Sunday, April 5, 2009

April launch report

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.

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