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Sorry but I was replying to this comment.

If there was a way to get aluminum tape to shear cleanly off I'd say go for it. But since aluminum tape isn't THAT sticky,

And the glue on 3M 425 WILL rip layers of glass apart. And the tape comes in all different thickness. I have some that is .010 thick, that would for sure hold up better than the .0015 stuff.
 
Some pictures of the damage.

The fin can was almost entirely unscathed. Just a little chip out of the leading edge.PXL_20240123_014927911.MP.jpg

The nosecone is a bit worse. The tip got broken, and there are a few points of abrasion or mach rash. The blue indicates that it impacted the top of the avbay at some point. I'm not sure if I'll make a new nose or if I'll just fix this one.
PXL_20240123_014946860.MP.jpgPXL_20240123_014953961.MP.jpg

The avbay was the worst. The Featherweight GPS antenna got pretty smooshed, and the Blue Raven sustained some damage. Fortunately both units seem to be largely functional, so the damage shouldn't be that bad. Still going to consult with the manufacturer before flying them again.

PXL_20240123_015026056.MP.jpgPXL_20240123_015243591.MP.jpg
 
Neutronium95 said:
Some pictures of the damage.

The fin can was almost entirely unscathed. Just a little chip out of the leading edge.View attachment 625597

The nosecone is a bit worse. The tip got broken, and there are a few points of abrasion or mach rash. The blue indicates that it impacted the top of the avbay at some point. I'm not sure if I'll make a new nose or if I'll just fix this one.
View attachment 625598View attachment 625599

The avbay was the worst. The Featherweight GPS antenna got pretty smooshed, and the Blue Raven sustained some damage. Fortunately both units seem to be largely functional, so the damage shouldn't be that bad. Still going to consult with the manufacturer before flying them again.

View attachment 625600View attachment 625601
Click to expand...
What’s that nose tip made of?
 
This flight really has me rethinking the recovery system design for this and future high performance projects. This failure mode has happened before, where the cable cutter worked perfectly, but the parachute refused to open. One such case is this project by @CarVac. I've always had the parachute deploy when the cable cutter fires in my sport and high performance rockets alike. I have seen it take a few seconds to open, so I opted to raise the main deployment altitude to 1200 feet for some extra margin, but that was obviously inadequate.

With that preamble out of the way, here are some things I'm considering for this rocket going forward and for high performance projects in the future.

  • Always fly with a drogue. 150 ft/s is a really spicy descent rate, and from the impact it looks like it was falling nose down.
  • The first idea I had was to sew a top loop onto the parachute. This would allow me to run a line out of the parachute burrito to a small drogue, which would ensure rapid and reliable deployment of the main.
    • Pros: Simple, compact, passes the reliability sniff test.
    • Cons: Drogue could possibly pull the main out of the nomex burrito, the attachment point could be torn off during main deployment.
  • Instead of wrapping the main into a burrito, the cable cutter could be put around the shroud lines, right below the parachute canopy to reef the main.
    • Pros: Simple, gets you a drogue without adding any parts
    • Cons: A reefed main would be a big drogue for a rocket this size, shroud lines could twist up during drogue phase, limiting how much the main can actually open.
  • An @AdrianA style parachute cannon attached to the top of the avbay.
    • Pros: It seems to work quite well for him. Squeezing it into the tube probably helps maximize parachute packing efficiency.
    • Cons: Might require a not insignificant redesign of the avbay in general.
  • A floating parachute cannon that is attached to the shock cord instead of rigidly mounted to the avbay.
    • Pros: Seems like it would offer most of the benefits of the parachute cannon architecture without a major redesign.
    • Cons: The recoil might shoot the cannon back into the avbay. Probably could be mitigated with the correct charge size.
  • Change to the dual deploy method used by Kip Daugirdas on Mesos, and by the Aeropac 100k rocket.
    • Pros: It seems to have worked quite well for multiple extreme performance flights. Extremely simple with no added parts.
    • Cons: It would require either relocating the electronics to the nose tip, or running long wires along the shock cord. Both of the implementations that I'm aware of had the main in a tube, a parachute in a tube that slips a little bit will still be held in by friction, but in a cone a small slip could lead to the parachute deploying early.
  • Rolling up a piece of stiff plastic with the parachute to make sure that the bundle springs open when the cable cutter fires.
    • Pros: Seems to be very simple.
    • Cons: Has been tested by @Zertyme, it didn't work well.
I'm currently leaning towards the drogue attached to a top loop of the parachute, and the floating parachute cannon. Both seem to be relatively simple to implement on my current design. The hard mounted parachute cannon and Aeropac style systems both seem promising for future projects, but probably won't work with this design.
 
I just got confirmation that I'm good to fly at FAR again this coming weekend.

Fortunately, the repairs aren't too bad. I've already printed a replacement avbay. The nosecone is currently back in the tip mold getting a new tip cast on it. That just leaves soldering on one leg of the big capacitor on the Blue Raven and adding the top loop to the parachute to prevent the same failure mode from happening again.

If this flight is successful, I think that I'll be confident enough in my skills to actually attempt the M record.
 
I painted on a layer of Proline epoxy onto the nosecone and sanded it smooth. Mostly just to smooth it out a tad. It could probably stand to get a bit more finish work, but I'm calling it good enough.

I decided to go with the top loop on the main parachute approach, since it seemed to be the easiest to implement on short notice. I sewed a length of cord from an old tent project onto the Top Flight Thin Mill parachute, and rigged everything up. I'm using a 9" thin mill for the drogue, and just a short length of kevlar to connect the two. When rigged up with a regular size cable tie and a Half Cat cable cutter, the main parachute is pretty well contained. I pulled pretty hard on the drogue line and couldn't get it out of the burrito when the zip tie was fully cinched down. My only concern about the recovery system is the volume. I cut things way too tight on recovery volume on this rocket. With the 30" parachute I used at BALLS, I needed all of my weight to press the nose onto the coupler so that I could install the shear pins. With the new drogue it's not quite as tight, but it is close. I've already cut down the size of the nomex sheet for the main to save volume, I hope it's good enough, since shortening the shock cord is my only other way to reduce recovery volume, and with the oversized ejection charges I prefer to use I want to have as much cord in the system as possible.
PXL_20240201_091151372.MP.jpg

I also cleaned up the divot in the leading edge of the fin can by dremeling off the top eighth inch or so and then sanding a new bevel into the lip. Finally to finish up the prep work, I fired a few ematches with the ground test on the Blue Raven to confirm that it was working.
 
@Neutronium95 --

I really like your drogue -to- main setup !

I googled 'Half Cat Rocketry Cable Cutter' and I did find the Half Cat rocketry site but never found a site that sells or describes the 'Half Cat Cable Cutter',

Is that something you made yourself ?

It looks kinda-sorta like a hexagonal all thread coupler ?

Something I never considered ... it seems it would be easy to seal one end that-a-way ...

-- kjh
 
kjhambrick said:
@Neutronium95 --

I really like your drogue -to- main setup !

I googled 'Half Cat Rocketry Cable Cutter' and I did find the Half Cat rocketry site but never found a site that sells or describes the 'Half Cat Cable Cutter',

Is that something you made yourself ?

It looks kinda-sorta like a hexagonal all thread coupler ?

Something I never considered ... it seems it would be easy to seal one end that-a-way ...

-- kjh
Click to expand...


They never really went into production. They just made a few batches to sell, which is unfortunate since it's my favorite cable cutter and I'd really like more.

It's machined out of 3/8" Aluminum hex stock.
 
With a bit of finagling I managed to make everything fit into the nose. The surface finish on the nose still isn't great, but it's not going to make or break the flight, so I'm calling it good enough to fly. I'm driving out to FAR this weekend, mostly to hang with friends. If the wind isn't too bad I'll launch.

PXL_20240202_011116161.MP.jpg
 
Another successful boost, another recovery failure.

Tge GPS reported a steady 90 ft/s descent rate after apogee, but after descending a few thousand feet it rapidly increaded to 300 ft/s. I found the bulk of the rocket, but all of the electronics and fiberglass parts were trashed. I think that the shock cord may have been worn through from rubbing on tge hole in the nut it was tied through.
1000010896.jpg

I'm feeling pretty dejected right now. This was supposed to be a proof of concept for future high performance projects, and I'm really not sure where to go from here. I think that the recovery system design is alright, but I don't want to fly it untested on an even higher performance flight with a nearly irreplaceable motor.
 
Neutronium95 said:
Another successful boost, another recovery failure.

Tge GPS reported a steady 90 ft/s descent rate after apogee, but after descending a few thousand feet it rapidly increaded to 300 ft/s. I found the bulk of the rocket, but all of the electronics and fiberglass parts were trashed. I think that the shock cord may have been worn through from rubbing on tge hole in the nut it was tied through.
View attachment 628232

I'm feeling pretty dejected right now. This was supposed to be a proof of concept for future high performance projects, and I'm really not sure where to go from here. I think that the recovery system design is alright, but I don't want to fly it untested on an even higher performance flight with a nearly irreplaceable motor.
Click to expand...
Do you have a picture of the shock cord where it likely wore through? Could you bore out the nut and smooth the edge so there’s less chance of wear. Alternatively, could you add a bit of heat shrink to the shock cord at the wear spot?
 
boatgeek said:
Do you have a picture of the shock cord where it likely wore through? Could you bore out the nut and smooth the edge so there’s less chance of wear. Alternatively, could you add a bit of heat shrink to the shock cord at the wear spot?
Click to expand...
No. I wasn't able to find the nose cone, parachutes and shock cord. It likely drifted significantly farther down range, and the tracker wasn't attached. I didn't have the energy to search a bunch of scrub land for it.
 
Wow, @Neutronium95 !

You've made a lot of progress with this bleeding-edge concept -- that shock cord failure was plain-ole, pure-d bad luck.

Thank you for this thread -- I've learned a lot from your analysis and design.

These are your three submin flights, side-by-side:

neutronium-submin-flt1-crop-2-scale-4.pngneutronium-flt2.jpegneutronium-flt3.jpeg
Note that I cut, cropped and scaled flight 1 from @UPscaler's video back on post #34 -- sorry about the quality and I hope that's OK with him !

Flight #1 was a K1103X, Flight #2 was a K2050ST.

What motor did you fly on flight #3 ?

Is your RMS 54/1706 casing OK ?

Does your fin can look OK other than any damage from the landing ?

Did you get any GPS downlink data for the flight ?

This is advanced rocketry and you've done some amazing work !

I wish I was still a member of TRASD so I could be there :)

Seems like if you solve the issue with your shock cord, you'll be good to go with your up-scale.

Hang in there and thanks for sharing your experience !

-- kjh
 
kjhambrick said:
What motor did you fly on flight #3 ?

Is your RMS 54/1706 casing OK ?

Does your fin can look OK other than any damage from the landing ?
Click to expand...
Flight 3 was also a K1103.

The hardware seems intact. Maybe a few scratches, but nothing obviously wrong. It'll get a more thorough inspection before flying again.

The fin can is almost salvageable. Unfortunately some of the impact damage goes down below the top of the fin roots. I might remove the fins and attach them to a new tube in the future.
 
Neutronium95 said:
Flight 3 was also a K1103.

The hardware seems intact. Maybe a few scratches, but nothing obviously wrong. It'll get a more thorough inspection before flying again.

The fin can is almost salvageable. Unfortunately some of the impact damage goes down below the top of the fin roots. I might remove the fins and attach them to a new tube in the future.
Click to expand...
Yes, the exhaust from flight #1 and flight #3 look VERY similar, especially factoring in my crappy frame-grab.

You've definitely got the boost-phase down pat !

Good news that the fins can be salvaged and that the RMS 54/1706 looks OK.

I've got to say that your fin can is a work of art and I am with @Brainstormz123 -- I really like your alignment jig !

I've been wondering if my Kevlar shock cords should be considered 'consumables' ... if not every flight then 'when they wear out' ...

Especially the shock cord that's deployed at apogee. It seems that poor little fella can take a lot of abuse on the way down -- especially as the two ends get heavier.

Thanks again @Neutronium95 this is one of the best threads I've ever read !

-- kjh
 

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