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:

I ♥ sanding!!

It's my favorite. No really.

After about 90 minutes of dust generation I turned this rough, UV Primed surface into a very smooth one:

I put one final coat of UV Smooth Prime on tonight and the surface is very uniform. I think I filled in all the pinholes so after one more [really fun] sanding sesh tomorrow I can apply the red car paint. I'll let that dry overnight, paint the black on the top of the airframe and nosecone on Wed., let that dry overnight, apply decals on Thursday, and finally overcoat those with clear coat. That should be dried and purdy by the time I head up to LDRS.

Plaster City @ 108˚F... but it's a dry heat!

Yesterday was the last Plaster City launch before the summer heat break. However heat arrived early as it was 80˚F at 8AM and 108˚F when I left at about 3:30PM!!

My first flight of the day was the Viciously Mean Machine 0.75 with a CTI J1520 Vmax motor (static firing video). I prepped everything and got it out to the pad only to find that the 250G Parrot 2 altimeter would not arm. I pulled it and took it back to my prep area to find that it wouldn't even power on. I swapped 9V batteries but still now power up. Then I hooked the altimeter up to my computer to find that 4 of 5 memory banks held data. I knew that I'd purged all flights the night before so this was confusing. I then figured out that the Parrot 2 stores a bank of data every time it's powered on and I must have cycled power a few times while setting up. After purging those four data banks the altimeter again operated as expected. This still doesn't explain why it wouldn't power up the final time as one bank was free. Whatevs. I reassembled everything and again set the rocket on the pad for flight.

I knew this would be my fastest flight ever so I had really gone to great lengths to ensure the whole setup was reinforced, taped, and positioned for a neck-snapping liftoff. When I pushed the button VMM 'sploded off the pad, burned out quickly, then literally disappeared for a few seconds. Here are 3 of 5 frames at 30 fps from my Flip MinoHD video cam (video below):

(I estimate that flame to be ~4.5' long)

Only when we saw the tracking smoke did we understand the rapid progress of the flight to between 6000-7000 ft. I watched as the 17 seconds of smoke burned and the rocket passed apogee without an ejection event. Unfortunately as the smoke burned out we lost site of anything. I had a radio beacon in the rocket so I thought I was fine until I turned on the tracker and got no beeping even with long range and high gain settings. Bummer. It's very likely that something connected to the altimeter had dislodged under the tremendous acceleration and the rocket had come in ballistic destroying my $500 investment (excluding the price of the reload by the way). Sad. I made three attempts to find the crash site sweeping over quite a large area including KO's help on the third, highest temperature slog (click for larger version):

I had planned to fly a CTI L730 Classic in my Vertical Assault but was pretty daunted after that first failure. Instead I flew one of the new Pro29 G250 Vmax motors in my Dark Star Lite and it was shockingly fast! My third and final flight for the day was on a Pro29 I204 Imax motor (6G) where I'd planned to set up a new camera angle at 8 fps. The dude who launched before me didn't check to ensure that only his pad was armed and launched our inadvertent drag race before I could set my camera up. He was super cool about it and offered to buy a replacement motor but his offer sufficed and I thankfully declined as it wasn't a big deal. I'm hoping I've shaken out all the back luck prior to LDRS next weekend because I need successes there!!

3" nose cone with avionics bay

I needed to add 22 oz of lead shot nose weight into Der Red Mix's nosecone today but only had one ($30 spendy!) tube of 3M DP 8005 adhesive. It's the only material I know of that will stick stuff to polyethylene at room temperature. [Maybe I'll try this much cheaper stuff next time]. Once you pop the adhesive tube open it also doesn't store well so I planned to use it all today. This forced me to start another project that's been sitting in my mind recently to best use the 8005.

For some time now I've had this Public Missiles Ltd. screw-cap assembly (search the page for RETAINERCAP) for their CPR3K electronics mounting system. I've been wanting to put that on a length of 38mm tubing and place the whole thing into 3" nosecone to enable electronics in a stubby 3" rocket w/54mm motor mount. That came together quite easily today and here are the progress photos.

Here I've used my bandsaw to cut off the mounting features from the nosecone base, cut a 38mm hole, and six outer holes through which to thread the Kevlar™ mounting cord. I think this pattern should add margin to an already pretty tough structure:

Here I've test-fit the retainer cap assembly on the length of 38mm BlueTube.

This shows the relative length of the two parts. The tube seats perfectly in the narrowing region of the nosecone interior:

This is what the assembly will look like when prepped for launch:

Here I've dumped 7 oz of lead shot + 8005 adhesive into the nose tip, added more 8005 to the interior, placed the tube down in there, and more 8005 at the tube/base/cone interface to hold it all together:

Everything's curing overnight now.

Der Red Mix's attractive derriere. Oui, no?

I JB welded all the motor retainers on last night then dumped in a layer of West Systems epoxy + white pigment on the bottom plate to improve the aesthetics... at least before the first flight chars it up!:

I also finished the fin fillets and mounted the rail guides today. She's just about ready for finishing but I need to decide if I mount the hinged door before or after finishing. Decisions decisions.

Der Red Mix - fins in place

Today I coaxed the final fin into place and it's curing now:

All that's left construction-wise is to JB Weld the motor retainers in place, drill the rail guide holes, load the nosecone tip up with 22 oz of lead shot and epoxy, and tether up the recovery system. Cool! Oh but then I need to fill, prime, sand, fill, prime, sand, fill, prime, sand, fill, prime, sand, fill, prime, sand, fill, prime, sand, fill, prime, sand, fill, prime, sand, fill, prime, sand, fill, prime, sand, fill, prime, sand, fill, prime, sand, fill, prime, sand, fill, prime, sand, fill, prime, sand, fill, prime, sand, fill, prime, sand, fill, prime, sand, fill, prime, sand!!! Dammit!

All work and no play makes Jack a dull boy...

Der Red Mix - fin reinforcement time lapse video

I sped this video up roughly 50x so as not to bore you. The fins turned out pretty well. They were initially fairly warped so I took them to work and placed them in an environmental chamber at 30C/80%RH to rehydrate the over-dried plywood. As I depleted one partial roll of 6 oz. carbon fiber fabric I decided to dip into my Kevlar/CF hybrid roll for the final 2 of 6 fin swatches. I should have used three Kevlar/CF swatches but this was a last thought for durability:

Oh and, once cured, the fins were surprisingly difficult to separate despite the use of vacuum film between each fin. The resin content is quite lean so the technique worked and I'll use it in the future.

Leaps and bounds

All of a sudden this thing's really coming together. I cut all the airframe holes tonight and everything's piecing together peachily:

Despite all my Illustrator pre-work and all the iteration I still managed to aim the camera basically down a fin. It's a 16:9 aspect ratio camera and it's focus is fixed below the fin but still. Duh. The final motor tube/e-bay assembly's curing now. Tomorrow night I'll reinforce the fins and epoxy the entire booster together when that's done. I really need to complete the construction soon because I want this to be super glossy when painted and I have all those awesome Sticker Shock decals to apply before LDRS...

Now featuring even MORE progress

Yesterday I added one wrap of 6 oz. fiberglass to Der Red Mix's main airframe using Dave Triano's technique. This is mainly for aesthetics and secondarily for durability. It's very difficult to apply excess resin to this much area so there are many gaps in the otherwise glossy finish. It's also tough to apply adequate hoop stress on the 14 mil Mylar™ film so that didn't help this surface defect either. It'll finish up nicely anyway so I'm still happy with the result:

Here also are some studio shots of progress on the electronics bay and I think they better convey the final layout. This whole assembly will be epoxied into the above airframe after I cut fin, e-bay door, and video camera slots into it:

Construction progress

I continue to make progress on Der Red Mix's electronics bay and motor tubes. Right now I only have e-bay pix, however, so here they are:

The Flip MinoHD camera fits nicely through the side and I have room for both Parrot 2 and Raven altimeters + 2 9V batteries on that removable G10 board. I'm also working on the hinged door for the front and a simple plywood cowling to reduce drag on the dangle-cam.

I also finished building my Madcow Squat for the drag race at LDRS 29. Now I just need to finish and paint that puppy and it's all set: