The Back 40
July 20, 2008
SARC Home Station
Alvin Buckwold School
715 East Drive
Once again, the weather gods were smiling on us. Sunday, July 20 was a great day to be outside doing something like launching a balloon. The winds were light and there were almost no clouds.
After SABRE-2, we realized that we had over-filled our first two balloons. With SABRE-3 we wanted to get as much altitude as possible. Our payload consisted of a redesigned still/video camera module, two redesigned APRS trackers, and an ATV module. We also added more line between the parachute and the payload hoping that it would help to reduce the pendulum effect that we saw in previous flights. This made SABRE-3 our heaviest payload to date so we paid extra attention to our lift measurements.
As Gus, VE5SPI took care of filling the balloon, I started to power up the payload. First one tracker, then the other were turned on and they began sending position reports very quickly. I thought this would be a good omen.
Meanwhile Bob, VE5RGM had set up his ATV receiving station inside the school. When he was ready, I powered up the ATV transmitter. Bob reported that re was receiving a great picture and that the payload walls were acting like a giant ear drum and he could hear everything that was being said on the ATV audio channel. Yet another good omen, we thought.
After our previous tracker failures, we learned to double check the trackers before releasing the payload. It was during this check that I realized that both tracker had lost the GPS satellite signal. I immediately suspected interference from the ATV transmitter. Sure enough, when I turned off the ATV module, the GPS's locked very quickly. To be certain, I powered up the ATV module and confirmed that the GPSs had lost signal again. I knew then that we could not fly the ATV module. My first thought was to remove the ATV module to save weight, but I soon realized that doing this posed a high risk of accidentally disconnecting something else. We decided to fly the payload with everything installed and the ATV module turned off. Everyone felt very bad for Bob because we knew that was looking forward to ATV on this flight.
Gus and Taylor (Who's the real kid?)
With our payload issues resolved, we went back to filling the balloon. Our calculations showed that we should have about 400 grams of lift so we sealed the balloon and prepared to lift off. As we let it out on the tether line, we realized that we had under-filled. The payload lifted up about 6 feet off the ground and then slowly dropped again, crushing the delicate ATV antenna. Fortunately that didn't matter for this flight. We pulled the balloon back down to the ground and prepared to add more helium. Our balloon uses a rubber stopper to seal the neck, so adding more helium was as simple as putting the filler in the neck and letting the helium pressure dislodge the stopper. Soon we had enough helium in the balloon and we let it up on the tether again. This time the lift was just what we had hoped for.
Our small test balloon showed us that the payload would start moving east almost immediately after lift off. Upon lift off, SABRE-3 did the same. After a few packets were received, it was apparent that out ascent rate was a bit over 500 feet per minute, less than the 700 feet that we had hoped for but still very acceptable. It was time to pack up and start chasing.
The prediction showed that the flight path would be parallel to a main highway and the landing would be about 120 km ESE of the launch. VE5SPI with his wife Lori at the wheel were in one vehicle while I and my wife Leigh, VE5LEE at the wheel were in another vehicle. We were also accompanied by Nate, VE5NAT in his car and Richard, VE5RH and his son in their truck.
The winds aloft were between 50 and 100 km per hour so we were able to overtake the balloon as we traveled down the highway. The small town of Gurnsey, was an ideal location to stop and wait for the eventual "POP". While there, we received a call from air traffic control asking for our balloon's location. It seems that a commercial airliner was nearing our balloon's location and they wanted to ensure they knew exactly where it was. We were able to give them an exact location and they diverted the airliner away from our balloon.
Soon the altitude reports showed that the balloon had burst and it was time to continue the chase. The trajectory showed that it should land near the predicted landing point. As Leigh and I approached from the north and Gus, Lori and Nate approached from the east, we received the last position before touchdown. Leigh and I made out way toward the position and relayed it to the other chase vehicles. As we neared the last know position, I was surprised to hear a faint beacon. It was too weak to decode so we have to try to find it based on signal strength readings. Soon Gus called on the radio and relayed the position that it was beaconing.
Gus and Nate retrieve the payload from the pea field
Gus, Lori and Nate proceeded to last known position, parking on a road north of it. Leigh and I made out way to a road west of the landing side. As Gus and Nate headed into the field, I scaled a nearby grain bin to get a better view. Soon Gus called saying that they had found the parachute and were following the 25 meter line through a dense pea crop toward the payload. By the time they emerged with the payload they were soaked from the waist down from the moisture on the plants left from the previous night's rain. With our payload safely tucked in the car we all headed to the sub shop in the nearest town for a long overdue lunch.
Google Earth KML
Payload Video 1
Payload Video 2
Payload Video 3
Payload Video During Decent