Design, Optimization and Additive Manufacture of Generalized Helium Outflow Unit for Latex Balloons to Float

Sounding balloons are cost-effective, small-scale platforms used for atmospheric study and engineering research. Latex balloons are the cheapest option, allowing researchers to launch equipment reaching 35km heights while briefly transiting through altitudes of interest. The scientific ballooning community carries an interest in the ability to decrease a latex balloon’s ascent rate to 0 at desired altitudes (referred to as ‘floating’). This paper details progress in the design and capability of a device which floats latex balloons, known as GHOUL (Generalized Helium Outflow Unit for Latex), created by the University of Maryland College Park Balloon Payload Program (BPP). There is a focus on the design of GHOUL and its unique advantages gained through additive manufacturing (3D printing), as well as its flight history and floating capability. GHOUL achieves float by opening a hole in the neck of a balloon for helium to vent out passively, and it has produced successful floats within 5 minutes of venting. GHOUL includes fully autonomous functionality, though it can also receive live commands to start/stop venting, vent for a specified time, or terminate its flight. GHOUL terminates by heating a nichrome burn-wire which allows a Marman clamp staging mechanism to separate; this sacrifices only a small 3D-printed balloon insert. After 8 flights with the BPP, GHOUL has demonstrated significant ascent-rate control capabilities and achieved a 3-hour float. Since then, the GHOUL mechanical system has been distributed to seven universities participating in NASA’s Nationwide Eclipse Ballooning Project and was used to achieve floats during the totality of the October 2023 U.S. annular solar eclipse.