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:
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!]
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.