Blue Variable - 38mm K627 Altitude Record Attempt - My Failure

[Neutronium95]

I'm really liking this thread. You're thoughts about high performance rocket design mirror mine pretty closely. I am a bit more interested in flying case style rockets, but that's probably due to following the Bare Necessities build as a teenager. The new high performance single use motors from Aerotech also make that easier, since you can bond the fins onto the motor much easier than with an aluminum motor case.

I'm looking forward to seeing how you packaged the electronics. That's always one of the trickiest parts of a fully optimized design, and something I'm working through right now on a few of my projects.

Any plans to put a J1026 in it and smash the J record? I love the idea of rockets that are capable of breaking two different altitude records.

 

[StreuB1]

I had a lot of long phone calls with some of my aerospace engineer friends and fin design turns out to be very nuanced in super sonic flow. Sadly, none of them are dedicated aerodynamicists. Most of them do systems, propulsion, structures. If there happens to be anyone reading this that specializes in this area of aerospace Im sure we would all love to learn how this works. Im also especially interested in why stability increases before rapidly decreasing.

What I am confused about is how the longer more swept leading edge in the foreward swept (design picture 3) design goes so much higher than the smaller forward swept design (design picture 2). The tip chord should be in the same exact place in both designs. Is it just the shallower angle of the longer root chord produces less drag in the mach cone?

A trailing sweep sheds high speed flows off the trailing tip and away from the airframe.

 

[charrington]

I've been thinking along similar lines for a while now and had come to the same conclusion without arriving at much of the way of a workaround. My only thought would be to bond aluminum fin slots to the case (for it should be easier to bond aluminum to aluminum) and cover the slots with a fillet that might be best if not as rigid as we typically make fillets.

Wacky is good:

"The reasonable man adapts himself to the world: the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man.” - George Bernard Shaw

I had an idea for this too. I think using epoxy additives that dampen vibration along with the correct epoxy might be a good start. I was planning on doing simple tests using some 6061 T6 piping and fiberglass squares. Bond using multiple methods and then heat in the oven and then start hanging weights off of the fiberglass squares. If similar strength values are achieved then I think the vibration dampening can be looked into at that point. There are some options here. There has been some research into using dried and shredded plant material to dampen vibrations and reduce cracking in composites (I think it was banana peels or some sort of husk?) - https://www.researchgate.net/public...tes_Mechanical_Properties_and_Fire_Retardancy.

There is also other types of adhesives that I was looking into, specifically: https://www.permabond.com/resource-center/mma-methylmethacrylate-adhesives/
There is also something my grandfather mentioned which sparked a light bulb in my head but I am going to wait on disclosing this one until I can prove it works.... maybe on Scott's L record he keeps begging someone to steal @watheyak

...Just give me 1 or 2 years lol

 

[charrington]

Mine actually simmed to ~44k', but I think it was the pretty hard left turn due to high upper level winds that stole a bunch of the altitude.

I left the window wide open, and eagerly await someone else's cool project to steal the record

You know, if the window was wide open someone would have grabbed it already! It's going to be a hard record to beat!

Just curious if you have the time, what would your altitude be if you simmed with a thin wall composite airframe vs. the fin can? Does it match what I am seeing where the thin walled airframe typically goes much higher?

 

[charrington]

A trailing sweep sheds high speed flows off the trailing tip and away from the airframe.

Ooooh... That makes so much sense! Thank you!

 

[charrington]

I'm really liking this thread. You're thoughts about high performance rocket design mirror mine pretty closely. I am a bit more interested in flying case style rockets, but that's probably due to following the Bare Necessities build as a teenager. The new high performance single use motors from Aerotech also make that easier, since you can bond the fins onto the motor much easier than with an aluminum motor case.

I'm looking forward to seeing how you packaged the electronics. That's always one of the trickiest parts of a fully optimized design, and something I'm working through right now on a few of my projects.

Any plans to put a J1026 in it and smash the J record? I love the idea of rockets that are capable of breaking two different altitude records.

Aerotech coming out with the long burn composite motors is a game changer. I am hoping to see you or someone break 20K on an H motor!

The electronics was definitely the hardest part of this whole endeavor. I will try to be as thorough as I can when I get to it. Im going to have to rely on drawings and diagrams a lot because I forgot to take a picture of the final AV config (I really thought I was gonna get it back...). I do know exactly how everything fit though and once I order another set Ill be able to post pictures. Plus I wouldnt follow this method to a T because It didnt quite work as we know lol. I have some ideas on how to fix the issue though and I plan on keeping this thread updated with the progress of my next attempt.

And actually yes! As it turns out, The current configuration smashes the J record with either the J1000 or the J1026! Since I have a whole year to do this I plan on trying both on the same day, same airframe. The J1026 is pulling 110 Gs though which could be an issue. I wanted to try to get both done this time but ended up running out of time and didn't purchase the motor thankfully.

Even if a manufacturer comes out with something super long burn that will be impossible for me to beat with the K627 I still will launch. I think a 38mm Mach 3, 30k ft launch is something amazing to do anyways!

 

[Neutronium95]

And actually yes! As it turns out, The current configuration smashes the J record with either the J1000 or the J1026! Since I have a whole year to do this I plan on trying both on the same day, same airframe. The J1026 is pulling 110 Gs though which could be an issue. I wanted to try to get both done this time but ended up running out of time and didn't purchase the motor thankfully.

That's great to hear. Also gives me time for a J510 attempt before that motor becomes totally obsolete for the record.

 

[charrington]

That's great to hear. Also gives me time for a J510 attempt before that motor becomes totally obsolete for the record.

Please do it! I think the J510 needs one more hoorah. @AeroTech any plans on throwing a long burn load into the J510 case?

 

[AeroTech]

Please do it! I think the J510 needs one more hoorah. @AeroTech any plans on throwing a long burn load into the J510 case?

Stop, you’re giving me ideas…

 

[watheyak]

You know, if the window was wide open someone would have grabbed it already! It's going to be a hard record to beat!

Just curious if you have the time, what would your altitude be if you simmed with a thin wall composite airframe vs. the fin can? Does it match what I am seeing where the thin walled airframe typically goes much higher?

I never simmed the Loki L Record with a full case. But the current 4" version sims a bit higher that way. Not much, but still an improvement.

Other advantages are the fact that

1. You're not using the motor closure as structure

2. You don't really have to spend one year and a gallon of epoxy on a nosecone mold. (Maybe that only applies to people with an unhealthy relationship with their rocket hobby).

3. It opens up some crazy outside the box thinking that's still in it's embryotic stage...

 

[DAllen]

Putting a red motor in a rocket with Blue in the name?

shame

 

[charrington]

Mini update: Sorry for letting this thread go dark this last week. Work has been crazy and sadly my dog passed away yesterday so Im down in southern california seeing my parents. I should be able to continue the thread tomorrow assuming my return trip goes well.

 

[charrington]

Putting a red motor in a rocket with Blue in the name?

shame

The red flames have great performance

 

[charrington]

Chapter 1 cont.​

1.6 - Recovery Architecture​

The way I designed this flight was to have a drogue-less dual deploy using the piranha line cutter from tinder rocketry. 20 feet of 350lb chord would be the shock chord and that would be spliced using the finger trap method described here: https://www.rocketryforum.com/threads/finger-trap-technique.137003/
Splicing is a much better option than knots which can significantly decrease the strength rating of your chord. When using chord that is much stronger than what you need, knots aren't going to be a huge issue but in my case, I needed to make sure that the chord retained its full strength properties.
Here is a general schematic of the setup:

The red stars are all points of attachment for the Kevlar shock chord.

This was the idea up until the day of the launch where there was some last minute changes due to fitting issues. The changes were probably the second biggest mistake made on this project and I will go into detail on that and what I am doing to correct it for the next launch.



Here is the photo of the splicing on the motor eyebolt. One thing you want to make sure of is that the finger trap splice is long enough to where it doesn't pull out. There is a general calculation based off of diameter of the chord that you can search up but I just did about 3 inches. It became so tight that I couldn't pull the rest of the chord through so I just taped the excess down. I tried pulling it out and the splice didn't let up an inch so I decided that was good enough. This was done again by splicing the nomex and parachute (always make sure that your nomex is not free floating, this can prevent a parachute from opening). Then the e-bay was attached by making a very small spliced loop that sat tightly between two nuts on the threaded rod. These were loctited in place. Finally the other end of the chord was spliced around the bolt that goes into the aluminum tip, making sure that the loop was much smaller than the head of the bolt. Note: There are some things I need to do very differently for next flight in the AV bay area. The lower architecture will stay the same.

Being a biologist I obviously elected to use my new favorite ejection charge method of free floating microcentrifuge tube. I chopped the centrifuge tube top down substantially and then drilled a hole into the bottom just large enough to slide the wires from my e-match through. Before pulling the wires all the way through, I took some hot glue and put some on the bottom of the e-match head so that a seal was created. (Photos to come).

1.7 Electronics​

Sadly, it seems that I forgot to take a picture of the final configuration but I did my best with this. The blue capacitor that belongs to the raven needed to be desoldered and then moved around the back where the green square is. This was resoldered to some thin gage stranded wire. The same was done with the green terminal block on the featherweight GPS. With these out of the way, the GPS could fit nicely in the space between the raven and the raven battery. All of the threaded rods had heat shrink tubing applied to them to prevent shorts and then wrapped with electrical tape to hold stuff together. Note: Do not block the barometer on the raven!
The passive bulkhead was not used so that the unit could be pushed into the top of the nosecone farther.

Number 1 mistake!!!: Spoiler, the thing that most likely damaged the GPS after looking at the data points was the ejection charge. After talking to @Adrian A he believes that the hot gases from the ejection charge caused the failure. Going forward, I need to find a way to completely seal the electronics from the gas.

I thought that placing the Nomex wrapped parachute right up against the electronics while I ran the free floating ejection charge to the other side (pointing towards the top of the motor) would be enough to seal from the blast but it probably wasn't. Granted something else could have damaged the GPS but sadly there is no way of knowing without the rocket. This is just my best guess.

 

[charrington]

Chapter 1 cont.​

1.7 Structural integrity:​

I am mainly adding this into anyone using this as a build thread for a general min diameter build*
I was not worried about the airframe structure strength since the entire carbon tube was supported by the motor and the nosecone shoulder. There was only about .25 inches between the nosecone and motor tube that was not supported. IF you plan on giving yourself more space, make sure your airframe is strong enough to prevent a collapse. To fit my motor into the McMaster carbon tube I sanded off quite a bit of material (maybe a lot of material) and the tube was noticeably weaker than stock wall thickness. If your tube is going to be unsupported then I would recommend going with a tube from Wildman. It is going to have a slightly higher OD but your motor is guaranteed to fit. In my case I wanted the airframe to be as light as possible and as thin as possible.
Note: Loki research 38mm hardware has a larger OD than Aerotech. My Aerotech motor case could fit into the McMaster tube but it was EXTREMELY tight, your experience may very. The loki hardware would not fit at all without heavy sanding.

Regarding the nosecone, the wildman cone is strong as h*ll. Maybe a little too strong in my case. I might sand out a little bit of the shoulder next time if I go with it again over a custom cone.

The fins are where things get a little bit tricky. I needed to use 1/16th inch fins and after running my geometry on finsim the numbers were worrying to say the least.
For material i used CFRP T300 as I was unsure how to add a custom material.

Here is the NACA 4197 method of calculating flutter and divergence:

Here is classic 2d lift slope:

and here is barrowman 3d:

This was my first time using this program and it was a little bit overwhelming to say the least. The values between the three methods were drastically different and I was not sure which one to choose so I went with the conservative estimate and figured if I used normal CF I could run into flutter. If anyone is more familiar with this program and sees something wrong or has advice on which model to choose please inform me!

1.8 Fin material strength​

With the previous flutter calculations in mind I decided to go with a high modulus plate from Mcmaster. This plate is about twice as stiff as normal CF and 50% stiffer than aluminum if I remember correctly. If you are going to be machining or cutting your CF then make sure you choose a twill weave over a unidirectional weave which will splinter.

 

[charrington]

Chapter 1 finale​

Launch tower design:​

I wanted to thank @manixFan for helping me with this design. He showed me his adjustable tower and then I modified it to make it fit my needs. My design can fit up to a 54mm rocket with fins that have a 1 cal span. This can obviously be upscaled or downscaled depending on your needs. Just a warning, this was quite expensive.
Materials:


Not pictured here is the 1/8th inch and 1/4 inch steel that was used to make the tower base, upper slot, and top piece. These were laser cut by my grandfather. Aluminum would obviously work too but he had some steel laying around and I don't mind the extra weight and strength (also saving money). You will also need either a machined or 3d printed insert that adapts a 1/4-20 bolt to the ID of the aluminum round tube.











Note: You really want that countersunk or else the bolt will hit the top and not allow you to have full adjustability. Or you can just cut off the ends of the top.

Here is the laser cut top:

Here is the base:

Here it is built:


The large gussets were added to the bottom and the small ones are added up top.

​

I didnt countersink which is why the bolts are sticking out like that. Big mistake and had to cut off the ends of the top so that they would slide through lol!​

 

[GrouchoDuke]

Thanks for the continued info sharing & great writeups. Good stuff.

...The blue capacitor that belongs to the raven needed to be desoldered and then moved around the back where the green square is. This was resoldered to some thin gage stranded wire. The same was done with the green terminal block on the featherweight GPS. With these out of the way, the GPS could fit nicely in the space between the raven and the raven battery.

For your future attempts, it may be worth touching base with the Records Committee to see if these electronics modifications are allowed. 2.0.1 has this sentence about electronics: "No modifications to these commercially manufactured units are allowed." That's for flights under 30k though. For flights over 30k (2.0.2), it just says an approved GPS must be used - it does not say it can't be modified. My guess is that's their intent though. Anyway, it would really sting to miss a record because of desoldering something.

 

[charrington]

Thanks for the continued info sharing & great writeups. Good stuff.

For your future attempts, it may be worth touching base with the Records Committee to see if these electronics modifications are allowed. 2.0.1 has this sentence about electronics: "No modifications to these commercially manufactured units are allowed." That's for flights under 30k though. For flights over 30k (2.0.2), it just says an approved GPS must be used - it does not say it can't be modified. My guess is that's their intent though. Anyway, it would really sting to miss a record because of desoldering something.

Thats a good point and I will have to ask. I dont think the capacitor matters since I will be using GPS for altitude verification. I really wouldn't think that the battery terminal modification would be grounds for disqualification as it only affects how the power is delivered. moving the terminal off to the side with wires instead of it directly on the board. I'll ask and then post here when I get the answer. Also, with Adrian's new design with the 29mm blue raven integrated onto the circular board I think I may not even need to make this modification: https://www.rocketryforum.com/threads/blue-raven-in-29mm-bulkhead-form-factor.180287/

 

[Adrian A]

Thats a good point and I will have to ask. I dont think the capacitor matters since I will be using GPS for altitude verification. I really wouldn't think that the battery terminal modification would be grounds for disqualification as it only affects how the power is delivered. moving the terminal off to the side with wires instead of it directly on the board. I'll ask and then post here when I get the answer. Also, with Adrian's new design with the 29mm blue raven integrated onto the circular board I think I may not even need to make this modification: https://www.rocketryforum.com/threads/blue-raven-in-29mm-bulkhead-form-factor.180287/

Keeping the GPS stock is what the records committee cares about; the deployment altimeter can be anything. I'll vouch for removing the power connector as a manufacturer approved mod if there's a question about it.

 

[rfjustin]

Sick tower!

 

[charrington]

Sick tower!

Thank you!

 

[charrington]

Keeping the GPS stock is what the records committee cares about; the deployment altimeter can be anything. I'll vouch for removing the power connector as a manufacturer approved mod if there's a question about it.

Thanks Adrian ill let you know what they say when I get the chance to contact them.

 

[GrouchoDuke]

Thanks Adrian ill let you know what they say when I get the chance to contact them.

I thought the same as Adrian, but they wouldn't give me an answer about using a Quark or my own homebrew flight computer for deployment while using one of Adrian's GPSs for an H record attempt at NSL. Granted, that was for a sub-30k record attempt, but there's a sentence in the rules that says if you use an approved GPS it trumps the requirement for a commercial flight computer. Since I couldn't get an approval to use a non-commercially manufactured flight computer with a FW GPS, I shoehorned an EasyMini, FW GPS, battery & switch in a 29mm nosecone. (Not super fun...and I turned them all into tiny bits anyway.)

I'm certainly not on the records committee and I very much appreciate the work they do, but things seem to be changing. I think it's worth being extra careful in how we all interpret the rules - going to the current source for clarification before you spend time & money on flights seems way worth it to me.

 

[Neutronium95]

Sadly, it seems that I forgot to take a picture of the final configuration but I did my best with this. The blue capacitor that belongs to the raven needed to be desoldered and then moved around the back where the green square is. This was resoldered to some thin gage stranded wire. The same was done with the green terminal block on the featherweight GPS. With these out of the way, the GPS could fit nicely in the space between the raven and the raven battery. All of the threaded rods had heat shrink tubing applied to them to prevent shorts and then wrapped with electrical tape to hold stuff together. Note: Do not block the barometer on the raven!

That is an impressively compact avbay.

Why did you decide to put the altimeter in the tip of the nosecone? That location always seems to be a bit space inefficient, especially in smaller diameters. My preference is to put the avionics on top of the motor.

It's nice to see other people flying high performance flights with cable cutters, I really like them and they've served me well for the most part.

I also really like your tower design. I'm thinking about building something similar in the future. How much did it cost to get the top and bottom plate cut out?

 

[charrington]

That is an impressively compact avbay.

Why did you decide to put the altimeter in the tip of the nosecone? That location always seems to be a bit space inefficient, especially in smaller diameters. My preference is to put the avionics on top of the motor.

It's nice to see other people flying high performance flights with cable cutters, I really like them and they've served me well for the most part.

I also really like your tower design. I'm thinking about building something similar in the future. How much did it cost to get the top and bottom plate cut out?

Thank you! It was definitely the most difficult aspect of this project.

Regarding the location, I do think that on top of the motor would probably be a better location, however I am running into a couple issues. One being how do I attach the featherweight 29mm AV bay to the top of the motor? The main issues im seeing is that the featherweight antenna needs to he pointing up towards the nosecone which would require the passive bulkhead to be on top which means the active bulkhead would be motor side. I dont know how I would attach the active bulkhead to the top of the motor without damaging the active bulkhead or modifying motor hardware. I am open to ideas though!

The other issue im thinking of is will GPS signal be hindered by the carbon fiber airframe. The airframe fits the shoulder of the cone so i’m thinking that it may cause gps interference. Im unsure about this though as I have not tested it.

Regarding the plates, I am actually not sure how much they cost. My grandfather owned a large metal supplier and fabricator in Las Vegas so he hooked me up and did it for free. They have a large laser cutter so I sent them a DXF. I can ask him how much they/ the average fabricator would charge for the service and material. I can also upload all of the files for the tower including the DXF if you are interested in using my design.

 

[kjhambrick]

charrington --

Nice tower design !

What is the max airframe diameter that the tower can handle ?

Thanks !

-- kjh

 

[charrington]

charrington --

Nice tower design !

What is the max airframe diameter that the tower can handle ?

Thanks !

-- kjh

For this, it should comfortably fit a composite airframe for a 54mm motor with a fin height of one body diameter. This design can be scaled up tho very easily in cad to fit larger airframes and fin spans. I can upload the cad files for this though if that helps!

 

[Adrian A]

Thank you! It was definitely the most difficult aspect of this project.

Regarding the location, I do think that on top of the motor would probably be a better location, however I am running into a couple issues. One being how do I attach the featherweight 29mm AV bay to the top of the motor? The main issues im seeing is that the featherweight antenna needs to he pointing up towards the nosecone which would require the passive bulkhead to be on top which means the active bulkhead would be motor side. I dont know how I would attach the active bulkhead to the top of the motor without damaging the active bulkhead or modifying motor hardware. I am open to ideas though!

The other issue im thinking of is will GPS signal be hindered by the carbon fiber airframe. The airframe fits the shoulder of the cone so i’m thinking that it may cause gps interference. Im unsure about this though as I have not tested it.

Regarding the plates, I am actually not sure how much they cost. My grandfather owned a large metal supplier and fabricator in Las Vegas so he hooked me up and did it for free. They have a large laser cutter so I sent them a DXF. I can ask him how much they/ the average fabricator would charge for the service and material. I can also upload all of the files for the tower including the DXF if you are interested in using my design.

The way I'm planning to do it for StratoSpear is to make a passive bulkhead which has a central hole for the motor closure bolt, which is surrounded by the threaded rods. The new passive bulkhead needs to have the threaded rods clamped on first, then it's bolted with the central screw to the motor forward bulkhead, then the active electronics and batteries are attached to the threaded rods, then the av-bay is surrounded by a coupler tube and another passive bulkhead is used to attach a chute cannon in the mirror image way to the motor attachment.

I thought about trying a cable cutter, but then decided I really liked having a nosecone ejection piston located at the top of a chute cannon that positively pushes the nosecone off of the airframe. The BP is completely contained in a small volume the size of the bp powder itself, consistent with high-altitude BP techniques.

The GPS very likely not work through the carbon fiber. To have the installation work in that location you would need to add a fiberglass window over the GPS antenna

 

[Neutronium95]

The way I'm planning to do it for StratoSpear is to make a passive bulkhead which has a central hole for the motor closure bolt, which is surrounded by the threaded rods. The new passive bulkhead needs to have the threaded rods clamped on first, then it's bolted with the central screw to the motor forward bulkhead, then the active electronics and batteries are attached to the threaded rods, then the av-bay is surrounded by a coupler tube and another passive bulkhead is used to attach a chute cannon in the mirror image way to the motor attachment.

I thought about trying a cable cutter, but then decided I really liked having a nosecone ejection piston located at the top of a chute cannon that positively pushes the nosecone off of the airframe. The BP is completely contained in a small volume the size of the bp powder itself, consistent with high-altitude BP techniques.

The GPS very likely not work through the carbon fiber. To have the installation work in that location you would need to add a fiberglass window over the GPS antenna

That pretty much mirrors my thinking on packaging electronics into a 38mm avbay. I'm currently focused on some 54 and 75mm projects, which are significantly less painful packaging wise.

For rf reasons, I've decided to keep things simple and just use fiberglass for all of the structural parts around the avionics. Sacrificing a tiny bit of weight to make my radios work trouble free is a tradeoff I'll gladly make.

 

[watheyak]

A shorter rocket should go much higher than one that is longer but Scotts didn't. There is a good chance this is due to the step of the fin can.

Disregard.... I just noticed that I made this observation earlier in the thread. But for reinforcement of my sentiment... here it is again..

I just noticed this quote. Going forward, I am definitely anti-fincan and associated step. The total frontal area is the same whether you have a teeny fin can or a full airframe. The weight of the full airframe has to be... well... weighed. But I think the aerodynamic improvement from omitting the "step" way outweighs the weight savings.