Update on High School Rocket Lab-Final M Characterization Motor Tests + UCLA bi-prop

Hi everyone,

It's been a long time since I have posted on here, but I thought I might share with you my high school club's progress on our minimum diameter boosted dart concept.

Last Saturday, after a whirlwind of last minute machining (finished tapping the retaining bolt holes at 3 the night before), we got out to the MTA (the RRS' Mojave Test Area) to burn our last 4 grains, finishing the characterization process for our fuel composition. These tests went extremely well especially considering the nozzle we used was a modified USC nozzle which I picked up from their rocket lab the night before.

Before our tests, we got the chance to watch a group of middle-schoolers from downtown launch 13 (far too many) zinc-sulphur Alpha rockets to 5-7,000' each. After our first test, UCLA tested their bi-prop kerosene NO motor which made 650 lbf nominal thrust for 15 seconds!

Here are the videos of our two tests and their pressure+thrust data: https://youtu.be/jZHtt2CPc9g

Here is a link to UCLA's powerful liquid motor test (most recent post): https://www.facebook.com/rocketproj...oAdsUySO7UiaHrf6ac2A_BWXCTDqzyTupnjPw&fref=nf



As it says in the video, from here, we will be designing and testing a 5" 10,000 lbf-s motor to launch our boosted dart rocket to over 150,000' in the coming months!

-Jack

You highschoolers are beating several accredited colleges at this!!! SEDS a L-1 multistage HPR college competition only set the altitude at 3,000ft with every 200ft after as bonus points. Only 20 out of 88 registered teams even competed. At SpaceVision UCSD said they spent over $100,000 on a liquid fuel rocket for a different project. And $35,000 of that went to the engine. You can stage two N L-3 solid APCP motors and hit space much cheaper.

qquake2k said:

Awesome tests! And these are high school students?

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We all are. I (I'm 16) do the vast majority of the work, but I have a team of people at school learning and ready to help. I often bounce ideas off of Derek Deville, and we work closely with out mentors from the RRS chiefly Dave Crisalli; his expertise makes everything safe and therefore possible.

Andrew_ASC said:

You highschoolers are beating several accredited colleges at this!!! SEDS a L-1 multistage HPR college competition only set the altitude at 3,000ft with every 200ft after as bonus points. Only 20 out of 88 registered teams even competed. At SpaceVision UCSD said they spent over $100,000 on a liquid fuel rocket for a different project. And $35,000 of that went to the engine. You can stage two N L-3 solid APCP motors and hit space much cheaper.

Click to expand...

Thanks Andrew! It's funny you say that; we work closely with USC who has a composite motor ready to send a single-stage to 400,000'. Their current record is 148,000', and we just want to beat that record before they do it themselves. Have to admit though; our work doesn't truly compare to the sophistication of a liquid motor. Hat's off to UCLA for that test.

Here's the Burnsim for the flight motor. 10,000+ lbf-s in under 3 seconds at ~1000 psi. Core diameter opens up for bottom three grains to minimize erosive burning; bottom grain is a slower prop for the same reason. Should be exciting.

JackO said:

We all are. I (I'm 16) do the vast majority of the work, but I have a team of people at school learning and ready to help. I often bounce ideas off of Derek Deville, and we work closely with out mentors from the RRS chiefly Dave Crisalli; his expertise makes everything safe and therefore possible.

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I hope you realize how awesome a set of two mentors Dave and Derek are. You really would be extremely hard pressed to top that combination.

Great work!


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JackO said:

Here's the Burnsim for the flight motor. 10,000+ lbf-s in under 3 seconds at ~1000 psi. Core diameter opens up for bottom three grains to minimize erosive burning; bottom grain is a slower prop for the same reason. Should be exciting.
View attachment 332956

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Are you planning on bonding the grains to the liner? I would hope you are to avoid a grain collapsing under acceleration, plugging the nozzle, and making the motor go boom.


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markkoelsch said:

Are you planning on bonding the grains to the liner? I would hope you are to avoid a grain collapsing under acceleration, plugging the nozzle, and making the motor go boom.


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Click to expand...

We plan to; what adhesive would you recommend?

JackO said:

We plan to; what adhesive would you recommend?

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I use BSI 30 min epoxy. Others use gorilla glue. The key is to dry fit the grains first. Make sure whatever you're using is thin enough that it won't bind up halfway through. Also make sure you leave enough space in the liner for the nozzle on the bottom end and the forward closure on the top.

Quick question- you're making a P motor, and you haven't glued grains into a liner before?

djs said:

I use BSI 30 min epoxy. Others use gorilla glue. The key is to dry fit the grains first. Make sure whatever you're using is thin enough that it won't bind up halfway through. Also make sure you leave enough space in the liner for the nozzle on the bottom end and the forward closure on the top.

Quick question- you're making a P motor, and you haven't glued grains into a liner before?

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Alright; thanks for the advice. No, this is our first custom flight motor; our only tests as a group to date were the characterization tests which were M-Class. Their L/D was very conservative (they're nicknamed the Stumpy series) so the issue of bonding grains is new.

Did you run this Burnsim past your mentors? All of these are red [or yellow] flags to me:
- 75 inches of propellant and only a 10% P?
- Only 72.5% Volume loading?
- A peak MF of 2.575?

This is not a very spiffy design and might very well CATO due to erosion.

FredA said:

Did you run this Burnsim past your mentors? All of these are red [or yellow] flags to me:
- 75 inches of propellant and only a 10% P?
- Only 72.5% Volume loading?
- A peak MF of 2.575?

This is not a very spiffy design and might very well CATO due to erosion.

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I saw that too, and agree.

I just looked up my 5" motor with 72" of propellant
83% loading and mass flux of 2.035
it worked with a "mild" propellant formula.

Your sim looks like it's going to eat itself alive.

Tony

FredA said:

Did you run this Burnsim past your mentors? All of these are red [or yellow] flags to me:
- 75 inches of propellant and only a 10% P?
- Only 72.5% Volume loading?
- A peak MF of 2.575?

This is not a very spiffy design and might very well CATO due to erosion.

Click to expand...

tfish said:

I saw that too, and agree.

I just looked up my 5" motor with 72" of propellant
83% loading and mass flux of 2.035
it worked with a "mild" propellant formula.

Your sim looks like it's going to eat itself alive.

Tony

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Both the low volume and to an extent the low P performance are due to the significant increase in core diameter for the bottom grains. However, with only a 4.13" grain diameter, I would think a 10% P aggressive; it should deliver over 240 ISP.

I can definitely get the peak MF down with a more intricate design for the lower grains; I didn't really play with that yet since 2.6 is still below the 3.0 max recommended MF for MF based erosive burning described by this article Derek recommended to me: https://rasaero.com/dloads/Erosive Burning Design Criteria.pdf but I most likely will now since we don't have the capital to not play it safe.

Tony, if you could PM me that sim to contrast I'd appreciate it. The major reassurance for this design is that we are simulating a pretty high burn rate exponent (.414) found from our characterization tests, but I expect that it is not really so high and the motor should under-perform. Regardless, we're using a 1/4" walled 6061 case with thick phenolic insulation, so we should be safe if the pressure doesn't run too far away before the bottom grain burns out and the pressure drops.

It's challenging, but we want a slightly progressive, high pressure, and fast-burning motor for the boosted dart similar to the Super Loki.

Thanks for both of your feedback; it's what I was hoping for when I posted the sim in the first place.

-Jack

Consider a case-bonded monograin with a Finocyl core.

FredA said:

Consider a case-bonded monograin with a Finocyl core.

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That was our original design, but Dave did not recommend it for the added casting complex plus he and the RRS have had lots of success with large BATEs motors.

JackO said:

The major reassurance for this design is that we are simulating a pretty high burn rate exponent (.414) found from our characterization tests, but I expect that it is not really so high and the motor should under-perform.

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I'm a little confused about this- you had a characterization test, but you don't think the results are accurate?

djs said:

I'm a little confused about this- you had a characterization test, but you don't think the results are accurate?

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We did not have the time or budget to run extensive tests; over .4 is typically a high n for APCP propellant, therefore, using it is a much safer method.

So what you're saying here is that you got a 0.4 for the burn rate exponent from the characterization, but you don't believe it? Or you just put in 0.4 thinking "it has to be better than that in real life"?

djs said:

So what you're saying here is that you got a 0.4 for the burn rate exponent from the characterization, but you don't believe it? Or you just put in 0.4 thinking "it has to be better than that in real life"?

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No, I am not saying that at all. I'm saying that .414 was what we recorded from our tests and since .414 was higher than expected, imperfect ignition methods on top of the general inconsistency of characterization testing in small quantities are likely to blame. If the exponent is accurate and we're on the upper limit of pressure sensitivity, than so be it, we've designed a motor with that parameter so the motor will perform as simulated. If it is inaccurate-too high- the motor will have a longer burn time. If it is too low, which is unlikely since it already exceeds typical n-values, the casing was designed to handle the additional pressure. In other words, I'm not blindly trusting sub-scale tests, and we are designing conservatively...

OK, I was off a tad on my numbers.(it's been 10 years since the build/flight)

It took awhile but I did find an original screen shot of the Burnsim for this motor.



(Disclaimer: I know more now {unless I've forgotten it} about that formula and Burnsim and Isp, then I did 10 years ago.)

Here is that same motor with better info.



I've never really like stepped cores...And don't knock those that do.

IIRC...I placed the igniter in the middle of the third grain...soft start.

[video=youtube;OZ2v48CoLqY]https://www.youtube.com/watch?v=OZ2v48CoLqY[/video]

The rocket was "misplaced" after tracking for awhile.


Tony

tfish said:

OK, I was off a tad on my numbers.(it's been 10 years since the build/flight)

It took awhile but I did find an original screen shot of the Burnsim for this motor.

(Disclaimer: I know more now {unless I've forgotten it} about that formula and Burnsim and Isp, then I did 10 years ago.)

Here is that same motor with better info.

I've never really like stepped cores...And don't knock those that do.

IIRC...I placed the igniter in the middle of the third grain...soft start.

[video=youtube;OZ2v48CoLqY]https://www.youtube.com/watch?v=OZ2v48CoLqY[/video]

The rocket was "misplaced" after tracking for awhile.


Tony

Click to expand...

Tony,

Thanks a lot for sharing; really impressive flight too sorry about losing tracking. It's encouraging seeing a motor so similar in dimension to ours work as expected. I don't like the idea of stacked cores in general but the high mass flux makes it necessary. Did this run on your own prop composition?

Jack

Anyone else think this discussion should be happening in the restricted section? Sounds like some pretty hairy details about motor composition that are generally not for general public consumption...

CzTeacherMan said:

Anyone else think this discussion should be happening in the restricted section? ...

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Not really, I'm good with it. There is no mention of formula's nor chems involved.
You need that part to get to here.
All this info is readily available on the web, through sites, books, etc.

This part is fascinating, considering the people involved and the time span covered....much has changed over the years. Basically young enlightened folks exchanging ideas/experiences with old farts and their seat of the pants/intelligent experiences for the benefit of all!

Let it ride.:wink:

I agree with Jim. This isn’t the risky part of rocket motor research; it’s the responsible part that’s seldom discussed in public.


Steve Shannon

JackO,

Have you been following Aerotech's development of the DMS 98mm O motor?

[video=youtube;05qW01aYKr4]https://www.youtube.com/watch?v=05qW01aYKr4[/video]

They've been working on it for almost 2 years. Any idea why?

You're 5" motor has a longer length to diameter ratio then the one Aerotech has been working on.

see photo below for comparison ...


bottom case: standard 98/15360 6 grain case
Middle case: AT DMS 98mm O motor (spent)
Top case: Dr Rockets 98/25600 "O motor case"

Tony

tfish said:

JackO,

Have you been following Aerotech's development of the DMS 98mm O motor?

[video=youtube;05qW01aYKr4]https://www.youtube.com/watch?v=05qW01aYKr4[/video]

They've been working on it for almost 2 years. Any idea why?

You're 5" motor has a longer length to diameter ratio then the one Aerotech has been working on.

see photo below for comparison ...

bottom case: standard 98/15360 6 grain case
Middle case: AT DMS 98mm O motor (spent)
Top case: Dr Rockets 98/25600 "O motor case"

Tony

Click to expand...

No, that's my first time seeing it; it's very impressive, thanks for sharing. Pumping that kind of thrust out of 98mm would be very difficult especially on top of getting it consumer certified.

CzTeacherMan said:

Anyone else think this discussion should be happening in the restricted section? Sounds like some pretty hairy details about motor composition that are generally not for general public consumption...

Click to expand...

No formulas being mentioned. It's some general discussion- I think it is fine.


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JackO said:

No, that's my first time seeing it; it's very impressive, thanks for sharing. Pumping that kind of thrust out of 98mm would be very difficult especially on top of getting it consumer certified.

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I think tfish was sharing this, not in a sense of "check out these motors!" but that these are similar cases of motors that have a very large length/diameter ratio. Yours is a similar problem in which your higher mass flux will come into play. How do you plan on mitigating this?

It took Aerotech 2 years to make the 98mm O motor. What is your timeframe to build your P motor, assuming you don't have the same expertise that Aerotech has? Yes, it's a larger case diameter, but the design problems remain.