On July 9th, 2016, we launched another foam glider flight similar to NSL-45. This time, the glider was configured with a wide-angled camera (808 #16 D) with lens extension cable. The lens was mounted half way up the vertical stabilizer. This would give a somewhat boring view of the glider nose and balloon on the way up and then a 'pilots' view on the way down. The 350g glider was balanced to produce a stall during descent. A 600g cell with H2 was used to shoot for a typical 33,500m. The flight was projected to stay close to home; zig-zagging across the county.
It was a clear, calm, hot day. To keep things simple, we set up at Paul L's. home in Apex and launched from the cul-de-sac.
During ascent we saw the expected solar heating, but we were also treated to some large gravity waves between 15-25km. It was a nominal ascent until two minutes before burst; then, for some reason, the camera shutdown. Burst occurred at 33,862m (111,096ft). At this point, the balloon typically unhooks itself from the payload, but on this flight it didn't. During free fall, the glider wrapped itself with the bridle and the bit of balloon neck. This changed the glider's balance. Instead of being tail heavy (slow stalling descent), it became more nose heavy (spiraled down quickly).
The glider came in faster than expected and landed short of projection... in the top of a tall tree (where else?). It was soon set upon by a pair of unhappy birds of prey. They repeatedly dove at the poor glider. Thankfully it ended up being a breezy day and after a couple of hours it blew down.
Note appearance of gravity waves during ascent. Camera shutdown was noted during chase as battery reserves increased.
So what shutdown the camera? This 808 camera and its microSD chip have flown several times before. They have been tested repeatedly, including a recent 6 hour battery run-time test. The camera extension cable is new to this flight. It tested good before and after the flight. I have used extensions before with mixed results -- they are just a bundle of a dozen of unshielded, 30-guage wires with finicky connectors. So that makes the extension the prime suspect in my mind. It was encased in a lot of hot-glue, but not shielded.
Which brings up another point. With the increase in small arduinio-ish systems that we are sending up; how concerned should we be about energetic particles? Not that we are going to shield anything against gamma rays, but this flight was wide open to beta across the board. Could a scrap of aluminum foil have made a difference? Sounds like an idea for a test flight!
This flight also tested another wide-angle (lens-D) unit. Sometimes my 808 #16 lens-D cameras suffer from going out of focus at high altitudes. The question raised in previous flights was, whether this was due to low temperatures or low pressures acting upon the cheap compound lenses? I have lens-D units that are always out of focus above 9km and others that seem to work fine over the entire flight. On this flight, the video started showing focus problems (near and far) starting around 9.5km (31kft) and then it came back into focus (!) around 24.6km (81kft). At these two times the INTERNAL temperature of the payload was 27C-and-falling; and then 0C-and-rising. That doesn't speak directly to the temperatures out on the rear stabilizer, but the trend of 'getting colder' and 'getting warmer' might mean something. It took several minutes for the video to go-out or come-in focus. So that rules out a quick depressurization of the lens. Interesting stuff.