Building three simultaneously = efficiency!

I'm taking advantage of my two-week break from work to complete construction on:

1. 4" Extreme DarkStar - This was my gift to myself this year after seeing KO's success with the all-fiberglass kit. I've decided to break this one in with the pink M1676 Pro75 motor.
2. Madcow Rocketry 4" fiberglass Nike Smoke - Thanks to the kind generosity of my parents who bought this kit for me for Xmas I plan to select motors with reckless abandon on this one.
3. 3" Vertical Ass... - This is my abbreviated kit bash of the Vertical Assault parts from Giant Leap Rocketry.

Those are the second and third all-fiberglass rockets I've built and they seem to go together quite nicely. Here are the first two in my studio for scale:

And here's the build progress on the Vertical Ass... I took this opportunity to neatly cut exact diamond shapes from the 3" tube to perfectly fit the fin can shape:

Here's the clamping setup while the epoxy cures:

And I'm very pleased with the final cured form of the assembly:

Further analysis for DRM II's first flight

I was chatting with my aerospace buddy Chris at work today and, having seen the blog entry and data below, he was as confused as I about the barometric altitude curve shape. I normally plot barometric altitude as that's accepted as the official peak. Accelerometer-based altitudes can suffer from integration errors caused by wobble, spin, coning or other undesirable flight behavior. Chris asked if it might have been caused by a Mach transition effect but I only hit Mach 0.58 so I was nowhere near the transonic region (0.8-1.2). I continued to ponder this irregularity and think I can explain the difference. In this alternate plot from the Raven you can see that the accelerometer-based altitude is shaped as one would expect with air-starts (slight slope increase when they kicked in):

I remembered that the aluminum tube that connects the electronics bay to the motor area was not plugged. When I pulled the camera it had a bit of smoke residue on it and the electronics board smelled sooty. This 7.5" rocket produces a great deal of base drag that I think forms a vacuum. I think that's why the barometric curve is steeper than the accelerometer curve and why there's an inflection point after the air-starts burned out. Then base drag decreased at that point which might have increased the pressure in the electronics bay just enough to flatten out the barometric curve in that weird region. In any event the rocket turned only once and otherwise flew straight up so I'm going believe the accelerometer curve in this particular case. Let me know if you have other thoughts. I'll definitely plug up the conduit with clay next time to reduce this pressure tomfoolery.

Der Red Mix mark II... For The Win!

Last weekend I flew DRM mark II for the first time on a central L730 Classic and 2 x I345 White Thunder air-starts 1 second after the L burned out. I couldn't be more pleased with the outcome. First off there was pretty much zero wind all day at Plaster City though that came at the cost of a persistent cloud ceiling at roughly 6-7k feet. I had prepped a bit the night before and mounted the Flip MinoHD video camera and altimeters/battery holders on the board and also assembled the recovery system. On the drive out I decided I didn't want to char the innards of DRM II with black powder and so committed to investing in the Rouse Tech CD3 Jupiter ejection kit with 28 and 35g CO2 cartridges. This added about 45 minutes to the prep once purchased and built so I flew at noon. Thanks KO for shooting some prep shots:

[Note to self: stop talking whilst being photographed.] I got out to the pad and realized it's pretty difficult to get that 6+ foot long, 26 pound thing on the rail myself. Luckily a few folks helped. Here's my buddy Frank reminding us where ALL of his flights land:

I was confident that I'd fixed all the problems from last time with this build and prep so all that remained was to push that button. The liftoff was much faster than I'd anticipated and I'd estimate that flame to be 6 feet long:

The ascent was beautifully straight and essentially rotation-free. It appeared to me that the 2 x I345 White Thunder air-starts kicked in before the L730 Classic had burned out. The video and altimeter data would prove me wrong, however:

Note the single rotation over the mile of ascent! I'm very pleased indeed. Watch full-screen on YouTube in 720p HD for best effect. Here also is the unabridged version of the video from liftoff to shut-off (~5.5 mins). Here's a recovery shot and altimeter data from both the Parrot2 and Raven:

The average barometric peak of the two altimeters was 5,550'. Also note the clear velocity decrease after the L730 burned out and then the spike as the I345s kicked in. Yay, data. Next time I plan to fly 5 motors (1 on the ground then 2 in the air then 2 more in the air). I'll shoot for Lucerne on January 8th to get some different video scenery. Great success!! Oh and here are some other shots from that day as well.

Plaster Blaster 2010: A new personal record of 21,915'!!

This last weekend's Plaster Blaster 9 launch featured amazing weather, many cool projects, more spectators than I've ever seen at Plaster City, and my parents even drove out from AZ to visit. Nice!

As always I'd planned more flights than I'm capable of completing on this three-day weekend. At a minimum I had hoped to fly Der Red Mix II (K635 Red Thunder, air-starting 2 x I345 White Thunder), my Nike Smoke on a pink M1675, and Em-Sem-Fity with a CTI M795 in a drag race with Frank Hermes and Art and Tom Just from AZ. Jack didn't have the K635 in stock and I was too tired to prep the Nike Smoke on Sunday so the only flight I completed was for the drag race.

I started prepping the segmented M795 moonburner from CTI late on Friday night so it could cure for Saturday morning. Despite arising early on Saturday I was still tardy for our agreed flight time of 10AM. Art and Tom had their M650 rocket sitting on the pad for awhile then Frank headed out about 10:15AM. I was finally done prepping by about 10:30AM but, when I headed out there, Frank had just dropped a rail guide. He was confident that he could quickly a) swap boosters and b) increase the black powder load in his CD3 system. I set up Em-Sem-Fity on the pad, armed the electronics, and loaded the igniter. Astonishingly Frank was done with everything in about 15 minutes!! We were a bit concerned about the thin, uniform cloud veil right above us but we agreed everything should be fine. Upon ignition Frank's rocket leapt off the pad at astonishing speed and smoked both Art/Tom and I thus winning the first-to-1000' portion of the informal contest (Thanks to mom for shooting this sequence :)

Then our two remaining rockets lifted off almost simultaneously:

KO captured this video of the liftoff with her Flip MinoHD video camera (watch full-screen in HD on YouTube for best effect):

Upon liftoff my rocket appeared to be a bit overstable and coned some on initial boost. This is strange because this motor weighs almost the same as last year's M750 and that lifted off straight without even a wobble so I'm confoosed. The flight path was several degrees toward the southeast, it punched through the cloud layer, and I heard it burn for another 6-7 seconds!! Unfortunately Art/Tom's rocket failed under boost and they're not yet sure what happened. Those dudes are super nice and they say they'll come back next year with a 20k attempt.

So I have my CSI radio beacon installed and I get a nice clean signal boost when the thing blows out of the carbon fiber tubing. Having heard that I told our RSO, Ken Sparks, that I had attained apogee safely and started following the signal with my Yagi antenna. I walked for several minutes with a nice clean heading NE toward the prison then... nothing. Static. Normally static means you've crashed the transmitter but, in this case, I knew it had been falling for about the expected amount of time under streamer/'chute. Undaunted I continued to pursue that last line toward the NE. During this long walk I thought I heard a periodic blip in the static and redirected to see if its strength increased. After about an hour of meandering I decided that I had to scale the highest 'local' feature and walked up to the abandoned quarry to the east. I removed my sandals and climbed the loose gravel to the top of the 40' mound, turned on my receiver and... I had my signal back!! It was pointing me north right toward where it had earlier so I should have simply stuck to that line. As I continued walking the signal would strengthen and fade as a function of elevation. Keep in mind this was on 'long range' so this thing still had to be far away or in a really deep ravine. At one point I feared that it had landed on prison grounds or in one of trees hiding the prison from view. Finally I found the thing laying on the ground about 0.2 miles north of the prison:

I used Google Earth to map the landing destination. The red straight line is roughly 3.2 miles as the crow flies and the yellow, meandering path is my best guess on my walk of ~4.9 miles:

I was in almost constant phone contact with Frank who had just recovered his 22,176' flight 6.8 miles north of the launch site. He was kind enough to trek out to pick me up. I didn't notice my exhaustion until after I'd found Em-Sem-Fity but I was pooped. Frank took this photo as I approached:

I downloaded the altimeter data and here's the ARTS2 summary and graph with a barometric peak of 22,080':

And the Raven summary and graph showing 21,749' for an average of 21,915':

I also plugged the flight info into the ARTS2 software and here's the motor analysis:

Now allow me to be very clear: I am not taking anything away from Frank's second victory on peak altitude here!! However, none of those motor attributes match those on the ThrustCurve site. Who knows how accurate this analysis is but, again, I'm left wondering if reload aging impacted performance. One of these days I'll need to buy a pristine motor and eliminate this aging variable for my peace of mind.

This was a great launch and I'm grateful to all the club volunteers who made it happen! The spectators, including my folks, were really stoked so I consider Plaster Blaster 2010 to be a great success. I posted the rest of my pictures here if you're interested. Thanks for reading this saga and cheers to a great PB 2k11!

Lesson learned: Inspect thoroughly then comment

At Plaster Blaster 2010 this last weekend I was asked to inspect the connections in a friend's electronics bay. I immediately noticed that the stripped portion of the e-match wires were too long and likely to short out. I requested the fix then didn't dig much deeper due to other distractions. In seeing that high-level issue I had failed to notice that the e-matches on both altimeters were connected to the wrong positions. Luckily the rocket managed to save itself after failing to eject the main 'chute at apogee and landed safely and without issue. From now on, whenever I'm asked to inspect a prepped rocket, I'll record all my comments with pen and paper then submit the sum total as a group to prevent this error. Duh!!!

Finally! Great sanding success!!

On the way home today I decided to stop off at Home Depot and buy some form of different hand sander than the two B&D 'Mice' I have now. I surveyed all their sanding wares and, in the end, I selected the Rigid R2501 sander for $50. It has a vacuum function with an enclosed cloth bag and claims to retain 90% of the dust generated. BIG... FRIGGIN'... FAN!!

The raised handle on this sander absorbs most of the vibrations and the vacuum bag actually works and retains most dust. Also the coarsest grit sandpaper included was only 120 but I decided to take it for a whirl on the second, properly cross-linked layer of UV Smooth Prime anyway. I was still done in about 1/2 the time it took with the big Mouse using 60 grit sandpaper!! The efficiency of this thing has already significantly reduced my hatred of finishing. If you've struggled with sanding in the past as I have I suggest you pick one up.

As time is running short for Plaster Blaster I'm considering applying a layer or two of Kilz spray primer and again leaving Der Red Mix mark II unfinished for the maiden flight. It's a bit of a cop-out but there just aren't enough hours in the day recently. The flight should still rock. I decided to keep it RED and will fly a central 1994K635 Red Thunder on the ground but air-start the 2 x I345 White Thunder motors. After I finish the paint and decals then I'll fly the central L730 and air-start 2 x H399 White Thunder (perhaps at RocStock XXXII the weekend after).

UV Smooth Prime aging... fail.

For the second time I'm reminded that the yellow cross-linker included with the UV Smooth Prime product has a maximum shelf life of only a few months. On Friday I opened the little jar to find a rubbery solid therein. The white primer itself seemed fine so I rolled the dice and slathered it on Der Red Mix mark II anyway. Over the course of sanding for an hour today I noticed several spots where the dried primer was flaking out of the tube seams. I'd never seen this before with cross-linked primer so lesson learned: Use that $51 can of product quickly!!

They really should sell the cross-linker separately because of the aging difference of the two parts. In order to finish this rocket by Thursday I'll need to drive up to Aircraft Spruce in Corona tomorrow to buy another can. Hopefully they'll sell me a spare jar of yellow failure. Good... traffic... times.

Improvement via iteration...

I hate crashing expensive, time-consuming rockets but there is one advantage: the same design turns out WAY better the second time. I wasn't very happy with the carbon fiber fin reinforcement on Der Red Mix last time because the fabric texture was pronounced, I had to pry the fins apart after they'd cured, and, of course, the carbon/kevlar hybrid was impossible to sand.

While 1/4" plywood is pretty rigid I still wanted to add some cloth reinforcement because the fins are high profile and I don't want them shredding or breaking off during flight or recovery impact. Last time I used a mix of carbon fiber cloth and remnants of carbon/kevlar cloth. I also used a material-efficient stack while laminating but it's that configuration that caused the fabric bumping and layer separation difficulty:

For this mark II build I decided that carbon fiber was overkill so I reverted to 6 oz fiberglass. I also added 3/8" ply layers between the fin layups to force a smoother surface and to completely segregate each stack for easy separation ('CF fabric' below should read 'Fiberglass cloth'):

This layup worked much better although the surface still isn't as smooth as I'd like so, again, priming/sanding is the best!! Here are some pix of the layup:

Oh and I completed the motor assembly/e-bay, cut all the slots and doors, epoxied the goodies together, and this baby is ready for fins:

Build progress update

Der Red Mix mark II suffers only from a lack of motivation. I am making progress and the build is far smoother the second time but, honestly, I should have been done by now. Here's the upper portion of the motor tube assembly with the e-bay door. I propped it upside-down in the airframe tube whilst it cured:

I'm also making marginal progress on the >2000MPH rocket. I completed the carbon fiber reinforcement of the coupler and grafted 12" of BlueTube 2.0 on the booster to fit the payload coupler and recovery system:

Yes I SHOULD have just used one continuous 48" length of 75mm BlueTube but I had committed the Slimline motor retainer to the 36" phenolic some time ago. I'm gonna wrap the whole thing with three layers of 6 oz carbon fiber so I think it'll be strong enough for an M3700 [shivers].

Plaster City... The DARK launch

No not a night launch... Last weekend it was thunderstorming in the east and the sky was supa dark so I bought an M795 reload for this year's M-moonburner-drag-race, tied KO in an I445 drag race, then high-tailed it outa there before my car got stuck in ex-lakebed sludge:

Then last weekend I was too lazy to get up and fly at Lucerne despite epic conditions. Again I'm a jenius.

1000 hits!!

Nice. Thanks, readers.

After 5+ hours of arduous construction today...

...I completed the following:

• Der Red Mix mark II - cut, sanded, and JB Welded retainers to all motor tubes. Drilled and marked all centering rings and attached U-bolts to top centering ring. Epoxied top centering ring assembly onto 54mm central tube as a carefully aligned datum for the remainder of the complex motor assembly. Cut and sanded the electronics bay coupler.
• 2000 MPH design - cut and sanded booster extension tube to accommodate 34" motor casing. Trimmed excess carbon fiber from interior of coupler.
• Half-a-Vertical-Assault - This is the kit bash for which I designed the e-bay in the 3" nosecone. I got the motor/fin can assembly started today. This bonus design should complete fairly quickly as I won't need to reinforce the Blue Tube 2.0 airframe.

Starting is the hardest part so I'm moving again. In addition to the above I also need to rebuild the electronics bay for my 54mm minimum diameter and build another custom booster for the same.

On the mend

So I've now overcome the sadness of Der Red Mix and embarked on DRM mark II:

• Last night I think I thoroughly mastered both the Parrot2 and Raven altimeters via manuals, testing, and marking of the terminals. I will not repeat my mistakes of last Saturday.
• I decided that DRMII will use all BlueTube 2.0 rather than phenolic and just ordered four tubes. This should greatly improve strength overall and will reduce my finishing time demonstrably over mark I.
• I made some small positional adjustments to the mark II design in RockSim as refinements. I think I'll need less nose weight this time for a typical flight.
• In mark II I can revert to the original position of the Flip video cam cowling so there should be no fin visible this time.
• I'm considering cutting my own fins and centering rings this time but might still go with laser cutting at BMS. TBD.
• I'll combine some of Kurt Gugisberg's painting advice with a new support rig I've devised to minimize dust kickback. Hopefully I can avoid car paint pitting this time. I'll also apply the decals before flying to underscore confidence in my revised approaches.

Cathartically this rebuild is now more important to me than attempting 2000MPH at Plaster Blaster in November. Also I just bought my own Pro75 6G hardware set for that flight but I wanna put some miles on that casing elsewhere first. Oh and KO sent her shot of the DRM fail. It better shows how the Flip camera landed safely:

Lucerne, 8/14/10 - Der Red Mix FAIL on maiden flight

Let's start with the onboard video and then I'll explain:

First off can you BELIEVE my Flip MinoHD video camera survived that high-speed impact?! That has to be one of the few surviving onboard video accounts of a high-power rocket crash. Props, Flip!
OK so this was to be the maiden flight of my scratch-built, 7.5", clustered upscale of Estes' Der Red Max but cluster = Mix in my case. While I had access to 7 motor slots I wanted to walk before running so I chose to ground-start a CTI K500 Red Lightning, wait 1 second, then air-start 2 x I345 White Thunder motors. It shoulda kicked ass. However, operator error resulted in a great ground start, no air-starts, and no ejection of the main parachute at apogee. Jenius.

After the flight I downloaded the data from the Parrot2 and Raven altimeters from www.featherweightaltimeters.com. Those little devices never cease to amaze me as they're tiny yet record a large number of data streams at high temporal resolution. Nothing leapt out at me at first so I decided to e-mail the data to Adrian at Featherweight. SERIOUS props to him because, independent of his workload at NASA, he quickly responded that none of my four e-matches had shown continuity. Despite reading both manuals numerous times I'd made the following three mistakes:

• Raven - responsible for air-start ignition & main parachute ejection - This was my first time using the Raven. While I thought I understood the wiring of this device I had clearly allowed my familiarity with other altimeters to lead me astray. The 9V battery does not connect directly to the altimeter as in most other altimeters. Instead it's grounded in the altimeter but the positive lead is connected to one of each of the e-match leads and optionally through an arming switch. The other leads of the e-matches feed into the relevant output connectors in the terminal block. [Addendum: if not using an arming switch you can also gang the second e-match leads in the + terminal slot. I verified this with a test connection.] Lesson learned: RTFM ad nauseum!
  
  
• Parrot2 - backup altimeter for main parachute ejection - I lost my original Parrot2 (250G) model a few months ago in the J1520 minimum diameter flight. I was able to purchase an unused Parrot2 (70/30G) model from a fella on the forums. In re-reviewing the wiring diagram I mis-marked the power inputs for the 9V pyro battery so the thing was running solely on the LiPo battery the whole time. The apogee e-match never had a chance of igniting. I don't use separate arming switches so this wiring option consistently confuses me. Lesson learned: When in doubt get a second opinion.
• Finally I left the K500's motor ejection in place as a secondary backup for parachute ejection. I was so confident that one of two altimeters above would do the trick, however, that I didn't shorten the delay from 17 seconds to 14 seconds. Let me tell you that 3 seconds is a LOOOOONG time when a rocket is coming in ballistic! Lesson learned: When possible trim the motor delay to simulated apogee + 1 second.

Here are some other pix:

Oh and KO and I were finally able to run our "Squat redemption" drag race on matching CTI I140 motors:

I edged her 'Cheshire' out by a length but the the motors look slightly different to me. I bought them at the same time so I'm not sure what's up with that. I will say that it appeared to be a tie to me until I downloaded the photos.

Lucerne launch report, 7/10/10

Yesterday started cloudy but windless on the lakebed. I quickly prepped my newly-stable Squat rocket for the drag race my friend KO and I had planned. She was stuck in traffic so I then prepped and flew my Dark Star Lite with the new CTI H410 Vmax motor. That thing is insanely fast!! The following two shots were taken 1/8th of a second apart at 1/800th of a second shutter speed. Note the excessive motion blur on the second shot:


And I've zoomed in on the very cool glow of the motor ignition here about one millisecond after ignition. Vmax propellant is very efficient and barely visible were it not for the blast plate accumulation:

KO finally overcame the ridiculous I-15N traffic and prepped her Cheshire-style Squat. As I mentioned in my LDRS report below these kits are unstable with 54mm 1-grain motors unless one adds at least 8 oz of weight to the nose tip. KO and I used Crazy Glue's Plastic Fusion epoxy to bond the lead into the polyethylene nosecone. According to their claims this should have worked except that, as I we walked up to the RSO table, I heard a clunk and knew my weight had slipped out of the nose tip. For the second time I can't fly my damned Squat!! KO decided to fly hers on a CTI I140 Skidmark anyway in the hope that her nose weight would stay in place:


Well her flight started straight as you can see but then the weight slipped, the flight went unstable, and the rocket looped about five times before hitting the ground. Luckily she built hers well and it survived the impact with only cosmetic damage. Lesson learned: only the expensive 3M DP 8005 resin will truly stick stuff to polyethylene and polypropylene! You can use regular epoxy but you must use expanding foam to hold that mass in place. Stupid inert polymers!

The wind started kicking up after noon but I prepped my bullet for an AT J340 Metalstorm flight anyway. This motor is Aerotech's first foray into sparky motors and they've elected to back the flaming titanium chunks with white smoke rather than black. They also demo'd their Skidmark equivalent called 'Dark Metal' at LDRS so those'll be cool. One can never incinerate too much loud, impressive elemental titanium in one flight. All of my flights seem to drift well beyond all others independent of wind level. Today, however, this particular flight landed within 100' of the pad and that's some serious luck!:

I also shot a few sequences with the intent of stitching together a virtual drag race in Photoshop. Normall I don't like sooty Blackjack/Smoky Sam motors but the wide-angle perspective of this frame intrigues me so I shared it in isolation here:

Finally Frank Hermes brought his dog River out so I could get my yellow Lab fix. He's a good buddy and I thank him for braving the 100˚F heat!