Sunday, October 12, 2014

Der Red Mix mark II Skidfest at ROCTober 2014

After talking it up for over a year I finally flew my scratch-built Der Red Mix mark II on a full complement of seven burly Skidmark motors (as always switching to 720p in full-screen mode is the shit):

A formidable liftoff featuring loud, flaming titanium granules:

And notably angled ascent:

I arrived at the lake bed later than I'd have preferred but the conditions were perfect all day with light, intermittent wind and perfectly clear skies.  I had prepped all the electronics two months ago so I only needed to load up the seven Skidmark motors, set up the CD3 ejection system, mount the Flip Mino camera inside, and button everything up.  Upon checking in with the RSO he seemed confident in my design and flight plan but cautioned that the far pads were angled away from the spectators.  He specifically asked me not to adjust the rail to a more vertical orientation (and that's some foreshadowing).  Kurt Gugisberg was out at the pads and helped me to get the 30.5 pound rocket loaded up on the rail.  I powered up the two Ravens, installed the air-start igniters, started the Flip camera, closed the electronics bay door, installed the central motor ignitor, and was ready to go.
     The ignition of the central CTI 2010K675 was instantaneous as expected and, at a 7.3:1 thrust-to-weight ratio, the ascent was expeditious.  Now normally I would have set the launch angle at 1-2 degrees from vertical because this rocket is incredibly stable and there was no wind.  Instead the angle I was asked not to change was closer to 4-5 degrees from vertical so the angle you see it the picture above is real.  The one second air-start gaps I programmed into the altimeters seemed a bit long but the sequential pairs of 543I297, 258H180, and 176H123 Skidmarks otherwise popped as expected.  By the time the H123 pair fired the rocket appeared to be approaching a horizontal flight path but, in reviewing the onboard video above, that was mostly an optical illusion.  From the ground it also appeared that the ejection was 3-4 seconds too late but the video once again proves that wrong and the 'chute popped right at apogee.  Unfortunately the initial launch angle essentially lobbed the rocket on an arc rather than straight up so that extra velocity at apogee served to zipper the top of my rocket rather severely.  I can repair it but, from now on, I'm trusting myself to set the optimal launch angle. Once again DRMII stuck the landing:

Here's the zipper damage from the energetic ejection (Grrr...):

And here's the interesting thrust curve showing acceleration surges from the four motor phases in red on the left of the graph:

The altitudes from the Raven 2 (tabular, graph) and Raven 3 (tabular, graph) only differ by 10 feet (!) and average to 4,483 feet above ground level.
     So I'll repair the damage, shorten the air-start delays to 0.1-0.5 seconds, and fly DRMII again soon with a K815 Skidmark in the center. I'm not yet sure of the outboard motors but they'll likely max out the motor tube lengths.  Thanks for reading!

Back in it on the Lucerne tip

I'm sad to report that I hadn't burned a single molecule of ammonium perchlorate since November 2013.  Many factors including the FAA arbitrarily denying the SD club's waiver renewal (after 10 year of continuous good will), the struggle to find a new launch site, excessive heat, and Saturday timing issues forced my protracted break.  I finally attended Lucerne's September launch and lobbed two sport flights into the blue:

2.5" Madcow Nike Smoke on CTI 286H100 Imax

Dark Star Lite on CTI 93G80 Skidmark

No you're not passing out after viewing that second shot...  I just wanted to share that, after 14 year of rigorous photographic training, I remain focus-challenged.  :)

Saturday, March 8, 2014

Quadcopter amazingness

With the cancellation of the Lucerne launch due to water on the lakebed I just realized I haven't flown since Plaster Blaster in November '13!!  That's a bummer, man.  I'm not slacking, however, and just took receipt of an amazing DJI Phantom I RC quadcopter with GoPro Hero camera mount:
I flew it in my local park yesterday and, despite my lack of RC experience, I don't think I did too badly although this is designed to fly very easily (watch in full-screen, 1080p HD and stoke out!): I'll definitely be shooting liftoffs from above with that combination if only I could find a high-power rocket launch...

Sunday, January 5, 2014

Welcome to 2014!!

I tried to employ a bit programming fun and entitle this entry "Welcome to 2013++" but the increment operator is apparently not blogger-friendly so there it is in quotes.
     I want to provide a quick launch update as things have been/are getting kinda weird hence the sparse blogging on my part:
  • December Plaster City was blown out on Saturday for the first time in a year.
  • After a decade of flying at Plaster City we lost our FAA waiver for that chunk of land on January 1 due to reevaluation of the airspace.  The club is working with the FAA to identify a new site but, until that time, it's model rockets only at least for Jan/Feb so I'm planning to attend Lucerne only in the interim.
  • I'm hoping to attend Lucerne on 1/11 but a post-work conflict might prevent that.  
  • Grrrrr...
  • So February in Lucerne then?
Thanks again to my loyal readership and cheers to an amazing 2014!

Leveraging RC electronics for active vertical stabilization

I just found this on Rocketry Forum and this budding rocket scientist, Alyssa Stenberg, has become my new heroine!

At some point in the last decade I'm certain I read that active guidance was disallowed for hobby/high-power rocketry.  I cannot find that/those rule(s) now, at least for Tripoli, so perhaps the prohibition has been lifted?  I just skimmed my Tripoli rules from 2001 and could only find in the Prohibited Activities section: "The use of a high power rocket or high power rocket motor as a weapon against a target."
     In any event I've never understood why the rule [I thought I read] seemed to categorically disallow active guidance.  I realize such steering could be used by malefactors for bad things but Alyssa's 2D active guidance is clearly intended to improve the safety of the flight. I hope her work and excellent presentation open the door to additional research to actively maintain flight perpendicular to Earth. Bonus: This Guardian controller from Eagle Tree Systems is only $75. One needs to buy a slew of other hardware and electronics to enable such a system but that seems cheap for such a controller.
     After watching Alyssa's presentation several things occurred to me:
  1. When set to 3D mode and using one servo per fin one could also actively counter roll in addition to pitch and yaw.
  2. It might prove worthwhile to enable some sort of inhibition system to prevent post-apogee servo thrash unless...
  3. Leaving it active could reduce drift by actively steering the rocket against the wind under parachute.  I think one might need to invert the servo responses post-apogee, however, depending on the fin/gimbal/recovery configuration.
Rawkit syence is good eats!  

Sunday, November 10, 2013

Plaster Blaster 2013 for the win!

What an amazing weekend with perfect weather and record attendance at Plaster Blaster!  I was grateful that my parents trekked from Cochise, AZ and they were the icing on the desert cake.  Let's jump right in shall we? (I recommend this full-browser 720p HD link for best results or lazily click below for a suboptimal experience :)

I love our digital age but, until yesterday, I hated even nonlinear video editing.  I thought I was better at the legacy Final Cut Pro 7 than I really was and it turns out, after 11 intensive hours of training and practice in its successor FCP X, that I now sort of know what I'm doing! The above video edit took only about an hour this morning including compression and upload and I especially love the frame-hold pauses in the retime segment.  Now onto the launch...
     Here are Roy and me after the load-up but before the 'misfire' cause by my failure to even hook up the leads AND not asking someone to push the button for me!  Duh.  I blame it on my lack of practice since May:

The CTI Pro75/6GXL 9977M2245 Imax is a new fave!  Damn that thing was aggressive:

Some observations:
  • For the first time all the photos, video, altimeter and GPS data turned out perfectly!  Hundredth time's the charm.
  • For the second flight in a row I'm getting about 0.75 seconds of pressure up time with this CuO/Mg thermite recipe.  I think I might use half an igniter cap next time and see if I can shorten that latency without risking overpressure.  Note the wicked smoke pattern as the M2245 fires up:
  • I think mach 1.7 (1,323MPH) is the greatest speed I've yet recorded.  In the video you probably noticed black bits of Gorilla Tape melting off after the speed of sound was passed.  Here's the result but the video still seems rock solid to me and the camera's fine:
  • Gerald Meux, Tripoli overachiever and super nice fella, kindly shared his full-res shots of the ascent (among many other shots of the weekend).  Who doesn't enjoy a nice rocket up-skirt?
  • Yay, drogue eject just before apogee!!  After last month's dreadful 5 second latency after apogee I contacted Adrian Adamson at Featherweight Altimeters.  He emphasized that everyone should be using barometric ejection at apogee on all Ravens.  I had been trying to soften the apogee forces by ejecting when the rocket passed below 20 ft/s but Adrian noted that I would have had to "game the system" and set the Raven 3 for less than 164 ft/s for that to work.  In any event I'm setting all my Ravens to baro at apogee and never looking back.
My recovery distance used to average a one mile radius.  That seems to have increased to 1.3 miles as that's the identical distance for two months now even with essentially zero wind:

Roy and I drove to the south edge of the wash (0.5) miles and I walked 0.8 miles there and 0.8 miles back.  I found her safe and sound lodged in a shrubbery:

Max altitude: altimeters = 19,357', altimeters + GPS = 19,705
Max velocity: 1,323 MPH
Max acceleration: 24.9 Gees

(ARTS2: graph, tabular, CD analysis, motor performance (9578M2661))
(Raven:  graph, tabular)
(GPS: ground-level, eye-level with apogee)

On Friday I also flew a CTI 567I125 White in my 2.6" Madcow Nike Smoke.  No photos or data here but that was a fine flight!  Finally I had planned to fly the freshly painted and stickered Der Red Mix mark II (below) but simply ran out of time.  By the time Roy and I got back from retrieving the above flight it was 3PM and I was spent.  DRM II will be my priority at Plaster in December and I hope to get her (him?) flown.
     Congratulations to: -Frank Hermes for his mostly successful, highly complex clustered/staged flight.  -Darrel Kelley for blowing away the President's Challenge with 23,232'.  -Jonathan Cowles for his beautifully successful L3 flight.  Thanks for reading and to all the volunteers who made Plaster Blaster 2013 an awesome event!

Wednesday, October 30, 2013

Wha's over that'a'way?


...designed and built Der Red Mix from scratch a few years back and promptly crashed it according to an otherwise impressive cacophony of errors on my part.

...rebuilt my design as Der Red Mix mark II a fewer number of years back and flew it perfectly well, twice, humbly sheathed only in white primer.

...finally finished DRMmarkII tonight as I'd original envisioned those years back and, conveniently, just in time or Plaster Blaster 2013.  This Saturday, nearer to dusk than dawn, I'll kick her off the ground with a K675 Skidmark, then two I297 Skids, then two I180 Skids, then two H123 Skids all one second apart.  This should prove sparktacular.

So come out this weekend and git ya some!

Saturday, October 26, 2013

Roctober, M2045: "...and when I get to one you push that button!"

It's been several months since I've flown so... feeling blog-rusty.  I attended Roctober at Lucerne Dry Lake on 10/12/13 and let's jump right into my first CTI 7388M2045 Blue Streak flight (as always full-screen 720p titillates best):

Yay, onboard video and perfect weather!  I'm very pleased with the ignition, flight, and data overall but what was with that five second latency after apogee?  I've flown this recovery combination several times now and have never observed such a delay with my trusty ARTS2 and Raven3 250G altimeters. The acceleration numbers from the ARTS2 below look way low so, again, I probably need to retire that thing.   That excessive latency could have been bad news but, luckily, the DarkStar remains a rugged tank and sustained zero damage.  I'll need to check my Raven3 settings again before the CTI 9977M2245 Imax flight at Plaster Blaster next weekend.
    This was, by far, the best Beeline GPS data I've yet seen.  Without any manual adjustment it plotted just like this in Google Earth (the apogee peak is actually 16,463' with the GPS data averaged in):

The other data were quite robust as well and here are the peaks:
  • Altitude avg: 16,463'
    • ARTS2 = 16,359'
    • Raven3 = 16,194'
    • Beeline GPS = 16,836'
  • Velocity avg: 1,178MPH (Mach 1.51)
    • ARTS2 = 1717MPH
    • Raven2 = 1186MPH
  • Acceleration (Raven3): 41 G
    • I'm dropping the ARTS2 here as it reported only 25 G and that's way too low based on my visual assessment of the flight.
There will be a test afterward... ARTS2graph, tabular, CD, motor performance (7583M2597) and Raven3: graph, tabular and Beeline GPSNorth, West, top
Recovery above.  Doesn't really look like 1.3 miles to the flight line does it?

                 (Thanks for the fun photo, ©Lisa Linden!)
Now let's talk ignition...  The GREAT thing is that 8g of stoichiometrically balanced CuO/Mg thermite really did the trick as shown in the video.  Had I used a nozzle cap the motor might have pressured up even more quickly but I don't want to risk overpressure.  I suspect that the reason people occasionally blow motors up with thermite is because they're using nozzle caps.  I'm using thermite because it showers 4500˚F sparks down the core and I'm not nearly as interested in the pressure generated by the combustion so I think I'll continue to leave the cap off.
     The BUMMER is that very few people, myself included, actually saw the pressure-up and liftoff from the ground view and here's why...  Lucerne's standing FAA waiver is 7,500' so my simulated 17,000' needed to be phoned in to extend the waiver temporarily.  In the mean time a little girl had become separated from her guardian(s) and the LCO was trying to entertain her until they were reunited.  There were many people on the range recovering rockets as the LCO tried to keep the little girl happy with: "I tell you what... I'm going to have her launch this rocket [my rocket] so when I count down from 5 to 1 I want you to push this button..."  Now, if you were a young child, how would you have interpreted that instruction?  You guessed it: you'd have pushed the button right when it was pointed out and that's exactly what she did.  I had been running back to my canopy to shoot liftoff photos when I heard "...push that button."  and then a thunderous roar of the M2045 leaping off the ground.  Still running I turned my head to see the motor just burning out and starting its coast.  I'd like to have seen the entire flight but, if I could have chosen any 5 second portion, it would have been pressure-up and liftoff because of the thermite experiment.  It's funny because the RocStock club is so hyper-focused on safety yet, through a series of unfortunate events, an M was launched with no countdown and the range full of folks recovering rockets.  I'm miffed that I missed my $350 flight but, more importantly, isn't it the LCO's responsibility to minimize the probability of such mistakes?  I can empathize with the situation but... shouldn't the arm switch have been off and the LCO's hand over the button just in case?  Moving onward...
     I also flew my cool little 2.5" Madcow Nike Smoke on an 338I180 Skidmark:

And Lisa and I never would have located the goods had she not brought her world-class, trail-blazing, rocket-hunting dogs. :)  For the record Agent, on the left, found it first:

Cheers to an amazing Plaster Blaster next weekend and you should come join us!