I spent the last two weeks of March in the SF/Bay Area, and while there decided to try a new balloon. My intent- record the sounds of California by air. I was inspired by the descriptions of listening to the world from in a balloon mentioned by gas balloon riders in Twenty Feet From Glory by John R. Goodwin, and other descriptions I’ve read from ballooning’s golden age.
This is the first large balloon (12ft tetrahedron) taped up using my meticulous step-by step how to guide instead of cribbed building notes. My mom surprised me with a visit the day I was planning on building the balloon, and although she is not inclined to geometry or building I convinced her to help me. With instructions in hand she was my best assistant yet- we built the balloon in an hour and a half. The seams were excellent and totally air -tight.
The new thing about this solar balloon was the blackening process and the launch process:
I taped the skirt up to the balloon without cutting excess material off the bottom until right before launch. In other words, until the launch there was nothing more than a dime-sized hole in the balloon. That way I didn’t get as dirty as I have previously when coating the balloon with charcoal, or in this case, black iron oxide pigment.
The method of blackening was new also- I dropped the powder straight into a centrifugal blower, which breaks it up and statically charges it. The result- a much darker balloon.
I also tested the wind with a tiny 5 foot “sounding” balloon before launch, which was advantageous to determining it’s path, a technique I adopted from the 19th aeronauts.
But there were two things I did wrong. Firstly, I did not check the line on my balloon before launching it, and there was a worn spot from previous launches. Secondly, the vent hole of the balloon was cut much, much too small (8 inches across) and so when the line broke it did not vent quickly. Result: my balloon landed in suburban Oakland, and I’m not getting it back.