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.