Wednesday, June 16, 2010

LDRS 29: A windy but impressive international launch!

I was able to attend LDRS 29 at Lucerne Dry Lake, CA from Friday@11AM through Sunday@3PM. With rare exception it was windy/gusty the entire time and the only relief came between pronounced wind direction changes. We seriously experienced wind from all directions except perhaps South-East. Despite those damned pressure gradients some amazing flights succeeded with few failures and no shreds that I saw. I'll start with my only flight of the event as I was enjoying watching/chilling most of the time and experience what turned out to be a caffeine withdrawal headache all day Saturday. Here's the 7.5" Nike Smoke I used for my L3 flying on an Aerotech M2400:

The initial angle is strikingly similar to my L3 flight on the M2030 Mojave Green motor back in 2008. So, in summary, I've had two arrow-straight flights (M1297 and M1939) and two seriously angled flights (M2030 and M2400) in this rocket. The first two motors use White Thunder propellant and the second pair are comparatively high thrust so was one of those factors the cause? Then I downloaded/analyzed the ARTS2 data for motor performance:

Wow that's a 2x average thrust spike in beginning of the burn. This points perhaps to erosive burning and almost identically matches the thrust curve shape for my M2030 L3 flight (motor later recalled/modified due to erosive burning issues at higher ambient temperatues):
I count myself lucky that neither flight cato'd but I think that initial kick might explain the less than vertical initial ascent off the rail. Here's the ARTS2 flight summary and graph:

That anomalous spike in the pressure altitude graph would indicate an instantaneous pressure drop. As that seems unlikely I rounded the ARTS2 peak altitude down to about 6703 ft. Here's the AltAcc2C summary and admittedly jacked graph data:

The y-axis range thing must be a BlackSky Flight Analyzer bug in Windoze 7. Dunno but the average of the two barometric altitudes is 6,996 feet or 4 feet under my estimated altitude of 7,000'. Who needs RockSim/OpenRocket?!! [Yeah I can solve differential equations numerically via fourth order Runge-Kutta in my head... what of it?] Dual deploy failed because the heavy nosecone dislodged at apogee. Also the booster did take a bit of damage near the top of the tube not because of a near zipper but because of a draggy impact on the lakebed. I found a phenolic chip on the ground near the tube that had drug into the ground. Bummer. So three of four flights have required repair after flight. Perhaps it's time to switch exclusively to Blue Tube?
During my lengthy observation periods I shot a number of photos, mostly from the comfort of my canopy, and posted them here. Highlights for me included (not in chronological order):
  • Visting/working with Frank Hermes and my friend KO and her niece Christina over that time. Frank's work on gyro-based, upper-stage ignition inhibition system is groundbreaking and he had better be recognized for this innovation soon.
  • It was an unmitigated pleasure meeting Dr. Jeroen Louwers from Cesaroni. That dude is sharp and kind. Also Mark Canepa is super convivial and his photo and writing contributions to Rockets Magazine remain top notch.
  • Watching numerous N and O motor flights including N1000, N2000, O8000 and others. I sincerely hope the CA State Fire Marshall lifts the arbitrary 10,240/20,480 N•s power limit for our state and brings us in line with the other 49. It's only fair, sir!
  • Bowing out of the Squat drag race due to marginal stability with a 1-grain Pro54 motor casing was a good call. I watched no fewer than 7 identically unstable flights with the I140 Skidmark motors everyone had bought for the Squat drag race. Most folks had checked the CP/CG relationship and added nose weight. I was so busy finishing Der Red Mix (which I never flew due to wind) that I thought I would be safe flying the smallest motor that would fit the mount. Nope. I'll modify mine and fly it next launch because those I140 Skids are loud and amazing!
  • The 6 x N10,000 drag race was stellar. I hadn't noticed that Kari Byron of Mythbusters was hosting the Discovery Channel show covering LDRS 29 (to air on July 5th on Discovery Science) until I saw her Sunday before I left. Then I got home, downloaded my photos, and see her posing in front of those ascending beasts!
  • Jack Garabaldi and his buddy Jim Daugherty flew another N10,000 drag race the next day using half-scale Patriots and it was no less amazing. Those motors are insane!
  • One of my favorite flights ever was Tim Lehr and team's 25 ft. tall Mega Dark Star flight on 3 x K2045 motors and one of the new CTI O3700 Skidmarks. Check my photo slideshow excerpted from above for the full sequence but here's a telling frame:
Overall this was an amazing launch and I want to thank everyone in the ROC club for hosting this year. I also want to thank Rob Greenlaw and his daughter Megan for being nice peeps and for driving me and my 50 lb. Nike Smoke back to my camp. That would have been a rough walk! Oh and thanks also, Rob, for the setup and recovery photos:

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