Greg Smith's quest to spend even more money on rocket science...

January was windless on flying days!

2012-01-22T08:19:00.000-08:00

I'm way behind in my blog posts but wanted to note that all my previous whining about wind was offset by two brilliantly wind-free Saturdays at Plaster City and Lucerne, respectively. Video, photos, and data are on the way soon. Mother Nature and I are BFFs again. Keep up the great work, MoNa!

Lucerne - December 2011 launch report

2011-12-30T19:01:00.000-08:00

Despite the cold morning it was sunny and clear most of the day with essentially zero wind. Every once in awhile Madre Nature gives back. For awhile now I've been wanting to fly the AT 486I59 Warp9 8-second end-burner with a cored White Lightning kicker on the nozzle end:

Per the instructions I used some Gorilla Glue to bond the end-burning grain place and then liberally coated the liner with grease to [hopefully] minimize casing damage. This was also the first time I'd tried the new Featherweight Altimeters magnetic switch armed externally using only a rare earth magnet:

Yeah the wires are long but I wanted to be able to swap the switch around to other electronics bays as necessary. I didn't capture any video or pictures of the liftoff but it kinda sucked. The initial kick wasn't as great as I'd calculated and my .38 Spatial immediately headed north after leaving the end of the rail. It arc'd out toward the mountain range and the only way I knew the main ejection had kicked was that my Comm-Spec transmitter signal shot up about when I'd expected based on the visual trajectory. From the following flight graph you can see that I still managed to attain ~2,200' of altitude and, based on the post-main slope of the altitude curve, the descent on the 12" 'chute was probably too fast at about 55fps/32MPH:

I say probably because this rocket is a tank and I found it completely intact well over 1.5 miles north. You can just see a thin, horizontal line of cars to the right of the hanging smoke trail if you click the image below:

This was, by far, the longest I've walked north at Lucerne and, for reference, I shot another photo of the power lines near the base of the huge mountain from that position:

My cellphone has a pretty wide angle lens but you still get the idea. I was about 80% of the way up the illuvial fan and I'm glad I didn't get caught in the power lines! Unfortunately the greased liner didn't protect my awesome 38/480 Dr. Rocket Millennium edition casing and the anodizing's partially burned now:

I'm sad but I've flown probably 10 reloads in there and it appears structurally sound (no bubbling).
I'll reiterate that I'm a very slow on rocket prep and recovery so I only had time for one more flight as the awesome ROC volunteers were talking of tearing the range down. Rob Greenlaw was parked next to me and he agreed to a drag race with our fiberglass 4" Nike Smokes on CTI 1408K2045 Vmax motors. I'll forego my typical drag race suspense and simply tell you that Rob won:

Good for Rob and I've already requested a rematch!

Belated thanks to Mike "Sparky" Jerauld!

2011-12-29T07:54:00.000-08:00

Near the end of this year's Plaster Blaster event Sparky, president of DART rocketry in SD, asked me to check out a rocket he'd found years ago and was trying to identify. My jaw dropped when I realized he'd found my long-lost minimum diameter 38mm design!

I'd flown/lost it at Plaster City on a CTI 512I285 classic motor. This flight predated my obsession with radio tracking as an invaluable insurance policy but I was out there with "Eagle Eyes" LL so what could go wrong? Well both of us lost site of it after burnout and, despite scouring the area for over an hour, were unable to find it and gave up. I'm not sure exactly who found it but Mike returned it completely intact including my long-lost Pro38 4G casing. So thanks again and props to Mr. Jerauld!

Lesson learned: I should travel back in time and include a radio tracker before the flight.

Wow it's actually 16,547 page views!

2011-12-15T16:31:00.000-08:00

Google just redesigned the profile page for Blogger.com and it now clarifies that the 'page' views I've been tracking are actually profile views. So that counter in the lower right of this page is correct. Thanks for reading, peeps!

PB2k11: Third annual M Moonburner drag race details

2011-11-24T08:10:00.000-08:00

After posting two foreshadowing images below I'm finally getting around to documenting our nifty drag race three weeks ago. I had trouble editing the Flip Slide video in Final Cut Pro 7.03 for some reason so I threw this together in Final Cut Pro X:

[I'm not really a huge fan of that software yet as it seems to be half way between iMovie and v7.03 in capability.] Three of us flew the CTI 7521M840 and Mark Clauson chose the AT M650. A HUGE thanks to Joyce Chan who skillfully photographed our drag race and was kind enough to share her source files with me. Please head over to her site for larger versions or to buy prints of these or any of her other awesome shots: http://fotos.nahcpj.com/
L-to-R: Art/Tom Just, Frank Hermes, yours truly, Mark Clauson

Mark smoked us all with his minimum diameter L3 vessel on the M650!

I was second off the pad, then Art, then Frank. I honestly thought we M840 flyers would have had an ignition advantage because there's a 29mm propellant grain with an embedded pyrodex pellet at the top of the core. That plus the insane 459 pounds of initial thrust has me scratching my head. Perhaps Mark was using a special igniter but, whatever the reason, he won the liftoff cleanly.
I again used my Beeline GPS module to track the rocket as it was well out of site. I threw in the beacon as backup and thought I'd need if as my Yaesu radio didn't receive any distance data until about 20 seconds before the rocket landed. Not sure what's up with that but, in the end, the Beeline did the job and the Google Earth data was robust as shown in the post below.

As a fun aside we all kicked in $20 and employed a scoring equation including liftoff rank, peak altitude, and distance from the pad (highest score takes all):

Mark won with the highest overall score so congrats again! While Frank didn't win this year he was the only participant to incur zero damage after a clean recovery. Mark hit a power line on the way down and burned a 1/2" hole through the airframe and aft motor closure. Art's 1/4" Kevlar shock cord snapped but he got all the parts back. Mine suffered a hard impact that ruined my motor retainer ring and it took hours to free my motor casing. I was able to salvage it however and will replace the ring with 10-32 screws through the retainer side wall. Here my altimeter data if you're interested:

ARTS2 - tabular data
ARTS2 - graphical data
ARTS2 - motor performance estimate (7521M840->7045M989)
ARTS2 - CD plot
Raven - tabular data
Raven - graphical data

Thanks to all who participated and I look forward to another fun drag race at PB2k12.

I posted my Plaster Blaster 2011 shots from Sunday

2011-11-15T19:31:00.000-08:00

And you'll find them here. I also cleaned up my M840 drag race GPS data and plotted in Google Earth (looking east):

More info coming this week-ish so hang tight.

Productive Sunday

2011-11-13T16:44:00.000-08:00

I'm a week late on my Plaster Blaster 2011 entry but I'm still waiting for a few elements to come together. I'll foreshadow a problem with an otherwise great M840 drag race flight last weekend: my Slimline motor retainer ring would not unscrew due to an impact with some harder soil. Frank Hermes suggested that the retainer tube was probably out of round due to angled impact and I think he was right. I started my Sunday trying to resolve that and get my motor casing out.

After 45 mins. of trying other methods I finally busted out my Dremel tool to grind a notch in the slot of the Slimline retainer ring. I then used a chisel to wedge down into the threads and snapped the ring at that spot. I was finally able to pop out the ring and extract my Pro75 6G casing. Although the retainer's threads are trashed I think I can drill into the sides of the retainer tube, tap them, and use tiny screws to retain future motors. This is cool because I really didn't want to trash the booster despite a heavier-duty version being on deck:

Those who have flown moonburner reloads know that they rank among the more difficult cleanup jobs; especially when stuck in a booster and untouched for a week! I was able to get the casing apart and the liner out without issue. As expected some threaded parts and the casing interior were filthy despite liberal use of grease during assembly of the reload. I emptied my tall-ish office trashcan, placed my casing into that, and poured hot, soapy water down into the casing. I repeated the fill and then added a bit of white vinegar to the solution. After soaking for a half-hour I flipped it over and started cleaning with a toothbrush taped to a dowel. A few iterations later I then dried the casing and busted out the screwdriver to scrape and the brake cleaner to dissolve the crud. This process took almost two hours in total today but my casing and parts are quite clean now.

During the soak I started repairing other rockets. My Madcow Squat suffered a minor zipper during the I445 drag race over a year ago. The short body tube is cardboard so I simply wrapped a swath of Gorilla Tape around the top of the tube. It looks pretty cool and should survive another I445 flight.

My '.38 Spatial' suffered a narrow Kevlar zipper in the payload section on its J350 flight. I used a length of 38mm coupler, two layers of release film, a slice of 38mm body tube, and carbon-fiber-loaded-epoxy to patch that up. I then wrapped the assembly in shrink tape and applied heat with a heat gun. This shrunk the film very tightly and I expect the gap to cure/fill quite nicely.

On its last flight my Loc Bullet suffered a 1x2" zipper/chunk due to an excessively long J500 delay. I used a technique similar to the above but this time I sandwiched a layer of carbon fiber fabric in the repaired area. It's worth a try as I was about to trash this rocket and start again.

I also scraped some unintended and ugly primer drips off of the 4' long payload section remnant of the otherwise lost Viciously Mean Machine. It looks pretty cool now and I think I'll fly it with the Fity-Fo booster:

If I were 2.72 miles tall...

2011-10-15T09:50:00.000-07:00

...the view might look something like this:

Here's the onboard video from my M1230 Imax flight this last Saturday at Roctober/Lucerne Dry Lake (best in 720p, full screen)(note the ill-fated desert beetle scaling the igniter just before the flame deluge):

This was my first solid, high-altitude Beeline GPS data set as plotted in Google Earth with a peak altitude of 14,434' AGL and recovery 0.8 miles S-SE from the pad:

It's interesting to note the the ARTS2 reported a peak barometric altitude of 13,915' and the Raven gave 13,925' for an average of 13,920'. That's the closest I've ever seen two altimeters! (Only 0.07% disagreement). I also passed mach 1 at about 3 seconds into the boost on the way to a peak of mach 1.15 or ~887MPH. Here are links to the data images if you're interested:

Raven - tabular
Raven - graph
ARTS2 - tabular
ARTS2 - graph
ARTS2 - motor performance (M1230 -> M1374)
ARTS2 - coefficient of drag performance

Next up is that same rocket on an M840 White moonburner at Plaster Blaster 2011 from November 4-6. We're hoping to pull together a drag race but approval is pending. You should come check it out!

Update: I forgot to include the cool liftoff shot by LL. Unfortunately the full-size shot is significantly back-focused due to the lens sitting in the sun for awhile. LL has razor sharp vision and manually focused about a half hour before the flight but even this smaller size rendering with significant sharpening is quite soft. Not complaining... just explaining. I recommend that you keep all your big lenses in the shade at all times if possible:

Belated: L585 with perfect dual deploy!

2011-09-15T16:23:00.000-07:00

My fourth and final flight at Plaster City's June '11 launch was my new 4" fiberglass Extreme DarkStar. I've sort of resisted the 75mm motor class for a decade but now I'm into it. I ran some calculations and the cost in $/N•s is identical between 75mm and 98mm reloads (~$0.06-0.10/N•s). This means the overall cost is lower with identical impulse per $. Big fan.
The wind was kicking up big time but I was confident that dual deploy combined with shear pins would bring the rocket down reasonably close. Unfortunately my keychain video camera died on the K740 flight below so I have no onboard or ground-based video. The pix are still good though. KO snapped this prep shot and I like it! (ignore my photo credit as that's an artifact of batch export):

Here's the pressure up:

And liftoff... note the excessive wind blowing the plume:

The ascent was arrow-straight but I lost site after apogee ejection because I was using CO2 deployment and a tiny drogue 'chute. This was also my first time using the Beeline GPS unit because the fiberglass structure doesn't attenuate the signal. Unfortunately I forgot to tape the unit down to the foam mount so I think it dropped to the bottom of the electronics bay on liftoff as my GPS altitude data was wonky. I did receive what appeared to be directional information, however, so I started walking NW. Then I heard a loud pop as the 4g main black powder charge blew at roughly 1200' as expected. I watched the rest of the descent and it landed only ~1/4 mile NW of the launch site (closer than most flights in low wind!). Luckily the dragging parachute caught on a bush so no damage was done by subsequent dragging. Stupid mass convection. Here's the Raven Altimeter data with a barometric peak altitude of 7,489':

And here's the ARTS2 altimeter data with a barometric peak altitude of 7,233' for an average of 7,361' (1.39 miles) at sub-Mach velocity:

I also ran the ARTS2 motor analysis and the report says it's an L680 (vs. the nominal L585).

Finally the ARTS2 coefficient of drag was roughly 0.5 at peak velocity.

I next plan to fly this rocket on the same propellant type but twice the motor size (M1230) so I expect roughly twice the altitude or ~14,000'. Fingers crossed for October 8th!

Belated: K740 C-Star = Must try!

2011-09-13T21:04:00.000-07:00

From the June '11 Plaster City launch... I finally got around to editing this simple onboard video:

The boost was loud and fast and I think I trimmed the delay to about 15 seconds. The coast to apogee seems supa long. I would have dropped in some frame grabs but the source video was overexposed for some reason and I didn't want to delay this entry further. Oh and after about a well-heated, 15-minute hike north I located the goods via radio tracker:

It's official + dedicated e-mail address

2011-07-23T13:37:00.000-07:00

I created a dedicated e-mail address for prospective L3 flyers yesterday (masked to prevent spamming d-heads from e-mail fishing):

TripoliL3TAP[at]gmail.com

In sending that change to Debra I noticed that Tripoli's TAP page has been updated to include myself and Richard King Ph.D (a central CA flyer simultaneously advocated by Jack Garibaldi).

Either address will work but the above is preferred and dedicated to the hobby. Fly high, flyers!

"L3 First Try!"

2011-07-11T21:25:00.000-07:00

I've wanted to author a primer to help those aspiring to their Tripoli level 3 certification. After sharing the initial draft I incorporated feedback from KO and Frank and here's the result:

L3 First Try! v1.0e.pdf

Enjoy and let me know if you have any additional feedback or questions.

Great TAP success!!

2011-06-22T19:02:00.000-07:00

Debra Koloms just informed me that I was promoted to Tripoli's L3 Technical Advisory Panel (TAP) and I'm elated! I could not have attained this honor without Debra and the board's advocacy, the sponsorship of Jack Garibaldi, the support of Paul Snow and Kurt Gugisberg, and letters of recommendation from Frank Hermes and Kris Olmstead.

Thank you all and I vow to do my very best to serve Tripoli and its membership for decades to come!

=G=

Greg Smith

TRA#8756, L3 TAP
TripoliL3TAP[at]gmail.com

P.S. Here's Tripoli's official Level 3 process.

June '11 @ Plaster City: Polecat Aerospace Super Raven x 2

2011-06-20T18:53:00.000-07:00

For once I finished the video for these flights last week but have been remiss on my posting punctuality. In any event I built the very pointy Super Raven kit from Jack Garibaldi at What's Up Hobby and it's a good time! At this month's essentially wind-free Plaster City launch I captured photos and vid of both flights so here goes... First up was the CTI Pro38 I180 Skidmark with an HD keychain camera Gorilla-taped to the side:

And a crop of the flame detail showing lovely mass convection:

Next up was the CTI Pro38 H400 Vmax for a flight that was so fast that I reverted to a ground-based 30 fps video to show the fun:

Here's the video featuring both flights (as always 720p full-screen viewing on YouTube satisfies best):

The date/time info is whack and only the time is useful in a relative sense. This was a great launch with solid weather and several folks whooped ass at our final launch before the summer break. Special props to Mike Caplinger who achieved 21,127' feet with a K300 to best the Club's 20K President's Challenge!!

NSL @ Lucerne 'blows'

2011-06-12T11:01:00.000-07:00

When I arrived at 9:15AM yesterday it was already too windy for my tastes. KO prepped her L3 flight and got it on the pad at 1PM only to have the range shut down at 1:30 due to excessive wind. I'm hoping she stayed overnight and tried again this morning as only minimal setup time would have been required.

Finally... amazing Plaster City conditions!

2011-06-04T22:33:00.000-07:00

I had 4/4 successful flights at Plaster today with excellent conditions. I gathered so many photos and so much video and data that I'll plan to post thorough updates for each likely as separate entries. Oh and I finally used my Big Red Bee Beeline GPS unit, Frank! I'm spent so it's a shower then off to bed for me now.

...and again. Plus Sport Rocketry Cover

2011-05-10T17:07:00.000-07:00

Everyone brace yourselves... Plaster City was once again blown out! I arrived at 9:30 on Saturday morning to find gusts at 20MPH. Two brave flyers still flew L motors and it turned out that this was a surface wind topping out at about 500'. I was still marginally disgusted with the conditions and bailed before noon. I admit that I'm a fair weather sort of flyer.
On a happier note I also learned that one of my photos of Mike Worthen's J500G liftoff made the cover of NAR's Sport Rocketry magazine:

Thanks to Larry Brand for linking me up with them. They're sending me a copy as one can only get the magazine as part of a NAR membership. Since NAR used to ban 'rebels' for flying G motors back in the early 80s I've elected to remain solely a Tripoli member. I'm stoked that I could help the magazine, however.

Blown out again + new blog gadgets + cute buddy

2011-04-03T07:49:00.000-07:00

The March Lucerne launch was windy enough that I didn't even unpack my car upon arrival. Then, yesterday, the Plaster City weather report looked prohibitively windy so I fought the urge to again torture myself via long-drive-no-flying and stayed home. I plan to hit Lucerne next weekend but we'll see. [Update: That was blown out too!!]
I also added a search field to this blog and also a hit counter with graph there on the right. Although the hit counter looks much higher than what Blogger currently reports, "Approximate Profile Views: 1334", but perhaps that's visits and the counter below increments page views? Dunno but I'll leave it there for awhile anyway. Signing off... here's a great shot of Zero by LL:

Sometimes ya gotta just give up on the video...

2011-03-25T22:13:00.000-07:00

I spent a whole bunch o' time since the beginning of March trying to get my new camera's video footage slowed down to look all cool. Ultimately I think that even 60 fps is inadequate to slow a fast rocket down. I punted on all the slow mo and just authored the best video I could here:
Again I only had two flights that day because I was trying out my new 1D mark IV camera. If you have the means I highly recommend it... It is SO choice.

I flew my Polecat Aerospace 4" V2 on a CTI Pro54 491I218 and it kicked ass outa there. Here's a cropped frame grab from the 1280x720x60p video:

I retrieved that perfectly intact about 0.3 miles NW from the launch site. Then I set up my Loc Bullet on an AT J500 Mojave Green and I thank Daryl for setting up the reload for me. As I was setting the flight up I learned that the fella next to me was flying an AT I245 Mojave Green with a camera so we agreed to fly a drag race. It's interesting to note that Daryl provided a longer Aerotech delay that I thought was 14 seconds and I trimmed 2 seconds off that with my delay adjustment tool and AT adapter. In the video you might have noted that the burnout-to-apogee time was actually 15 seconds and the ejection was 5 seconds after that! So AT is now shipping 21-22 second delays? Dunno but that was WAY too long and my CF reinforced Bullet took a bunch of damage. It's probably time to retire that thing and rebuild one more similar to the original BSD design. Here are three frames of the drag race where I get my ass handed to me once again (the keychain video cam is Gorilla-taped to the left side of the Bullet on the right):

I just remembered that KO pushed the button on that sequence so I take only partial credit for setting the camera up. Love those mach diamonds and 10 frames per second helps a bunch! Here are the rest of my shots from that launch as well.

Working on March 2011 Plaster City launch report...

2011-03-10T20:05:00.000-08:00

...and have been since Sunday. I finally have some 60 fps liftoff vid and I'm trying to get some good slow mo out of it yet continue to struggle. Here's an otherwise unrelated video of what my new camera should be capable of for reference (The 7D is a close cousin to my camera).

Plaster City Launch - Feb. 2011

2011-02-07T17:47:00.000-08:00

We benefitted from yet another late-winter, wind-free launch in the Imperial desert this last weekend. We're tremendously lucky to live in SoCal. I decided to be a Luddite and fly only motor ejection this weekend (no electronics) so I could fly more rockets and concentrate on video and photography. Shocker that I STILL only had two flights but at least the photos and vid didn't suffer. I posted numerous shots here (click play to start slideshow). Please post comments with corrections and/or motor info that I missed.

First I flew my fiberglass 4" Madcow Nike Smoke on a CTI K940 White Thunder reload. The flight was amazingly kick-ass and was far faster than I'd expected after the slow K400 Green^3 flight last month. The liftoff thrust:weight was 28:1 for a good time. I walked about 1.25 miles S-SE to find this sucker with my radio beacon. Just call me "1-Mile Radius G". Here's the liftoff:

I also Gorilla-Taped a $5 keychain camera to the side and the video is pretty good considering the convenience and cost benefits:

[That looks way more compressed than the original raw footage so I'll need to figure that out and post a better version later.] I adjusted the delay to 11.5 seconds for this 8 lb. 14 oz. flight but you saw that was about 3-5 seconds too short and the 'chute popped way too early. Also the shock cord wrapped perfectly around the camera's lens on the descent thus cutting the usable video short. I'll get it right next time and recommend those cheap Ebay perv-cams. Oh and the flight video file consumed roughly 1.05GB for 25 minutes so a 2GB micro-SD card should suffice for most folks. I bought two 8GB cards because I didn't know so save yourself some dough.

Then I flew my DarkStar Lite on an older AT I200 motor with perfect recovery just South of the launch site (note the inadvertent mini-roll of Gorilla Tape on the fin... D'oh!):

I'm as shocked as you that it didn't also drift over 1 mile South. Cheers to another excellent launch at Lucerne next weekend!

And... FINISHED!!

2011-01-30T13:16:00.000-08:00

Today I finished primary assembly of the Extreme DarkStar (right) and there's the final Nike Smoke my parents bought for me (left). [Update: While I was authoring this entry I figured out they'd shipped the wrong DarkStar fins to me. Awesome now that's it's friggin' built! The Nike Smoke is fine, however. Details below...]

I still need to foam the fin slots, fillet the fins, drill vent holes and static port, attach the rail guides, and layout the electronics board but it'll fly next weekend on a CTI Pro75 6162M1675 Pink. Based on KO's previous flights this rocket seems to get about 3 feet per Newton-second of total impulse. As such I would estimate about 17,000-18,000' from that motor. I'll also fly it dual deploy but plan to run both a Beeline GPS transmitter and my workhorse tracker beacon to assure recovery. Here are some build details from previous weeks:

On the above motor assembly I elected to use the SlimLine 75mm motor mount so no screws are required (unlike the AeroPac which is a very tight fit). I also left off the Kevlar strap as I prefer to link the recovery system to a drop-forged screw eye in the motor's forward closure. That longitudinal masking tape serves as a shim for the centering rings as the tube is tapered and they would have been loose during the cure otherwise.

For some reason Wildman provided WAY too much tab depth on those fins but my new carbide-coated bandsaw blade cut through the 3/8" high stack like butta. That blade was spendy at over $100 but there really is no other way to cut fiberglass on a bandsaw with any reasonable blade life.

I went retro and simply taped each fin pair on with manual alignment. This was a bit difficult because the slots were about 50% too wide for those fins. I chose to datum to the left side of each slot and they all look perfectly aligned to my eye. I'm now wondering if Wildman had intended to ship 3/16" thick fins with this kit? Hmmmm. Low and behold they WERE supposed to ship 3/16" fins as indicated in the kit specs. That's strange because the fin tabs matched the slot length correctly so I assumed they'd just messed up on the fin template. Maybe mine won't fly on any 75mm motor made then... Dammit.

Above is another view of the simple yet effective fin attachment.

Above is the electronics bay. Today I JB Welded those aluminum tubes to the sled so, apart layout out the board positions and switches it's all set to go. Wow I'm really bummed about that fin thing now. This was too much money and work to be uncertain of fin strength at this point.

Lagger: Plaster City 1/1/11 Launch Report

2011-01-20T21:08:00.000-08:00

The coolness of the date of this launch was exceeded only by the complete lack of wind and excellent flying conditions all day. The primary reason for this delayed report is that I was trying to improve the video I shot that day to no avail. My pictures sucked too so that's awesome.

Fiberglass Nike Smoke 4" - This is the kit mis padres purchased for me for Xmas (bah humbug :). It's designed like a tank with a weight to match -- 81 oz dry!! I purchased a Pro54 4-grain 1597K400 Green^3 reload from Jack. The liftoff was slower than I'd expected but, like all Nike Smokes, the thing flew straight as an arrow. I trimmed the delay to 11 seconds and ejection was about 1 second after apogee. I used a 48" parachute and the descent seemed slow until it got nearer the ground then it seemed speedier than I'd like. In any event it landed at the edge of the 'bowl' free of damage.

I think this kit needs some serious thrust so I purchased another 4-grain motor, the 1633K940 White Thunder, for its next flight. At the same time Jack offered me a mystery 4-grain motor for half-price. Others reportedly shied away earlier in the day but I wasn't skerd and bought it anyway. When I got it home I opened the package to find "VM" written on the ejection cap so I'm forced to assume it's the 1408K2045 Vmax. Score!! So I'll reserve that for the third flight of my new Smoke and it should be scootin'.

.38 Spatial - I last flew this minimum diameter, carbon-fiber-over-phenolic design on an I284 to ~9100'. The next logical step on the way to the insane 1115J530 was the J350 I've had sitting in my motor box for many years now. As always these minimum diameter flights take way too long to prep and there never seems to be enough internal room to fit everything despite previous successes there. Once on the pad I had trouble locating the Raven's arm button so I pulled the rocket, slightly rotated the electronics board, and tried again. The second time was sort of a charm. I was able to arm the Raven but, upon 'ignition', the motor pressured up very slowly as old motors will. After a sizable chuff the thing lifted off but was marginally stable. This is about the 10th photo of a 5 fps sequence and the motor took about 5-6 seconds to pressure up:

The resultant wiggle sent it NW and way out there. I had a radio tracker signal the whole time and figured everything was intact. After walking out toward the wash for over half an hour and circling about I finally found the transmitter.... just the friggin' transmitter!! It looked like someone had wrenched the thing off the shock cord, left it there, and kept the rocket; or so I initially thought. I ventured out on the original line and asked a camp of moto dudes if they'd seen anything. One fella seemingly sketchily answered "With a green 'chute?" Yes I answered to which he replied "Oh it's back from where you came about a quarter mile out." His answer didn't sit right with me but what was I gonna do? Ask to search their motor home? I bit my tongue and walked back toward the launch site only to find the rocket about 30 feet east of where I'd found the transmitter. I immediately felt guilty about my suspicions so I need to offer the benefit of the doubt in the future.n Here's roughly where I found it:

OK so the payload section and booster were still mated but the nosecone was off and the Kevlar™ cord had ripped through the payload tube about 1.5". Man that aramid fiber is tough!!

As I walked I pondered failure analysis... The apogee charge had blown but the motor and delay had already burned up so the delay hole in the motor must have vented too much of the gas and failed to pop the payload section off. As the rocket came in ballistic the main popped but I had only loosly knotted the 'chute lines the shock cord (no knot on the cord itself). So the parachute, mounted above the taped-on radio beacon transmitter, slipped up the cord, stripped off the transmitter, zippered the payload section, then promptly shredded off. As I walked back I even found the 'chute!:

I'm constantly destroying those TopFlight 'chutes at every single launch. The Raven survived and here's the flight graph:

Despite the serious flight arc I still attained about 8100' so I'm convinced it would have exceeded 10k were it straight. Also the velocity wasn't too bad at roughly mach 1.5. You can also see the blip after apogee where the charge failed to eject and then where the main ejected at ~800'. I wanted to swap nosecones with an extended design anyway so .38 Spatial will fly again soon. Lessons learned:

Burn those motors soon after you buy them! Chuffing (motor pressure surge before actual ignition) is dangerous. In the early 80s motors employed progressive thrust curves and weren't nearly as reliable as today's motors. I saw a few rockets chuff, pop off the launch rod, then fire off horizontally into the desert. If a motor is older and you still choose to fly it always use a long launch rod/rail as an insurance policy against chuffing.
RockSim's CP calculation is way too aggressive hence the metastable liftoff. I'm now relying more on OpenRocket's CP calculation as it's typically between RockSim and Barrowman.
[Just added] Plug those forward closures!! I'm certain I would have attained apogee ejection were it not for the unintended pressure vent offered by the motor itself.
In the unlikely event of a similar failure in the future place the transmitter above the parachute connection point or, even better, always tie a knot in the shock cord for parachute attachment. That way if the parachute strips off it won't take anything with it.
Offer the benefit of the doubt to those sharing the desert with us. I have a bad history with this so I have some trauma to overcome. When I was a kid I flew a Composite Dynamics 29mm F45 motor in my prized AeroRoc. It was a high flight on a windy day and the rocket landed on the side of the highway in the bay area. I ran toward it only to see someone pull over and drive away with it when I still had a quarter mile to run. Damn them! Epic recovery FAIL.

Building three simultaneously = efficiency!

2010-12-26T16:15:00.000-08:00

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

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.
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" 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

2010-12-16T16:30:00.000-08:00

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!

2010-12-12T19:24:00.000-08:00

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'!!

2010-11-09T21:16:00.000-08:00

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

2010-11-09T20:55:00.000-08:00

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!!

2010-11-02T17:14:00.001-07:00

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.

2010-10-31T16:28:00.000-07:00

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...

2010-10-24T09:03:00.000-07:00

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

2010-10-12T16:46:00.001-07:00

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

2010-10-12T16:32:00.000-07:00

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!!

2010-09-27T18:46:00.001-07:00

Nice. Thanks, readers.

After 5+ hours of arduous construction today...

2010-09-26T22:05:00.000-07:00

...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

2010-08-21T09:06:00.000-07:00

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

2010-08-18T17:43:00.000-07:00

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

2010-07-11T12:42:00.001-07:00

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!

A brief pause from rocketry...

2010-07-11T12:39:00.000-07:00

Megan Fox WIN!

LDRS 29: A windy but impressive international launch!

2010-06-16T15:40:00.000-07:00

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 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!!

2010-06-07T21:30:00.000-07:00

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!

2010-06-06T10:41:00.001-07:00

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

2010-05-31T14:57:00.000-07:00

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?

2010-05-31T14:53:00.000-07:00

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

2010-05-29T19:14:00.000-07:00

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

2010-05-25T19:35:00.001-07:00

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

2010-05-16T22:39:00.000-07:00

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

2010-05-16T17:30:00.000-07:00

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

2010-05-12T21:13:00.000-07:00

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:

Der Red Mix tube session and test fit

2010-05-02T21:44:00.001-07:00

Tonight I was inspired to drill the extra holes in all four centering rings, cut the motor tubes to length, and mark them precisely according to the plan a few entries below. Everything went together nicely but before I apply any epoxy I realize I need to finalize the electronics bay mounting board first.

You'll notice that I've elected to dual-attach the shock cord on the upper plate. I think this should reduce the tendency to zipper as the load will be divided in half. I'm quite sure the Gates Brothers used to employ that trick. Also that single aluminum tube bridges the electronics bay to the motor area and will facilitate e-match wire transport. Hopefully this week I'll get this whole assembly done and the rest of the build should prove fairly trivial. I think the first flight will probably be a central CTI 1596K500 Red Lightning motor on the ground then air-starting 2 x 408I345 White Thunders. Niiiice!

Viciously Mean Machine 0.75

2010-05-02T21:40:00.000-07:00

I'm still working on the full 48" payload for the 100% Viciously Mean Machine but, in the mean time, I bought a Performance Rocketry aluminum-tipped, carbon fiber, conical nosecone and it just looks bad ass with the shorter payload. That booster will fit a CTI 6GXL casing so I hope to fly an L935 in there soon.

[I corrected the lens distortion present in the other version of the image.]

Hey, blog spammer shitheads!

2010-05-01T16:00:00.001-07:00

I'm honored the Mandarin-fluent geniuses like [ElvisS_S blah blah blah] assume that enough people read not only my blog, but comments on individual entries, that it's worth spamming me. I will always immediately delete your drivel so find someone else to pester, shitheads!! Seek some less annoying way to earn a living.

Der Red Mix's precise design

2010-04-25T11:14:00.001-07:00

Last night and this morning I worked up several templates based on my size/position guide (click image for larger version):

As this will be my most complicated scratch-built design ever I found it necessary to plan all the part positions precisely up front. I highly recommend either Illustrator or CAD for this purpose and I used the former in this exercise. I just need a few more parts and I can start cutting and adhering.

Repair day

2010-04-10T16:33:00.001-07:00

After finishing my taxes today I decided to repair several ailing rockets despite needing to build/finish several others.

First off I fixed the 4" bullet after an early I366 Redline flight with yet another incredibly short delay. That was the last of the Redline motors I bought 'round about 2002 and, even storing the delays separately, these old motors accelerate the delay burn by roughly 6x. As such the ejection charge blows even before the motor has burned out (and yes I'm certain I assembled the motor correctly). This is the third old Redline that's behaved the same way so I sense a trend. The bullet suffered a zipper about 1.5" long right through the carbon fiber reinforcement so it was going damned fast at the time. Luckily I had enough room above the coupler that I could just slice the zipped section off and the nosecone still fits unmodified:

If this rocket suffers another event requiring repair I'm cutting my losses and tossing it!

Secondly I'm trying to correct a warp in my Viciously Mean Machine's 48" payload section. I'm quite certain this happened during carbon fiber reinforcement due to inadequate support while curing in the oven. Today I taped a 10lb. weight to the high point in the tube, suspended it in the curing oven on a contiguous 1" dowel, and post-cured for roughly 35 minutes. I'll check it in a bit but if that didn't work I might be scrapping a second payload section. Dammit:

Finally I had experienced a wall deformation in my 7.5" Nike Smoke on its last M1939 flight. I'm quite certain this was because I flew it single-deploy and, when the 16 foot Rocketman 'chute inflated from the payload section, the payload coupler came out an an angle and cracked/deformed the top of the tube. I mixed up a batch of West Systems epoxy, dropped in a liberal amount of Kevlar pulp and white pigment, and slathered that mess on the inside of the tube. I then used packing tape on the bottom of the tube to prevent leakage, topped it with a sheet of vacuum bag film, laid in a section of 7.5" tubing, and clamped the whole thing together. I think this will work pretty well after I grind off the excess epoxy:

I'm way behind in my blog posts so I'll list what I still owe here so I don't forget:

March Plaster City launch report
April Plaster City Launch report (featuring 9,140' I284 flight which I think is a record)
Inexplicably wacky ARTS2 altimeter behavior
Mad Cow Squat build (due before LDRS 29 in early June)
2000MPH President's Challenge build (Due before May Plaster City launch)
Der Red Mix build (Due before LDRS)

Darkstar lite build

2010-02-22T07:48:00.000-08:00

I recently purchased an all fiberglass Darkstar Lite kit from Wildman Rocketry:

I needed an easy sport flyer for 29mm motors as my Arreaux is aging. This kit goes together so fast! Here's the AeroPack motor retainer end:

And the forward end:

And the overview of the motor tube assembly:

And, using this stupidly simple masking tape rig, I was able to tack all 6 fins to the motor tube at one time. Big fan!:

And these last two pics complete the assembly. I forgot to take them before flying this three times on Saturday so that's why the white tail end epoxy looks soiled:

And no the top fins are not tilted. Chalk that up to wide-angle lens distortion. Now onto finishing...

Slightly late... Plaster Blaster 1/1/10 launch report

2010-01-25T20:01:00.000-08:00

Yeah this has taken awhile but I sorta got hung up editing vid. I marvel that Apple's Final Cut Pro 7 supports neither AVCHD nor Flip MinoHD formats natively. Guess what though -- Adobe Premier CS4 does!! WTF, Apple? Git yo shite togetha. Rant mode off.
I didn't think I'd be able to fly this month because I was backup shooter at a wedding for my buddy Jaime on Saturday. However, our club scored an FAA waiver all day Friday, 1/1/10, so I went for it. El Bee accompanied me and fun was had by all even though the crew was sparse. Actually when you have Jack Garabaldi vending AND flying, Russ Sands successfully attaining his L3, and Paul Snow bustin' out a K1999 no options exist except to have a good time. Here are my select photos for the day.
I flew light-ish today as it was short notice but I'm still happy with the results. I started with my Loc Bullet on a J825 for a thermite ignition test. I experienced ignition system issues and had three sequential misfires with an electric match + 0.5 g of thermite. The fourth time was sort of the charm with the match popping, the thermite doing something without emitting smoke, and the J825 igniting about 8 seconds too late for me to catch a photo. The flight was awesomely fast and now I know to use at least 1-2 g of thermite next time since instant ignition is my goal.
Then El Bee and I took it easy and flew a super convenient Cesaroni Pro29 159G118 Blue Streak motor in my trusty Aerotech Arreaux for a very quick and cool ascent. Again we captured no photos but the rocket landed on a moto burm and again managed to avoid destruction.
Next we flew the same Arreaux on a Cesaroni Pro29 176H123 but this time El Bee caught a great video with the Flip MinoHD video camera (watch in HD on YouTube):

Finally I started prepping my new Viciously Mean Machine design which suffered from unusable curvature of the payload section last month. I substituted the Em Sem Fity payload section, dubbed this kludge as VMM v0.75, and planned to fly it on the Cesaroni Pro54 1016J360 Skidmark. As always the dual deploy electronics took awhile to prep but the flight was pure greatness (prep photo ©El Bee):

Unfortunately I did an awful job of catching the liftoff because I was busy pushing the launch button and watching the flight. I like that our club offers control over one's own flight but it greatly complicates photography and videography. (Watch in HD on YouTube):
The flight portion sucked but El Bee caught a nice liftoff sequence and here's the best frame (click for larger version):

I recently had my 1Ds III serviced and it nailed the focus on most shots today. The detail in the flame of that shot is awesome! It looks sorta like flamey fur:

Oh and here's another bonus... this flight attained 9,217' and I believe that's a record that should make it into Rick's altitude record database! There's another Pro38 J360 record from 2005 but this Pro54 J360 Skidmark wasn't released until 2009 so it must be new and different! :P Heh heh.

The windless, perfect day ended beautifully with one of the most enduringly stunning sunset's I've seen in my life! (photo ©El Bee):

Kick-off: 7.5" Der Red Mix

2009-12-21T10:15:00.000-08:00

This will be my first scratch-built, upscale design. As a kid I built the 1.6" diameter Estes kit "Der Red Max" and found the design appealing and the decals amusing. I'm not a fan of huge fins so on my design I've taken the liberty of scaling them down to just enable a static margin of 1.16 with the heaviest motor array (L935, 2xJ530, 4xI224). While 1.16 might sound low for a cluster I've learned to trust RockSim's stability equations and find the original Barrowman equations to be too conservative. Also I'm not likely to fire the cluster on the ground and will probably always start with a powerful 54mm motor to send the rocket up and away before igniting outboard motor pairs. Here are some screengrabs from RockSim 9:

I'm still working out the details of the electronics bay but I plan to seat a removable trap door just above the fin tops to conveniently seat two multi-function altimeters and a Flip MinoHD video camera. The onboard video should rock! I've slowly been buying components for this design from Jack at What's Up Hobbies as well as Loc Precision. I also ordered my first set of laser-cut fins and centering rings from Balsa Machining Services and an AMAZING set of decals from Mark Hayes at StickerShock23.com. Here's the array of parts pre-assembly:

The fins are only 1/4" thick so I'll reinforce both sides of each with one layer of 6 oz carbon fiber to improve rigidity. Having just cleaned my garage I plan to start on this build ASAP!

Plaster City Launch, 12/5/09

2009-12-06T18:32:00.000-08:00

I had three goals for this month's launch:

Test my Beeline GPS on a lower altitude flight to visually verify the position data. I also wanted to test a G10 fiberglass support I'd cut to stabilize the otherwise fragile electronics board/antenna.
Test thermite ignition on an older Redline motor like the I366 I've had for seven years as these are notoriously slow starting.
Fly my Viciously Mean Machine on a CTI J360 Skidmark (Pro 54, 3-grain).

I was mildly breezy and very cloudy when I arrived at about 10:15AM. If we weren't in the desert it probably would have been raining. I headed over to Jack Garabaldi's trailer to buy some components and a CTI 55F29 Imax motor for my GPS flight. I set up the GPS unit in the payload of my AT Arreaux and Frank Hermes helped me set my radio up to receive the APRS packets to monitor the flight's position every 5 seconds. I trimmed the F29 motor's delay from 12 seconds to 9 seconds forgetting how weak an F29 was. I really haven't flown mid-power for about a year now. Basically I should have used a 5 second delay on this cold day because 9 seconds was way too long. I came painfully close to crashing my $300 GPS unit on it's first otherwise underwhelming flight! I stripped two parachute strings but the whole thing came in tethered and fluttering. Everything was intact and I was able to download the flight profile successfully:

At first I was trying to figure out why the rocket only flew to 269 feet then realized that GPS altitude is recorded in meters. As such I actually attained 882 feet. Much better. :) I'm also confused by the region marked "What's this?" That's about where the 'chute finally ejected but it certainly didn't shock upward or sideways. Besides this isn't an accelerometer-based device and should only be storing actual GPS coordinates every second. Weird.

Then I spent another two hours prepping the Viciously Mean Machine for a dual deploy flight using the Parrot2 altimeter and the predictably spectacular J360 Skidmark. I finally got it out to the pad to discover a) I had managed to misalign the rail guides so there's no way I could fly it and b) looking up the 8+ foot skinny rocket that the payload section was warped. I had used Blue Tube 1.0 for the payload section and read that it was subject to warping at higher humidities. I had never noticed the curve while building so perhaps it happened afterward. I threw that part in the trash today as it's a total loss. I need to decide now if I want to try Blue Tube 2.0 for the rebuild. I feel pretty burned right now because I spent a great deal of time and money reinforcing the tube and coupler with two wraps of carbon fiber each. I disassembled everything and packed it away.

Finally I quickly prepped my horribly battered and thrice repaired LOC Bullet with a CTI 660J381 Skidmark. I really can't get enough of these loud and impressive motors. The flight was cool and uneventful except the ~1.5 mile walk east since I'd used a 45" parachute. I was able to track it visually but I'm still glad I put my radio tracking beacon in there as an insurance policy. I left the AVCHD camera on it's tripod during my roughly half-hour walk and captured some other flights before the wind wall kicked up effectively shutting down the launch for the day:

The song is Tenori by Francois Dubois. I never got around to the thermite ignition test but I vow to git 'er dun one of these days!

PB2k9: 7.5" Nike Smoke on M1939

2009-11-12T20:55:00.000-08:00

For my 2008 birthday present my parents kicked in half of the cost of an Aerotech M1939 motor. They drove all the way out from Cochise, AZ for last year's Plaster Blaster which was almost completely blown out by wind. We made several other attempts to link up in the ensuing year to get that motor flown. Mother Nature cooperated this weekend and, on Sunday, I was finally able to launch the beast. I used my L3 7.5" Nike Smoke as I'd actually built and reinforced it for this particular motor. Here's a liftoff photo:

Some might notice that, much to my chagrin, the shot is clearly back-focused. I'm certain that I had a clean focus lock on the rocket before flight so I'm not sure what went wrong here. In any event you get the idea and I attained just under 10,000' on this impressive flight.

Update: Thanks to Scott Eadie who shot video of the flight. My AVCHD hard disc was full so I had no video documentation until now:

For some reason the Parrot2 altimeter did not record any data so I only have the AltAcc graph and summary:

I dedicated this flight to my parents 'cause they rock! Again Roy and I had to walk north over a mile to get this 50 pound beast back. We were exhausted! I can honestly say that this was THE best launch of my life and I'd like to thank my parents, Frank Hermes, my friend Kristine, and Mother Nature for that!

Pb2k9: .38 Spatial in the Skidmark mass launch

2009-11-12T20:38:00.000-08:00

I'd planned many flights over the weekend but prep and recovery took much longer than expected so I only had three flights total. The middle flight was on Saturday night and my new .38 Spatial was one of 21 rockets launched simultaneously on the new CTI H123 Skidmark motor. This propellant formulation isn't new but, with recent California State Fire Marshall approval, these impressive motors pretty much dominated the launch. They employ particles of titanium metal in the propellant that burn bright white/orange and pop loudly. In aggregate a single Skidmark motor yields thousands of these sparks and, as a result, roars loudly well above a normal motor's decibel level. Here's a video of all 21 rockets launching at once (well 20 if you exclude Frank's entry which failed to ignite due to my error):

Here's another of the seven including .38 Spatial (third from the right):

And here's a photo of my design isolated with some nice dusk lighting:

This launch was the clear crowd pleaser of the weekend. John Bowman did an excellent job of coordinating the event and the crowd loved it!

PB2k9: Em-Sem-Fity on M750 - 20,212 feet!

2009-11-12T19:06:00.000-08:00

Frank and I conducted the successful M750 drag race just after 10AM on Saturday. Here's a video covering prep and flight:

Here's a liftoff photo verifying Frank Hermes' clear victory in this M750 drag race:

The flights were quick, impressive, and invisible after the smoke charges burned out. I should also note that frank topped 21,000' and, in a separate flight, Mark Clauson attained his level 3 AND topped 22,000' for a club record! Here's his video of the race:

Here's my Parrot2 Altimeter graph and summary:

Here's the way too simplistic summary from the G-Wiz LCX:

I'm likely to sell the LCX and buy the HCX at some point because that's just not enough data to bother! Note the lack of calibration 'cause this is the first time I'd used the device and failed to RTFM. Therefore the acceleration and velocity numbers are wrong. The barometric sensor does not require calibration so the altitude number should be correct. The average of 20,788' and 19,635' is 20,212'. Yay! President's Challenge mission accomplished.

I'd planned to use my GPS transmitter for this flight but realized the fragility of the antenna and the carbon fiber exterior of Em-Sem-Fity was guaranteed to insulate the device from satellites. In the end I used my trusty radio tracker system and walked right up to the rocket roughly 2+ miles north of the launch site. The rocket was entirely intact and dual deploy appeared to have worked perfectly:

While cleaning up the photo sequence of the drag race I noticed something interesting... my flame clearly appears weaker than Frank's. I normalized our two flights using Photoshop and added ruler lines for comparison:

In prepping my motor I heard rumor that I shouldn't use the disposable forward seal disc. I checked with Gary Rosenfield and Karl Baumann from Aerotech (conveniently in attendance at the launch) and Karl was surprised that I had a disposable seal disc. He asked for the lot number but now I only have my nozzle pack serial: 071007. Unfortunately I disposed of the four grain boxes. In any event Karl commented that this M750 reload must have been from an early production batch. As such I must assume that a) my reload was in the neighborhood of 2+ years old and b) there could be an aging effect on this motor that reduced its total impulse and/or average thrust. I'll follow up with Gary and request his input.

Frank challenged me to a rematch at Plaster Blaster 2010. If we do this I'm going to request two sequential serial number reloads built in the same recent lot. For now I'm elated that I exceeded 20,000 feet for a new personal altitude record.

Plaster Blaster 2009 report forthcoming

2009-11-12T06:36:00.000-08:00

I'm still editing video, cleaning photos, and reducing data. I hope to have my report done this week. Executive summary: GREAT SUCCESS!!

New Vessels for Plaster Blaster

2009-11-04T19:21:00.000-08:00

From left-to-right:

4" Em-Sem-Fity (also known as "Frank's worst nightmare")
54mm minimum diameter Viciously Mean Machine (106" long for a roughly 50:1 aspect ratio)
3" Vertical Assault mark II - fixed and freshly painted
Me in a sport coat and Prada loafers (so as not to offend those who fear the casual look and bare feet)
[By popular demand] .38 Spatial minimum diameter (Up and... gone... Oh wait there's the beacon!)
4" V2

Thermite ignition tests

2009-10-24T13:26:00.000-07:00

[Disclaimer: I assume no responsibility for use or misuse of this information. It's available elsewhere on the Internet and I'm simply sharing my engineering interpretation of that information. Use these materials with great caution. Do not mix reactants until just before use. Do not mix or ignite them anywhere near flammable materials. Do not look directly at the reaction as harmful UV radiation is emitted. Be careful!]

If you watch Mythbusters then you'll likely have seen their experiments involving thermite. According to Wikipedia Hans Goldschmidt discovered and patented this thermite reaction in 1893 and used it to both cut and weld metal. These powdered mixtures require very high ignition temperatures (2000˚F) but then burn at 4,500˚F swapping oxygen, producing molten metal, and releasing a bunch 'o' heat and UV radiation. Common reactants include elemental aluminum or magnesium with metal oxides like copper (II) oxide (cupric oxide) or iron (III) oxide (ferric oxide).

Many folks in high-power rocketry are successfully using thermite as a source of instant ignition of even the largest rocket motors using a guideline of roughly 1 g thermite per 1000 N•s of total impulse. I'm intrigued both by the reaction itself and its utility in this hobby so I decided to give it a try. I ordered 1 pound each of aluminum powder, cupric oxide, and ferric oxide online. I'm quite certain I overpaid as well so you should definitely compare prices on the Internet(s). :) I was finally able to use my chemical engineering degree and calculated the appropriate mass ratio of the reactants using stoichiometry and atomic and molecular weights. For the aluminum + ferric oxide reaction it's:

Fe₂O₃ + 2Al → 2Fe + Al₂O₃ + heat + UV

2 moles of Al = 26.98 g/mol * 2 moles = 53.96 g

1 mole of Fe₂O₃ = 159.69 g/mol * 1 mole = 159.69 g

So the mass/weight ratio is almost exactly 1:3 Al:Fe₂O₃

For the aluminum + cupric oxide reaction it's:

3CuO + 2Al → 3Cu + Al₂O₃ + Heat + UV

CuO: 79.545 g/mol * 3 mol = 238.635 g
Al: 26.981g/mol * 2 mol = 53.962

Mass/weight ratio: 4.4:1 CuO:Al

I set up my video camera intending to share the clips here but the ignitions were so fast that they only show up on about 4 frames at 30 frames per second. As such I've simply grabbed the key frames and assembled sequences for both tests. This camera method also eliminated the need to directly observe the reaction although the emitted UV might have improved my tan a bit. Here a single electric match ignites 0.5 grams of a molar ratio of ferric oxide + aluminum powder thermite:

Ignition was fairly rapid but continued to sputter for about 30 seconds afterward. In this second experiment I again used a single electric match to ignite 0.5 grams of a molar ratio of cupric oxide + aluminum powder thermite:

This second combination appeared to be far more energetic and burned to completion without sputtering. Most folks have been using this cupric oxide+Al combination but I wanted to try the classic ferric oxide+Al combination as well. It's clear that cupric oxide works way better so I now have my empirical answer. Again... exercise caution!!

CD3 ejection ground test for M750 flight

2009-10-19T22:14:00.000-07:00

It worked perfectly with only 12g of CO2!

CF minimum diameter build progress

2009-10-19T20:32:00.000-07:00

So I've made some progress on the Viciously Mean Machine and unnamed 38mm spike below. I've applied Cotronics 4525 high-temperature epoxy fillets to all fin/body interfaces and laid up tip-to-tip carbon fiber reinforcement on all fin pairs with Aeropoxy. I've also post-cured both tubes in the oven for 1.5 hrs and, let me tell ya, those fins aren't budging even 1mm!!

This week I plan to build/reinforce the payload sections and couplers and start the finishing process. Both should be lookin' purdy by PB.

M750 for EM-SEM-FITY

2009-10-18T22:43:00.000-07:00

One 9,345 N•s, 14 second burn M-motor now in stock for Plaster Blaster:

Thunder & Lightning mark II pix

2009-10-15T22:32:00.000-07:00

Thanks to Jeremy Rich for these shots of the I357/I211 flight covered below!

A reminder that... yes I did get all parts back intact. I don't buy into miracles yet I'll admit that this vessel should not be sitting in my garage ready to fly again immediately!

Even more carbon fiber success

2009-10-03T13:25:00.000-07:00

I was finally able to lay up two new 38 and 54mm minimum diameter designs with 2 wraps of 6 oz carbon fiber cloth and cure them in 1 hour with a nearly perfect finish. The key seems to be plugging in the curing oven right when you place the part and then unplugging at exactly 1 hr. I then let both tubes cool down in the oven for about 1/2 hr then pulled the Mylar™ film and release fabric off while they were still warm to the touch. Here are the finished tubes and I'm tacking the fins on with JB Weld Quick:

I have one batch of high-temp black epoxy left and I want to use it on both designs so all fins need to be tacked down and ready. Knowing that Derek Zoolander stands 5'6-1/2" tall I've built this comparison to my new designs for scale:

I really shouldn't even be talking about these designs because they're really-really, really-really, ridiculously good looking.

Lucerne launch report, 9/12/09

2009-09-13T11:37:00.000-07:00

I arrived on the playa at about 8:45AM yesterday to extremely calm conditions. Jack Garabaldi had already opened is awesomely stocked What's Up Hobbies store and I dove right in buying components and new motors. The ROC folks were just beginning to set up the range but this seemed fine due to the complete lack of wind.
I'd begun prepping my main Thunder & Lightning mark II flight the night before to save time on Saturday morning. It still took another hour to assemble the motors, finalize the electronics and black powder charges, pack the 'chutes, and load up the tracking beacon. Just as I was finishing the preparation i felt the "breeze" kick up. This rapidly increased to 10-15 MPH winds so once again Mother Nature enjoys throwing challenges our way. Rockets and wind simply don't mix. I'd intentionally chosen a punchy booster motor, the AT I357 which burns for 1 second, and also shortened the sustainer's AT I211 ignition delay to only 1 second after booster burnout. Both of these tactics targeted minimal wind arcing to improve the likelihood of success.
I got everything set up on pad 21 but then asked the launch control officer to wait for a lull in the wind before launching. When finally launched everything on the I357 boost looked good. The one second delay before the I211 ignited in the sustainer felt more like three seconds. Then the I211 chuffed and conveniently popped off the booster section thus eliminating flame damage. After another chuff the I211 finally pressured up when the rocket was roughly 40 degrees from vertical. Oops. It powered off into the desert blue and, after I lost it visually for a bit, I again saw it drifting downward under the main 'chute. I had to walk roughly 1.2 miles out to retrieve it and the whole time I could see the parachute popping up and dragging my beautifully painted rocket along the lakebed. Here I've tucked that main back in and shot a quick photo indicating the distance:

Nice. Did I mention I'm not a huge fan of wind? I was surprised to see that the main parachute ejection charge had not worked. So why had the main popped out? Dunno yet but I considered myself very fortunate and would analyze the next day.
After gathering up both the sustainer and booster. I started cleaning the cases and it became very apparent that the wind wasn't planning die down any time today. I packed up and headed to the Pomona Fairplex to view a Dock Dogs competition.
Fast forward to today, Sunday, and I was able to disassemble the sustainer's electronics to analyze the near failure. I was surprised to see that the 9V NiMH rechargeable battery had bloated and warped in several directions. Also the electrical tape had burned a bit so something must have shorted after the drogue charge popped and killed the battery before the main charge could kick off:

The force of the drogue ejection must have fortuitously popped the nose cone and released the main 'chute thus saving the rocket to fly again.

Based on some reading on the ARTS2 altimeter I rigged up the above battery connector to bypass the current limiter and run both the flight computer and pyro charges off of a single battery that fits in PML's CPR3K ejection system. I've flown this configuration successfully several times but took a bit of damage on the battery connector cap last time. I thought the electrical tape would have sufficed to insulate the connectors but either that or one of the battery wires must have failed. I'll build another bypass connector and replace the battery to get back on track. I should also note that the I211 I used was manufactured in 2001. I've never had issues with older motors when ground starting but another important precaution in the future will be to only use fresh Aerotech motors in upper stages or air-start clusters. I think the instant-on nature of Cesaroni motors also lend themselves very well to these air-start configurations.

I wasn't able to take any flight photos but a flyer named Jeremy Rich did snap some and gave me his card. I e-mailed him this morning and look forward to hearing back. I'll post his photos here when I receive them.

Thunder & Lightning mark II

2009-08-27T18:02:00.000-07:00

Several years ago it took me 5 years to build and fly my first PML Thunder & Lightning. I was psyched on the paint job at the time and my amazing and beautiful ex took this photo for me:

Unfortunately I set the upper stage timer for three seconds rather than 0-1 seconds and that beautiful rocket powered into the hard desert dirt at about mach 1 on its maiden flight. That flight also killed my prized AltAcc2A altimeter. Undaunted I lucked out and replaced that altimeter with the 2C version and purchased another T&L kit. While I had this kit lying around for about a year and a half I finally started it and finished the sustainer build and paint in under two weeks. It'll look very much the same as my first build above with one exception: car paint!:

Now that's some gloss!! This was my first and only paint job in the paint booth below before I realized it wasn't going to work and abandoned it. My final option to master car paint will require adequate ventilation in my garage and I'll park my car outside while I paint. The 500th time's the charm right?!
Finally I should note that, while I'm leveraging the original booster, I still have parts to build a second booster for a 3-stage version:

I'm a bit surprised that it remains totally stable without additional modification. That should be a fun flight if/when I attempt it.

Spray booth as dust buster?

2009-08-22T08:06:00.000-07:00

It's seriously frustrating to build something for weeks or months then only to fail on the last step, the paint job, due to dust. I bit the bullet and built a semi-permanent paint booth in a spare area of my house. Fisheye lenses make indoor photography a snap and here's a side view of the booth:

Here's the entrance view:

And here's the lovely view I'll enjoy while spraying fumes:

That fan is very powerful and pulls the 4-mil plastic walls all the way inward with it's high setting. I think it'll remove most of the fumes and overspray particles on its low setting. I plan to try some clear coat as a test this weekend and this setup should nail the problem.

L610 motor build in only 1 minute!

2009-08-20T20:51:00.000-07:00

Clearly this must be a new record:

Man I'm fast! :)

M750 flight APPROVED... Drag race style!

2009-08-19T21:07:00.001-07:00

I completed my altitude prediction report for EM-SEM-FITY on an M750 and our president and range safety officer approved the flight for Plaster Blaster! (click the thumbnail below for a legible JPEG):

Yay. My best prediction is the unweighted average of all the simulations and historic data: 21,333' (4.04 miles!). I tried to post this as a PDF as well as the RockSim file but I'm having way too many FTP issues right now so I give up.

I also shared this packet with Frank Hermes who's also attempting the President's 20K challenge. He had the excellent idea to launch our attempts simultaneously as an M750 drag race. Our club president, Paul Snow, approved this drag race as well! This should prove spectacular and Frank has promised to be a good sport when he loses. :)

4" V2 painted but not quite perfect

2009-08-19T20:51:00.000-07:00

So several entries below you saw below that the white paint applied perfectly, then I masked (and re-masked 3x), then painted the black. Again dust was my enemy outside and the black ended up severely pock-marked. I patched the diffuse color with a black paint pen and, while not perfect, it looks pretty good from this distance:

Next I plan to set up a paint room inside my house (with robust ventilation of course) and I'll apply a clear coat to remedy the specular gloss. It'll probably still be dimpled but the clear coat should dampen the craters and obscure the bronzing of the paint pen patches. I vow to get this right some day!

12,744' FTW!

2009-08-09T11:19:00.000-07:00

[that's "For The Win" not "F*#k The World"]

Yesterday at Lucerne Dry Lake I flew EM-SEM-FITY on a Cesaroni L610-Classic motor to 12,744' and that's a new personal record!:

Here are some flame details (hot day, distant shot means serious convective optical warping):

That motor burns for 8 seconds and the flight was very cool with two exceptions:

I've optimized this rocket for motors of full-M weight so the CG/CP relationship yields a static stability margin of ~1.6 fully loaded. Since the L610 motor is half that weight the static margin shoots up to ~2.1 making the rocket slightly overstable. This caused mild coning on the way up and I lost some altitude as a result.
The drogue ejection charges popped exactly at apogee but the nose cone popped off as well thus dragging out the 7' main 'chute. This was supposed to be a dual-deploy flight so popping the main at over two miles can mean a big walk. And walk I did. I could see the parachute the whole time and found it about 1 mile out across the road. Luckily a fellow flyer named Steve kindly drove out to pick me up otherwise it would have been a long walk back.

Oh and I encountered a highly improbably coincidence yesterday. It took about 2 hours to prep the flight and before I carried it out to the pad I wanted to verify that my radio tracker was working. I turned on the receiver and got two out-of-sync signals. I walked around for a bit and located a flyer named Julian whose transmitter was running on the same frequency! There are roughly 50 transmitter frequencies available so how insane is this? I pulled the battery from my transmitter, Julian successfully recovered his rocket, and kindly pulled his battery shortly thereafter so I could reassemble and resume.

Now for some data... the initial fully loaded weight was 25.3 pounds and length is 94". Here are the flight summary and graph from the ARTS2 altimeter:

And the same for the Parrot 2 altimeter:

The average of the two barometric altitudes is 12,744'. I assumed a CD of 0.45 in RockSim and this predicted an altitude of 14,120' so this represents a large error. I attribute this both to the overstable coning I mentioned above as well as a guessed CD. If I iterate on CD in RockSim to match the average altitude I get 0.57. If I then re-run the M750 simulation with this CD I get 20,147' which is well below the San Diego club's 25,000' FAA waiver. More on this in my next blog entry.

Car paint + dust + wind = FAIL!

2009-08-07T20:23:00.000-07:00

OK so you can't really tell in this photo but the booster has a large number of crater repellencies that I've narrowed down to a serious dust concentration in the air:

This was my second attempt to get it right and, while it's better than the first, there will be a third to nail it. Anyway the finish is very close to final from a coefficient of drag perspective so it will yield good data tomorrow.

P.S. I'm normally a much more rigorous photographer and post-production guy but I need to start packing...

Electronics bay, sled, and layout

2009-08-04T22:16:00.000-07:00

I'm really very happy with the final electronics bay. Again Jack Garabaldi provided these fine components and the results exceeded my expectations. Here are the top and bottom of the sled sandwiched between the two plywood/composite caps for illustration purposes:

On the top-most image at top right is a Featherweight Parrot 2 altimeter. This is an unbelievably capable device and this will be the first time I've used it. On the lower left is my trusty ARTS2 altimeter and there are three total 9V battery mounts as well.

I should also note that I had a design epiphany during a meeting this morning... I always struggle with the best way to mount external switches to arm the electronics in a vertical position. Every hole you drill or slot you cut has the potential to weaken the structure under potentially tremendous flight forces.

Both altimeters use barometric sensors to determine altitude over the course of the flight and descent. Therefore you must drill a static port (hole) to allow access to external pressure. I calculated that I needed a single 1/4" diameter hole to ventilate the bay. I then carefully mounted the screw switch for the ARTS2 at top center of the sled aligned with that static port. I also positioned the side-mounted arming button for the Parrot 2 right next to the screw switch (mostly obscured in the photo). Now all I need to do is place a skinny screwdriver into the static port, screw the switch down to turn on the ARTS2, and then track right to push the button on the Parrot2 and arm that device. Nice!! One hole serves three purposes. Heh heh. And I have no external switches or extra weak spots!! Ist fantastisch!

Finally I wanted to strengthen the thin plywood caps so I simply laid out two circles of carbon fiber/Kevlar fabric on polyethylene film, saturated them with 15 minute West Systems epoxy, placed the caps on the fabric discs, overlaid another layer of polyethylene, and placed a 10 pound weight on top. Once cured I end up with a super smooth, glossy composite reinforcement on each cap:

Build/paint progress and simulation refinements

2009-08-04T21:53:00.000-07:00

I've made quite a bit of progress on EM-SEM-FITY in the last few days. I applied car primer to the booster section and found a few more rough areas. I allowed this to dry then sanded down the remaining asperities. Tonight I applied the final coat of primer and that's drying now. Tomorrow I'll spray the booster and part of the nose cone glossy white and allow them to dry/cure overnight. Then on Thursday I'll apply the vinyl decal and at least one layer of clear coat to seal the decal and maximize gloss overall.

Now rewinding back to last night I fully assembled the rocket including an M1939 reload to determine an optimal amount of nose weight to yield a static stability margin of 1.65. This turned out to be 25 oz of led and epoxy in the nose tip. I butted the nose cone against the wall as the center of pressure and center of gravity are measured and reported from the nose tip. The wall makes it easier to use a tape measure:

Here's the technique I've always used to determine the amount of lead shot required for good stability. This allows easy addition of shot to the bag and the position provides and accurate static moment:

In addition to ensuring an optimal amount of nose weight I also recorded center of gravity and overall mass measurements that allowed me to further refine my RockSim design and simulations. That program does a pretty good job of calculating starting points for component mass and center of gravity but you really need to override both with measured values to generate the best simulations.

Here I've built a bulkhead for the nose cone, fit it into the shoulder, and applied 15 minute West Systems epoxy thickened with colloidal silica. This increases viscosity and prevents the epoxy from running down gaps around the disc while curing:

Tomorrow I'll add a single wrap of carbon fiber/epoxy to the inside of the shoulder to strengthen it and render the bulkhead impossible to extract.

Coefficient-Of-Drag-Tard

2009-08-04T21:16:00.000-07:00

Ya learn something new every single day... Jack Garabaldi of What's Up Hobbies informed me of a feature of my ARTS2 altimeter that I didn't even know about. After a flight you download the accelerometer data to your computer and enter pertinent flight info (initial weight, size, etc). The program will then provide a motor analysis (letter class and average thrust)(I knew about this feature) but also calculates a coefficient of drag (CD). This coefficient ranks among the most influential unknowns in flight simulations. The good news is that it remains roughly constant as long as the structure and finish of the rocket stay fixed. In summary a single flight in the regime of target speeds will yield a CD that you can use to vastly improve future flight simulations in RockSim 9. I was floored when I performed the following post-analysis of my successful level 3 flight:

The original, optimistic RockSim 8 simulation was roughly 6,100' on an M2030 motor.
The actual, average barometric altitude of the two altimeters was 5,257' (ARTS2 = 5113, AltACC2C = 5400). This is 14% lower than the simulation.
I re-loaded the ARTS2 data into the Data Analyzer v1.6 program and ran the CD analysis. The data is noisy but the visual high average CD is roughly 0.44.
I took this actual CD and plugged it into the original RockSim design and the revised simulation is 5,215'!! That reduces the error to 0.7%. Damn. That's some predictive power.

Here's the calculated CD as a function of mach number (speed):

This, in combination with predominantly constructive feedback from The Rocketry Forum, has convinced me to pre-fly EM-SEM-FITY on either an L610 or L952 this next weekend at Lucerne. After this flight I can then calculate an actual CD and provide an excellent prediction of altitude for the actual M750 flight at Plaster Blaster.

This will be required as the range safety officer (RSO) is concerned that I'll exceed the club's standing 25,000' FAA waiver with an M750. If I preliminarily assume a CD of 0.45 for EM-SEM-FITY RockSim predicts a peak altitude of 22,087'. My research turned up only one flight with an M750 that attained 26,000 feet at Black Rock (Jack also provided this data point). I've found only four other historic altitudes all below 23,000'.

If my justification still cuts it too close to the waiver then I'll take a step down in motor size. Right now I'm looking at the Cesaroni M1060 but that sims to only 19,443' so that's not likely to exceed 20,000' which is the reason I'm doing all this in the first place. Fingers crossed...

My blog is like watching primer dry

2009-07-29T21:51:00.000-07:00

Finishing is becoming easier and more rewarding so I continue to muddle through but this remains my least favorite phase. I wanted to share the final approach to booster section greatness with some pics, info, and time stats:

Since I used only gravity on the fin reinforcement (no vacuum or shrink tape) I did my best to squeegee out the excess resin to optimize weight/strength. The resultant texture was very pronounced and 10^6 coats of primer never would have filled it. Instead I used the miraculous SuperFil to fill and obscure that fabric texture as well as ramping the motor retainer lip down.

Mixing/application time: 45 minutes

Curing time: overnight

Here I've just applied the two heavy coats of UV Smooth Prime:

Mixing/application time: 60 minutes

Drying time: overnight

This is my new favorite trick from Dave Triano... spray a light guide coat of matte black paint, let dry, and start sanding. This pre-coat takes no time to apply and dry and it's easily the best way to ensure your final sanded area is completely uniform. It also shows gaps that require subsequent SuperFil. Buy those ShadowAero videos right now!!

Sanding time: 90 minutes (even with 60 and 80 grit sandpaper dammit!)

The very smooth, uniform sanded result:

I applied yet another ramping layer of SuperFil to transition/smooth out that motor retainer lip. I also found some areas with pits too deep for primer and filled those too.

Mixing/application time: 20 minutes

Curing time: overnight

Here are the final two heavy layers of UV Smooth Prime

Mixing/application time: 40 minutes

Drying time: overnight

I'll be sanding that off tomorrow and vibrating my hand nerves so they'll be numb for hours afterward. Seriously... can I hire someone to sand for me? Anyone? It'll pay better than minimum wage.

I should also note that, if you're using car primer and paint, there's literally no need to use finer than about 80 grit sandpaper. In fact it's obvious that the resultant grooves improve paint adhesion and Napa's single-stage paint film is still astonishingly glossy. I'll probably apply a couple of layers of clear coat as well once the vinyl lettering is on.

The mask of... V2

2009-07-27T21:52:00.000-07:00

Best masking job I've ever done...

I should note that I found a masking mistake as a result of shooting this photo. It's fixed now and all we need is black car paint.

Bonus: for the ULTRA observant you might have noticed that my masking job is mirrored from the yellow/black paint guide image in the previous post. This was indeed intentional as I wanted to paint over a small tube defect near the top and mirroring was the only way to achieve this.

Bonus #2: I realized I made yet ANOTHER mistake on the nose cone!! The wrong two regions are masked so I'll switch those. In retrospect I suck at masking.

First successful car paint sesh

2009-07-25T10:50:00.000-07:00

Last weekend I'd posted pix of the priming session. Well that primer was ready to sand in 2 hrs so I did. I then enthusiastically proceeded to apply paint and here are the results:

I'm very pleased with the outcome this time although there's still room for improvement:

I left the primed V2 (white rocket) booster outside drying for awhile. I should have then cleaned off the dust before applying the white paint and that would have eliminated the repellencies you can still see up close.
Also the metallic purple Vertical Assault still shows some pinholes in the fiberglassed surface. This paint is thick and coalesces/covers well but not for pinholes. As such I'm paying extra attention to the EM-SEM-FITY exterior finish with filler and primer prior to car primer and paint.
Finally I erred on the side of less paint overall to reduce the chances of ugly drips forming. As a result there's a low amplitude, low frequency ripple on the surface of the purple Vertical Assault. This isn't a big deal and I'll probably be a bit more aggressive in wetting out the paint evenly on my next attempt.

I've also decided to paint the little V2 authentically:

...although mine will be white where the yellow is. In searching for this paint scheme I also came across a logo that was used in the WWII days called "Frau Im Mond" which I think translates to "woman in the moon":

I really like this logo 'cause I'm a perv so I'm either going to render the moon, stars, and rocket in 3D and superimpose a picture of a real girl or ask my friend to try to paint that logo. Either way I'll print it out on adhesive white film and spray clear coat over the whole rocket as the final step. Should be cool.

StickerShock23.com rocks!

2009-07-24T21:47:00.000-07:00

The consensus was that the all caps version of the logo won. I contacted StickerShock23.com and Mark quickly replied with a mock-up and a quote. I had mentioned the font in my quote inquiry and Mark cleverly downloaded the font, fed it into his CAD cutter software, and exported a JPEG preview for me. I paid via PayPal and the vinyl lettering arrived two days later:

The price was a bargain and I can't recommend Mark's services highly enough! Cheers to another custom build soon so I can design and order a new logo.

Big automotive primer session

2009-07-19T14:51:00.000-07:00

After two previously failed car paint attempts the stars finally aligned today. I had queued up six parts that had been sanded and ready to spray prime with Martin Senour Crossfire primer. I carefully sprayed each part with their cleaner, wiped each down, and allowed all to dry. I then sprayed their plastic adhesion promoter on one PE nose cone and a fin can to ensure a good bond. Here's my spray setup on my upper deck outside having just finished all six parts:

It turns out that I WAY overestimated the amount of primer I'd need so I ended up wasting about half. Good thing it's only $40/quart... dumb ass. :( Here are four of the parts are drying:

I probably shouldn't be allowing these isocyanate-cured parts to dry near my kitchen but ya can't live forever. Also I can't praise my respirator sufficiently! I can't even smell a hint of acetone while I'm wearing that thing.

This just in...

2009-07-19T11:25:00.000-07:00

The entire phenolic/plywood/carbon fiber/Kevlar/motor retainer booster section weighs only 4 pounds!! [G's jaw drops] Now it's into the curing oven for a one hour of post-cure on the fin layups:

Progress galore

2009-07-18T14:44:00.000-07:00

Alright so I masked off the fins and applied the black high-temp epoxy fillets:

I had a scare while preparing the epoxy. It's approaching its shelf life of 6 months and the curative is yellowing. According to Dave Triano the resin:curative ratio is critical so he provides the former in a white cup and the latter in a syringe. I began to squeeze the syringe into the cup but the plunger stuck then slipped and splashed a bunch out onto my work space. I'm grateful that it splashed back and not into my eyes! Always wear goggles, kiddies. Since the system was aging I guessed the failure mechanism would be unintended polymerization so I chose to roll the dice and assume the ratio would work. This expensive 500F Tg resin appears to have cured correctly as the Kevlar pulp-augmented fillets seem incredibly strong.
I then cut a piece of Kevlar/carbon fiber hybrid fabric to just fit inside the perimeter of each fin and bridge the body tube. I also cut a slighly larger piece of 6 oz carbon fiber cloth to extend just beyond the first piece. I mixed up a 50g batch of Aeropoxy and added a bit of colloidal silica to prevent it from running down the fins as it cured. I also added 3 wt. % white epoxy-compatible pigment as a visibility aid. Here's the third pair of fabric layers laid up and curing:

Once I finish the fourth fin pair surface I'll post-cure in my oven to maximize strength and temperature resistance. Then begins the fun process of filling, priming, sanding, priming, and painting. Wish me luck.

Ist eine Rakaten fantastisch!

2009-07-12T13:49:00.000-07:00

Sorry I was channeling Brüno for a moment there... So I pieced the beast together and it's looking just as I'd hoped it would:

The metal-tipped, filament-wound carbon fiber nose cone doesn't quite fit yet and, since it's the single most expensive part, I plan to finish that fitting last. I love the high aspect ratio and carbon fiber reinforcement allows me that luxury for an M-powered rocket. I also wanted to share a macro-ish shot of how thin the CF wall is on the exterior of the phenolic:

Three wraps of carbon fiber is only ~2/3 the thickness of the original phenolic wall! Very thin. Very strong.

EM-SEM-FITY fin attach

2009-07-12T12:54:00.000-07:00

For months now I'd planned to reinforce the 1/4" fins with at least one fascia layer of carbon fiber/epoxy prior to attaching them to the booster. I mentally devised several layup scenarios ranging from vacuum bagging individual fins through stacking all four, stratified, and curing simultaneously under a 10 lb weight. In the end I decided the risk was too high for pre-reinforcement and reverted to what I know -- bonding plywood fins to the tube then post-reinforcing. This results in a less optimal resin:reinforcement ratio but oh well... this thing is already extremely lightweight!! I started by laying out the fin positioning guides in Illustrator:

I then printed this on a 13x19" sheet of HP Advanced Photo Paper using my HP B9180 printer. I cut the two guide patterns out using a sharp X-Acto knife and set the freed inner areas aside leaving inset guide patterns in the larger sheet. I laid these guides on a piece of 3/16" foam core, traced them, and again cut the inner pattern leaving these two 12x12" fin alignment guides:

I then test fit the four pre-sanded fins with these two guides on the booster tube:

All parts fit perfectly so I then marked a single, silver line for the first datum fin. The purpose of this first fin is to prevent unintended rotation of the two guides relative to each other for the three remaining fins. I applied JB Weld Kwik to three points on this first fin and ensured it was perfecly aligned along the silver guideline:

JB Weld Kwik sets in 4 mins but I let this first attachment cure for 45 mins before doing the same for the other three fins (one at a time with ~10 mins in between). The final fin is curing now and I'll pull the guides off and cheer. Next comes the ultra-high-temp black epoxy as key fin attachment and fillet material.

M750 = Em-Sem-Fity or EM-SEM-FITY!?

2009-07-05T19:16:00.000-07:00

I've decided to channel my rap alter-ego and name the as-yet-to-be-named-vessel-under-construction "Em-Sem-Fity" or "M750" as 50 Cent would utter it. Which logo do you prefer: mixed or all caps?:

You can vote via comment below. And please do.

Success on the most expensive part yet

2009-07-03T10:34:00.000-07:00

I'm, like, sorta happy... or something! I test peeled some of the film this morning and the part had obviously cured. When I cut the Mylar™ film free it popped right off exposing a virtually perfect surface! There are still some surface voids in the resin but far fewer than when I first cured the part in the oven on previous failures. The blue peel ply is still intact here and the motor retainer is at bottom:

I decided to peel the blue fabric off before post-curing the part in my convection oven. Once you get it started it peels easily and leaves a very rough surface for bonding high-strength, high-temperature fins:

Now it's into the oven for an hour...

M750 build progress

2009-07-03T06:21:00.001-07:00

Can ya tell it's a holiday weekend and I'm fired up?! Happy early Independence Day by the way, my vast readership.

Last week I used JB Weld to bond the 98mm Slimline motor retainer to the end of the 48" long booster section and this worked well. I should also note that it took me roughly 20 minutes to grind off the lip several months ago using a griding wheel. This is some seriously hardened aluminum!

Last night I got a second wind at about 8:30PM and, over the course of three hours I:

Pre-cut all materials: 48x37.5" piece of carbon fiber cloth, 48x16" piece of waxed/buffed 14 mil Mylar™ film, and 17x13" piece of release fabric for the exterior of the fin section.
Correctly mixed up a 180g batch of Aeropoxy
Laid up three wraps of 6 oz carbon fiber on the exterior of the booster section forward of the motor retainer.
Applied the blue, coated 17" release fabric directly north of the motor retainer lip. When removed this fabric leaves a perfectly rough surface for subsequent bonding of the fins.
Wrapped the Mylar™ film around the part and applied many individual pieces of gaffer's tape to hold it in place. I employed a great deal of tension on each piece so this should be a smooth surface.
Spiral-wrapped the exterior with 2.5" wide heat shrink tape and secured the ends with gaffer's tape.
Placed this final part into my curing oven for only 15 minutes. I was trying to get the tape to shrink a bit and to kick off the epoxy's polymerization. I then moved this part back into my garage to finish its cure cycle overnight.

I checked the part this morning and it looks good through the films but no resin has squeezed out:

As such I'm guessing the aesthetics will rock on this part but the resin:reinforcement ratio will be much higher than desired. This will add weight but I can say that this sustainer section still feels comparatively light to me. I'll post pictures later today and then pop the excavated part in the curing oven for an hour to post-cure it.

Finally I also filled the surface-challenged payload section with SuperFil filler. That is some great stuff. I'll rough up the surface with some coarse grit sandpaper then apply two coats of UV Smooth Prime at some point this weekend:

Continuing composite saga

2009-07-03T05:53:00.000-07:00

OK so I've worked in chemical engineering-related R&D for almost 15 years now. As such I can attest to the fact that, when you're pushing the limits of your personal or collective knowledge, things can fail.

My most recent rocket science failure stemmed from a) the hasty use of b) a handy resin ratio spreadsheet I cooked up for some odd materials. For those of you who have used two part systems like epoxy you'll know that most employ simple ratios like 4 parts resin to 1 part hardener or the even more common 1:1 ratio.

Well Dave Triano teaches that "UV Smooth Prime" is the best possible filler and primer for rocketry use and I agree. I calculated its "resin":hardner ratio to be ~79:1. Gee that's easy. Similarly Dave recommends Aeropoxy as the resin system of choice for rocketry composite material lay-ups. It's ratio is exactly 100:27. So, as I prefer to tailor each material batch size to fit the job, I assembled a table to get those odd ratios right:

This table has proven invaluable to me this year. However when you're rushed and throw together a batch of Aeropoxy to test a new part design and refer to the first block of columns, UV Smooth Prime, you're ratio will be WAY off!! And how the hell did I not notice the ridiculous imbalance of otherwise familiar Aeropoxy components?!

The result of this error was that my vacuum-cured, carbon fiber-faced fin never cured and all the gelled monomer selectively sucked into the breather/bleeder fabric. Sadly I'd also used the excess resin to bond the reinforced coupler into my M750 rocket's payload section. All this did was wet both parts with monomer. Good thing this only affected about 7 previous hours of work on the constituent parts!! :(

Yesterday I stopped moping, manned up, scrapped the fin, and cleaned the payload/coupler up with acetone. I got the latter clean enough that I was able to properly bond the other ends of each part and all is well again. Lesson learned: think before you pour!!

Layup... FAIL!! Then success!

2009-04-28T21:28:00.001-07:00

Alright so I completed my layup as planned below. Again the Mylar stuck preferentially to roughly 50% of the cured surface. It took me 3+ hours (no exaggeration) to peel/cut/scrape/wedge the film off the part. Note the voids, scrapes, and residue:Having failed to release the film cleanly with all three methods to date I contacted Dave Triano and here's his reply:

"Are you oven curing this laminate right off the bat? If you have 'pre-heated' the oven (not good, you should plug it in when you insert the part), and leave it in too long (over 1 hour, or too hot), the laminate will stick as you describe. Try just allowing the laminate to cure at room temp overnight, then remove the mylar, then post cure the laminate."

I was confused by this reply since it seemingly contradicts the advice in Dave's videos and instructions. Perhaps I'd missed something. In any event I laid up another test part last night with only a single layer of Teflon release on the Mylar and... it worked perfectly! While I'm elated to now fully understand the recipe I'm a bit bummed that I can no longer cure parts in an hour. :( I wanted to share his feedback in case others were frustrated as I was. On a side note that's a single wrap of Carbon/Kevlar hybrid fabric on a 38mm cardboard tube with the glassine layer peeled off and... it's insanely strong! I'll reiterate: 1 wrap over cardboard tube!! It would likely survive aJ570. Composites frickin' rock.

M750 payload section layup

2009-04-19T15:25:00.000-07:00

I had purchased two 48" lengths of 98mm cardboard tubing for the M750 rocket below. However design stuff nags me in my sleep and lucid dreams so, instead, I purchased much stronger phenolic tubing from Public Missiles Ltd. just to be sure. The added weight will probably cost me margin for the 20,000' goal but I eventually plan to fly it on much more punchy motors so... oh well.

Today I cut the payload tube to 26" and laid up three wraps of 5.6 oz. carbon fiber cloth with excess resin. This time I mostly painted the epoxy on axially rather than radially so the fibers should be much straighter than my first two attempts. I also applied two coats/buffs of carnauba wax to the Mylar™ film this time to lower its surface energy and mitigate/prevent stickage to the cured Aeropoxy. My curing oven has been cooling down since about 1PM so I'm gonna pull the part soon (nice asymptotic cooling!). I'm hoping that it's light, smooth, and devoid of voids.

April launch report

2009-04-05T13:36:00.000-07:00

Yesterday was the April Plaster City Launch. Again the weather was almost perfect so that makes three months in a row for San Diego now! Coincidentally both the March and April launches were preceded with excessive wind gusting to 35+ MPH the Friday before. Then as of Saturday morning calm to mild gusts all day. Great success!

This month I only had three flights due to setup complexity and the fact that our FAA waiver closed between 1:30-2:30PM for local flight maneuvers:

Minimum-diameter, carbon fiber "Fity-Fo" on a brutal J800 -
this was the first flight for my custom design and it was just supposed to a) verify the strength of the carbon exterior and b) test the radio tracking system mentioned below. After the incredibly fast and straight ascent we could see that the 36" green 'chute had ejected at apogee. This means that dual-deploy hadn't worked and I'm guessing that the nose cone popped off during drogue ejection. I'll need to friction-fit that better next time. The rocket touched down very close to the launch site so the radio tracker wasn't necessary but it was good to practice with that system anyway. When my buddy Doug's son Brandon picked up the rocket the ARTS2 altimeter beeped out 12,235'!! I later downloaded the data and the exact barometric altitude was 12,012' (2.23 miles) and max speed was 1162.7 ft/sec (mach 1.02). I had just smoked my personal altitude record of 8,079' so I was happy. Having just read this unofficial compendium of altitude records (Word format here) by motor type I recalled that the J800 motor checked in at ~8,100' so I might have a record here. In any event I plan to register this as my 10K altitude flight with Extreme Rocketry magazine. [Update: Rick Saunders accepted this as a record on that site. I also checked it in as my 10K+ flight with Extreme Rocketry.]
Then I flew my primed yet not yet painted 4" V2 on a 54mm I229 Blue Thunder motor. Very punchy and cool. I synthesized this FAKE composite image from two separate frames (one of the boys reacting and a second of liftoff) because it amuses me to do so:
Finally I'd planned to fly a K270 in the carbon fiber Fity-Fo above. However as I assembled everything I realized that there wasn't enough room to fit the recovery system because the motor was too long!! I'm convinced that combination would have topped 16,000' but I had to move to plan B. I prepped the 3" Vertical Assault for the K270 and included the radio tracker since the previous flight on a K185 hit 7,076' (below) and this motor is roughly 33% bigger. The ascent was rapid and impressive but nobody saw anything after burnout. I could tell that the transmitter had ejected because the signal pulse jumped in intensity. I audibly tracked that which I could not see for roughly 3 mins and then then the signal seemed to cut off. I experienced some panic here until I fiddled with the controls and again the pulse resumed. I meandered out into the desert for a mile or so and found the rocket between two bushes. Unfortunately the main parachute had not ejected so the exterior was a total write off. I did recover the motor casing, altimeter, radio tracker, and some internal parts however. I should also note that I NEVER would have found this rocket without the tracker. Those transmitters are a bargain at $95 and the club offers the free use of a receiver. Highly recommended equipment! The altimeter was beeping an error tone having collided with the ground so hard. I was able to download the data and was astonished at both the altitude of 11,485' and speed of 978 fps (mach 0.86). That's a slower burn motor in a 12 pound rocket so those stats are impressive:

Here's the state of the remnants (note the car paint job on the top portion):

I just ordered a replacement Vertical Assault but without the pre-fiberglassing this time and I requested that they not cut the slots for the fin can. I plan to carbon fiber the exterior myself in the hope that this second version will last much longer.

Belated March launch updates

2009-04-05T13:22:00.001-07:00

The March Plaster City launch featured amazing, wind-free flying. I must say that this is the first year of many when the stars have aligned to allow confident flying so I'm going as often as I can. I had four flights that day:

Vertical Assault 3" on a K185 - 7,076' with successful dual-deployment recovery using the ARTS2 altimeter.
Talon 2" on a Redline H210 - altitude unknown with higher altitude direction shift and successful recovery.
Bullet 4" on Redline I285 - altitude known with early ejection causing zipper. Nosecone lawn-darted but, surprisingly, remained intact.
Jayhawk 5.5" on a J415 - perfect and impressive flight with ejection exactly at apogee (10 second delay is ideal in this warmer weather). I also swapped out the 7' parachute for a 10' so there was no canard fin damage unlike the first flight.

I was busy flying all day so I didn't shoot any photos of my stuff. However, as I was about to leave at dusk, Ken Sparks flew an M1850 motor in an 18' tall rocket. Both flight and recovery were perfect. You can see most of my photos in this album.

Electronics inventory update

2009-04-05T12:36:00.000-07:00

Dok and Kurt encouraged me to build experience with varied electronics packages. As such I've been stocking up. At the time of my L3 cert I was using:

Ozark Aerospace ARTS2 altimeter
BlackSky AltACC 2C altimeter (BlackSky is now defunct but here's a review on this page)
Missleworks PET2 timer
Xavien Timer 2 (obsolete?)

Since then I've added:

G-Wiz LCX altimeter
Featherweight Parrot 2 altimeter
a radio beacon transmitter

And plan to rev them up this flying season. Also, while not electronic, I purchased a Defy Gravity tether to enable dual deploy recovery from a single internal volume. Very cool. I'll keep you posted on my progress with these new devices.

First carbon fiber tube wrap

2009-03-18T17:28:00.000-07:00

Last night I finally mustered the energy to lay up my first carbon fiber tube. In this case I reinforced a partially built booster for a 54mm minimum diameter craft. I roughed up the phenolic tube to better take the resin, followed Dave Triano's layup schedule to the letter, and ended up with the following structure:

In this oblique shot you can just see the heat shrink tape spiral:

Finally I placed this structure in my curing oven and let it sit for 90 mins:

Here's a close-up of the cured result:

Most of the structure is smooth but I picked a varied area for the blog. The Mylar film I used to smooth out the cured surface was not treated with a release layer. As a result some spots of higher surface energy didn't want to release the film so I've got some point defects to deal with (white flecks). Also, despite saturating the structure with resin, there are still some voids down to the fabric. I'm thinking I'll fill, prime, and paint the booster fully and hopefully the payload section will turn out better. I can then leave the beautiful carbon fabric appearance on this upper section. Overall I'm very pleased with this first effort.

I'll reiterate here that Dave Triano is my hero 'cause he chooses to share his wealth of composite material knowledge with the high-power rocketry community. Thanks, Dave! Please consider buying his videos.

Vacuum-bagged fin half

2009-03-17T22:53:00.000-07:00

I was supposed to provide an update on my fin layup weeks ago. Well I finally cut it out and here's the result:

You can see that the perforated film drew too much resin out so the texture undulates rather than being smooth. You'll also notice the slight profile near the edges so that pretty much worked. I'm not sure I'm going to continue with this design.