With the jet stream spoiling my plans for a latex balloon launch, I decided to try a foil balloon flight instead. Latex balloons stretch with altitude, eventually bursting at roughly 100 times their volume at ground level, and typically at altitudes of 30km or more. Foil balloons however do not stretch, so their altitude is limited to around 5km or so. They do however offer a number of advantages – they’re cheaper, need a lot less Helium, and do not need a NOTAM assuming the entire assembly is always within 2m in any direction. The latter means that the launch site can be decided on the day (though not anywhere can be used – you still have to avoid launching into a restricted area for example).
For the tracker I opted to use one that I dunked in the English Channel in my last flight. The tracker in my larger payload (Cloud3) was did not survive, but the one from my smaller payload (Buzz3) did. I didn’t want to use that on an important flight so it was ideal to use (and probably lose) on this.
So I tidied up that tracker (removing deposits from the salt water) and made a simple container from sheets of foam polystyrene:
With the batteries connected and the payload closed up, I inflated the 2 foil balloons and adjusted so they gave the same amount of lift (measured by tying down to a small weight on sensitive scales). Then they were tied together, attached to the payload and taken down to the launch site.
Originally I planned to launch from a high point (on the Ridgeway) but the wind seemed gentle enough to launch from the village green. Big mistake. We took the balloon there, checked for the wind direction and then took the balloon to a far corner to give it plenty of space to fly into. However the wind change direction for the launch, and the balloons went up then down again a little before swinging back up again near the trees. It was a close thing, with the payload just escaping from one branch before tangling on the next:
Well, I’m not the first to launch a foil balloon payload straight into a tree (easy to do as they rise very slowly compared to a Latex balloon), and I wasn’t concerned about the loss of a salt-damaged tracker, but even so I was pretty dejected when I returned home.
Well, there’s only one thing to do after a failure, and that’s to replace it with a success. So after some deliberation I decided to use my tiny “egg” payload and launch with 2 more foil balloons. It was likely I would lose it, but I could just make another for next week’s latex launch. The payload was ready and just needed the batteries connected and the two halves of the container glued shut. So with that done, two more balloons inflated and tied to the new payload, we drove off to the original launch site.
We checked for the wind direction and then made sure we found a spot with no chance of hitting either of the trees! Here’s PicoBuzz1 (B) heading off on his journey:
Foil balloons don’t get up into the jet stream, so don’t generally travel fast. So we had plenty of time to follow the balloon around at a leisurely pace, trying out my car PC software for real for the first time:
After the first stop we looked at the projected path and decided to go to Goring by the Thames, near where we believed the balloon would go. As we parked up we could see on the live map that the balloon was approaching, and it got to within 150 metres of our position (but 6000m up!). Too far to see, even with binoculars. Anyway, we had a pleasant hour in Goring:
AFter following the balloon around for a while, it settled into a float so we headed home for food and to track from there. However by the time we got there, one of the 2 foil balloons burst so it started to head down to the ground. So we headed out again, armed with warmer clothing, a Yagi aerial for direction-finding, and a couple of large torches. We were quite close to the balloon when it landed and we lost the signal. With no internet we were struggling to get decent mapping, but eventually we found some roads closer to where we believed the payload to be. Once we got to the area the rtty signal started coming in, weak at first and then strong enough to decode, so now we had an accurate position to aim for. He we are on the map trying to get closer to the payload.
The Sat Nav got us close, then we parked up and set out on foot, but before a passing police 4×4 and later a security guard asked what we were up to! I guess we worried the locals! Here’s the gate next to where we parked:
A short trek later and we found the payload and balloons:
Here’s the full path:
and the hole in the balloon: