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.
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!
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