Sunday, September 13, 2009

Lucerne launch report, 9/12/09

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.