Wednesday, March 15, 2017

100,000+ blog views!

Thank you, loyal readers, and I hope to increase my content output as 2017 proceeds.  Fly fast! Fly high!

Sunday, January 8, 2017

Holtville, Jan. 7, 2017 - TWO successful L3s! In 4K!

Frank Hermes AND River made it out to Holtville yesterday so those were already wins right there. Congratulations to Mark Treseder and Dave Nord who successfully earned their L3 yesterday for NAR and Tripoli, respectively:

I brought a couple of things to fly but instead opted to shoot mostly 4K video with my new GoPro Hero 5 camera. I just watched the above video on a 4K TV and it looks so crisp! Also the 240 fps slow-mo has been upgraded from 480p previously to 720p natively and I then upscale it nearly 3x into 4K. Fun!

Sunday, January 1, 2017

Lucerne Dry Lake, November 2016: The L1500 is a bad-ass!

As noted previously, and now that it seems to be out of production, my Madcow's 8" Mega Cowabunga was finally complete and ready to go.  I selected Aerotech's 98/5120 5089L1500 Blue Thunder beastie for a first flight and that was a good, thrusty choice as the hefty stub weighed 39 lbs on the pad.

Near the beginning of the video I included a CD3 ejection test with a 16g cartridge, 98/2560 motor assembly, and three shear pins as a worst-case pressure combination.  I also seek to minimize nosecone velocity since it alone weighs 10 pounds and I want to optimize separation and stress/strain at ejection.  This 16g cartridge was so gentle that I bumped up to 25g for the flight to add margin.
     The motor defied thermodynamics and self-assembled (😁) without issue. I followed Aerotech's revised assembly guidelines that now include bonding of grains to the liner for certain reloads:

This also represented the inaugural test of my 3D printed electronics bay for a stroll.  It houses two Featherweight Raven altimeters with Power Perches and the two halves are bolted through against the airframe wall and down against the top centering ring like so:

I used a stock, heftier CTI dipped match for ignition which proceeded expeditiously.  From a distance the rocket appeared to wobble a bit off the rod but stability should be rock solid so... more on that in a bit.  Again I used a deployment bag for a 12' Rocketman 'chute and both proved good choices as recovery proceeded in a beautifully uncomplicated manner:

Here are the data from the altimeters in very solid agreement:
  • Raven 1 (70G/30G) peaks [graph, tabular]:
    • Altitude, barometric: 6,208'
    • Velocity: 541 MPH
    • Acceleration, axial:  11.44G
    • Acceleration, lateral: 8.93G
  • Raven 3 (70G/30G) peaks [graph, tabular]:
    • Altitude, barometric: 6,182'
    • Velocity: 545 MPH
    • Acceleration, axial:  11.67G
    • Acceleration, lateral: 9.64G
  • Averages:
    • Altitude: 6, 195'
    • Velocity: 543 MPH
    • Acceleration, axial: 11.55G
    • Acceleration, lateral: 9.29G
Now about that liftoff torque... It took several views of the slow-mo pad video to (mostly) realize what happened. Lucerne's pads use a hinge as an airframe support at the bottom of the rail and I probably did not have that aligned axially with the rail slot. Additionally it's now obvious to me that nozzle's throat was not aligned with the apex of the roof-shaped thrust deflector. This high-thrust motor therefore vectored its thrust toward the camera and induced a clockwise moment of the pad from the thrust deflector upward. Now why would everything above the pad's legs be allowed to rotate ~70 degrees? No idea but, rest assured, I'll be checking that and other alignments from now on. Here's the unfortunate but minor and reparable damage to the bottom 1515 Delrin rail guide:

Overall I consider this flight to have rocked! Subsequently I purchaseed both CTI 4807L3150 Vmax and AT 4668L2500 Super Thunder reloads for future, authoritative sky-hole-punching.  Oh how the viciousness will delight.

Friday, November 25, 2016

Holtville: October 11, 2016 launch report

I didn't feel like packing that morning but, rather than shirking all responsibility, I elected to throw the trusty 2.6" Madcow Nike Smoke and minimally supportive gear in the car.  I also had that CTI/AMW 542I297 Skidmark that failed to fire in DRM mark II at LDRS so that was handy for this robust, 38mm-motor-mount beastie.  Finally, and most importantly, I wanted to test the Jolly Logic Chute Release gifted by my parents in September.  That site link covers the device thoroughly but this small, non-pyrotechnic parachute tether will now figure prominently in my electronics arsenal.  I somehow failed to secure liftoff video or photos but will attest to the perfection of the flight and single-volume, dual-deploy recovery.  Here are the other photos I captured that day as already shared with the Tripoli SD email distribution.  Oh and it's quite a rare bonus that I missed landing on the runway by about 8 feet this time:

I think I set the device for 500' to unbind the parachute but it looked more like 200' to me.  Next time I'll try 700-800' and see how that looks.  Note that Holtville is very close to sea level so this wasn't an MSL/AGL disagreement.  In summary: git one and git 'er done, 'Merica!

Thursday, November 24, 2016

https:// connections recommended, cookies used here, daily puppy no longer being updated

From Blogger:

Your HTTPS settings have changed. All visitors are now able to view your blog over an encrypted connection by visiting Existing links and bookmarks to your blog will continue to work. Learn more.


European Union laws require you to give European Union visitors information about cookies used on your blog. In many cases, these laws also require you to obtain consent.

As a courtesy, we have added a notice on your blog to explain Google's use of certain Blogger and Google cookies, including use of Google Analytics and AdSense cookies.

You are responsible for confirming this notice actually works for your blog, and that it displays. If you employ other cookies, for example by adding third party features, this notice may not work for you. Learn more about this notice and your responsibilities.

So... are cookie notices working for EU visitors? PSA: Don't get cookies in your sand. (That's a joke EU visitors. :)

Finally the "Daily Puppy" widget will no longer be updated so I have removed it.  I'm sad as that's the only reason I even bother to check this dumb, rocket-sciencey blog.  :(

Sunday, November 20, 2016

Belated: LDRS - June 2016 launch report

I haven't felt much like blogging in recent months.  Could you tell?  Well I'm attempting to catch up now so I suppose that's something... onward and upward.

LDRS was conveniently hosted by at Lucerne Dry Lake this year in June.  The San Diego club carved out a cozy little portion of the parking area a couple of rows back on the east side.  East side represent!  Mark Treseder was kind enough to shoot photos of the event using my camera and they're on Flickr if you'd like to glimpse into the recent past.
     I've wanted to fly Der Red Mix mark II fully loaded for some years now and this third flight seemed like a great time to try.  My aging Flip Mino HD's battery gave up the ghost unbeknownst to me until I was prepping the flight.   As such I have only ground-based slow-mo and hand-held iPhone 6s slow-mo footie but it's still sort of a good time:

You might recall that I took some airframe damage at the top of the tube, patched that at home, then spent literally hours on the playa sanding the tube interior and nose cone shoulder trying to make the nose cone fit.  In the end I got close enough but still had to use 2" wide Gorilla tape to create a gap at the top of the shoulder so the base would fit and move properly during ejection.  You can see the [tape] gap between the two 8 decals in this liftoff shot,  That did, however, shift the CG north a bit thus adding bonus stability margin (Photo Mark Treseder):
Skidmarks remain my personal motors of choice for this clustered/air-start vehicle so I stocked up on a central 2304K815 as the ground-start motor.  As always I got the thing moving up and away with this single motor before attempting to ignite subsequent motor pairs.  Once off the ground I use both Raven 1 and Raven 3 altimeters in series to theoretically fire 2x 543I297 then 2x 305H226 then 2x more 305H226.  For this third flight I set the air-start delays to 0.1s to maximize seamless titanium amazingness but noted two problems: 1) Only one of the I297s fired and 2) The gaps between motor pairs was more like 1-2 seconds.  I still have no idea what happened with the I297 pair's delay since the capacitor should have been fully charged at that point but all the other motors fired at some point.  If you look at the graph links below you'll see that the second pair of H226 motors were staggered unintentionally.  Also the missing I297's ematch had fired so I suppose this was a rare time when a pyrodex pellet missed its spark:
     Here are the data from the altimeters and both four-phase (really 5-phase) graphs look quite interesting (average altitude: 4,925' AGL) :
Oh and I forgot to mention that deployment bags rock!  The previously documented damage to DRM mark II was cause by an unnecessarily steep launch angle mandated by the RSO.  I was not interested in a second set of repairs and remembered that I have a couple of Rocketman deployment bags in storage.  I used to think of them as parachute blast protectors back when I was using black powder for direct ejection.  I have since moved all my large rockets to the CD3 CO2 system so melting/burning is no longer an issue.  Remember that the primary function of a deployment bag is to gradually and gently allow a parachute to inflate thus eliminating the shock of unhindered inflation.  I'm happy to report that zero incremental damage was done to my semi-fragile repairs on this flight so I'm all over deployment bags once again.
     I had planned a second flight but, despite significant amounts of work on the Madcow Rocketry Mega Cowabunga, I could not pull that one together.  Thanks for hanging in despite the protracted gap.

Sunday, July 31, 2016

M2080 recovery failure analysis - Part 2

Since I posted part 1 of the M2080 recovery failure report I have been in contact with Jeff Garvey at He's been very patient while I worked through his requested testing and here's what I emailed him today in its entirety:


Good afternoon, Jeff.

I just completed three phases of testing, fired a total of six M-teks with 7' leads, and added some knowledge but I still lack water-tight conclusions. As such I defer to your judgment on whether any form of warranty replacement is merited. I will post a version of this report to my blog and append the previous entry with a less certain conclusion in an addendum.

Thanks for your patience while I worked through this.


Executive Summary

While I cannot know if the impact damage of the previously failed recovery changed the ARTS2 altimeter, battery/ies, and/or initiators in question I have concluded that:
  • Both initiators connected to the low-altitude CO2 system measured high and well out of spec in post-mortem testing (3.5 and 4.1V, respectively). None of the initiators sampled from the same two boxes measured anywhere near that high. It seems unlikely that both were outliers in light of the population data so it's possible that the flight impact and/or post-mortem extraction might have changed their resistances somehow. 
  • Altimeter one, a previously reliable Featherweight Raven 2, likely functioned as expected during the flight so the failure to actuate the CO2 ejection system at ~800 feet AGL remains a mystery. After the impact a component separated from the board and that's the likely cause of its inability to fire initiators in test mode. 
    • I have [linked to] the Raven2's acceleration, current, and main/apogee voltage graph and it suspiciously cuts off at about 29 seconds into the flight. It appears that the altimeter fired the apogee channel successfully and was in the process of recharging the capacitor when the data cuts off. To my knowledge this has never happened before with Featherweight altimeters so it could have been impact damage to the memory, a battery failure, or other unknown factor. 
  • Altimeter 2, a Loki Research ARTS2, was unable to fire even nominally resistive M-tek initiators with a fresh 9V battery in single-battery mode. When I switched to the two-battery configuration both the apogee and main channels fired as expected. This leads me to think that this copy of the altimeter, unlike my previous copy, is incapable of firing initiators in single-battery mode. 
So I learned something about this particular ARTS2 today but its failure in single-battery mode serves to underscore the prior recovery reliability of the Raven 2 altimeter. In every case I can recall the Raven 2 operated effectively solo with the ARTS2 as failed backup in single-battery mode (but I was able to download seemingly accurate flight data from the ARTS2 after impact). I think that's all I can conclude from this post-mortem.

Experiments and Conclusions

Part 1 - Initiator resistances (all in Ohms) as measured with an MN36 Autoranging Multimeter:

Box M1 - Box of (originally) 40 M-tek initiators with 7' leads purchased from

Box M2 - Box of 40 M-tek initiators with 7' leads purchased from

J D.R. - J-teks with 3' leads purchased from a third party solely for use in rocketry

J1 - J-teks with 3' leads purchased from a third party solely for use in rocketry

J2 - J-teks with 3' leads purchased from a third party solely for use in rocketry

Conclusion: With the exception of one J-tek at 1.2 Ohm all measure high relative to the spec.

Part 2 - 7/10/16 - Altimeter tests

ARTS2 test (used in M2080 flight with failed recovery)
9V battery voltage - 9.43V, single-battery mode
M-Tek box 1 = 1.7 Ohm match (second highest measured resistance)
Connected to software, fired main twice, but the match did not fire.
Switched to apogee, fired it twice, but the match did not fire.
Connected it directly to 9V battery and the match fired.

Software not firing channels in test mode so... ARTS2 dead after hitting ground? Before? [see conclusions from part 3 below]

Raven2 test (used in M2080 flight with failed recovery)
Freshly charge LiPo battery
M-tek box 1 = 1.9 Ohm match for main (highest measured resistance) and 1.7 Ohm for Apogee connected simultaneously.
Ran the launch sequence twice but neither match fired (apogee/main)

Raven3 test (control)
Would not initialize the test for some reason even with a fresh battery. After some research on the inter webs... It turns out that the Raven3 needs at least 3.85V at startup to initialize properly. This results in 4 high beeps then one low beep at startup. Once I used a new and freshly charged LiPo then even the 3.0 Ohm initiators fired properly. (I also learned that the altimeter can be powered up in any orientation and then moved to long-axis-vertical for flight readiness without powering down first.)

Raven1 test (control)
Using battery from last fight without refreshing the charge
Test initialized correctly and I watched as both the apogee and main matches fired on time from the sim. (flight counter 14)


Part 3 - 7/31/16 - Explore the ARTS2 altimeter further

After the first test session on 7/10 I realized that the ARTS2 itself might not be working. Since the unit has already impacted the ground I can never know if it was defective (in terms of firing initiators) before the M2080 flight. I suppose it could have been defective but I never saw issues because there was always a Raven running independently next to it.

Today I'll try the following tests with the ARTS2:
  • Single battery with lower resistance M-teks (1.3 and 1.4 Ohm, respectively). 
  • Dual battery with the same lower resistance M-teks (assuming they don't first in the first test). 
  • If neither test succeeds then I'll leave the board configured as in test 2 but swap in two J-teks from my stash and try again. 
Test 1:
9V battery voltage, board and pyro power: 9.60V
Apogee channel: 1.3 Ohm initiator
Main channel: 1.4 Ohm initiator

Setup: beeps on power-up meaning both initiators were recognized. First attempt with board horizontal:
  • Apogee: No fire 
  • Main: No fire 
Switching the board to vertical:
  • Apogee: No fire 
  • Main: No fire 
Powering off the board and powering up vertically, chirp test OK:
  • Apogee: No fire 
  • Main: No fire 
Conclusion 1: In its current, post-impact state this ARTS 2 would not fire even with lower resistance initiators using a fresh, tested 9V battery.

Test 2:
9V battery voltage, board power: now 9.37V
9V battery voltage, pyro power: 9.63
Apogee channel: 1.3 Ohm initiator
Main channel: 1.4 Ohm initiator

Setup: Hooked up pyro battery, switched board to 2-battery config. Held board vertically on power-up and got the expected three beeps.
  • Apogee: FIRED! 
  • Main: FIRED! 
Conclusion 2: Both channels fired correctly in the board 2-battery configuration. I'm not certain but I don't think I've ever flown this ARTS2 solo and have always used it as a backup on two-altimeter flights primarily for motor performance and CD estimation data.

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 Pokémon  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

[Updated] M2080 recovery failure analysis - Part 1

[Please see the notes in the entry in brackets, the addendum at the bottom of this entry, as well as part 2 of this report above this entry.]

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:
Untitled Untitled
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 [lot numbers are on the underside of the taped lid but I had only been accessing them from the sides of the boxes and I shared them with the vendor] 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 just be sure to test the initiators for resistance and verify that they work with your electronics.] I will [likely] 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.

Untitled Untitled Untitled
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:
Untitled Untitled Untitled Untitled
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.

Addendum:  After additional testing at the request of the initiator vendor and considering that the system changed post-impact I can no longer assert that the matches were definitely to blame with any certainty.  All I know for sure is that both initiators measured high and well out of spec for resistance after extracting and measuring them post-mortem (3.5 ad 4.1 Ohms, respectively).  See part 2 of this report above on 7/31/16 for details.