Lessons Learned For Tandem Launches

The Maryland Space Grant Consortium Balloon Payload Program (BPP) run by the University of Maryland College Park (UMD) has devoted considerable effort in the last few years to developing techniques for tandem balloon launches with the objective of achieving a float configuration using latex balloons. The procedure is to launch a payload string with 2 weather balloons tied above the parachute in a Y-shaped configuration. Approximately 200m below the desired float altitude, the ascent balloon is cut free and the payloads then float on the remaining float balloon, which ideally has been filled to have exactly the lift necessary to counteract the weight of the payload string. This procedure, though very simple in concept, has proven to be surprisingly difficult to execute effectively. The UMD BPP has attempted over 17 tandem balloon flights, of which only 1 achieved a successful float (defined as having an ascent rate of less than +/- 1 m/s) but another 9 attempts came close (defined as having an ascent rate of less than +/- 2 m/s). This paper will discuss the challenges encountered, as well as the best practices developed for a successful tandem float, including necessary weather conditions, filling operation, release procedure, and cut-down devices. Lastly, this paper will provide ideas for future tandem float attempts, including a system that might prevent balloon collisions on ascent.