This article follows on from the attempt to fly a tethered weather balloon in July 2015, see the blog here.
An opportunity arose early in 2016 to fund another flight of our Helium filled Weather Balloon. This time it was to be used to observe the Isle of Wight Festival. The school I work at is used each year, along with other parkland, for this large music festival. As part of a community involvement by the organisers, the school is given a number of tickets for the event and these are given to students in return for them becoming involved in various projects. This year the Geography Department wanted to look at the environmental impact that the festival has on our community, in particular the problems of litter and the waste generated by the festival.
I was approached to see if the weather balloon could be used to photograph the festival site and the quest for funding started. I had several short meetings with the Geography teacher running this project, but it was not until funding was confirmed in April/May 2016 that planning began in earnest. The price of Helium had increased since 2015, but I managed to track down a supplier who sold us five 0.42 cubic metre balloon gas cans for just over £120. These cans are supposed to fill 50 x 9 inch balloons and from experience will provide about 250 gms of lift.
From our experience the biggest problem was to stop the electronics package from spinning and the original idea was to suspend the package from the balloon, then attach the kite string to the bottom of the package. However, I was concerned about the package surviving the forces involved and went for attaching it as we had done last year (see the blog here). A suggestion was made that we use a wind sock to stop the package from spinning, but as with everything else involved in this project we had nothing to guide us. Eventually we settled on a wind sock about fourteen inches long with the mouth about four inches in diameter (see the photograph below). Four pieces of cord were used to attach the windsock to the end of the package.
We were limited to one of four days, 4th to 7th June as the festival started on the 8th June. The long term weather forecast at first did not look too promising but by the week before it seemed that Tuesday 5th looked our best bet. It was forecast to be overcast with only a small chance of rain, but more importantly the wind speed was forecast to be about 2km/hr. When the day arrived it was warm and sunny with partial cloud cover, and almost no wind.
It took about an hour to fill the balloon and we used four and a half tins to fill the balloon and provide about 1200 gms of lift. The balloon was then walked to the geography department where the electronics package was started, set to record video then attached to the balloon. The wind sock was fitted to the end of the package and we walked the balloon down to the field alongside the festival. Weather conditions were perfect and the balloon rose easily to about 100 feet, but the wind sock was too heavy and simply hung below the package, blocking the camera. We brought the balloon back down and stuffed the wind sock onto the top of the package and sent the balloon up several hundred feet.
showing the windsock mounted in the best position
Lady Luck was certainly on our side because the wind blew the wind sock off the package in such a way that it was supported on the top of the package. At this point it did exactly what it was designed to do and kept the electronics package perfectly still! Over the next two hours we sent the balloon up to various heights and it was not until the end of the day that increasing winds started to move the balloon horizontally. On the last time we brought the balloon down we pulled it down, laying the kite string on the ground, with out winding it onto the reel and this allowed us to measure the height that it reached.
At the end of the day we decided to burst the balloon rather than try to store it overnight, much to the delight of several classes of students who had come out to watch the balloon.
We achieved all our aims with this flight as far as the balloon was concerned, we were able to control it with ease and confirmed that each container of Helium gave about 220 to 250gms of lift. However, the electronics package did not perform as expected. I had been testing it for almost a year, running it on battery power for up to eight hours at a time, and it performed perfectly. As I wanted to control it using the LPRS radios I would start the python program using VNC or ServerAuditor on my iPad. However, when the iPad went into screen saver mode it shut down the python program. The solution is to start the python program using WiFi, then to turn off the router. VNC or ServerAuditor can be switched off and the python program will continue to run, I have no idea why the python program stops when the header less control program is shut down, it just does!
The day before the launch, the control of the Raspberry Pi became erratic (it later turned out to be one of the small heat sinks plugged onto the back of the USB sockets that had fallen off and was rolling across the Pi, shorting out connections as it went). As I seal the package with cable ties and wanted to make sure we were filming I set the video to run for 30 minutes. It performed perfectly, it just took 20 minutes of video of the ground as we fitted it to the balloon then walked it to the launch site. For the remaining 10 minutes it filmed the wind sock as it flapped about in front of the camera. As a result we recorded almost no useful video.
The students took plenty of video and still pictures of the event and I am sure the report they write will justify their festival tickets. The students were fascinated by the balloon and followed us wherever we went. Teachers brought their classes out to watch and I am sure the students appreciated the chance to lie on the grass in the sun rather than be stuck in a classroom.
bursting the balloon at the end of the day. The white substance is the French Talc in the balloon.
I would like to thank Ann and Toby for their help and suggestions and to Caroline for coming up with a project that allowed us to fly the balloon again.