Buzz2 – To the UK Altitude Record, And Beyond!

Buzz2 aka Buzznik was my second attempt at getting a payload up in amongst the top of the UK high altitude table for amateur weather balloon launches. Buzz1 burst earlier than planned, though was otherwise a successful flight recovered in a field in Cambridgeshire.

Gaining high altitudes is an inexact science because of variables such as the atmospheric conditions, launch conditions, balloon variability etc. However the basic plan is to use a relatively large balloon and a lightweight payload. Larger balloons burst higher, and a smaller payload means you need less gas for the same ascent rate. Also balloons from the Chinese manufacturer Hwoyee seem to burst higher than others, though not always (e.g. Buzz1). The final variable is the amount of gas, but this is where it gets tricky. Less gas means the balloon needs to be higher to burst (because it needs the same pressure differential between inside and outside), however it also means less lift so there’s a tendency for the balloon to run out of lift and to float. A floating balloon can go a long way (the last UK floater got as far as Poland and was lost).

For Buzz 2 I didn’t want the balloon to get that far (!), but I also wanted it to cross the English Channel. The forecast winds for the launch day meant that without a float it would land somewhere in northern France, though previous predictions said South West Belgium.

Too much gas would see it land quite close to the coast (bad – I didn’t want another sea landing!), but too little could mean us giving up chasing the balloon as it headed east. Also, with the balloon covering such a large distance, I wanted it to stay up at high altitudes for a while, where hopefully the wind speed would be a bit lower, to give us a chance to catch up in the chase car. So my plan was for a lowish ascent rate of about 4 – 4.5m/s (normal would be about 5) which had a small risk of a float but maybe, just maybe, enough time to get nearby before we lost signal as it came down.

Timing then was crucial, so I prebooked a Eurotunnel crossing for a time where there were several trains within 10-20 minutes of each other in case we were early or late. I then needed to launch at a specific time (and most launches tend to be quite a lot later than planned!), then get moving in the chase car sharpish.

For Buzz2 I used the electronics taken from the recovered Buzz1. I decided not to use the same payload housing, because that didn’t have enough insulation meaning that the radio transmissions drifted in frequency very quickly as the transmitter got colder (down to -53C!). I had a foam polystyrene ball left over from the stuff I bought for Buzz 1, so I put everything in that. I removed the tiny camera (very poor quality) and excess flashing LEDs, and replaced the set of 3 AAA batteries with 4 AA batteries for longer life (in case of a float). Finally, since Buzz payloads have to actually look like space vessels (Buzz1 was a flying saucer), I arranged the aerial and ground plane wires to make Buzz2 look like Sputnik. So here’s “Buzznik”…

The day before launch I put the payload together and checked that it was still running OK and showing online, and simplified the software a little (fewer lights to flash!). I also got the car PC set up ready for tracking the payload and uploading the car position to the live tracking map. Normally I use my car but that’s curently in bits at the garage awaiting a part that is apparently now unavailable, so instead I installed in Julie’s car. Into that went a car PC for handling the telemetry and uploading the car positio, a netbook for online chat, and Samsung Galaxy Tab to show the map. The roof was then adorned with aerials for UHF radio downlink from the payload, GPS to get the car position, and 3G aerial. The latter connected to a 3G dongle and wireless access point that provided all the computers in the car with an internet connection throughout the journey (except, unfortunately, whilst in the channel tunnel!). Using a single internet connection meant a single bill for roaming in France and Belgium, and I opted for a £5 deal with T-Mobile for the time abroad.

The morning of the launch was quite windy, and normally I’d probably have decided not to launch, but I had of course already paid for the chunnel tickets! Also, the wind did die down for periods so I knew that although the balloon would be a handful during gusts, there would be times where we could measure the balloon’s lift (very important) and a time to launch without the payload being carried horizontally (as happened to Cloud2!). So final preparations were made, the car electronics all powered up and the payload started and put online. With bags and helium packed in the car we set off to the launch site just down the road, put down the ground sheet and started through the process of inflating the balloon and connecting the parachute and payload.

There were, as expected, some alarming moments where the wind tried to pull the balloon out of my hands, but I just held it as safe as I could and waited for the calm period that would follow. Here’s Buzz2 just before launch. The eagle-eyed will see what I forgot to do ….

…. the aerial wire (poking out the bottom) is bent towards me and then down. It got that way during preparation for launch and was supposed to have been straightened out. Bent aerials don’t work too well!

As I said earlier, the amount of helium added is key to the flight achieving its targets. For mine I wanted enough to give a “neck lift” of around 800g, which meant that the balloon would just lift the filler (around 150g) plus a water bottle that I’d pre-filled to 650g. However after stopping the inflation at what I thought might be about enough helium, when I measured the lift it was too high. I did try getting some helium out but it’s at such a low pressure that takes forever to do. The idea of sucking it out, and the ensuing hilarity of talking in a squeaky voice, got old after a couple of lungful’s so I opted to tie the balloon off and launch anyway.

With a large balloon and small payload the initial ascent is quite slow as the balloon is basically under-inflated and forms a rather un-aerodynamic floppy shape. Here’s Buzz2 shortly after launch:

With Buzz2 whizzing eastwards, we had little time to waste. So after dropping the helium cylinder off at home we set off to the M4, then east to the M25 and south to the M26 then M20. The balloon made better progress than us reaching speeds of 100mph and higher, but eventually it reached slower winds as it gained altitude. In the car we tracked using the computers I mentioned earlier, some of which are here:

Tracking wasn’t helped by that dodgy aerial. We didn’t know the reason at the time, but telemetry reception in the chase car was poor, and everyone else who was receiving the telemetry for me complained that the signal level was much lower than normal. I suspected an aerial issue (there’s little else to go wrong), but the proof didn’t come till I checked the launch photos later.

We eventually caught up with Buzz as we got to the channel tunnel. By then Buzz was creeping up the UK altitude record table for amateur latex weather balloon flights. This was a very exciting time! The ascent rate was high meaning that although it moved up the table quite quickly, I was convinced all along that it was just about to burst. As well as watching the altitude on the map, and coming in directly from the balloon telemetry, I was chatting online to other enthusiasts including the Australian chap who held the existing UK record. The chat room is a friendly and very supportive place with some gentle ribbing as the UK record was brought back into British hands “for Queen Elizabeth and the realm” as one put it. 🙂

Here I am on the phone to a friend who called at that time. I think this photo was taken just after Buzz2 broke the previous highest record.

During this time we were held up for security checks at Eurotunnel. I had the Yagi aerial on the rear shelf, plus GPS, UHF and 3G aerials on the roof. After the usual checks the security guy comes over and asks, “Sir, why do you have so many aerials on your car?”. LOL! He seemed happy enough once I explained.

Shortly after that, the balloon burst having achieved an official altitude of 40,986 metres (just under 25.5 miles, or 134,468 feet). Unofficially it reached 41,008 metres, but although 2 people received that altitude nobody received a complete telemetry string containing it. So now I hold the record (but probably not for long), having beaten the previous record by 411 metres. It also stands at #2 in the world record table for latex balloons. Here’s the current UK record table:

And the altitude plot over time …

So now attention turned to where the payload might land. I didn’t include a “cutdown” device this time, so the descent speed was dependent on how much latex was still attached, and whether that tangled itself up around the parachute. Initially the descent was very rapid because of the thin air at that altitude, but it did slow afterwards. Unfortunately though the received signal level was poor (that aerial again, plus the payload was spinning) and the last reading was at 23km altitude (normally I would expect someone to have received a position down to about 4km). Here’s the predicted landing path:

Our chunnel train left about this time, so we didn’t get back online (WHY don’t Eurotunnel put wifi in their trains??) till we got to France. We pulled over at the terminal petrol station while I signed up for T-Mobile’s roaming deal, then I went straight to the highaltitude IRC channel to see if there was an udated landing prediction. Sadly not, so I had a choice of spending the afternoon in a possibly fruitless search for the payload, or give up and have a day out in Bruges (our backup plan). We opted for the beer and waffles! Initially we were going to try searching on the way back from Bruges, but by then we were both very tired so we just headed for the chunnel.

We did though have a great time in Bruges – a lovely little city that’s not very far from Calais. So here are some photos from our day out.

*** UPDATE ***

This afternoon (the day after the flight) the payload was recovered in Belgium by a fellow enthusiast. It sounds like a difficult recovery, with the payload in a muddy field a long way from the calculated landing point. This is the final flight path:

into this field:

where it was retrieved by Peter of the Belgian HOWest team:

This is Buzznik ready to be packed up and sent back to me:

Also, see The Register and Newbury Weekly News

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