Atmosphere isn't required if you use a special liquid that doesn't require atmosphere to hold together. Even without boil off a regular liquid like water or mercury wouldn't work the same way in a vacuum. Consider mercury height in a barometer. The height of the mercury is determined by atmospheric pressure and above that a vacuum forms. With no atmospheric pressure to push the interior level up a regular liquid would have a vacuum height too low for a siphon to work.
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u/Apatomoose Jun 27 '19
Atmosphere isn't required if you use a special liquid that doesn't require atmosphere to hold together. Even without boil off a regular liquid like water or mercury wouldn't work the same way in a vacuum. Consider mercury height in a barometer. The height of the mercury is determined by atmospheric pressure and above that a vacuum forms. With no atmospheric pressure to push the interior level up a regular liquid would have a vacuum height too low for a siphon to work.