Sven was trying an experiment with a foil balloon where he used concentrated sodium hydroxide to wipe off the aluminum layer from a Qualatex 90cm balloon. The removal of the aluminum worked fine, but we couldn’t measure any weight loss. At least it was below 0.05g. Still we wanted to launch this balloon to see if there is any difference. At our typical night launch we have lost visibility of the transparent balloon already after 200 meters. Usually you can see the reflections of the metallic foil balloon even after a mile at a regular launch, but this time it disappeared after a minute already.
The flight path during the night was unexpectedly low. There must have been a cloud layer that pushed the balloon back down at ~2700 m altitude. Possibly there was some little rain involved. In the morning hours when the sun came and dried the balloon, it finally continued the ascent up to 6521 m. Then the signal was lost just before the Russian border.
We’ve used a tiny Pecan Femto tracker powered by an AA Lithium Ultimate Energizer battery. When the balloon was lost, it certainly had still enough power. Many APRS packets were lost which indicates that the transmission was certainly not optimal. We’re investigating about the reason, but this was the first Femto flight with APRS software (Femto was originally RTTY only). Despite the small tracker, the payload weight was still ~20g due to the heavy AA battery.