Abstract
Stack rotation is a nemesis for many ballooning experiments, especially photography when trying to keep a specific target in view such as the Moon’s shadow (or the Sun itself) on eclipse flights. Ascending weather balloons tend to slow or even stop rotating once in the stratosphere and out of most cross winds. However payload stacks can continue to rotate with respect to the balloon right up to burst, especially if attached to the balloon neck by just a single main line. Our passive “rotation mitigation” device attaches directly to the neck of the balloon and runs four parallel lines separated by 6 inches from the balloon neck down to the payload stack, significantly diminishing stack rotation with respect to the balloon, especially at high altitudes. This arrangement complicates the placement of the parachute, but we have successfully deployed parachutes from a hook on the side of the upper-most payload box. This also complicates the placement of a flight-termination line-cutter, be that Montana’s “OCCAMS” razor cutter or something like a Tungsten hot-wire cutter. We have developed a compact payload box to enclose both an OCCAMS razor cutter and a Tungsten hot-wire cutter, both of which can independently release the multiple lines of our rotation mitigation device. We can fire the OCCAMS by XBee commands relayed through our RFD 900 payload, as an alternative to the Iridium text-message system. The Tungsten cutter can be fired by XBee command, by timer, or by autonomous GPS-sensor-based decision making.
Rotation Mitigation and "OCCAMS + Tungsten" Flight Termination for Eclipse Balloon Missions
Stack rotation is a nemesis for many ballooning experiments, especially photography when trying to keep a specific target in view such as the Moon’s shadow (or the Sun itself) on eclipse flights. Ascending weather balloons tend to slow or even stop rotating once in the stratosphere and out of most cross winds. However payload stacks can continue to rotate with respect to the balloon right up to burst, especially if attached to the balloon neck by just a single main line. Our passive “rotation mitigation” device attaches directly to the neck of the balloon and runs four parallel lines separated by 6 inches from the balloon neck down to the payload stack, significantly diminishing stack rotation with respect to the balloon, especially at high altitudes. This arrangement complicates the placement of the parachute, but we have successfully deployed parachutes from a hook on the side of the upper-most payload box. This also complicates the placement of a flight-termination line-cutter, be that Montana’s “OCCAMS” razor cutter or something like a Tungsten hot-wire cutter. We have developed a compact payload box to enclose both an OCCAMS razor cutter and a Tungsten hot-wire cutter, both of which can independently release the multiple lines of our rotation mitigation device. We can fire the OCCAMS by XBee commands relayed through our RFD 900 payload, as an alternative to the Iridium text-message system. The Tungsten cutter can be fired by XBee command, by timer, or by autonomous GPS-sensor-based decision making.