Обсуждение:Вега (космический аппарат): различия между версиями
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{{Статья проекта Космонавтика|уровень=II|важность=высокая}}
== Question about lifting gas in Vega mission balloons ==
(Sorry for writing in English; I have written this same question in the English Wikipedia but got no answer. I hope someone who knows a lot of Vega can answer here.)
I have a question: The balloons in the Vega mission used '''helium''' as lifting gas. As explained in '[[:en:Lifting gas]]', this is not necessary in this quite dense atmosphere. Helium has the disadvantages of diffusing easily through a balloon's wall, the need to be transported in a compressed cilinder, and having to be inflated into the balloon at the right moment.
That raises the question why they didn't simply bring some water in this balloon? During the journey in interplanetary space it would stay compactly frozen; as soon at it will enter the hot venus atmosphere (during a parachute descent) it will be heated to '''steam''', automatically inflating the balloon. No pressure vessel needed, no special valves to let the gas into the balloon: fewer things that can fail. The lifting power of steam on Venus will certainly be sufficient to float a balloon in Venus' dense atmosphere and it will not easy diffuse through the balloon wall.
Who can explain why they have particularly chosen for helium? [[User:Erik Wannee|Erik Wannee]] 15:55, 15 апреля 2015 (UTC)
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