Having said that, I do think the fiber orientations on those filament wound nosecones are... not ideal. I'd bet the matrix carries a lot more the load that it should have to.

 

[StreuB1]

A bit dismissive.

I ran it in abaqus over lunch.

 

[robopup]

I ran it in abaqus over lunch.

Nice! Happy to take this off to another thread if we're getting too off topic for @watheyak . How did you model it? What were your results? Want to share your .inp? Prove me wrong but a bunch of actual flight data says otherwise. EDIT: Not intended to be snarky in any way, genuinely curious about your results and how you modeled it.

 

[charrington]

Wow! Scott you are one mad lad can’t wait to see the next version. I was wondering if you have ever looked into 3d printing a nosecone using a SLS printer with a FG or CF impregnated nylon? Ive been looking into it for a second attempt at the K627 record I tried this last year.

 

[watheyak]

Ehh, I'm not so sure I buy that. These ebays are pretty light - my 54mm version with a very similar design weighs 105 grams for example. I've hit them fairly hard - up to 80+ g's in 38mm, 35 g's in 54mm. So my max acceleration load on my 54mm version is putting 0.105kg*350m/s2 = 35 N on that edge. EDIT - with aluminum nose tip, the whole package is 125 g so load goes to 44 N. That's nothing; I bet I could stack the whole book case next to me on that NC edge and it wouldn't bat an eye. And I suspect that's worst case - at least in my design, the ebay is screwed into the nosetip and the oring is taking some of that load.

I'm not saying it's simply aero loads either, but continuing with my example, that 54mm flight above hit mach 2.5. So dynamic pressure on it was 0.5*1.225kg/m3*(2.5*340m/s)^2 ~= 442,000 Pa. So apprx load on the nosecone would be 442,000Pa*pi*(.054m/2)^2 ~= 1000 N. I'm obviously cheating here - with a proper cd, total drag is probably more like 300-400 N but you get my drift... In short, I'm a lot more worried about aero loads than the acceleration on my ebay.

And I'd be willing to bet the discrepancy between aero and ebay acceleration loads is quite a bit larger for @watheyak 's flight then mine - his frontal area is going up by the square, while the ebay probably isn't that much heavier.

Having said that, I do think the fiber orientations on those filament wound nosecones are... not ideal. I'd bet the matrix carries a lot more the load that it should have to.

Quick stream of consciousness blast here...

I definitely think there's something to this. Looking at the wreckage, it appears the noseone tip fell off to one side. The fit of the metal nosecone tip was problematic from the start. It's so slightly different diameter than the opening in the nosecone. I spent a lot time making sure it was concentric, but I think I'm the crush to get it prepped that got messed up. The space just aft of the tip should really have been potted in epoxy. The L rocket was that way, potted with Cotronics.

As far as the avionics hanging off there, and the effects of acceleration has on the nosecone structure, I feel like if the nose wasn't rapidly turning into a ball of yarn, it would have been ok. This av-dingus (it's official name) was four times the mass of the L rocket's av-dingus. It's a solid hunk of resin. I'm gonna ponder rearranging or flip-flopping the layout.

I also need to re-read your post a couple times. Much to absorb.

About to go on a long airplane ride. More later.

 

[watheyak]

Wow! Scott you are one mad lad can’t wait to see the next version. I was wondering if you have ever looked into 3d printing a nosecone using a SLS printer with a FG or CF impregnated nylon? Ive been looking into it for a second attempt at the K627 record I tried this last year.

Thanks!

I can't stand filament 3d printing. Too weak for everything due to layer strength. To me, they're just an overcomplicated hot glue gun.

And I own two!

 

[charrington]

I can't stand filament 3d printing. Too weak for everything due to layer strength. To me, they're just an overcomplicated hot glue fun.

And I own two.

Im talking about SLS printing not filament. Its a powder that uses a laser to sinter. My friend at HP uses it for high strength parts! Super super strong stuff, nothing like the normal 3D printers that use filament. These machines usually start at $25K but there are online services that will print out desings you upload.

Edit: also is there a video?!

 

[robopup]

Quick stream of consciousness blast here...

I definitely think there's something to this. Looking at the wreckage, it appears the noseone tip fell off to one side. The fit of the metal nosecone tip was problematic from the start. It's so slightly different diameter than the opening in the nosecone. I spent a lot time making sure it was concentric, but I think I'm the crush to get it prepped that got messed up. The space just aft of the tip should really have been potted in epoxy. The L rocket was that way, potted with Cotronics.

As far as the avionics hanging off there, and the effects of acceleration has on the nosecone structure, I feel like if the nose wasn't rapidly turning into a ball of yarn, it would have been ok. This av-dingus (it's official name) was four times the mass of the L rocket's av-dingus. It's a solid hunk of resin. I'm gonna ponder rearranging or flip-flopping the layout.

I also need to re-read your post a couple times. Much to absorb.

About to go on a long airplane ride. More later.

Like you said earlier, these failures are always hard to find a root cause on -everything takes such a beating after things let go. But I'll give my no-hard-data-armchair-speculation swag. If it was actually the nosecone that let go first, I have two guesses:

• Looking at pictures of those filament wound nosecones, the fiber angle is so close to the hoop direction (assuming it's a single winding angle, maybe it's not?) the fiber can't be taking much of the load. So matrix failure somewhere due to aero loads then kablooey? @StreuB1 has inspired me to put a quick model together, which I'll try and do in the next couple days. I think the problem he's pointing towards would actually be really hard to get the physics right on, but simple aero loads and looking at fiber and matrix strains isn't so bad. EDIT: Was this fiberglass or carbon? What was the laminate thickness? And does the winding angle on the inside look the same as the outside - or any other data on what the stacking sequence actually is? I took a quick look at Wildman's site and couldn't find this info. EDIT2: What was your simmed max speed, and altitude at which it was supposed to occur?
• You mentioned the nosetip fit wasn't quite right? Do you have a close up picture? One thing I was worried about on my project was that my nose tip was about 0.010" smaller diameter than the composite section of the nosecone, and that this could lead to delamination immediately behind the tip (sort of like how fin leading edges can get smoked). Unfortunately, my buddy I make these with doesn't have a lot of free time so I had to go with it, and fortunately I lucked out.

Safe flight!

 

[watheyak]

Im talking about SLS printing not filament. Its a powder that uses a laser to sinter. My friend at HP uses it for high strength parts! Super super strong stuff, nothing like the normal 3D printers that use filament. These machines usually start at $25K but there are online services that will print out desings you upload.

Edit: also is there a video?!

Oh I see! Lemme look into that.

 

[watheyak]

 

[wsume99]

I don't have any experience with ultra high speed rocket flights but I am familiar with composite layups and their use in aerospace applications. You said the NC failure occurred near the end of the flight, so effectively the NC was under a high temp heat soak. Granted it was not a long soak but my theory is it was long enough. It's very likely the bulk temp of the NC exceeded the Tg, not just the outer surface. I don't think this a pure overloading failure, it was overloaded in a weakened condition. Not sure how you'd model the material properties of the NC if it's been overheated and the resin has softened. Maybe elevated temp performance data is available from WM or his supplier. You said earlier that you're flying beyond the capability of the off the shelf materials and that sounds right to me.

If the failure occurred just prior to the end of boost then perhaps some minor changes to your design can give you enough margin to ensure the off the shelf components survive the extreme flight conditions. This seems like what you are planning based on the discussion.

Still an impressive flight and it's been fun watching your journey.

 

[charrington]

Hey Scott,

Is there a video of the launch?! Id love to see it. Im sure it was an insane boost.

 

[Neutronium95]

The fins for this are machined from G-11. It has a max temperature of around 335 degrees F and is hard and dense. I arrived at this after seeing regular G-10 survive high-Mach flights good as new. In addition to flight loads, they also needs to withstand the temperature of the oven while the prepreg reinforcements cure. This was a major hurdle that caused a couple do-overs in the previous iterations. Fingers crossed for a fins that aren't crispy and warped this time around.

The leading and trailing edges have a generous bevel, and a pocket is routed from the center of the plate, allowing the tip to tip reinforcement to be recessed, out of the slipstream. This will prevent any sort of seam or step at the leading edge to soften and spilt due to aerodynamic loads and heating. This is one of the ideas I stole from the "what would I have done differently" post in A5tro Anon's N-5800 thread a few years back.

I'm considering a similar fin design for one of my projects. Where did you get the fin cores machined?

 

[watheyak]

I'm considering a similar fin design for one of my projects. Where did you get the fin cores machined?

https://www.hubs.com/
Glad you asked, it motivated me to search my emails from 2020 to find it.

I couldn't remember where and I'm about to get the fins going for v2 of the N5800 attempt.