"Contents Under Pressure" - Static Test Cato

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Aksrockets

Now with 8% more aluminum
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Contents Under Pressure.jpg
That should almost say it all.

A friend from UROC and I are in the process of designing an extremely high performance 54mm based around PR FWFG or FWCF tubing. This build thread will document our findings and process during construction.

Short intro:

Build rocket. Go fast. Much fun.

Long intro:
Motor design: The motor case / airframe tube will be either filament wound fiberglass or filament wound carbon fiber, depending on our burst tests and strength testing. Since the TG of PR tubing is much less then the softening point of aluminum, extra steps will be taken to ensure that the casing will not take much heat. The way we plan to do this is with a monolithic grain geometry with inhibited ends (ignore the drawing). This means that the burning surface area of the propellant will not reach the liner until the very end of the burn. We will also be using a propellant with a low metal content, which should remain relatively "cool" compared to other propellants. Of course these measures to insure case protection come with setbacks. A low metal content means a low ISP and less performance. A monolithic grain geometry means a low initial KN and a high max KN (although this depends on nozzle design). Overall, I think the tradeoffs are worth the extra protection.

Another important topic is burst pressure. Since we don't know the burst pressure with PR tubing, we'll be doing destructive tests to figure that out. Final motor design plans can't be made until we have that data.

Besides motor design, the rest is very simple. CF fins, a few layers of T2T. The deployment design will be similar if not identical to my "Peacemaker" build last year. I was pretty happy with how well that worked.

That's about all i've got for you guys right now. Fear not! Even though this is an EX build, I'll be careful not to talk formulas or specifics, though I may post a picture of propellant casting or two.

Bye.

Alex

P.s. This is for Aeronaut 2015
 
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Subscribed!!
Awesome!
I'm really looking forward to this build. Very, very interesting stuff.

Nate
 
Yo Alex,

Cool project! I did some experimenting using PR G-12 last year for flying motor casings for Hamster Dance where the motors must be single use, EX, and non-metallic. I ran a 8 grain 38mm semi-long burn Bates LINERLESS just to see if I could. The static burn was great 'cause the linerless bates setup showed the bright red glow between grains through the translucent G-12. It worked great and got the highest altitude.

I mention the above not to gloat, but rather to inform that I was personally flat out amazed at how well the unprotected G-12 held up. As you mentioned, the interface above the nozzle is the area of greatest concern....the bottom grain or three were the areas affected most.

Also did some testing of various epoxies used for fin attachment on the hot case...careful of those fins directly over the nozzle...it will retain heat for a while and likely soften just about any epoxy out there eventually. I placed my fins just forward of the nozzle just to be safe.

Again, great project with lots of potential. Filament wound casings are fun!!!

-Eric-
 
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Definitely subscribed, looking forward to seeing it completed.


Alexander Solis

TRA - Level 1
Mariah 54 - CTI RedLightning- I-100 - 6,345 Feet
 
This is almost exactly the same as my LDRS project dimensionally. I will be using an aluminum case with a thin wall FWFG tube "sleeve," with a Telemetrum located in the exact same spot. Major difference is that I will be deploying a very small main at apogee, not a dual deployment arrangement with a cable cutter.

I am going for max velocity while staying under 23,000'. Should be cool!
 
Awesome! I expect regular video chats on FB showing me this... :p
 
I've done several composite cases with Curtis tubes, always fiberglass (been to cheap for CF thus far) in 4", 4.5", 5", and 6.5" (N-P). Highest I've gone is about 1200psi with it. Save for the 6.5", all have been linerless. No issues so far. I've always played it safe and made them thicker than they needed to be, essentially combining the would-be liner into the case to have the same amount of material (weight), but reap the benefit of having the liner be pressure-bearing. None of them have been monolithic so far, but not a bad idea, something Mat and I have been considering for our own Aeronaut project, which projects an 18 second burn time and introduces some new variables into the equation in terms of thermal issues.

Good luck with the project - see you at Aeronaut. If all goes according to plan, we'll have with us our biggest composite cased motor yet by quite some margin.
 
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Subscribed!!
Awesome!
I'm really looking forward to this build. Very, very interesting stuff.

Nate

Definitely subscribed, looking forward to seeing it completed.


Alexander Solis

TRA - Level 1
Mariah 54 - CTI RedLightning- I-100 - 6,345 Feet

you know I'll be following....


Glad to have you guys on board.
This is almost exactly the same as my LDRS project dimensionally. I will be using an aluminum case with a thin wall FWFG tube "sleeve," with a Telemetrum located in the exact same spot. Major difference is that I will be deploying a very small main at apogee, not a dual deployment arrangement with a cable cutter.

I am going for max velocity while staying under 23,000'. Should be cool!
Sounds cool! So is it or isn't it a flying case if it has a sleeve over it?

I think this could see 25-30k. Depends on motor specifics.

I've done several composite cases with Curtis tubes, always fiberglass (been to cheap for CF thus far) in 4", 4.5", 5", and 6.5" (N-P). Highest I've gone is about 1200psi with it. Save for the 6.5", all have been linerless. No issues so far. I've always played it safe and made them thicker than they needed to be, essentially combining the would-be liner into the case to have the same amount of material (weight), but reap the benefit of having the liner be pressure-bearing. None of them have been monolithic so far, but not a bad idea, something Mat and I have been considering for our own Aeronaut project, which projects an 18 second burn time and introduces some new variables into the equation in terms of thermal issues.

Good luck with the project - see you at Aeronaut. If all goes according to plan, we'll have with us our biggest composite cased motor yet by quite some margin.
Im glad to hear they've been working for you. What have your wall thicknesses been? The standard wall thickness for 54mm tube is about .06in. Pretty thin compared to the standard .09in case wall in most 54mm cases. See you guys at Aeronaut!

Alex
 
Could a phenolic nozzle help? It may help protect the case from heat as well as opening up throughout the burn, which should reduce the Kn at the end of the burn. I have personally never flown a phenolic nozzle with EX, so this needs to be taken with quite a few grains of salt.


Sent from my iPhone using Rocketry Forum
 
Im glad to hear they've been working for you. What have your wall thicknesses been? The standard wall thickness for 54mm tube is about .06in. Pretty thin compared to the standard .09in case wall in most 54mm cases. See you guys at Aeronaut!

Alex


3/8" thick. Not only did that include a "all-in-one," linecase but FWFG (I think .094" thick) was used as a casting tube. As prophecy mentioned it is thicker than needed. Do you have a target pressure or at least a range, if so what is it? I think there are a lot of variables as to how your 0.06" FWFG case will perform, but most manufactured motor cases are also made thicker than averagely needed. Nonetheless it will be very interesting to see how this does… I have one of these laying on the floor lol. The steeper (higher) the wind angle the greater the hoop (radial) strength and vice versa for helix (axial) strength. The cases prophecy also mentioned were made with them being pressure vessels in mind, but it would be interesting to see how "off the self," tubes hold up. FW composite pressure vessels can provide greater structural efficiencies than all-metallic pressure vessels of similar volume and pressure rating. Anyways have fun and may the probability be with you!


Mat
 
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Could a phenolic nozzle help? It may help protect the case from heat as well as opening up throughout the burn, which should reduce the Kn at the end of the burn. I have personally never flown a phenolic nozzle with EX, so this needs to be taken with quite a few grains of salt.


Sent from my iPhone using Rocketry Forum

Phenolic nozzle is a "whole nother realm". Burnsim will give one an estimate for a non-erosive environment only. It is hard to predict erosion consistently.
Example: I used a characterized propellant for the 38mm AT system using AT bits and emulating a commercial motor. I used Burnsim values and
Kn's to start, knowing that it will be wrong and err on the side of hardware preservation. First video shots using a Kn for graphite nozzle was like an augmented road flare that chuffed into the burn, stopped and flared out at the end. I had to use smaller nozzle throats and walk my way "up" to a consistent burn on the videos. It's a max-min problem to find the ideal state. The 720NS case still had a small chuff at the end but I was able to get the 2 grain 240NS one to burn nicely to the end. The deal with phenolic is if one "goes a little too small" on the throat, the rate of erosion might go up enough to keep the motor from over pressurizing and disassembly as opposed to the non-errosive graphite. Not "small enough" and the burn might start out ok but
rapidly go to road flare status or chuff mid-burn due to the erosion. For fun, I plugged the "final" smaller nozzle throat sizes back into Burnsim and got artifically stupid high Kn's and case pressures which of course isn't what is actually going on.

If one has a well characterized propellant with a graphite nozzle and perhaps does a ground test shot on a set of grains out of the same batch, should do o.k. Especially if they have grains out of the same batch to use for the flight. With phenolic, one needs to do a fair amount of testing to get it to work just right. Unless you have a guru who can hand you some numbers for a given propellant type, you'll be at risk of an underpowered road flare. It's fun stuff to do though. I felt more confident with phenolic ground testing because once you get through the first burn, you'll feel confident in cutting down the throat size and work up to a good burn. With graphite, you really want to make doggone sure you don't use too small a throat to start out. If your propellant has some microbubbles or a few voids, a non-erosive nozzle could mean kaboom even if you use a throat size that "someone" or a "computer program" told you was safe to use. Kurt
 
Something I've always wondered about this style of rocket: is it essentially single use? Can the propellant be reloaded, or is the motor rocket hybrid a one shot wonder? Regardless, this is a seriously cool protect, and I really admire the amount of knowledge and the skill set it must take to pull off these demanding flights.

Nate
 
Something I've always wondered about this style of rocket: is it essentially single use? Can the propellant be reloaded, or is the motor rocket hybrid a one shot wonder? Regardless, this is a seriously cool protect, and I really admire the amount of knowledge and the skill set it must take to pull off these demanding flights.

Nate

You got it Nate. One shot wonder. Especially with a filament wound case. Keeping the fins on will be one laminating problem as will the epoxy softening
from heat soaking either from the motor and or aerodynamically. Best to follow Eric's advice and move the fins foward from the nozzle to stave off heat transfer from there for awhile. The tip to tip laminating the poster plans is the best bet too. Some exotic adhesives are out there that will have 700F for lunch and stay strong but cost an arm and a leg Kurt
 
You got it Nate. One shot wonder. Especially with a filament wound case.

I am curious what you are basing that on? I personally believe composite cases can be designed to be reusable, albeit with "a little," maintenance and the like. The shuttles FW SRBs for example, were designed to be reusable for up to 4 times. On the amateur side of things, the Trunnion composite case from USC's RPL was reused twice which proves amateurs can also do it.
 
Do you have a target pressure or at least a range, if so what is it?
Right now, maybe 700 psi, but i'll have to run it past Clay. Anything below 700 psi and we may have to switch to carbon or aluminum. Tonight I ran the pressure calculations to find my KN and nozzle throat with tiger tail propellant at 700 psi.
ImageUploadedByRocketry Forum1413523293.081560.jpg

And that, ladies and gentlemen is why monolithic grains aren't fun to work with. Initial pressure of 212 psi and a final pressure of 700 psi. Talk about progressive. I may look into finocyl or star grain geometries to raise my initial Kn.

Alex
 
Just run an erosive configuration to get the initial pressure up. Better volume loading loading this way too. All my long motors are done this way (3" x 48", 6" x 104"). 13% metals with a low exponent run in monolithic core burning grains.

Ethan - did you make a 6" x 104" motor and not post anything about it? Would love to hear more about that project. Man, I can't believe it's been over five years since I was down there. Hope all's well with you and Chris.

-Steve
 
Could a phenolic nozzle help? It may help protect the case from heat as well as opening up throughout the burn, which should reduce the Kn at the end of the burn. I have personally never flown a phenolic nozzle with EX, so this needs to be taken with quite a few grains of salt.


Sent from my iPhone using Rocketry Forum
I briefly considered using a phenolic nozzle, but it's a little iffy. I'd feel more confident with a graphite one.
Something I've always wondered about this style of rocket: is it essentially single use? Can the propellant be reloaded, or is the motor rocket hybrid a one shot wonder? Regardless, this is a seriously cool protect, and I really admire the amount of knowledge and the skill set it must take to pull off these demanding flights.

Nate
I doubt it will be reloadable.
Just run an erosive configuration to get the initial pressure up. Better volume loading loading this way too. All my long motors are done this way (3" x 48", 6" x 104"). 13% metals with a low exponent run in monolithic core burning grains.
I'll consider that. I'm just worrying about heat with high metal propellants.

Alex
 
I am curious what you are basing that on? I personally believe composite cases can be designed to be reusable, albeit with "a little," maintenance and the like. The shuttles FW SRBs for example, were designed to be reusable for up to 4 times. On the amateur side of things, the Trunnion composite case from USC's RPL was reused twice which proves amateurs can also do it.


Based upon 26 firings in AT hardware of thick walled Garolite liners. Unless one uses a bulletproof liner from top to bottom your filament wound "rocket motor tube" will be lucky to last past 3 firings. I can get a maximum of 3 reuses out of a liner after running a
brake hone through it. The liner eventually gets carbonized and too brittle to depend on. No doubt a rocket could be used as an engine casing but no way is it going to last as long as a standard motor setup. Maybe 3 firings if you're lucky. Consider it a fun exercise but if you think the rocket is going to last as long as a conventional one see if you get by with 10 firings without it coming apart, then we'll talk. Either the end will burn off or the forward portion will give way. If you come up with a super duper impervious liner share it with the masses. Don't get me wrong, if someone is trying to squeeze every last bit of performance out of a propellant, makes sense to save on every last bit of non-essential weight including saving weight by using the rocket as a motor case. Kurt
 
I am curious what you are basing that on? I personally believe composite cases can be designed to be reusable, albeit with "a little," maintenance and the like. The shuttles FW SRBs for example, were designed to be reusable for up to 4 times. On the amateur side of things, the Trunnion composite case from USC's RPL was reused twice which proves amateurs can also do it.
The shuttle booster casings were steel, not FG. BTW it cost more money to recover and recondition them than they were worth.......

Bob
 
The shuttle booster casings were steel, not FG. BTW it cost more money to recover and recondition them than they were worth.......

Bob

Yeah, I believe 1/2" thick steel. I believe it is a pipe dream to think one can use a filament wound tube as a rocket body tube and motor casing that is as
resilient as a standard aluminum motor case. It certainly can be done and successfully flown, once or twice but anything after would be borrowed time. Kurt
 
Based upon 26 firings in AT hardware of thick walled Garolite liners. Unless one uses a bulletproof liner from top to bottom your filament wound "rocket motor tube" will be lucky to last past 3 firings. I can get a maximum of 3 reuses out of a liner after running a
brake hone through it. The liner eventually gets carbonized and too brittle to depend on. No doubt a rocket could be used as an engine casing but no way is it going to last as long as a standard motor setup. Maybe 3 firings if you're lucky. Consider it a fun exercise but if you think the rocket is going to last as long as a conventional one see if you get by with 10 firings without it coming apart, then we'll talk. Either the end will burn off or the forward portion will give way. If you come up with a super duper impervious liner share it with the masses. Don't get me wrong, if someone is trying to squeeze every last bit of performance out of a propellant, makes sense to save on every last bit of non-essential weight including saving weight by using the rocket as a motor case. Kurt


I am glad we cleared up that composite cases can be more than a "one shot wonder." As 3 uses is reusable and quite amazing on a amateur scale, at least IMO. I made no claims that it would last as long as a standard Al. case. You don't build a composite case and the respected motor to have a "conventional," rocket… nor is it something, I for one, would except it to be. To clear things up I am talking about designing/building your own composite case and not buying one from AT, CTI, etc. IMO it is to maximize performance per se and that is something that only a small percentage of amateur rocketeers actually do, hence I have no thoughts on it being a conventional setup. I think 3 uses would be great seeing as all the ones that I have taken part in building have been designed to be single use and the two others that I am just starting to undertake are also designed to be single use. I tend to scrap rockets after they fly.

I think that composite technology will in the future advance much further and reusable composite cases/rockets will be achievable… especially as commercial space companies continue to grow and explore.

The shuttle booster casings were steel, not FG. BTW it cost more money to recover and recondition them than they were worth.......

Bob


Yes, No. Some were steel and some were not. I never stated that they were FG. No argument that the shuttle program was as a whole extremely costly and at times poorly ran.

https://www.scribd.com/doc/72867746/Space-Shuttle-Filament-Wound-Case-SRM-Test-Results

https://en.wikipedia.org/wiki/Space_Shuttle_Solid_Rocket_Booster#Filament-wound_cases (See Filament Wound Case)

https://onlinelibrary.wiley.com/doi/10.1002/pc.750080304/abstract

https://ntrs.nasa.gov/search.jsp?R=19860057889

https://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=ADA305654



Yeah, I believe 1/2" thick steel. I believe it is a pipe dream to think one can use a filament wound tube as a rocket body tube and motor casing that is as
resilient as a standard aluminum motor case. It certainly can be done and successfully flown, once or twice but anything after would be borrowed time. Kurt


Again no mention of a composite case being as durable as a standard Al. case as it seems to be what you perceived me to have hinted at, but maybe you did not. I think that the pipe dream statement is not accurate or at least short sighted… especially with new composite technologies being developed and progressed there is no telling what aerospace companies (amongst other companies/labs) will achieve in the future. May be a long time (relatively speaking) for hobbyist to obtain a similar capability but that does not mean it is not possible.


EDIT:

USC has now fired their composite case motor 9 times! I guess they have some really good pipes!
 
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Well,
Everything's been ordered! I placed an order tonight with Speedy Metals and The Graphite Store. All that's left to do is drive down to RCS to pick up a bucket or two of AP and we can get to work!

Alex
 
Well,
Everything's been ordered! I placed an order tonight with Speedy Metals and The Graphite Store. All that's left to do is drive down to RCS to pick up a bucket or two of AP and we can get to work!

Alex

Carefully inspect what you receive from Speedy Metals. They typically just bundle your items together and wrap them with a bunch of Saran Wrap and then packing tape, no box or padding.

I received 12" of 76mm tubing for a 76/1700 case and it has a nice ding about halfway up. The case has flown successfully three times, but a bulkhead won't travel all the way through when cleaning because of the ding.

Sometimes it's worth paying a little more to get a better shipping method from a different supplier.
 
Carefully inspect what you receive from Speedy Metals. They typically just bundle your items together and wrap them with a bunch of Saran Wrap and then packing tape, no box or padding.

I received 12" of 76mm tubing for a 76/1700 case and it has a nice ding about halfway up. The case has flown successfully three times, but a bulkhead won't travel all the way through when cleaning because of the ding.

Sometimes it's worth paying a little more to get a better shipping method from a different supplier.

Thanks for the heads up. I've ordered from them before so I've had a similar experience. This tubing will all be turned down anyway so small dings and gashes won't matter that much.

Alex
 
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