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.

Saturday, November 14, 2015

Wow I'm a shiftless varmint

My maternal grandfather, Hank, used to call people of questionable drive "shiftless varmints" [vemin] and that's how I would classify myself in the last several months in the rocketry context.

I last flew at Lucerne in June and at Holtville in October.  I sort of took the summer off from flying because we're making the planet nearly unbearably hot.  Yes its true.  We are changing our planet's climate.  We should reject the disinformation created by the fossil fuel oligarchy and disseminated by corporate shills beholden to them in our government.  But I digress... I couldn't make the November Holtville launch because of an amazing cause.  I was planning to attend Lucerne today as it's no doubt amazing up there but I wasn't sure what to fly as of yesterday.  As such I started designing and 3D-printing electronics bay caps for what remains of the Viciously Mean Machine.   After struggling for a few hours trying to make nylon adhere to the printer's bed I reverted to trusty fluorescent green ABS .  Here's what I modeled in Modo:
And here's the 3D-print preview in Simplify3D:
And here are the final prints from my CreatorBot 3D:
These 3D-printed electronics bay caps are not quite what I modeled...
Not quite what I modeled right?!  I think a raft would have remedied the edge curvature near the base but the curved edges at higher elevations confuse me.  I think it's time to re-level my heated bed and try again.  With a little sanding/drilling those caps probably would have worked with an AT 1417K185 today but, by the time I finished the two E-bay caps last night, it was too late to start packing.  Now, at 8:47AM, I can't fathom the concept of driving up there through Saturday morning traffic to hurl a couple of sport flights.  I will commit to doing more rocket building and repair this weekend and hope to post more updates soon.

Tuesday, October 6, 2015

Holtville Launch / October / 2015

You'll find this launch was slash-a-rific:

I realized that I don't have a ton to add here except that:
  1. My pictures of the launch reside here.
  2. The CTI 1115J530 Imax is a friggin' beast... as are all Pro38 6GXL reloads?!
  3. I'm a dunce and somehow reduced my delay about 4 seconds too short.  The rocket felt so heavy as I was prepping but there was no wind so I'll take responsibility for 2 seconds of that.  The other 2 seconds continue to perplex.
  4. That delay shortage caused a 1.5" zipper in the tube and also flung my AltimeterTwo somewhere in the desert; lost on its maiden flight no less.
Did I mention that it IS rocket science?

Friday, September 11, 2015

So I had this idea for a Punisher fin alignment jig...

Modeled in Modo, sliced in Simplify3D, printed in white ABS on a CreatorBot 3D:
So I had this idea for a fin alignment jig...
I'll give 'er a shot tomorrow.  And I wish these and their inhabitants hadn't fallen victim to subjective indoctrination:

Saturday, September 5, 2015

And the Punisher replacement commences...

A few updates:
  • I missed the July and August Lucerne launches so nothing to see here from there.
  • Just last week I realized that I'm unable to attend BALLS this year so that's a bummer.  Hopefully in 2016 I will have repaired my Frenzy Massive and travel will come together.
  • I did, however, begin rebuilding my Punisher airframe today and here's the motor mount as visual proof:
Finally rebuilding a Punisher booster...
More soon and thanks for pushing my blog to 55k views.  Yay, you!

Sunday, June 14, 2015

RocStock 41: Punisher got punished, M3100s kick ass!

For me it was drag race central at RocStock 41 at Lucerne Dry Lake. David Reese, Mr. Wildman West, organized an amazing deal for a Punisher kit, 2372K1440 White Thunder reload, Pro54/6G casing, and 54mm closure.  It was a bit breezy when arrived at ~8:15AM on Saturday morning only to learn that I was supposed to be ready to fly by 8:30AM!!  I managed to pull everything together for the Punisher drag race by 8:45 and mine was the sixth rocket on the table for weigh-in/check-in so I wasn't the last.  Of the ten planned flyers only nine checked in and the following video summarizes the results (along with the M3100 drag race later in the day):

Not that I'm being cross-examined but I certify that I did nothing special to my K1440 reload.  I added a bit of SuperLube to the threaded portion of the brand new Pro54/6G casing before inserting the reload, left the delay intact as an apogee backup, and used the stock igniter from CTI.  I'm guessing my two counterparts who CATO'd would say the same so one theory was that the propellant might not have cured fully in this batch of reloads.  This, in combination with the excessive heat and perhaps humidity, might have played a role in the 33.3% failure rate. Here's a link to an amazing liftoff shot from "Apex Horizon" on Flickr and mine is the center CATO (thanks to Mark Treseder for forwarding but this photographer has sharing turned off so I can't show it inline with my blog). The nosecone, electronics bay, and most of the recovery harnesses survived but here's what's left of my booster (I piled the other parts together atop the parachute):
Punisher remnants after K1440 CATO. :(
Here are the Raven3's graph and tabular data from the brief flight. Note that the accelerometer maxed out at 315 Gees so I'll need to check with Featherweight Altimeters on that before flying it again.  In the image above one fin is stuck in the ground and the other two presumably blew out as I assume the casing wall failed and overpressure the booster.  This fiery activity also likely ignited the 2g bag of black powder and popped the three shear pins securing the electronics bay/nosecone thus saving those costly components.  The Raven 3/250G also seems to have popped the nosecone after apogee, such as it was, thus releasing the parachute and further reducing impact damage.  The booster was still smoking and, when I picked it up, flames arose.  I then buried it in the lakebed clay for a minute or so and the flames extinguished.  I returned the booster to David for failure analysis, unscrewed and kept the otherwise intact enclosure, and David immediately replaced the casing and reload.  I'm hoping that a few months of extra curing time along with a plan to fly in cooler conditions will render this second K1440 viable.  I plan to buy parts for another Punisher booster as this strikes me as a phenomenally volumetrically efficient design.
     I was a bit shaken at this point but David verified he still wanted to fly our planned DarkStar Extreme/6118M3100 White Thunder drag race if I did. Since I'd already bonded the grains into the liner I really didn't want to leave that loaded up in my closet and decided to proceed as planned.  As always it took awhile to disassemble the CD3 system used in the Punisher and rewire it, along with my second CD3, into the trusty DarkStar Extreme but I was ready at about 1PM(?).  Kurt Gugisberg was our RSO and chortled as David and I approached.  I asked what he wanted to know about this juggernaut of a rocket and he replied "Ummm... what color is your parachute?" and, while I answered factually, I later suspected he was referring to the business book of the same title.  :)  David and I set up on pads 41 and 42 and I'm very pleased that we both took off like bats out of hell and recovered our rockets safely.  David noted that he heard applause after the race and both of us could clearly see our rockets from apogee all the way down.  Here are the GPS plots from Google Earth as well as a recovery shot showing my landing less than 1/3rd of a mile away -- a rarity for any flight of mine:
M3100 GPS plot facing due North
DS Extreme recovery after successful M3100 drag race with David Reese.
Here are the M3100 altitude summaries:
Velocity / axial acceleration peaks:
  • Raven2: 1121 MPH / 54 Gees
  • ARTS2: 1195 MPH / 38 Gees
And here are the Motor Performance (6451M3506) and Coefficient of Drag plots from the ARTS2.  Thanks to all my fellow drag racers and I look forward to future challenges!