Development of a Flexible Vent for Latex Weather Ballooning
Abstract
Controlled venting of lift gas from a balloon while in flight allows one to slow the ascent, stop the ascent (AKA "float" the balloon), or even initiate a slow descent without going through the violence of "post-burst chaos." The ability to vent can allow balloon flights to reach altitude more quickly, loiter there as needed for experimental purposes, and/or take data during float or slow descent (which can be advantageous since the payload sensors are sampling “clean air,” rather than being in the wake of an ascending balloon). The stratospheric ballooning team at xxx has developed several vent devices over the years, some autonomous and others commandable by radio, but all were inordinately heavy and not particularly reliable nor efficient at allowing lift gas to escape, even when fully open. Inspired by an exceptionally lightweight, radio-commandable, but single-use (that is – intended to fly away with the balloon rather than being recovered) vent built by balloonists at the University of Colorado Boulder, our team has developed a vent which has sensors so that it can operate autonomously, as well as a radio so that it can be commanded, either from a nearby payload or from the ground (if an uplink radio system is in place). Our mechanism is designed to be used with 1600 gram (wide-neck) Hwoyee weather balloons and has a relatively large vent opening, so it is quite responsive as long as venting is done before the balloon becomes too stretched out to provide the needed overpressure to efficiently expel lift gas. The mechanism construction is nearly all serviceable and the vent is reusable because it features a "waist line" cutter, which allows it to detach itself from the balloon (and subsequently be recovered). It also has a "main line" cutter for emergencies (since the vent would then fly away with the balloon and not be recovered). In flight tests to date the vent has proven to be strong enough to hold a “full” (12 lb) stack, efficient enough to vent 6 lb of excess lift (needed to stop a “full” stack from ascending) at altitudes in excess of 70,000 feet, and capable of detaching from a balloon and being recovered (though admittedly we lost some vent mechanisms during testing). The autonomous logic allows us to program the vent to seek specific ascent rates, including targeting zero ascent rate to “float” a balloon, and to call for terminations based on elapsed time, gps fences, and/or specific target altitudes on ascent or descent. We have flight-tested the ability to control the vent by XBee radio from a nearby payload. In the near future, we plan to integrate our radio system with the Iridium uplink system that will be used by the Nationwide Eclipse Ballooning Project (NEBP), making our vent commandable from the ground. Ultimately, we intend to use this vent to float balloons during eclipse ballooning missions in 2023 and 2024. Indeed, we already refer to it as the “e-vent” (AKA “eclipse vent”).
Keywords: stratospheric ballooning, weather ballooning, vent
How to Cite:
Larson, S., Cook, J., Wallo, S., Thompson-Jewell, E., Posey, A. & Flaten, J., (2023) “Development of a Flexible Vent for Latex Weather Ballooning”, Academic High Altitude Conference 2022(1). doi: https://doi.org/10.31274/ahac.15638