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Chaminade Rocket Club High Power Rocket

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JackO

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Hey guys,

It's been a while since I last posted. I'll be using this thread to casually document Chaminade's Rocket Club's High Power Attempt. Progress has been slow, we are behind schedule but on budget. For those who missed this post, http://www.rocketryforum.com/showth...ltitude-Questions-for-High-School-Rocket-Club, I'm leading a high power attempt at Chaminade College Preparatory in West Hills, CA. We are collaborating with a mentor from NASA, Aerojet Rocketdyne, and Environmental Aeroscience Corp. So far, we've taken delivery of the chemicals (no details, I know the rules), graphite rod, casing, and bulkhead. All that's left for our two characterization burns are the o-rings, fabrication, and assembly. These will be M-engine tested in a 5" diameter steel tube with an aluminum bulkhead. Following these tests, we'll step it up to a full static test and launch by next Christmas.

Jack Oswald
 

JackO

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We're going to have to wait to order the pohenolic insulation for the full test (aluminum casing) and will be using cardboard tubing for the characterization tests (steel casing). Anyone with experience in this field please DM me if you want more details.
 

ksaves2

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You should see about being able to join the Research forum on this site.
If steel is just being used for your ground/static tests only, make darned sure the casing is contained because of the dangerous shrapnel that can result if it blows.

I've been told that the allowed aluminum casings for rocketry have a tendency to blow out the ends or if the case blows in the middle, it opens up in one area, relieves pressure and that's it. Well............ That's what they say.

I've witnessed an aluminum casing ground test where the supposed "safe" aluminum blew into dangerous pieces and flung them far and wide. We were lucky we were in the right place but a big nasty chunk still flew off to the side of us.
I think the prefect saved that piece.

Suffice it to say though I have witnessed far more aluminum motor failures that occurred in a "safe" fashion like closures blown out or burn throughs that did not result in frangible pieces being scattered willy-nilly.

Again, be very careful in using steel even for ground testing. Some of the commercial folks do burns in a horizontal test stand inside of a used shipping container, one of those big steel jobs and leave the doors open for the exhaust plume.
Make sure the static tests can be done remotely with no one near the stand. That's what video cameras are for. Kurt
 

JackO

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You should see about being able to join the Research forum on this site.
If steel is just being used for your ground/static tests only, make darned sure the casing is contained because of the dangerous shrapnel that can result if it blows.

I've been told that the allowed aluminum casings for rocketry have a tendency to blow out the ends or if the case blows in the middle, it opens up in one area, relieves pressure and that's it. Well............ That's what they say.

I've witnessed an aluminum casing ground test where the supposed "safe" aluminum blew into dangerous pieces and flung them far and wide. We were lucky we were in the right place but a big nasty chunk still flew off to the side of us.
I think the prefect saved that piece.

Suffice it to say though I have witnessed far more aluminum motor failures that occurred in a "safe" fashion like closures blown out or burn throughs that did not result in frangible pieces being scattered willy-nilly.

Again, be very careful in using steel even for ground testing. Some of the commercial folks do burns in a horizontal test stand inside of a used shipping container, one of those big steel jobs and leave the doors open for the exhaust plume.
Make sure the static tests can be done remotely with no one near the stand. That's what video cameras are for. Kurt
Hey Kurt,

You're absolutely right. Our mentor is the former president of the Reaction Research Society, so we have access to the Mojave Test Area which has two bunkers and several test and launch stands. We won't be anywhere close I can assure you.

I'd love to join the Research Forum but am unable to at the moment being a minor. NRA/ Tripoli cert. is not administered to minors.

If all goes well, we'll be able to launch the rocket to upwards of 50,000 feet by Christmas.

Jack
 

JackO

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Nozzle 1.jpgNozzle 2.jpgNozzle 3.jpg
Just got our nozzle machined! It turned out great! I drew up the specs, one of our members CAD'd, and a third coordinated machining. We also have the casing, propellant chemicals, and bulkhead. We just need to order the radial bolts, O-rings, and cardboard insulation. We'll static test before April.

-Jack
 

JackO

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Just cast the fuel grains for the characterisation tests. Have the bulkhead getting machined and we will be building the test stand in the next week or two. We should be on schedule to test the motor on

either the 25th of March or first week of April.

-Jack
 

AlphaHybrids

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View attachment 310616View attachment 310617View attachment 310618
Just got our nozzle machined! It turned out great! I drew up the specs, one of our members CAD'd, and a third coordinated machining. We also have the casing, propellant chemicals, and bulkhead. We just need to order the radial bolts, O-rings, and cardboard insulation. We'll static test before April.

-Jack
Nice looking nozzle - though it might be prudent to put a step on the convergent side that fits into your liner. That way hot combustion gasses don't have a direct path to your casing - you can at least make them go through a couple of bends.

I've mentored a few projects before and they have cut a few cases at that interface because it didn't have step.

Edward
 

Dwatkins

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Nice looking nozzle - though it might be prudent to put a step on the convergent side that fits into your liner. That way hot combustion gasses don't have a direct path to your casing - you can at least make them go through a couple of bends.

I've mentored a few projects before and they have cut a few cases at that interface because it didn't have step.

Edward
+1! Without the step I see bad things happening in this size motor.
 

cherokeej

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No doubt about it. Definitely want to machine a step on that nozzle to fit into the liner. And when you assemble it, don't be stingy with the grease.

And check the machining of the nozzle. Check for stress risers. The inside corners of steps, like the o-ring grooves, should be radiused. Sharp corners are stress risers. You'll want to avoid those.
 

JackO

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Thanks for the advice everyone, I'll talk to our mentors about it. Here is the picture of the nearly-completed thrust stand-

 

JackO

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So you guys agree that lip on the nozzle would be worth sending back to the shop? We were planning on forming a seal/insulating layer with red silicone at the joint. Would this be sufficient with the 1/4" carbon steel 5" OD. Super over-kill. Not debating the previous advice just adding details. Want as many opinions as possible. Thanks all.

-Jack
 

tfish

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So you guys agree that lip on the nozzle would be worth sending back to the shop? We were planning on forming a seal/insulating layer with red silicone at the joint. Would this be sufficient with the 1/4" carbon steel 5" OD. Super over-kill. Not debating the previous advice just adding details. Want as many opinions as possible. Thanks all.

-Jack
Your current nozzle design might work if your formula has less then 2% Al, very short burn times and you have great liners. Might''s not a great feeling when working with rocket motors. Here are some links to drawings of Aerotech's single throat nozzles
http://s3-eu-west-1.amazonaws.com/static.fw1.biz/Templates/170652/myimages/rcs_01880_nozzle_dwg.pdf
http://s3-eu-west-1.amazonaws.com/static.fw1.biz/Templates/170652/myimages/rcs_01770_nozzle_dwg.pdf
http://static.fw1.biz/templates//170652/myimages/rcs_01670_nozzle_dwg.pdf

Tony
 

AlphaHybrids

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You don't want to seal the liner completely to the nozzle and forward closure. You then make the liner the pressure vessel and it cannot equalize pressure behind the liner. This could lead to the liner cracking. As Tony referenced, RCS has steps on all their nozzles. I don't think I've seen a step-less nozzle from a manufacturer.

Edward
 

JackO

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Sounds good; dropped the nozzle off to our mentor today to have the step machined. We'll give ourselves a small amount of space for some red silicone and have the liner (PVC) run an 1/8" over the nozzle.

-Jack
 

amarillo_rocket

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I'm just curious why are you using steel instead of aluminum? Is the person who is helping you with the motor familiar with building rocket motors. The reason I ask is not having a step on the nozzle to me is a big red flag that you may not be getting the best guidance for this project. I work with minors and rocketry in my daily job and safely is my #1 priority when we do research motors and large rockets.
 

JackO

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I'm just curious why are you using steel instead of aluminum? Is the person who is helping you with the motor familiar with building rocket motors. The reason I ask is not having a step on the nozzle to me is a big red flag that you may not be getting the best guidance for this project. I work with minors and rocketry in my daily job and safely is my #1 priority when we do research motors and large rockets.
We're going with steel for 4 reasons: it's cheaper, much stronger, weight does not matter for this test, and shrapnel is not a concern thanks to the bunker at the test location. The step was something I intended to have, but I put it off and was banking on the red silicone as it was a suggestion I had received directly from Derek Deville. Our primary mentor is a professional contractor with every major aerospace company in the nation, and he quite literally taught a class on AP fuel manufacturing and motor construction, among the students in the class were professionals from Orbital (guys building the SRB's) because they wanted to work more hands-on. But, thanks to your guys' advice, we've machined the step and crossed our T's.
 

cherokeej

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It will be interesting to see how this goes. Please keep us advised, and let us know how well she performs.
 

AlphaHybrids

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That is a step? I would have thought it would be deeper, something like 1.5-2x the width of the flat before the convergent section. What is your end margin on your bolts? Have you calculated the pullout force?

Edward
 

JackO

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To recap, the tests went flawlessly. Coined Stumpy 2 and Stumpy 3, the characterization engines both performed very near the simulated results. We got good pressure readings, very good thrust measurement (Thanks again to Steev G. for the Dataq+amp!!), and a great time. I'll be making a youtube video later today and will send you guys a link.
 

JackO

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Here is the clip! Hope you guys can check it out.

[video=youtube;BJSg2elL_KQ]https://www.youtube.com/watch?v=BJSg2elL_KQ[/video]
 

JackO

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The first test made a total of 1830 lbf-s; the second made 1422.
 

JackO

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Update:

The initial simulations were likely a little low on total impulse. It looks like the motor will be more in the 12-13,000 lbf-s range, need to nail down our pressure coefficient and exponent to get that number any more exact. It's a 5" OD 12* BATES grain motor and we're trying to stay right around 1000 psi.

After we static test this engine, we're going to design a boosted dart configuration. On the same trip as the static test, we'll be testing the timers and streamer design as well as the video transmission and gps on some small RRS Alpha rockets (very powerful g-forces). We want to mount a very dense 1.5" OD dart atop this massive engine, transmitting all performance data and video back to base, and hopefully hit well above 150,000'.

-Jack
 

JackO

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To fill you in on my team’s progress, after sending an update to my contact at Aerojet Rocketdyne, the company’s outreach program contacted me and offered to help us fund raise for our project! In addition to this fortunate sponsorship, I have been running simulations of our large 10,000 lbf-s motor with some modification, and to be cautiously optimistic, it appears that our motor will perform with a delivered specific impulse between 250-260 seconds. As soon as the design is finalized, we'll start ordering hardware and hopefully test the engine in 2 months.
 

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Am I calculating correctly that this will generate over 44k Newton-seconds of impulse?
 

JackO

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Am I calculating correctly that this will generate over 44k Newton-seconds of impulse?
Yes, that has been our design goal, 10,000 lb-s total impulse, 44,482 NS. I've been running simulations over the past week with Derek Deville pointing me in the right direction. It's a pretty progressive burn because that is best for a boosted dart and it serves to counter the core mass flux based erosive burning typical of such a long, thin engine.
-Jack
 
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