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!

Friday, June 12, 2015

Dude built a Punisher!

BAM!! Finish ya after the K1440 drag race tomorrow?
Punisher_GSS26425
And here's a very aggressive 12g CO2 test for the nose cone:

Saturday, May 16, 2015

Throwback to c.1981

I recently dug up and scanned a bunch of old photos for my friend's birthday and came across a few of possible interest to the rocketry community:
Gaudior-F67and3xE45
That's me at roughly 12 or 13 years old proudly sporting tethered, fold-up Vuarnet sunglasses; one of two pairs my grandmother had generously purchased for me on her vacation in France.  Note also the custom-built Aerotech fanboy shirt with velvet, iron-on lettering.  On the back I had made an attempt to run a popular slogan of the time: "Aerotech Gets High On NH4CLO4" and yes that's a capital L.  Gary Rosenfield expressed confusion when he first saw my shirt and, in short order, having mentally inventoried the periodic table of the elements, was unable to recall this "L"ement.  He was kind about it but, as a chemical engineer now, just know that I'm cringing and yes it should have read NH4ClO4.  Duh.
  I think that rocket was about 2.5" in diameter and ~5' tall and I called it Gaudior having recently read Madeleine L'Engle's A Swiftly Tilting Planet.  I was having trouble with the motor mount diameters just now until The Google turned up this Canadian Crown Rocket Technologies (CRT) catalog [and check out the cornucopia of other retro gems on his site!].  The central motor was a 29mm F67 and the three outboard pods with individual nosecones held CRT 24mm E45 motors (with ejection charges removed).  At the time the ignition method du jour for clusters involved sleeved Thermalite Fuse rigs with flashbulb initiators hence the disconcerting business end.  Despite a slightly angled liftoff I was convinced the flight had gone as planned. Upon recovery, however, I observed that two of the E45s had CATO'd just after liftoff so I was a semi-sad kid that day and I don't think I rebuilt Gaudior.  Damned bleeding edge rocket science!  :)  Oh and I used to paint all my rockets so I've only become lazy on finishing in the last decade or so.
  Next up is Jim Jaworski prepping with a group of early high-power flyers in deep conversation JimJaworski-PreFlight
I'm at far left, Gary Rosenfield can be seen just behind me, Jim Jaworski is on the ground setting up his igniter, Jerry Irvine has his back to the camera, and I don't remember the other four fellas on the right.  Despite Jerry's infamy in recent decades I always found him to be an extremely intelligent and thoughtful rocketry mentor and a good friend.
  Now onto the flight...  Jim Jaworski was in/famous for his beautifully built and finished rockets that pushed the total impulse boundaries beyond most of the group but, unfortunately, they often failed in some new way.  I'm quite certain this was a J- or K-class ~2" motor with low initial thrust typical of case-bonded, progressive burn geometries of the day.  Upon ignition the motor mega-chuffed the rocket off the rod then it laid horizontally on the ground awaiting additional chuffs and eventual ignition.  Upon final pressure-up it then shot out horizontally across the desert in spectacularly undesirable fashion.  Nobody was hurt and Jim recovered the rubble.  We've come a long way with BATES grains and peak thrusts in the beginning with nice regressive traces that don't shred rockets.  Someone must suffer these learning setbacks to advance our collective knowledge so... thanks, Jim!
   I should note that Aerotech was already employing an early BATES grain precursor where they cast propellant into a cardboard tube.  Once core-drilled this "cartridge" of propellant was dropped into the phenolic liner with glass-phenolic nozzle and the forward end sealed up with delay and ejection charge.   As such AT motors were bleeding edge and featured end- as well as core-burning geometry.  This gave them a nice initial kick off the pad but the high aspect ratio of the cartridge produced a humped thrust trace that wasn't quite the ideal regressive burn yet.  Anyway kudos to Gary!

Sunday, May 3, 2015

Sunday build-day

I'm sad to report that I missed the Holtville launch yesterday but I got a second wind today, cleaned my garage workspace a bit, and did some building today.
     David Reese of Wildman West Rocketry is hosting a Punisher drag race at Rocstock 41 in June at Lucerne.  He offered up a limited edition Punisher kit bundle along with a Pro54 5G casing, closure, and K1440 White Thunder reload and I lucked into buying one before they stocked out.  I know that David and Kurt Gugisberg are in on the drag race so I'm looking forward to losing to them.  :)  Here is Crazy Jim's version and he has has also posted a useful build thread on The Rocketry Forum:
So I started building my 3" Punisher today and a whole bunch o' sanding prep was required for the motor mount, motor retainer, and centering rings but here's the assembly now curing in my garage:

This kit features a novel dual deploy scheme where the electronics bay resides in the nosecone shoulder and that coupler is shear pinned into the airframe and nosecone.  It's a solid design and uses volume very efficiently.  It's therefore atypically small and that 2372K1440 is going to kick it's ass into the sky with reckless abandon.  K1440 don't care.  K1440 just brutalizes what it wants.
     I also continued the build of my Polecat Aerospace 7.5" V2 with 75mm motor mount.  This this second build step anchors the motor tube with centering ring in the boat tail (one large centering ring and the airframe tube are used temporarily to center the motor tube in the boat tail while the epoxy cures below the fin slots):

April Lucerne launch report - Go, K300, go!

I flew my first CTI 2546K300 at Lucerne last month and I'm a big fan.
I busted out my robust but rarely flown Vertical Assault from Giant Leap Rocketry and the flight sim'd to 14,000' AGL.  While I left my DSLR at home and my onboard keychain camera failed inexplicably just after starting it I did get some solid Beeline GPS data for Plotting in Google Earth:

I'm hoping that David Reese might have grabbed a liftoff photo that I can cross-post to this blog.  :) [Update: David is my hero!]
IMG_8695.jpg
The liftoff was relatively quick but the rocket exhibited coning at about 1000'.  This makes sense since the Vertical Assault is overstable, even with a Pro54 6GXL motor, and was at a 2.8 static margin at liftoff.  After the coning ceased the flight quickly sprinted out of site so I'm grateful I had GPS running.  It's been awhile and I managed to forget that GPS reports via APRS to my radio report MSL (Mean Sea Level) numbers so I was a bit befuddled when the altitude reports stabilized at 3,079' high and 1.3 miles due north.  In following the heading North I eventually saw an orange parachute briefly blow up above the heat convection ocean as if the rocket were saying "Howdy! I'm here!"  Yet another 1+ mile jaunt found the rocket in solid condition:

There were some scrapes on the maroon-ish car paint but I'll wipe most of those off.  The Raven2 (tabular, graph) reported maxima of 13,814' AGL, 799 MPH, and 38 Gees (that acceleration seems way too high).  The GPS maxed out at 14,160' AGL so the average was 13,987' and that's pretty damned close to RockSim/OpenRocket's simulations!  Since the Vertical Assault is mostly set up I think I'll fly a CTI 2772L640 Dual Thrust at Lucerne in May.  Yay.

Sunday, April 5, 2015

Holtville Launch - April 2015

This last Saturday was amazing at Holtville and here's some slow-mo evidence...

I completed three simple flights using only my 3D-printed V2 and all with progressively longer CTI Pro24 reloads.  I didn't risk an altimeter in any of them so all I have is my visual memory:
  • 2G 50F51 Blue Streak:
    • In all three liftoff vids I see some lateral wiggle on the rod so perhaps the integrated rail guide isn't quite long enough.  That's odd though because there seemed to me too much friction in the rail channel so I was planning to reduce the guide's cross section by a few percent.  Dunno.
    • Jittery liftoff above the rod so there's still not quite enough lead in the nose tip.  
    • The altitude was lower than expected and the 10 second delay about 4 seconds too long.  More on this below.
    • The landing was in some rock-laden dirt in the bowl and one of the fin bottoms broke.  It was still attached, however, so I just CA-glued it back on for the second flight.
  • 3G 60F50 Skidmark:
    • Even these tiny 24mm Skidmarks ignite instantly and are impressively loud!  Good titanium times.
    • I had shortened this delay to 8 seconds but that was still about 2 seconds too long.
    • The parachute fouled after eject but, surprisingly, there was no fin damage after landing in our bowl.
  • 6G 140G145 Pink:
    • The liftoff was most expeditious!  I sort of noted some pink shades in the flame from a distance but it's hard to tell unless you're watching slow-mo video of the liftoff.  :)
    • Because of the higher thrust and total impulse I left this third delay at 8 seconds.  The flight still ejected about 2 seconds after apogee and, upon watching that, it finally sank in that the uniform, 0.3mm high, radially oriented bands resulting from 3D-printing induce MUCH drag.  For the next print I'll try 0.2mm layers and that will take several more hours to print but should reduce the drag coefficient somewhat.
    • This flight achieved a surprisingly lofty altitude.  Darrel had packed the parachute for me using the burrito method so it popped cleanly at ejection.  Wind was building a bit so I had to walk to the north runway to retrieve the vessel.
    • Having landed on concrete that same fin tip broke once again and this time the top 1/4" of the nose tip chipped off.  This was OK because testing of this version zero design is a wrap and I'll move it to archive.
Apart from the issues I found over the four total test flights everything else worked surprisingly well.  The structural integrity of the airframe and shock cord mounts proved more than adequate.  I observed no melting from the casing heat or black powder ejection.  But, in addition to the modeling improvements I'd planned previously, I think I also need to edit the following:
  1. Remove the vented portion of the motor mount - this doesn't seem to be necessary for robust motor orientation and it just adds complexity, tail weight, and print time.
  2. I think I'll maintain the rail guide length on version 1 and decrease the cross-sectional size by perhaps 2%.
  3. In the Simplify3D slicer it's possible to vary print parameters by layer height.  As such I think I'll go with 60-70% internal fill from the glass plate to above where the fins meet the airframe to reduce the likelihood of damage upon landing.
  4. I think I'll use the same trick to beef up the nose tip and reduce it's tendency toward damage on concrete impact.
  5. I'll try 0.2mm layer height but this will increase print time on the airframe from ~15 hours to ~21 hours.  Longer print times mean more opportunities for print defects so reprinting would necessarily delay the time to v1.  Fingers crossed.
  6. I just realized I forgot a vent hole but the nosecone didn't pop off during ascent so I just lucked out.  Rather than modeling and printing a hole I think I'll cheat and use a drill bit.  
Onward and upward on the 3Dp tip!

Sunday, March 22, 2015

First flight of 3D-printed V2 a marginal success

I headed off to a local park this morning to test fly the 3D-printed V2 on a one-grain, Pro24 CTI 26E31 White Thunder:

It was tail-heavy so I predicted metastability and that's just what I got:

I've epoxied some lead shot in the nose tip and that's curing now.  Next up will be a two-grain, Pro24 CTI 50F51 Blue Streak.

Saturday, March 14, 2015

Holtville March 2015 launch report

It was another beautiful day in the desert although a tad windier than we're used to. I've been wanting to get my drone in the sky to shoot some liftoffs and that worked our rather dandily:
For some reason I forgot to set the controller to GPS mode so I was struggling to keep the thing where I wanted on the first few clips.  The 480 fps liftoff of Mark Treseder's Skidmark is quite nice although I think that slow mo is generally wasted from the air. In the future I'll probably switch to 720p 120 fps mode as a nice balance between spatial and temporal resolution.  Also, for the first time, I used Pocket Wizards to remote fire my DSLR while I flew the drone.  Shit's gettin' complicated!  Also Google rocks overall but I've officially switched from PicasaWeb to Flickr for my image posts from now on.
     I had only two flights but was pleased with both.  The first was the trusty 4" fiberglass Madcow Nike Smoke on an AT K1103X Propellant X reload for the 54/1706 casing.  I should note that AT included the wrong seal disk O-ring but Paul Snow saved me with a spare from his archive.  Thanks, Paul!  Thermite seemed in order so I ran with 2g which was a bit higher than the 1g/1000 N•s guideline.  Ignition was instantaneous according to Darrel who pushed the button for me (these two frames are 0.5s apart):
Darrel and I trekked my standard mile to retrieve the thing in a depression.  Even with line-of-sight on descent I think I would have lost the rocket without the CTI tracker:

Upon recovery I noticed that all of the nozzle's divergent section and most of the throat were missing:

Lucky for me no other issues arose as a result of this blow out.  I'm not sure if that was a faulty nozzle or perhaps the 4,500˚F Thermite caused a thermal gradient in the glass-phenolic nozzle and it shattered on pressure up.  Dunno.   The CTI 217H170 Blue Streak was next in the similarly trusty DS Lite and it landed in site of the launch pad:
Neato.

Third time's a charm

Photos of 3D prints always make them appear far more coarse than they do to my eye but this third print is now ready to test fly:

This took 14 hours to print so, at some point overnight whilst I slumbered, that region near the top of the fins suffered from at least a one layer gap.  My extruder is running very reliably after cleaning it out so I'm not sure why that happened.  To patch it I simply ran a bead of thick CA glue around the perimeter and the airframe feels solid. Even before the test flight there are already things I need to change: 1) The bottom ring needs to be wider to ensure the motor retention washers do not hang out beyond the airframe edge.  2) I'm using #8 machine screws there but I think I'll switch to long #6 diameter equivalent wood screws and size the pilot ports accordingly. Right now they are very narrow so I ended up drilling out a bunch of material to fit the #8s.  Again this should be good enough for a test flight... which I should have done today at Lucerne but I awoke wanting to continue sleeping instead.  3) There's a slicer setting in Simplify3D that's either "inside out" or "outside in" for shell print order.  I'm quite certain I used "inside out" above so I'll try "outside in" next time and hope that it minimizes exterior noise.  Now it's time to edit that vid...

Monday, March 9, 2015

I fixed my 3D printer!

After a grace period of seeming success I managed to clog my left nozzle and even shear the right one off! I fixed the left extruder and now I'm trying, for the third time, to print the V2 airframe:
On a hunch I suspected that I've had a mild to severe clog in the left nozzle ever since I bought the printer.  I rolled the dice and ordered a tiny chuck and miniscule 0.38mm drill bit that cleaned 'er out and now I have yet to hear even a minor filament feed hiccup:

I just ordered a hand chuck and that, combined with a reverse-threaded extraction tool and replacement nozzle, should fix the right extruder.