Building on the success of Launch 3, we will use the same APRS beacon and 150g balloon. We will just add a micro-camera and a little “Charlie Brown” doll to the payload, in honor Todd Brown's father Charlie, who is battling cancer.
The payload landed 3.1 miles from the forecasted location, and hung up in a tree about 80 feet above the ground. Recovery teams were able to locate it, but could not get it down immediately. Adam & Char (KC2ANT & KC2ULK) did some door-knocking in the area to get permission to go back into the woods. As it happened, they came upon Chris Preston, a local arborist. Though busy at the moment, he very generously climbed the tree the next day and retrieved our payload.
|Payload||Tracker, Micro camera, Charlie Brown Key Fob|
|Payload container||Plastic bottle and bubble wrap|
|Max Payoad Weight||200g|
|Flight Time||45-90 min|
|Tracking||300mw APRS tracker loaned to us by Alan Adamson (W7QO)|
|Telemetry||GPS and temperature data.|
|Batteries - (2) 300ma LiPo||18|
|Tracker + Counterpoise||23|
|Parachute + guyline||32|
|Balloon attachment (tape)||10|
|Charlie Brown Doll||23|
|Tie off for doll||10|
|Total (goal: 350)||336|
|Latex Weather Balloon (150g)||$25 - Donated by Todd Brown|
|Helium or Hydrogen (80 cu ft cylinder)||$66 - Donated by fox hunters|
|Additional 80 cu ft lifting gas tank||$150 - Donated by Mike Hojnowski|
|Mini cameras & SD cards||$60 - Donated by Mike Hojnowski|
|APRS Tracker||$100 - Donated by Alan Adamson (W7QO)|
|Packaging, Parachute||$10 - Donated by Mike Hojnowski|
|Balloon Mass||200g Kaymont|
|Target Ascent Rate||5.0 m/s|
|Descent Rate||6.55 m/s|
|Start Location||Southwest of Watkins Glen|
|Burst Altitude||14630 m|
|Ascent Rate||5.93 m/s|
|Neck Lift||784 g|
|Launch Volume||33.9 cu ft|
|Flight Range||48.7 km|
|Flight Time||66 min|
*Note: The balloon manufacturer claims 15,000m burst altitude. The GPS on this tracker is rated to 18,000m.
We wanted to get the neck lift as close as possible. It's difficult to measure while filling, so we decided to base it on the size of the balloon. These smallish balloons are nearly spherical when filled. So, we elected to calculate how full the balloon should be based on the volume of a sphere. We knew the volume of gas we needed, we just needed to measure the balloon. From the spherical volume formula, and given the volume of gas we had, we could calculate the circumference we needed.
We called it 12 1/2 feet in circumference. We measured out some para-cord and made a loop of that circumference. We filled the balloon, and slipped the cord around it. We stopped filling when the balloon was just touching the cord all the way around. We slipped off the paracord and gave the balloon one more little squirt of gas.
An infrequently used ball field outside Watkins Glen was selected as the launch site. It was abandoned, and sufficiently out of view that we weren't worried about anyone bothering us. We filled the balloon without incident, attached the payload, turned on the tracker and cameras, and let 'er go.
Only one of the two video cameras had data onboard after launch. It's entirely possible that the other camera was improperly activated. It was very difficult to see the status LED on the camera at launch time due to the bright sun.
We captured about 3 minutes of “fussing” getting the payload ready, and about 17 minutes of flight.
The balloon was launched at 11:36 (the video camera showed 11:33). The video cuts out at 11:50 on the video (11:53 actual). At that time, the balloon was at 16,555 feet.
Here are a few photos of Charlie, swinging around under the balloon:
The balloon climbed steadily until something happened at 12:17. The GPS telemetry stopped updating, though the tracker kept beaconing. The tracker was at 39,961 feet at this time. According to Winds Aloft data, the temperatures at that altitude were below -57 degrees. We believe that the GPS module (which was mounted outside of the protective plastic bottle and bubble wrap) failed. It is rated to -40.
At 12:26, some 9 minutes later, the telemetry started updating again. The balloon was now descending, and was reporting 43,995 feet.
Extrapolating ascent rates from prior to the loss of telemetry and descent rates just after, we estimate that the balloon burst at approximately 14856m, quite close to the predicted altitude.
|Burst Altitude||14630 m||14856 m|
|Ascent Rate||5.93 m/s||6.33 m/s|
|Descent Rate||6.55 m/s||5.5 m/s|
|Flight Range||48.7 km||48.10 km|
|Flight Time||66 min||64 min|
The balloon followed the track very well. A later prediction was run the morning of the flight which more closely matched the final result. Unfortunately, the web page was inadvertently closed and the prediction was lost. Still, this prediction from the night before was quite accurate. The payload landed 3.1 miles from target.
The high descent rate may be attributable to the fact that a large portion of the balloon remaining on the tether. It probably interfered with the full deployment of the chute as it flopped around, as the balloon was attached to the center of the chute.
On our third balloon mission, we lost telemetry when (we presume) the tracker got too cold. This time, we wrapped the tracker in bubble wrap, and fit it snugly inside a sealed bottle. While the tracker definitely got cold, it never stopped transmitting. We added temperature data to the telemetry, so we were able to graph it post-flight.
On this flight, we lost telemetry for 10 minutes at the peak altitude from the GPS, but the tracker continued to function. The GPS module was mounted outside of the bottle. Winds Aloft data indicates that, at that altitude, air temperatures were below -40c, the rated temp limit of the GPS module. For the next mission, we'll put the GPS module inside the bottle and bubble wrap.
Had we consulted Google Earth before going in for the recovery, we would have guessed the outcome.
Given that the tracker was in this “block” somewhere, we attacked it from two different directions. Hojo went due north and ran afoul of the big pond pictured, and had to circle around. Adam and Char went at it from the East, after getting permission from a landowner to traverse their property. They had a much easier go at the landing site.
After about 1/2 hour of walking around, we discovered the payload high in a tree. We were unable to retrieve it. However, Adam and Char had met Chris Preston, who was visiting his Mother's house nearby. He's an arborist, and offered to climb the tree the next day and retrieve our payload.
Chris climbing the tree:
Here he is descending after knocking the branch down. Tiffany, the camera operator, pans down so you can get an idea of how high up this thing was!
Tiffany triumphantly displays the fruits of their labors. Charlie Brown is back on the ground after spending a rainy night in the tree.