9 May 2012
My payload was pretty standard fair. My 900 MHz 1 watt radio and a Garmin eTrex H GPS unit. For a camera I used one of my old Aiptek DV4500 cameras with AA lithium primary cells. I used a 14.8 volt Lipo battery pack for the radio with an extra power tap to supply power to one of my HLA altimeters. For close in tracking I taped a Beeline high power 70 cm tracking beacon to the 3' diameter parachute shroud lines. The Beeline 70 cm transmitter was powered by a pair of Lipo batteries in parallel.
The altimeter was programmed to beep out current altitude. That way there would be a way to know altitude while watching the video. I was also hoping to get apogee data from the video. The foam box I made from 1/4" fan fold. I've been making some homemade foam RC planes and had the foam available so I used it. It really worked very well. I doubled up the foam on the top and bottom, hot glued it together and then taped it on the outside with strapping tape. The camera looks down, that's an angle I'd never shot before so I thought it'd be interesting to do something different.
There's my mom on her backyard deck and "wildman" Bill holding the balloon as it fills. Natural gas line pressure in a house is very low, so low in fact that it took 3 hours to fill the balloon! I'm thinking if I do this again I may use larger diameter tube to speed up the fill process. I kept the payload weight as low as I could so we could keep the balloon diameter down at launch. Natural gas isn't nearly as light as helium or hydrogen so to get any altitude at all I'd need to keep the payload light. I also cut the skirt off the balloon, as I'd done in HAB3.
After 3 hours we finally had about 3/4 pound of free lift, again keeping free lift down to keep the balloon as small as possible at launch. The balloon was already a good distance off the ground when this photo was taken. Initial ascent rate was slow, about 300 fpm, then increased to about 600 fpm.
Here's a shot from the on board camera just after release. The wind was light at ground level and the balloon slow to rise, so we sat out in front of the house for some time before we felt the need to start chasing the balloon.
This is the east side of Paullina with the lake in the upper right hand corner. It still isn't going anywhere in a hurry...
Until the balloon hit about 10,000', then it took off like a bat out of hell to the southeast. The camera ran out of memory at about 30,000' and this was one of the last frames recorded.
The chase was on! The problem was, the balloon just kept going faster and faster, until it reached about 65 mph. There just wasn't any way to keep pace, let alone catch up. We were 10 to 15 miles behind and falling even farther back. I ran into a rather odd problem during the chase. Whenever we got up to highway speed in the car, I'd lose signal lock on the radio. When we slowed or stopped the signal locked in again. I don't have any reasonable working theories on the cause. Never the less we did our best to track and keep up. With the balloon at about 51,000' I got my last GPS data packet. We drove a few miles in the same direction it had been moving but we didn't get a lock. So I had Bill stop and I switched antennas from the roof top omni antenna to the high gain Yagi, still no luck picking up a signal. In desperation I assembled the high gain Yagi antenna for the 70 cm beacon, low and behold I picked up the beacon, still high in the sky! We drove about 5 or 6 miles farther and tried again, I still had the signal, but it seemed lower in the sky. We drove another 5 miles or so and I swept the sky, picking up the signal once again, only this time much closer to the horizon. Then nothing, no signal from either radio. The good news was that I had a directional fix on the beacon when the payload landed. Now it was just a matter of following that path, checking for the beacon every mile or so.
There were now 2 problems. I didn't have a good detail map of this area, with a map showing every road I can follow our progress and mark off where we've been. But the only map I had of this county was a highway map and almost useless. The other problem was we had no idea how far down range the payload was when it landed, it could be a few miles or it could be 30 miles. The transmitter has tremendous range line of sight, I was trying to get a signal strength indication on my radio right when the payload landed, but just didn't quite have time to do it.
We searched an area of about 12 miles along the flight path, spending about 3 hours. It was getting close to sun set so we decided to call it a day. I'd print out detailed maps when I got home and Bill was ready to go out again the next day. It was a tough day that only got tougher, on the way home I hit a deer with my Blazer. Luckily the damage to the car was minimal, but still...
The next morning I was awakened early by the phone. Low and behold a local farmer had found the payload on his way out to a field. I got directions from him and Bill and I headed back down to pick up the payload.
Here's a Google earth map of the balloon flight until the GPS quit.
On this image you can see in the upper left where the radio quit sending data, and on the lower right where it landed.
Click Here for the gpx data file from the flight.
What's sort of sad about the whole thing is that the payload landed within a mile of where we searched. I'm not
sure why I wouldn't have picked up the signal. I may need to range test the transmitter to make sure it's working
as expected. The camera recorded just over an hour of video, so it only had video up to 30,000' or so. It's certainly
not a real dynamic video, but the first 10 minutes or so it got some good video over town.
The real question is why did I lose all GPS data at 51,000'? When we picked up the payload the next morning I was surprised to see the GPS was turned off, I assumed the batteries had run out. I even commented to Bill it was odd the batteries died so quickly, I had calculated they should last almost 2 days. After I got home and started looking things over, I powered up the GPS and the batteries were reading a full charge. So if the batteries didn't run out, it seemed logical to assume the reason I lost the GPS data was simply because the GPS had turned off. But why would it turn off? It's possible the balloon burst at 51,000' and the jostle of that event caused the batteries to lose contact, or perhaps the "off" switch had been pushed during the burst event. The distance covered by the payload between 51,000' and the landing site would seem to indicate the balloon did indeed burst at 51,000'. I don't think the GPS would turn itself off is the "G" limit or altitude limit was reached, but more research may be in order to determine if that could be the cause.
In summary I'd say it was at least a somewhat successful flight. The HLA altimeter worked great at reporting altitude and the digital camcorder recorded the audio very well. Using natural gas as a lifting gas was at least proven to be viable, if not a great alternative. With a newer balloon I think a light payload and natural gas would have given us 75,000' or so. Natural gas might be a great, inexpensive way for someone to get their feet wet in high altitude ballooning. The cost of the gas for the balloon would be about $1.20 with current prices.
Postscript: I did a little more testing of the GPS unit. I can get it turn off by gently thumping it in my hand. It would seem the battery contacts are just a little loose. If I use this GPS again I may just solder battery wires to the contacts and not worry about it. It does seem likely the jostle of balloon burst caused the GPS to turn off, somewhat colder conditions may have caused slight contraction and made the problem even more prevalent.