Musket Chops ~ 5" diameter rocket

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mannyskid

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Outdated: See post #12

Overview:

To preface this post, I want to say that this thread is going to be more of a diary than a build thread in order for me to keep my head straight on this project. Tentatively I plan on flying this rocket at Aeronaut next year, August 2015. Some of you may have read my last build thread on my 3” minimum diameter rocket “Torn Between Scylla and Charybdis”. (https://www.rocketryforum.com/showthread.php?60703-Torn-Between-Scylla-and-Charybdis) That rocket is my current personal altitude/speed record with an apogee of 41,800’ and max speed of M3.2. I have been thinking about what I can do to further challenge myself, and the next logical step would be to do a similar rocket but in a 98mm minimum diameter. This build will be sharing many of the same design philosophies, while introducing new, more challenging aspects to the project.

Etymology:

When naming rockets, I like the name to have some meaning related to the project. My last project was in reference to the two rocket of vastly different construction techniques that I had built. This year, it’s a bit different. Every once in a while, you meet a person who is so interesting that you will never forget them. This past August at Aeronaut, Alex (aksrocket), Bryce (Bandman444) and I were standing outside of Bruno’s country club having a chat about new missile works products. While talking about the avionics, an older, scruffy looking man came strolling over to us and asked “Sleds, altimeters….what are you guys talking about over here?”. The first thing that I had noticed about him were his glorious mutton chops. It was quickly discernible from his appearance and the way he spoke that he was in town to attend the annual burning man festival. We talked to him for a while about our rockets, which he thought were the coolest thing ever, and we listened to him talk about shooting anvils into the sky with BP. When talking about rockets, he gave what is now my favorite description of high powered rockets “They’re like muskets….of the future!”. There in lies where the name “Musket Chops” came from. This guy was so awesome, I just had to name a rocket after him, and so that’s why this rocket will be called what it is.

Basic Design Principles:

I am currently in the very early stages of designing this rocket right now, but I have a general idea of what I want to do. This rocket will be built mostly from the ground up. I have decided that this is going to fly on an experimental motor with home made propellant and a home made motor case. I haven’t decided yet if the fins are going to be made out of carbon or aluminum yet, but either was, they will be bolted directly to the motor case.

Like my last project, this will be a multi-phase build. Unlike the last project, instead of a 2 phase build this will now be a 4 phase build.

Phase 1 - Recovery: First, I will build a 4” diameter fiberglass rocket with a 75mm motor mount and will set the recovery up similar to TBS&C with Wildman’s HEDD end dual deploy. I took my HAM radio technicians exam this past weekend and passed (yet my call sign isn’t in the ULS yet), and this rocket will serve as a way for me to practice using the AIM XTRA system.

Phase 2 - Propellant: A large portion of this project will be in the manufacturing of the propellant. I haven’t decided on what formula I’m going to use just yet, but it will be a standard propellant with moderately high performance. In the recent Tru-Core sale, I purchased a 98-6GXL snap ring case that I will practice with. The first will be to make a tiger tail motor for it first to get acquainted making 98mm motors, then I will start toying around with turning knobs and dialing in the performance. I will be detailing this end of the rocket in the research forum when that time comes.

Phase 3 - Motor Case: The current plan is to manufacture my own motor case. I have found some reasonably priced 3” and 4” diameter 6061-T6 aluminum tube that will fit the nozzles and bulkheads I already have, while being thinner and lighter. I haven’t quite decided how I will manufacture it. I will be detailing this end of the rocket in the research forum when that time comes.

Phase 4 - Structure/ full systems integration: The last phase is putting it all together and making it work at Black Rock. This part of the project is a very long way off, but I still need to keep it on my radar when it comes to manufacturing the case/propellant. I am currently thinking that I want to bolt the fins directly to the motor case and put an aerodynamic fillet over it, but I’m not sure.

In the upcoming months, I will be working on getting a fin design made and doing other general design work. This will be a slow moving build thread as was my last, it will be almost a year before this rocket flies but there will be other action between now and then.

Manny
 
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I for one will be following "the little taco" along this adventure.
Even though I have no idea what "the little taco" means. (well, I do have SOME idea, but I'm pretty certain I'm wrong about it).

This rocket will be built mostly from the ground up.
I suggest that you plan to fly this rocket in the same manner.

s6
 
Overview:

I haven’t decided yet if the fins are going to be made out of carbon or aluminum yet, but either was, they will be bolted directly to the motor case.

Manny

If you plan to bolt them onto the motor case then how are you planning on sealing where the bolts are? I take it you might also be considering having the bolts not go all the way through the case. If thats the case then how thick is your case and do you think that having the bolts only minimally (assuming a average case thickness) in will provide enough to keep the fins on? I think one of the better ways to bolts fins on is countersunk bolts from the inside out. In any case I wish you well and think you will do good! Oh and my vote is for carbon fins and why are you not considering putting a fin can over the motor case? Drag? Shocks from the step? Just curious.
 
I for one will be following "the little taco" along this adventure.
Even though I have no idea what "the little taco" means. (well, I do have SOME idea, but I'm pretty certain I'm wrong about it).


I suggest that you plan to fly this rocket in the same manner.

s6

I'll certainly take that advice into consideration!

"Little Taco" is because the guys I worked with over the summer called me "Taquito" since I had to do a lot of work in deep, confined spaces (200 ft in a 20" diameter pipe) and I am skinny enough to shimmy my way into most tight spaces.

If you plan to bolt them onto the motor case then how are you planning on sealing where the bolts are? I take it you might also be considering having the bolts not go all the way through the case. If thats the case then how thick is your case and do you think that having the bolts only minimally (assuming a average case thickness) in will provide enough to keep the fins on? I think one of the better ways to bolts fins on is countersunk bolts from the inside out. In any case I wish you well and think you will do good! Oh and my vote is for carbon fins and why are you not considering putting a fin can over the motor case? Drag? Shocks from the step? Just curious.

All of the above. I am also not confident that I could make a tube that wouldn't explode if M4 air got under it. Your idea is what I have already been looking at. Countersinking the bolt from the inside and having some sort of rubber gasket on the backside, hit it up with thread sealant and put epoxy over the bolt head once the fins are bolted on. I thought about not having the bolts go all the way through, but frankly the case will be too thin for that, likely 0.125".
 
Im starting to think he was the ghost of some civil war general. Anvils, Muskets and Muttonchops! Ah, the people you meet at Bruno's....
enhanced-buzz-8588-1281024405-16.jpg

I am currently thinking that I want to bolt the fins directly to the motor case and put an aerodynamic fillet over it, but I’m not sure.

It'd be cool to start off with a really thick aluminum tube, then mill fin slots and fillets into one side, then turn the other side down to the final OD. That way the brackets would be part of the original tube and wouldn't compromise strength at all. Of course all that hinges on how much machining you can do and how much a big old 4in tube would cost. Flying cases are what's up. :cool:

:pop:

Alex
 
Manny,

This is cool! Great talking with you over the weekend. If I can help in any way, let me know.

I look forward to watching this project develop; and I look forward to watching it fly in late July/early August!:)

-Eric-
 
I'll certainly take that advice into consideration!

All of the above. I am also not confident that I could make a tube that wouldn't explode if M4 air got under it. Your idea is what I have already been looking at. Countersinking the bolt from the inside and having some sort of rubber gasket on the backside, hit it up with thread sealant and put epoxy over the bolt head once the fins are bolted on. I thought about not having the bolts go all the way through, but frankly the case will be too thin for that, likely 0.125".


I think that will be challenging to say the least, in regards to countersinking and sealing. If you go that route I can offer my experience… but will say now that it was a pain to countersink all those holes. On the Airfest rocket the area where the fin can slid on, was turned down so that once the can was on it was more or less a "smooth," transition. You may remember that. That might be a possible solution to eliminate your concern on air getting underneath the fin can. Although at 0.125" you don't have much to play with. Look forward to the build Manny and especially seeing it in person! Best of luck and I think you will be fine on your motor making skills!
 
Time to resurrect an old thread that I barely even started:

So in the past few months, I have done much searching for parts and thinking about this project. Instead of the original 98mm rocket, I decided that I would dumb down the project and go with a bigger motor. The project has now evolved to a 5" diameter by 66" long full O motor. I will also no longer be flying this in a "flying case" configuration, and have instead opted to go with a simple design that is essentially an upscale of last year's 3" MD.

The motor will be a 37,000 Ns O6300. According to my simulations, the rocket will have a max speed of around Mach 3 and reach a maximum altitude of ~45,000'.

Here are solidworks renders for two the two parts I have sent off to be machined, the graphite nozzle and the forward bulkhead.

11287516_821790451244434_320388532_o.jpg


11255028_821791207911025_2066610655_o.jpg


The case will be manufactured from a 5"OD x 4.625" ID 6061 tube with the closures retained by 16 x 1/4"-20 set screws. The casing will be hydrostatic tested to 1.5 x MEOP (1200 psi) before flight. The propellant is also heavily tested as well. Hopefully I am still on track to finish this bird in time for Aeronaut, July 31st - August 2nd.

Manny

(ps. Wow those pictures are obnoxiously large)
 
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Just a word to the wise, you may want to instruct the machinist to break all edges with a small chamfer. That will keep your o-rings from being cut on installation and, more importantly, keep the graphite from crumbling. There should also be a radius of sorts at the inside corner of the aft diameter reduction to prevent a stress failure upon loading. I didn't do it on my recent 76mm nozzle and I am a little concerned with how it will perform. The web is pretty thick, however...

ImageUploadedByRocketry Forum1432413940.727404.jpg
 
Any chance you could email me those solid works files? Trying to figure out how you cut the nozzle.
[email protected]

In simplicity and with some assumptions made probably like this.
1) Drilling. Drill the center bore to desired dimension. Depending on your throat specifications you may need to bore that hole out later.
2) Convergent bore. This is tapering the entrance part of the nozzle to a desired degree.
3) O-ring grooves. If you needed to bore the throat larger then I would do it now, after the o-ring grooves.
4) Divergent bore. This is tapering the exit part of the nozzle to a desired degree.
5) Turn down exterior portion of the nozzle to desired specification.
 
Just a word to the wise, you may want to instruct the machinist to break all edges with a small chamfer. That will keep your o-rings from being cut on installation and, more importantly, keep the graphite from crumbling. There should also be a radius of sorts at the inside corner of the aft diameter reduction to prevent a stress failure upon loading. I didn't do it on my recent 76mm nozzle and I am a little concerned with how it will perform. The web is pretty thick, however...

View attachment 264561


Better idea - don't extend your exit cone with graphite. You're asking for trouble.


Break edges .010-.015 is a standard machining note and should already be on all your drawings.
 
Here are two renders from the updated nozzle design. The changes made are as follows:

18468818241_a7f53ca6e8_z.jpg



18462739622_d89159125d_z.jpg


- Reduced alpha to 20deg
- Added 0.06 x 45deg bevel to aft side of nozzle step (reduces stress concentration)
- Added length, now 3.75"L vs. 3.5"L
- Added thickness to aft of exit cone
 
The glands look a bit deep for the width.

Agreed. You're looking for approximately 8-15% radial compression on the rings, and a width of groove 50% (or more) greater than the uncompressed width to allow for the squeeze.

https://www.allorings.com/gland_static_radial.htm

Trust me (and Prophecy), there's nothing more dejecting than trying to push a nozzle or bulkhead into a case with grooves that are too shallow.
 
Agreed. You're looking for approximately 8-15% radial compression on the rings, and a width of groove 50% (or more) greater than the uncompressed width to allow for the squeeze.

https://www.allorings.com/gland_static_radial.htm

Trust me (and Prophecy), there's nothing more dejecting than trying to push a nozzle or bulkhead into a case with grooves that are too shallow.

+1 :)
 
Not a ton to report on, but there has been a bit of progress on this project.

For starters, I am currently on nozzle design Mk.iv. The following changes have been made since the last iteration.

- Redesigned O-ring glands (Now 0.185" wide, 0.121" deep for 0.139" thick O-ring)
- Reduced alpha to 15 deg.
- Nozzle length is restricted, therefore the expansion ratio is only 4.08 (2.842")
- Reduced throat diameter to 1 26/32 (1.40625")
- Max chamber pressure is now 843 psi

So the nozzle will be pretty under expanded so I will only be seeing an Isp of about 200s, pretty pitiful, but I'm over it. I have to make due with what I have in the time allowed before the launch, and at least I'll get some cool looking shock diamonds. Besides, absolute altitude isn't the goal of this project, the goal is to fly a large, minimum diameter O motor and get it back intact.

In other news, final simulation is completed and the Aeropac high altitude window request has been submitted. With the current design configuration, I am projecting a maximum altitude for this bird to be between 46,000-47,000 feet with a maximum velocity of M2.66.

I will begin construction on the fin can in a bit over two weeks, once class is over and I have some free time. Current plan is to use 3/16" thick G10 fins, bonded to a FWFG tube and large fillets (shaped with 54mm tube) made from proline 4500 high temperature epoxy. Then 5 layers of vacuum bagged carbon fiber reinforcement with aeropoxy. This rocket will look like and be constructed much like the 3" diameter rocket I flew on the M2245 last year at Black Rock, which hit a higher max velocity (M3.2) so I am confident this will work. To be sure, I'm going to try and get a friend of mine to run aeroelastic analysis on this in NASTRAN.

I will update once I being construction.

Manny
 
I picked up the nozzle and forward bulkhead from the machinist today.







I'm still on track to have this finished by Aeronaut. I will be mixing propellant this weekend.
 
I hope to have a good portion of the work done for this rocket by the end of this weekend. The propellant is mixing as I type, and I have bonded the first two fins and it is now sitting in the curing oven. It's only set at 120 deg, so I shouldn't have damage like I did with the curing oven last year.

ImageUploadedByRocketry Forum1437245852.069853.jpg
 
I made a little bit of propellant tonight...

11781863_844792072277605_7479920911756754343_n.jpg

(For a sense of scale, those are 4.5" couplers by 12" long)

Three grains of five total, took 11.5 kg to make those three. Currently sitting in the oven, should be ready to go in the morning. Round 2 of 3 for Aeronaut tomorrow night. Wash-Rinse-Repeat.

Also, the fin can is done minus T2T which will be done this weekend.
 
I made a little bit of propellant tonight...

I]

(For a sense of scale, those are 4.5" couplers by 12" long)

Three grains of five total, took 11.5 kg to make those three. Currently sitting in the oven, should be ready to go in the morning. Round 2 of 3 for Aeronaut tomorrow night. Wash-Rinse-Repeat.

Also, the fin can is done minus T2T which will be done this weekend.

Very impressive. I have been privy to helping someone pack 75mm fuel, but never anything to that scale.
 
Very, very nice Manny. Looking forward to pics of everything as it's ready to go!

I assume those little cups in the oven with the grains are the R45/Curative for pre-treating the FWFG casting tubes? I also assume you scuffed the ever living crap out of those things.
 
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