A couple of weeks ago I launched a few projects I had been working on over the last year or so on a 1200g Pawan latex balloon. These projects included:

The CHDK rig from the conference last year, sending live 600 baud SSDV images encoded straight on the camera. A Navspark based tracker. And A Cheapo Mini flying backup.

I did plan to launch a nasty looking GPS UKHASnet node, but the AVR got stubborn just as we were about to launch and refused to accept any new code.

The launch went off pretty much without a hitch and roughly on schedule, with some much appreciated help from Lewis.

Launch video to be added at some point..

Things seemed to be going according to plan, until SPARK hit about 19KM and decided it had enough. The altitude stopped ascending and the GPS wandered off course, shortly followed by the GLONASS satellites dropping down to 0 and GPS to 3. I posted my results to the navspark forum, but their only theory was that it couldn’t handle the temperature. I’m not exactly sold on this, as it seemed to die at exactly 19km (hey, that could be a coincidence) and the board should feature a TCXO. Perhaps some modes need changing. I will repeat this experiment sooner or later.

Just as the flight started to get interesting, cheapo also decided today was not a good day for HAB. The battery voltage plummeted as the temperature dropped and silence fell. Luckily on the descent things started to warm up, increasing the battery voltage and bringing the tracker back in time to track the landing. I have not seen a lithium battery drop quite this much in voltage before, so I suspect I had a bad cell.

Surprisingly the part I thought most likely to fail actually performed perfectly! The camera sent down SSDV images throughout its flight, with no packets being missed! A great success and a final thank you to Reyalp from CHDK and Phil Heron for their help with the project. The next step will be to implement the whole thing again on a more modern camera with GPS, but I think a well earned break is due first!

The flight photos will appear here at some point, along with the 15gb of gopro footage…

Left this write up a little late… But this was my first successful float! Using a cheapo R3 board powered from a cheap ebay boost regulator. These things are designed for > 0.8v input and 5v regulated output. It turns out by changing a resistor value you can modify them for 3.3v output. These things are not very efficient so only lasted about 8-10 hours.

We filled the 36″ foil balloon carefully using 1.5g of solder to measure the free lift. Which proved to be just about perfect (thanks Leo!). The tracker performed fine (still concerned about the GPS bug before, even though it did not reach 12km) and the balloon floated at a steady 3.7km for 10 hours before the batteries died over the north sea.

I have been working on a new tracker PCB which should be smaller, lighter and last longer. Stay tuned for updates!

This was a charity flight by Matt Downs to raise money for the Cats Protection League and Essex Air Ambulance. I offered to help out with launching and chasing with Matt and flew a cheapo R3 board as backup. Matt’s tracker worked perfectly and got some great stills from the gopro camera. However cheapo hit a bug at about 12km altitude and started giving incorrect GPS coordinates. The current theory is that the 808 camera I (stupidly) attached to the tracker in an effort to catch the burst, caused interference with the GPS. This caused the GPS to reset, taking it out of flight mode and defaulting back into pedestrian mode.

We were in the paper!

Filling the 1600g balloon.

Letting it up.

Running with the payload to launch.

Easy recovery! Trailed out along the pavement.

After the disappointing signal reports from cheapo3 I decided to investigate the cause of this. The most efficient, fast and cost effective way of doing this was obviously to just build up a new board and launch it. This also gave me a chance to play around with foil balloons which seem far more suited than small latex for this sort of payload.

I made the 1/4 wave antenna using cat5 cable instead of telephone cable this time around and it seemed to make all the difference! Had lots of great signal reports and a fair few trackers. The software had also been updated with some power saving code dropping the current down to 50mA, and a distance from launch site calculation added. The tracker complete with batteries and foam box weighed in at about 40g.

I aimed for a fairly low ascent, but by just measuring this by eye in quite a confined space (my garage) it was probably a little on the overfilled side. I cannot imagine having to fill one of these outdoors!

Instead of using a plastic tube for filling I simply opened the valve using a drinking straw then filled the 36″ qualatex balloon using the filler nozzle on a disposable 50 helium canister.

I filled 2 small latex balloons to use as wind indicators and to test for tree clearance. Just as well as the first one got stuck!

Launch video:

Unfortunately the balloon did not enter a float despite its fairly slow ascent rate. At about 5400m the balloon started to leak gas. This looked like it was leveling off for a float. But then started to descend at about 1.1m/s.

As the balloon descended I tried to decide if I should go to recover. My inverter went missing and I doubt my old laptop would have lasted long enough to be worthwhile. I sat there and watched as the balloon crossed the River Thames and bounced along between 100-200m altitude as it rode thermals over the town.

We lost contact with the payload at about 60m altitude over Bexleyheath golf club. Just then Steve (G0TDJ) stepped in to save the day! With his mate Ken at the wheel, they drove down to the golf club to take a look around. After a few minutes with nothing seen, one of the golfers pointed them in the direction of the A2 (eek!). Luckily it seems that the balloon was blown to the side of the road by the traffic and up onto the fence.

Steve caught a passer by just in the nick of time to pass the balloon over the fence to him after convincing him that the payload was NOT in fact a bomb and he did NOT need to call the police! A close shave!

As you can see below the payload had landed directly below the tracked position. I can only presume the balloon floated further on and was blown back down the road, or the wind was directed downwards due to the shape of the trees.

So all in all a successful flight. The new antenna is tried and tested. I have some experience with launching foils. The HC49 RFM22B showed slightly less drift than usual, I will be interested to investigate that one further.

Comparison of RFM22B’s (Standard HABsupplies on top, alibaba board on the bottom)

Thanks again to all those who helped track, and an even bigger thanks to Steve and Ken for going out to recover! CHEAPO5 to follow sooner than you may think 🙂