- Using a custom envelope provided by Jim / N2NXZ, rather than a pair of 36" mylars.
- Second flight using new, more rectangular, solar panels. Used a little crazy-glue after soldering to reinforce the connections.
- Modified the board voltage to 2.96 volts. See previous post, yielding 11.4 mw of output power.
- Modified voltage divider for Solar charger to make 4.6 volts. Testing showed it making 5.02v, which exceeds the rating of the supercap.
- Improved braiding of the dipole wires (practice makes perfect).
- More careful measurement of both dipole elements to 209.4 inches.
- Code modified to use DMA rather than polling for DMA calculations.
- Transmit frequencies: 20m only. 6m intervals.
- Gatewayed to APRS at kd2eat-7.
Building the boards:
Braiding the dipole wires with 2 strands of thread:
Tracker run through its testing, and the antenna built.
Setting up a dummy weight on a clip for balancing the balloon. 14.2g tracker + 5g free lift = 19.2g.
Tracker and dummy load:
Balloon balanced to 19.2g, sealed, and attached to the tracker. All set for flight:
I stretched the envelope at 0.4psi to assure it could take the pressure. It seemed to hold up fine, though my pressure testing rig still has some leaks, so I could not maintain it at pressure for exhaustive testing. I removed the fill nozzle and quickly sealed the envelope, still under some pressure. I then hung weights on it until I achieved neutral buoyancy. I used this weight, and the known lift of helium to estimate the volume of the envelope at 0.270 cubic meters. Unfortunately, I misplaced the numbers for that, though I had the final result recorded. For the record, this envelope measured 37" x 51". The seams were heat sealed and reinforced with mylar tape.
Using the standard float spreadsheet, I put in the following parameters:
Envelope volume: 0.270 cu meters
Envelope mass: 78.9g
Payload mass: 14.4g
Calculating at 5.0g of free lift, it resulted in an estimated float height of 10,190 meters.
I'm planning launch for Thursday morning, August 3, 2016. The predicted flight path is below.
Well, the flight lasted 4 hours and 30 minutes. After seeming stable for more than an hour at between 9,111 and 9,333 meters, the envelope sprung a leak and descended, landing not far from Poughkeepsie, New York.