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Pinhole Effects on Venus Superpressure Balloon LifetimeExperimental results are presented for a series of experiments that addressed the effect of small pinhole defects on the potential lifetime of a Venus superpressure balloon. The experiments were performed on samples of a candidate balloon envelope material through which a single small hole of 80 to 300 microns in diameter was deliberately made in each one by puncturing with a metal pin. The material was mounted horizontally in a test apparatus and then a 2-3 mm thick layer of sulfuric acid was placed on top to mimic balloon wetting at Venus. Acid penetration and damage manifested itself as a darkening of the aluminum metal and adhesive layers around the hole in the balloon material. There were no test conditions under which the acid simply fell through the pinhole due to gravity because the surface tension forces always compensated at this size. Very little acid-damaged material was observed for the smallest 80 micron pinholes while gas flowed through the hole due to balloon-like pressurization: the black spot size was approximately 0.2 mm in diameter after 6 days with 86% sulfuric acid. The damage area grew more quickly in the absence of gas flowing out of an 80 micron hole, namely at a rate of 2 mm/day. It was concluded that the flow of escaping gas out of the hole provides a substantial reduction of the rate of acid penetration and damage. Larger diameter pinholes of approximately 300 micron diameter showed larger growth rates of 0.7 mm/day with gas flow and 1.7 mm/day without. The pinhole size did not change over the duration of these experiments because the material has an outer layer of fluoropolymer film that remained intact during the process and thereby held the hole size constant. None of the damage rates measured in these experiments pose a threat to the lifetime of the balloon over the projected course of a 30 day mission because the affected area is too small to cause a structural failure either through direct damage or increased solar heating and attendant balloon pressurization leading to burst.
Document ID
20150005586
Acquisition Source
Jet Propulsion Laboratory
Document Type
Conference Paper
External Source(s)
Authors
Hall, Jeffery L.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Yavrouian, Andre H.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Date Acquired
April 13, 2015
Publication Date
March 26, 2013
Subject Category
Mechanical Engineering
Spacecraft Design, Testing And Performance
Lunar And Planetary Science And Exploration
Meeting Information
Meeting: AIAA Balloon Systems Conference
Location: Daytona Beach, FL
Country: United States
Start Date: March 25, 2013
End Date: March 28, 2013
Sponsors: American Inst. of Aeronautics and Astronautics
Distribution Limits
Public
Copyright
Other
Keywords
Venus
balloon
acid
aerobot
pinhole

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