MLP (HB2.1) Rocket Flight to 63k ft, M3.9

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butalane

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For the past 6 months or so Oberth and I have been plugging away at another iteration of the rocket we flew last September. Last weekend at Aeropac's Mudrock we flew the rocket and managed to squeeze out a little more altitude and speed than the previous configuration. Now that we don't have a rocket to construct, its build thread time!

We hadn't really thought of a name for the rocket on launch day and Tony (tfish) decided the rocket should be called "My Little Pony." Tony put it on the flight card which I guess makes it the official name. Since the rocket is really an iteration on Honey Badger 2, and my creativity is limited, the intended name was HB2.1.

Improving the Design

The launch of Honey Badger Two was by all measures successful, but realizing that we were still not design optimized in a few areas we decided to take another look at polishing the design around the N5000 before moving to bigger and better things. The motor not the best for altitude but it had proven reliable and we had a baseline for comparison. We identified four categories of improvement; reliability, mass reduction, drag reduction, and motor efficiency and prepared to implement them across the following:

Fins:
Reliability, Drag Reduction, Mass Reduction

Motor Case:
Mass Reduction, Drag Reduction

Nosecone:
Serious Mass Reduction

Electronics:
Reliability, Mass Reduction

Motor Components:
Mass Reduction, efficiency

The ultimate goal was to move to a larger design with confidence in the fins and electronics. The secondary goal was to break 60k feet with a mid sized N motor.

We'll update this thread over the next couple weeks with all the pictures taken during the launch, flight and recovery.
 
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Simulation

We had a good idea of what needed to change, but before we simply changed things, the rocket was simulated what seemed like hundreds of times. Oberth had his motor file anchored to the previous flight whereas mine was purely based on the simulation data. The starting point of both simulations was HB2, and both simulations were close in reported altitude, though his provided a more reasonable speed result. We turned nobs on HB2 to try to eek out as much performance as possible, which is why the final design shown below did get a tailcone. We agreed that drag was our primary enemy, with mass being a close second. The simulations varied from 60-75K in final altitude which sounded good, so we set out to build...

CAD

In concurrence with the simulation came a lot of CAD. The main goal was to reduce a number of the components' mass so I virtually built the entire rocket to determine if this was even feasible. I matched up the material densities and used the mass analysis tool to confirm the mass. I also rebuilt the entire HB2 rocket in CAD with measure masses to confirm that we were in fact getting lighter. At the end of the day there was a 2-4lb mass savings.

There were also some configurations that would change from last year and laying them out in CAD confirmed they would work and provided us the drawings needed to go make the parts

I also included some features that would make the rocket more producible. Applying ablative putty was a serious chore on HB2 so there are aluminum features on the NC that make that an easier task.

MLP.jpg

This is an earlier version of the rocket that does not include the tail cone or the transition.
 
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Reliability

Getting capable fins was the first step in moving towards a more strenuous flight profile. The HB2 fins were adequate for high speed but ended up eroded and charred at the ablative surfaces, we wanted a better result.

Drag

The aforementioned eroded G10 leading edges left us with fiberglass fuzzballs on the fronts of our fins. No good.

Design

I laid out a design that was (relatively) simple and we proceeded building tools to make the parts to make the fins. The core of the fin would be 0.0625in G11 with 0.1875 Phenolic frame at the leading and trailing edges. This provided us a high temperature capable leading edge that also provided protection for our tip to tip layups.

Step 1: Build a router table, cut fins and phenolic and bond together:

My artistic photo of the fin blanks curing:
20140126_162343.jpg

Step 2: Build another router table, bevel fins:

Router table, building tools is getting old, luckily the lathe was turning the nozzle at the same time.
20140301_141344 - Copy.jpg

Prepared to bevel, and potentially lose a finger.
20140301_154155 - Copy.jpg
As you can see we actually made 5 fins. Since we weren't entirely sure how all the build processes were going at this point we decided to have it along in case we needed to make mistakes. We ended up dialing in the router on it and the layup process as well. Since it had about $2 of materials in it and took an extra 5 minutes to put together, it was totally worth it.

Boom! Took about 15 minutes
20140301_161713 - Copy.jpg
This jig took all the questions out of the equation in terms of bevel accuracy. Also, because of the way the jig is designed its almost impossible to screw up a cut (but alas, your fingers are still fair game). The design was inspired by a jig Al Goncalves explained to me once, it is really the only way to bevel fins.

Step 3: Carbonate

The test fin went first, then came the group.
20140309_152355.jpg

Slurp

20140309_153946.jpg

Done

20140314_173436.jpg
Yes I realize these look imperfect despite my toting a perfect process above; these marks are surface imperfections that we buffed out of the fins later. With a little finesse they would need no touch up sand, but I was worried about the router eating my finger so I was a little twitchy

I have about a million pictures of the fins, but I will save TRF storage space since no one is reading this thread. I know I should have put "Flown on a commercial motor" in the title...us EX bros get no respect. :p
 
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Just put N5800 in the title, that'll rustle their jimmies.
 
Can you describe how the jig is used? I have a router and most of my fingers still. Is it a commercial router :)

Jim
 
Very cool project!!:)

I'll be following this post

Best of luck on your project
 
We also decided to track cost more closely for this rocket to take most of the guess work out of the equation. The construction techniques and materials used were intended to keep costs low (primarily through the use of composites) but we wanted to see how low. For us, a composite fin can provided the biggest bang for the buck since we lack the equipment to make an equivalent can out of metal. Composite fin cans offer a reasonably cheap and light weight solution to high mach flights for those with a little patience and a fondness for epoxy…and may very well offer better performance than metal. Another money saver is being able to machine small parts (everything except the casing for this project). The summary below is only for single use items and is lumped into 3 categories since many materials were used on multiple parts. Re-usable parts (aka, the electronics) aren’t included.

Fin can & nose cone = $465
Motor/propellant/airframe = $507
Recovery & Misc = $124
 
Can you describe how the jig is used? I have a router and most of my fingers still. Is it a commercial router :)

Jim

Sure Jim, thanks for asking, this is the router we used. The depth setting makes it very easy to modify the depth of the bevel, though I have used a normal, full sized router before too.

The table is set at an angle relative to the base, this angle is equivalent to the angle of the bevel. A flat top router bit (3/4" mortising in this case) forms the actual bevel as the leading (or trailing) edge rides against the fence and the flat surfaces of the fin ride on the table. This configuration makes it very difficult to remove more material than intended. It does take a few test cuts to set the bit height correctly.

This side view might make it a bit clearer:

20140301_141358.jpg

Did that make sense?
 
The motor tube is a standard EX 98 tube (i.e. 3.50in ID) but it was turned down significantly and so we needed to wrap a fincan tube:

Nothing crazy here, we wrapped some carbon around a leftover piece of the motor case, shrink taped and heat cured. We learned a few things about mylar in the process:

20140405_180739.jpg

All done:
20140406_165048.jpg

Last year we had a bit of roll in the flight, and wanted to reduce it as much as possible for the onboard video. We had also been aligning fins by eye and although the process worked well it was drawn out and questionably accurate. So, time for another tool...

Enlisted a friend with a mill:

20140330_161136.jpg

This x3 was turned into a jig...

After wrestling the fins into the jig, we bonded them:

20140412_201004.jpg

20140412_201243.jpg

Ready for some high temperature fillets!

20140419_164812.jpg

All done, and also the layout for the tip to tip already drawn onto the fincan, ready for some layups

20140509_152431.jpg

As you can see the layups were staggered, this reduced thickness near the edges and avoided a sharp composite step on the fin.

No pictures of the layup, too sticky, but here it is in the bag. The tip to tip was done in two parts so this process was repeated for the second half of the fincan:
20140509_165701.jpg

Ablative
20140524_102437.jpg

Sanded and weighed. Final weight: 800 grams which is 1.77lbs. There is the mass savings we've been looking for
.
20140531_124927.jpg
 
I'm in. Looks really neat so far. I'm liking the phenolic leading edge! I'll have to consider doing that for my next flight.

I read your threads! I hope one day to be at your level on the EX side. For now, apartment living in Redondo Beach does not suit itself well towards making rocket motors.
 
Wow, just saw the fincan come together in the last post-very impressive! That's probably one of the nicest composite fincans I've seen. I really dig the phenolic leading edges! I hope they stay on!
 
Out of curiosity and a little panic, what happened with your Mylar? I'm about to subject 2mil Mylar to ~350F.

Yikes. Not sure what we did wrong but the mylar bonded to the tube pretty effectively. It came off in spots but was mostly still on there, we ended up turning the tube on the lathe to shave the OD and remove the remaining material. Some stayed on the ID, though most peeled off. We used 2mil on the ID and 4 on the OD. David will have to comment on the cure temp, I don't remember what it was.

Sorry to panic you, hopefully this helps you avoid peeling stuck mylar off your tube though!
 
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Sure Jim, thanks for asking, this is the router we used. The depth setting makes it very easy to modify the depth of the bevel, though I have used a normal, full sized router before too.

The table is set at an angle relative to the base, this angle is equivalent to the angle of the bevel. A flat top router bit (3/4" mortising in this case) forms the actual bevel as the leading (or trailing) edge rides against the fence and the flat surfaces of the fin ride on the table. This configuration makes it very difficult to remove more material than intended. It does take a few test cuts to set the bit height correctly.

This side view might make it a bit clearer:

View attachment 175611

Did that make sense?

So, the bevels are 3/4" wide and the fin is always pushed up against the fence?

Jim
 
Very cool project! Love the fins.

Where did you get the phenolic for the leading edges?

Alex
 
Ryan and Oberth,

Awesome build and congrats on the 63k flight at Mudrock! Pretty darn impressive for an N!!!!!

Can you tell us what the ablative is? Phenolic microballoons in a high temp resin (non-epoxy?) matrix?

Again, congrats; awesome project and fantastic result!

-Eric-
 
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Out of curiosity and a little panic, what happened with your Mylar? I'm about to subject 2mil Mylar to ~350F.

I've used mylar several times before when laying up tubes and never had an issue (all previous times were with room temp cures). However, for this tube I decided to wrap heat tape over the mylar (which I perforated about every inch or two) with the hopes that mylar would prevent getting those pesky heat tape lines/ridges while still allowing the epoxy to squeeze out. Cure temp was 175F using aeropoxy 2032. Anyways, layed up the tube, pulled it out of cure and the stuff wouldn't come off. I thought the perforations could have caused an issue but the release layer on the ID was stuck too (though not as badly). We ended up machining the tube to get the mylar off, live and learn...but there were no heat tape ridges haha.
 
I've used mylar several times before when laying up tubes and never had an issue (all previous times were with room temp cures). However, for this tube I decided to wrap heat tape over the mylar (which I perforated about every inch or two) with the hopes that mylar would prevent getting those pesky heat tape lines/ridges while still allowing the epoxy to squeeze out. Cure temp was 175F using aeropoxy 2032. Anyways, layed up the tube, pulled it out of cure and the stuff wouldn't come off. I thought the perforations could have caused an issue but the release layer on the ID was stuck too (though not as badly). We ended up machining the tube to get the mylar off, live and learn...but there were no heat tape ridges haha.

Interesting. The ridges are something I have worried about. If I get the tape lined up just right they aren't so bad, otherwise they're really bad. Did you wax the mylar? Was the tube hard to get off the motor case due to the shrink tape compression?
Thanks for the outstanding thread!
 
Awesome build and congrats on the 63k flight at Mudrock! Pretty darn impressive for an N!!!!!

Can you tell us what the ablative is? Phenolic microballoons in a high temp resin (non-epoxy?) matrix?

Thanks!

Without going into too much detail, basically yes. There are some subtle changes from last year to this year that made a pretty big difference in the ablative characteristics but phenolic microballoons is a good place to start.
 
Interesting. The ridges are something I have worried about. If I get the tape lined up just right they aren't so bad, otherwise they're really bad. Did you wax the mylar? Was the tube hard to get off the motor case due to the shrink tape compression?

I didnt wax the mylar but was thinking that might be the fix. The tube came off easily (I put a thin layer of grease on the motor tube before the mylar went on).
 
I texted this to Ryan but I'll leave it here too:

https://store.airtechintl.com/Airtechstore/product.asp?Dept_ID=11&ProductID=27

This stuff is AMAZING. Wipe on a layer and forget about it. (Or spray it on if you're feeling fancy.) While using it, we never stuck a mandrel, ever, even at prepreg postcure temps. A gallon will last your entire rocketry career-- it's definitely splittable/group-buyable.
 
So, the bevels are 3/4" wide and the fin is always pushed up against the fence?

Jim

The bevels are up to 3/4in wide if you set the table angle and bit height correctly. If the bit is set too high it will bevel more than half the thickness of the fin. For a thinner fin, a smaller angle will give a longer bevel.

Yes the fin must be against the fence in order to make a cut. If its not (it kicks out for example) then the fin material will not be cut; this is advantageous because it makes it nearly impossible to over cut the bevel. It usually take a few passes too get all the material and a smooth finish, but you can run the material over as much as you want.

There are a few more subtleties to building and using the jig, shoot me an email or PM and I can send you more pictures and what I have learned in using it.
 
The bevels are up to 3/4in wide if you set the table angle and bit height correctly. If the bit is set too high it will bevel more than half the thickness of the fin. For a thinner fin, a smaller angle will give a longer bevel.

Yes the fin must be against the fence in order to make a cut. If its not (it kicks out for example) then the fin material will not be cut; this is advantageous because it makes it nearly impossible to over cut the bevel. It usually take a few passes too get all the material and a smooth finish, but you can run the material over as much as you want.

There are a few more subtleties to building and using the jig, shoot me an email or PM and I can send you more pictures and what I have learned in using it.

OK, got it. This looks like a great approach. Next time I do fins, I'll give you a shout.

Jim
 
I texted this to Ryan but I'll leave it here too:

https://store.airtechintl.com/Airtechstore/product.asp?Dept_ID=11&ProductID=27

This stuff is AMAZING. Wipe on a layer and forget about it. (Or spray it on if you're feeling fancy.) While using it, we never stuck a mandrel, ever, even at prepreg postcure temps. A gallon will last your entire rocketry career-- it's definitely splittable/group-buyable.

Interesting. I've had problems with the mylar when I go above a room temperature cure, even if I wax it. This even happens when I use a PTFE release. I assumed it was some property of the mylar (that defeated the function of the releases in some manner).

Jim
 
Out of curiosity, did you perform a mass check before adding the ablative?

Mat
 
Ryan,

Awesome build and congrats on the 63k flight at Mudrock! Pretty darn impressive for an N!!!!!

Can you tell us what the ablative is? Phenolic microballoons in a high temp resin (non-epoxy?) matrix?

Again, congrats; awesome project and fantastic result!

-Eric-

Thanks Eric, really appreciate it! The rocket was as much (or more) of Oberth's doing as mine!

I'm glad you saw this, I was going to mention when I get to the electronics that your posts about your electronics experience at BALLS last year was fresh in my mind and we did some extra altimeter testing because of it. Its a good thing I read it because we ended up solving a GPS/altimeter problem on the pad that almost stopped the flight. I'll put up some more info about that when I get to the electronics section.
 
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