On the whole I was very pleased with how my 1st high altitude balloon flight went (despite the disastrous camera failure). Below is a summary of what worked and what didn’t.
Things that worked/I will not be changing in a hurry:
- Telemetry system – the gps/arduino/ntx2 worked fantastically despite my doubts due to dodgy wiring and a botch job of the 1/4 wave ground plane antenna on board.
- Backup tracker – worked exactly as described and I can see it proving critical to retrieval of future flights – a must have for every HABist.
- Payload box – with an internal temperature sensor the temperature inside the payload was monitored constantly and the polystyrene worked very well at protecting the components from the approx -50C outside (got down to a minimum of about 0C inside).
- Parachute – the 36″ chute worked very well with my 900g payload – although a initial very fast descent (to be expected due to lack of air resistance), the descent rate near the ground was around 8m/s.
- Balloon – 1000G Hwoyee balloon went even higher than expected (seems to be a common theme with recent Hwoyee flights). Balloon was easy to fill and tie.
- Camera – despite the extensive testing carried out before hand and the great shots it took on the ground, a last minute code change (changing a “6″ to a “10″) resulted in the integer (1 000 000 rather than 600 000) being too large for the camera to accept. I had made the change to make the camera “sleep” (pause) for longer before starting to take photos as in testing the day before the flight it showed that the 4GB SD card may reach capacity very near apogee. However, I’ve subsequently found out that whoever wrote the code for the CHDK coded in an arbitrary limit of 999 999 for integers, therefore my value of 1 000 000 was 1 out from working. This actually translates to being 1 millisecond (1 thousandth of a second!) too long!! I have definitely learnt NOT to fly code that hasn’t been previously tested even if the most minor of changes is made. Hopefully on the next flight I will get some photos.
- Buzzer – when attempting to locate the payload a buzzer is often very handy in case of landing in long grass etc. When the payload was found the buzzer was not on (which would’ve made locating it very difficult had the landing been in a worse location). After some debugging it appears as though one of the wires from the buzzer was removed from it’s slot during duct taping (during launch preparations). This will be corrected on future flights.
- External temp sensor – an odd thing occurred with the outside temperature sensor. As the payload rose in altitude the outside temperature dropped, as expected, until it reached about -3.2C. Then it remained around -3C, fluctuating by a couple of 0.1Cs every string received. I know for a fact because of previous launches others have done that it gets a lot colder than -3.2C on the way up! As of yet, the reason behind this has not been exactly pinpointed, however, there are a couple of suggestions. The more likely suggestion is a bug in the code that prevented values being sent below -3.2C, this would seem likely as there is a lot of temperature conversion code – but, after a quick scan through the code a bug doesn’t seem to be present. The alternative suggestion is that I managed to fry the sensor in the testing process – it initially took a while to get the sensors working and I might have put the volts through the wrong pin – but, this also is strange as the internal temperature sensor experienced the same dodgy testing of mine and worked perfectly (though didn’t experience temps of -3.2C). Further debugging will continue…
Last Saturday (02/07/2011) afternoon after 2 years in the making, HABE 1 finally took to the skies. A quick debrief is given below:
After arriving at the launch site, a local farmer’s field, the essential equipment was unpacked and set up. I brought along a camping table, which in the end proved to be a great decision as it provided me with a clean, flat surface to place the laptop, radio and payload while getting prepped for launch. The day before I had decided on a launch routine – essentially 4 stages: turn everything on inside payload and fix the lid firmly on; attach string from the payload to the parachute; fill & carefully tie the balloon and launch!
A few weeks prior a guy called Will Duckworth who lives very near me got in touch and told me how he was doing a similar project and wondered if he could come along for the launch and tracking. I was amazed that there was another HABist in the area as I was firmly in the belief that I was very isolated with my Ballooning project being situated well away from the HAB hub of Cambridge! Will was a fantastic help throughout the day – from expertly tying knots (which I’m useless at) to helping track – so a big thanks to Will. Hopefully I’ll be around for his launch and in the future we can possibly turn Worcester into a HAB hub!
Right, back to the flight details. After the launch (which took around an hour with all the preparations), the initial telemetry was coming through with many errors in, however this was quickly identified to be the result of the yagi antenna pointing in the wrong direction (panic over)! Tracking went great throughout the flight with people managing to listen in from Northern Ireland & near Aberdeen – with just 10mW of output I was extremely impressed. So – telemetry was a success. The payload initially drifted over towards Stratford Upon Aven but in due course swung back to head right overhead (about 300m away!) the launch site and then on to near Tenbury where it again swung back around and landed near Great Witley. Map of flight below:
The balloon was filled to burst at 33km up however we watched in amazement as it just kept going higher and higher – eventually reaching 35,824m (the highest reported alt). This placed HABE 1 the 2nd highest payload of all time in the UK (according to UKHAS records) however, we were subsequently pushed down to 3rd place on Sunday when Steve Randall’s payload reached about 180m higher than HABE 1.
The parachute worked a treat as the payload had a reasonably controlled descent (falling about 8m/s near the ground). Once the payload started dropping below ~10km listeners dropped out as it disappeared over their horizon. As we were driving to the predicted burst site, there were periods were telemetry couldn’t be received so we had to make rough guesses where the balloon was until we could pull over safely and decode a few more strings. Once the payload was around 2km up – I sent an sms to the backup tracker (which I’d bought off eBay for about £50); not expecting it to work great, I was surprised when almost instantly I received a text back with it’s exact location! I continued texting it until the payload had landed in case cellular signal dropped out at lower altitudes (the area where we where had very poor signal).
With a location from the backup tracker I plugged it into an Excel spreadsheet I had made to spit out the co-ordinates in a google maps friendly format. On powering on tethering from the iPhone, it quickly became apparent that there was extremely poor signal. I had thought of this, so no problem – a Garmin Etrex was on hand. One problem though – I hadn’t used it for about 2 years and after about 10mins still couldn’t figure out how to use it! So, despite a clear signal (surprisingly) from the payload and a matching location from the backup tracker we had no idea where it was (apart from within a 2 mile or so radius around us!). After some driving around and trying to triangulate the position using the directional feature of the yagi we bumped into Will who’s computer had just died! However, he managed to remember a co-ordinate obtained just before it conked out (impressive with no pen & paper!) – on comparing co-ordinates they matched so we were fairly sure that we had the location; but we just didn’t know where it was! After heading in the vague direction where we were getting the best radio signal, cellular signal fortunately improved slightly – just enough so we were able to load up google maps and get a location. Screenshot (green arrow is location):
When we obtained the above location we were infact situated just below the “A” marker (on the road that the marker is on). We decided it was best to head south and then west and up a tiny little track which led us fairly close to the payload. After some hiking off road (up & down, up & down… sheep fields and over barbed fences etc) the payload was spotted – “that doesn’t look like a sheep to me” was the call when the white payload box was spotted!
Remarkably – it landed with no damage whatsoever to the payload box (possibly helped by the fact it landed in thick/high weeds). The parachute was nicely spread out and the balloon had shredded cleanly. So, very pleased, we headed back to the cars with the payload.
On arrival back at the cars, the payload box was quickly opened (after extensive removal of duct tape!) – the SD card from the camera was removed, inserted into the computer, then…. 3.94GB available. Oh dear.. 0 photos had been taken – what a disappointment after such a fantastic flight.
This article will be followed up with analysis of what worked & what didn’t.