Sunday, July 24, 2016

Building resumes

After losing my stalwart DarkStar I decided that I would not rebuild it. Instead I purchased a 4" Punisher w/75mm mount at LDRS and the booster is already built:
I really dig this volumetrically efficient design and hope it lasts for several years.  Three years ago my parents gifted the now discontinued 8" Mega Cowabunga from  After barging toward LDRS the build was nearly complete. I had planned to finish it on Lucerne Dry Lake Bed and fly it on an AT L1500 Blue Thunder.  Well it turns out that I had way more to do than anticipated and it wouldn't have been ready anyway.  In the week after that launch I finally finished the build and it's now ready to go:
I was also able to rather easily modify the previously reported 7.5" ID 3D-printed electronics bay to fit the ID of this larger rocket (shown with one Power Perch base installed):
I also made some build progress on the 7.5" Skunkworks V2 w/75mm mount:
Those internal fillets are going to suck.  I bought some industrial, arm-length gloves for the task and I suppose I could move into the business of artificial insemination of livestock afterward if I didn't love critters so much.  They all deserve to live happy lives unhindered and unconsumed by our species.  Finally, have you caught them all yet?  Since I started Pok√©mon  Go on 7/12/16 I have walked 68.57 miles in the real world and attaining level 20 offered quite the bounty!

Monday, June 27, 2016

M2080 recovery failure analysis

This has been a rough entry to ponder but I need to commit to history and move on.  In memorium...  I had flown this Wildman Extreme DarkStar workhorse 10 times over the course of ~4.5 years before the April 2016 recovery failure at Holtville:
The recovery recipe I used for the first L585 flight remained consistent and served me well up through the M3100 flight.  The only difference in the setup for the most recent M2080 flight was the use of M-tek/Firewire electric matches (blue&white-striped leads) rather than J-teks (solid yellow or black leads). To my knowledge J-teks have never failed in any of my flights. I should note that at least one of the two Firewires used for apogee/CD3 deploy worked as the drogue was out but... Despite using separate, heterogeneous, redundant altimeters neither of the M-teks used in the main parachute's CD3 system fired as you'll see below.  For the record the Raven 3 used a freshly charged LiPo battery and the ARTS2, set for single-battery mode, used a fresh 9V battery.
     According to their website these Firewire Initiators should measure 1.0  +/- 0.2 Ohm:
Here I'm disassembling the CD3 system for the first time after impact: MTek-RemovalFromCD3
After dissecting the nearly totaled rocket I tested the intact matches and both measured high for resistance; 3.5 and 4.1 Ohm, respectively:
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I also fired both matches with my ground ignition system after measuring their resistances so I remain thoroughly stumped.  Click to play these videos:
Video May 13, 5 32 33 PM 4.1 Ohm Firewire Initiator test
I had heard that there were issues with early batches of these matches but I ordered two boxes with 7 ft. leads (40 per box) directly from the vendor on 12/17/2015.  I see no lot code or batch date on either box so I have no idea how to identify these except for the order date.  That's all I think I know except for sadness.  After colliding with the sturdy concrete, nozzle-first, I was only able to salvage one Pro75 threaded closure, the ARTS2 (I think it still works?), the Raven 2, and my Beeline GPS tracker.  If I were to replace all that I lost it would run a hefty toll, $850, + shipping:
Painful.  I will contact the Firewire Initiator manufacturer tomorrow but I highly recommend that folks not use that product for recovery. Instead I will only use the remainder of those two boxes for ground ignition where failure is an option.  Behold the carnage:
Direct impact on concrete with only a small drogue parachute.

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I had to saw the airframe off to try to get the bent casing out but no dice. After hacksawing off the forward end of the motor I discovered that the forward closure parts were dented and damaged beyond repair anyway:
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Similarly the CD3 for the main compartment bent on impact such that the red anodized aluminum cylinder was totaled.

And this demonstrates that the 16g CO2 cartridge remained intact. The only elements that failed were both of the main Firewire Initiators. Did I mention that? Ugh.

Saturday, June 4, 2016

Holtville launch report for 5/7/16

Brevity remains inevitable here as I had only one flight but here are the photos captured by Mark Treseder and myself.   Here's the one GoPro vid I captured of Mark  Treseder's Little John on a CTI 396I195 Red Lightning:
I flew only a CTI 538I303 Blue Streak in the 2.5" Nike Smoke, for which I captured neither liftoff photos nor video. I did, however, manage to record yet ANOTHER fucking runway landing marking this an unfortunate recovery two months in a row:
This time damage was negligible but... really?  I know I must attribute this to dumb probability but my rocket array won't survive much more of this concrete that acts like a fiberglass magnet. Ugh.  I  need a napping Lola to cheer this post up: Lola!

Sunday, May 15, 2016

Lucerne... Punisher... K1440... redemption!

I'll augment this entry soon but here's the video of yesterday's K1440 flight to 13,932' with full recovery:
My trusty Comm-spec tracking system led me to it but only after seeing nothing after burnout, walking several minutes North in marginal disbelief, and finally catching a glimpse of red 'chute. Here's the view back toward the flight line ~1 mile South (shocker!):
K1440 redemption recovery. Lucerne, May 2016.
Here's the flight data from my new Raven 3 (70G/30G):

  • Tabular, graph
  • Barometric altitude: 13,808'
  • Max velocity: 1,297 MPH
  • Max axial acceleration: 62.5 Gees (!!)
Good times.  I bought a CTI 2014K1200 White Thunder from the epic David Reese at Wildman West for another good time soon.

Friday, May 6, 2016

Holtville - April 2016 launch report

In looking at my todo list in the entry below I must admit I recall little from the February launch but I remember much about last month's launch.  Here are a few photos of Ron Rickwald's M flight, my M2080 Skidmark, and Larry Hermanson's L1000.  Thanks to Mark Treseder for shooting the away photos.  And here's the GoPro vid of Ron and my flights:

In honor of Mike "Sparky" Jerauld's lengthy service to the DART club many folks flew Skidmarks, Dark Matters, or Metalstorm motors.  I elected to bust out the CTI Pro75/6GXL 6827M2080 Skidmark purchased during last fall's Wildman sale.  As always the prep took much of the morning but I felt good about the setup.  Thanks to Darrel for helping out at the pad and that was a fine, joltingly quick liftoff:
GeeMuneh_4GS18138.jpg M2080Liftoff-blog
Mark Treseder later shared that he thought the motor had cato'd but I had used the stock CTI igniter and I'm guessing it was the high aspect ratio, 7G motor that caused the quick pressure up.  I never saw it after burnout but had GPS lock from about 14,000 feet until it landed. Later Darrel and I drove right up to it on the concrete runway about three feet North of the dirt.  It was clear that the apogee ejection had worked but there had been no main ejection at 800 feet.  Having flown this rocket based on a recipe that had served me well for about nine flights I was shocked and saddened at the recovery failure.  I forgot to shoot a photo but the booster was on the runway painfully close to the dirt (which would have saved it) and the payload section was in the dirt.  I'm guessing that the payload section had bounced off the concrete, however, as it's nearly totaled as well.  The booster clearly landed at an angle as the AeroPack motor retainer has a huge dent in it, the epoxy sealing the retainer in is mostly fractured out, and I can see that the casing itself is dented.  I will publish a separate entry on the failure analysis but I'm quite certain the new M-tek 'initiators' are to blame.  Kenny Harkema spoke to the folks at electricmatch dot com and they told him there was a defective batch of pyrogen material for these new matches.   Friggin' sheer awesomeness.  I should note that their J-teks have never failed me.
   The flight had sim'd to 14,800' AGL.  I still need to pull the ARTS2 data but the Raven 2 and Big Red Bee Beeline GPS appear to have survived the impact:
  • [Addendum] ARTS (graph, tabular, motor performance (7192M2197), CD)
    • Baro altitude: 14,263'
    • Max velocity: 1,510 fps (1,029 MPH)
    • Max acceleration: 657 ft/s^2 (20.5 Gees)
  • Raven2 (graph, tabular):
    • Baro altitude: 14,281'
    • Max velocity: 956 MPH
    • Max acceleration: 29.1 Gees
  • Beeline GPS (Google Earth screen grab)
    • Max altitude: 4,513m AGL => 14,803'
  • [Addendum] Averages:
    • Altitude: 14,449'
    • Velocity: 993 MPH
    • Acceleration: 24.8 Gees
Tomorrow's Holtville launch will be small but I'm gonna head out anyway in search of better luck.  Wish that for all of us. Thanks for reading.

Saturday, April 9, 2016


Hi, all.

Sorry for the lag but I've been in Swift/iOS app programming mode for work since January so XCode overrides blog authoring time when I return home.  I had planned to attend Lucerne today but it was cancelled due to inclement weather.  I vow to catch up soon and owe:

  • February Holtville launch report
  • 3D printing update
  • April Holtville launch report including a special failure analysis focus.  Grrrr....
Thanks, onward, and upward!!

Saturday, January 9, 2016

K185 = cable cutter test

I got a late start during last Saturday's packing because I could not find three important items and arrived at Holtville about 9:30AM. The AT 1417K185 did indeed fly...
...but there were several issues during prep and the primary reason for the flight, the cable cutter test, failed.   This was the first flight of what was supposed to be a super robust, carbon-fiber-overlaid, minimum diameter 54mm design.  I built this very high aspect ratio rocket to take any 54mm certified motor but the K815, while cool, would not be pushing any aerodynamic limits that day.

I specifically designed and 3D-printed the black caps [below] to fit in this rocket's electronics bay and cut a length of 1/4-20 all-thread that morning to hold the caps in place.  However, upon assembly, I discovered that the all-thread rod was ~2" too short.  I still have no idea how that happened as I'm somewhat familiar with ruler use.  I was about to give up but this was my only planned flight for the day so I quickly decided to shorten the already too long coupler to fit the all-thread assembly.  I bought a DC Dremel tool and that made quick work of the modification.

So now everything fits together as originally planned and the rest of the prep goes relatively smoothly.  The booster segment is only 36" long so a K185 with even a shortened coupler doesn't leave much volume for the recovery goods.  With Darrell's help I was able to get everything packed in and two pieces of masking tape seemed to hold the payload section into the booster.

Out at the pad I armed the Raven 3/Power Perch with the large magnet but rather than the expected "high high low low" dual-deploy beep pattern Darrell and I heard only "low low low pause high" (I think).  I admitted that I had not powered up the altimeter after prep as a test but this setup always works as expected so I had become overly confident.  In any even we agreed that something was wrong and pulled the rocket.  We undid all the careful packing work and checked the connections only to hear the same odd pattern after several iterations.  Once again I had planned to scrap the flight... defeatist!  Coincidentally I started talking to Russ Sands afterward who offered that it sounded like my LiPo battery below a safe voltage threshold.  I always charge my batteries the morning of a flight so I was skeptical but swapped to a different battery anyway.  Lo and behold it powered up with the expected dual deploy beep pattern! Well done, Russ, and thanks for the input.  I'll need to charge and test all my Raven batteries before the next launch.

OK so I crammed everything back together, got the rocket on the rail, armed the Raven 3, and loaded up the stock AT igniter.  Darrell was kind enough to launch for me but there was no ignition on this first try.  I've always found these Aerotech 54mm moonburners difficult to ignite and should have proactively metered some thermite.  Instead I used one of my older, dipped igniters on the second try.  There was a small puff of smoke upon ignition and then about 10 seconds of smoldering before the motor finally pressured up.  I was a bit worried about the moon burning thrust vector and minor curvature in the 4' long payload section but did everything I could to balance those forces during prep.  Ultimately the ascent was straight, true, and out of sight.  I used a 12g CO2 cartridge at apogee so there was no visible event at the top.  Luckily the Comm-Spec tracker signal boosted once the antenna was free from the carbon fiber shell so I knew I had separation.  Darrell and I walked right up to the rocket about 1/3rd mile away using the tracker.  Everything had separated but the main parachute's "burrito" remained intact with the cable cutter still in place.  D'oh!

I suspect that some of the BP leaked out of the cutter's cylinder despite a relatively thick wire to the ematch.  I had used a sealing o-ring around the wire in the previous night's test but it didn't seem to fit over the black wire I used for the flight.  Just in case I had plugged the cap with wall-tack clay but apparently that didn't help.  I suppose I'll force the o-ring over the wire next time and the new MTek leads are of apparently smaller diameter.

The bottom ebay cap had hit the ground and cracked another inch off of the coupler despite internal carbon fiber reinforcement.  This impact also  knocked the baro sensor off the Raven 3 and I have yet to be able to power it back up.  I might try to have it fixed but, with two abusive flights on it, the unit could be dead.  Good rocket science-y times!

Friday, January 1, 2016

Some 3D printing success

Over the holiday break I got my CreatorBot 3D printer up and running again and completed the following in the last few days:
On the left is the 3D V2 mark II with numerous improvements over my first design.  Unfortunately I still haven't built a lid for this large, open-top printer and you can see several warp/layer splits in the fins.  I can patch that before flight and the mark III should benefit from a laser-cut lid.

The middle two pieces represent my electronics solution for the Polecat Aerospace 7.5" V2 with 75mm motor mount in progress.  Before this design the two leading choices were to cut an door out of the airframe (not a fan) or add an E-bay tube in the nosecone tip.  The new alternative is to mount two Raven Power Perches into the smaller half and bolt that to the larger half in contact with the ID of the airframe.  There's a 3/8" static port to the outside, two 1/8" side outlets for ematches, and two top holes for screw eyes to minimize stress on the Power Perch's wire mounts.  I also increased the radius of the smaller half slightly so the bolt's threads will be loaded under a bit of force to prevent vibrational unthreading of the nuts. I may be able to refine the design some but this first one seems like it will do the trick. Here's the smaller half model detail: V2-PowerPerch-ebay-smallerHalf
Finally the two black ebay caps on the right are prints I completed at work on our Makerbot 2X.  I've been getting some very clean prints on the 2X lately as I added 4 mil thick Kapton tape to the heated bed and increased its bed temperature to 120˚C.  This mostly eliminates warp with ABS and gives a highly uniform glossy finish to the base of the part(s).  These caps will enable the aforementioned minimum diameter K185 flight tomorrow at Holtville.  I'll reiterate that every high-power rocketeer needs a 3D printer and a modicum of modeling/CAD skill!

Thursday, December 31, 2015

Test of Archetype Rocketry's Cable Cutter

I bought Archetype Rocketry's clever and compact Cable Cutter a couple of years ago because it enables dual-deploy from a single volume.  After struggling to find it all day I finally ran the following test tonight:

They recommend 0.1 ml of Pyrodex but all I have is black powder.  I could probably get away with 0.05 ml but, considering the parachute "burrito" will be outside the rocket when the cable cutter fires, I think I'll stick with 0.1 ml just to be sure.  I plan to fly a minimum diameter AT 1417K185 on Saturday using this system so wish me luck and [almost] Happy 2016!!

Sunday, December 6, 2015

Holtville Launch, December 2015

Here are the photos but I was having trouble with the GoPro and only caught three liftoff videos:

I was the first flight of the day for the first time with the CTI 260H194 Red Lightnin', helped Darrel with his perfect CTI 2771L990 Blue Streak flight, and socialized a bit.  The FAA just bumped our waiver from 10k to 15k so I need to get on that!  The only hitch is that we need to launch from the corner of the runway so that's quite a trek.  I could hear Paul Snow doing the remote countdown over the PA at the launch site and also on Darrel's phone about 1.5 seconds earlier.  We didn't specify which was the fire countdown so I was late on the button in the photos.  Also, when we got out there, my GoPro would not power on so I missed Darrel's epic liftoff.  Duh.