High Altitude Balloon Flight

Описание: High Altitude Balloon Flight, Oct. 4, 2011
Call Sign KJ4IES

Project Team: Ernest Legg and Richard Jandrew

Objective: To launch a high altitude balloon with HD video camera and temperature sensors. Altitude and lat/long to be provided by GPS.

Launch Site: 10 miles west of Culpepper, VA at the Reva Volunteer Fire Station

Recovery Site: Doswell, VA, approx. 7 miles west of King's Dominion theme park

Flight Summary: Balloon ascended to an altitude in excess of 75,000 feet before bursting due to very low atmospheric pressure. Temperature fell as low as -47 degrees F. Hardware payload returned via 3 meter parachute constructed of rip-stop nylon. Total flight duration was 93 minutes; 68 minutes ascending and 25 minutes descending. Distance traveled over land was 54 miles.

Balloon system: A 1500 gram latex balloon was purchased from Scientific Sales, Inc. Balloons are sold by weight. This balloon was chosen because of the payload total weight. There were 2 packages tethered that weighed 6 pounds each. This follows FAA rules for unmanned amateur balloon flights. Hydrogen was used to fill the balloon as the cost of Helium is just too high. A 300 cubic foot cylinder and a reserve 80 cubic foot cylinder were rented from Airgas of Fredericksburg. A custom filling tube and hose were constructed and equipped with a shut-off valve. A large tarp covered the balloon during the fill. It was tied to the ground with nylon rope and tent stakes.

Payload Hardware: Two cameras were used: a Kodak Playsport ZX3 HD video camera with a 32 GB SDHC card, and a Canon SD1000 Powershot 7.1 Megapixel still camera. The Canon camera was loaded with special firmware called "CHDK" that allows for interval shooting. This was set for 1 exposure every 20 seconds. The Kodak video camera was set to record just prior to launch and continued to record well after touchdown. The Canon camera was redundant, and the videos from the Kodak Playsport turned out to be preferable.

For tracking, redundant GPS receivers were used. They were coupled with "Tiny Track" TNC modems. Both GPS modules and Tiny Tracks were purchased from Byonics Corp. The modulated audio containing the GPS information was formatted per APRS standard, a system used by Ham Radio Operators. The 2 separate APRS "packets" were transmitted to the ground on 2 meter band Handheld Transceivers at 5 watts. The frequencies were 144.390 MHz and 144.140 MHz. A homemade J-pole twin lead antenna was used with one transceiver. A half wave monopole whip was used for the second transceiver.
Two 11.1 lithium polymer batteries were used in parallel to power the payload. A custom telemetry module was constructed using an Atmel Atmega 328p microcontroller. The temperature sensor was a Maxim 1-wire device. Voltage monitoring was also performed using the ADC functions on the Atmega.
A secondary payload consisting of a stowed 6 meter Parafoil failed to deploy during descent. This was intended to auto-steer the payload to a desired field or clearing (vice landing in a forest or lake). Since only the initial parachute was in use, the payload did indeed land in a dense forest.

Ground Hardware: The recovery vehicle was equipped with a Kenwood DX-710 2 meter transceiver. A roof-mount antenna worked as expected. A backup handheld Yagi antenna was available if more gain was needed. The Kenwood radio send demodulated APRS data to 2 laptop PC's. One laptop was using "Balloon Track" and "AGWPE" packet engine. The payload position was plotted automatically in "Microsoft MapPoint 2004." The second laptop was using "UIVIEW32" and "Precision Mapping 2010" to also plot the payload's position. Both laptops successfully plotted the entire flight. The payload continued to transmit after touchdown. This enabled us to locate it after 1.5 hours of hiking through the woods. Many thanks to Mr. Jandrew for this effort.

Special thanks to Zach Kenny for his video editing and uploading to YouTube.