Development of High Altitude Sprite Imagery Capability - Bruski

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United States Air Force Academy’s Meteorology Department. The flight reached a maximum altitude of 31 km and landed approximately 88 km north and east of the launch location. The unit was recovered successfully with the help of a last second SPOT® tracker unit from a local high school. B. Flight Two Flight two was a test of the SPOT® tracker at high altitudes, a new payload box, and a new parachute. The balloon flight was a launch and forgets mission since no live data was being sent down to the ground. The flight landed approximately 125 miles north and east of its launch location. The balloon was recovered at 11 pm in zero light conditions. C. Flight Three Flight three served as a test of the HD GoPro Hero Naked® video camera. The camera was pointed straight down to demonstrate that position for future flights. The flight also demonstrated the necessity of having a redundant tracking system as the APRS feed was lost when the balloon was approximately 762 meters in altitude. The SPOT® tracker successfully sent its position to the tracking website 170 miles from the launch site. The balloon was in the air for over four hours which contributed to the extreme distance the balloon landed from the launch site. A unusual wind pattern at 30 km was identified. Winds usually are calm at 30 km however, on this occasion the balloon picked up speed reaching a maximum velocity of 104.60 km per hour at 31 km in altitude. D. Flight Four Flight four served as a test for a new GPS receiver unit and to demonstrate a new flight profile used to track balloons near thunderstorms. This flight was unique in that it used almost exactly the same materials as the last flight to demonstrate rapid reuse and low turnaround time. A more accurate method of measuring lift was developed to guarantee a short flight. 4.54 kg of weights were tied to the bottom of the balloon which was then filled until they could be lifted off the ground. Approximate lift was 11 pounds at launch. At about 35 minutes into the flight and at an altitude of 17 km extreme turbulence was encountered. This combined with a small amount of ice buildup on the cord connecting the parachute to the payload box led to the payload box separating from the balloon and parachute. The payload box survived a free fall from 17 km to impact at almost 112.63 km per hour with little to no damage. Again, this flight demonstrated a need for a redundant tracking system as the violent force of the impact caused the SPOT tracker to turn off. The box was located using previous data points to calculate descent rate and then combined with the winds that day to draw a probability circle to where it landed. The system was still transmitting its position 24 hours later which was picked up by HAM radio and when entered into a handheld GPS led straight to its recovery site. VI. Future Test Flights Two final test flights remain before the system is considered operational. The first test will demonstrate the ability of the system to successfully cut the balloon away from the parachute using a HAM radio to send a signal to a receiver onboard the balloon. This signal will be in the form of a coded sequence of numbers that will be read by a DTMF (dual tone multi-frequency) board and will activate a relay switch. This switch will allow current to flow through a nichrome wire wrapped around the nylon cord connecting the balloon to the parachute. With the current flow, the wire will heat up and melt through the string in a matter of seconds. In all previous flights, the balloons have failed to shred as they are designed to do at altitude. They remain mostly intact as 2-3 kg of dead weight above the parachute causing it to only partially inflate enter into a fast than expected fall. The cut down system will allow a precise maximum altitude and a more predictable landing site. Finally the second test flight that remains will serve as a test of the high altitude long duration flight at a relatively stable position. Through previous flights and the advice of the USAF Academy Meteorology Department, a region at approximately 18-21 km has been found to contain winds that are below 16.09 km per hour. This altitude is ideal for long duration flights as it is high enough to be above most of the atmospheric distortion and out of the winds. Should this region not prove to be calm, the flight will continue to rise until a calm region is found. At launch, the flight will consist of two balloons connected separately to the payload box. The large main balloon will be filled to the point where its lift exactly matches the weight of the payload and the system will be neutrally buoyant. The second smaller balloon will simply to provide the lift needed to get the system up to the desired altitude. A separate cut down device will be connected to each of the balloons and at that desired altitude, the balloon providing the free lift will be cut away and the system will 4 American Institute of Aeronautics and Astronautics
ecome neutrally buoyant. After 4-6 hours, the main balloon will be cut away as helium will begin to diffuse through the walls of the balloon and the system begins to sink. This flight will be the final flight before the system becomes operational and long duration flights studying sprites are possible. Finally, a new spring scale was acquired to allow precise measurements of lift which will enable a more accurate relation between ascent rate and the amount of helium in the balloon. Appendix A Balloon Ground Tracks and GPS Coordinates Figure A1.Balloon Trajectory Forecast for Flight One Figure A2. Balltrack Online Forecast Flight One* 5 American Institute of Aeronautics and Astronautics
Page 1 and 2: Development of High Altitude Sprite
Page 3: Figure 1. Balltrack Online Input Pa
Page 7 and 8: Figure A6. Flight Two SPOT Tracker
Page 9 and 10: Appendix B Flight Imagery Figure B1

Development of High Altitude Sprite Imagery Capability - Bruski

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