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Tools - Tank estimator sheet updated

6 Sep 2016, 18:15 UTC
Tools - Tank estimator sheet updated
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I discovered and corrected a mistake in my tank estimator spreadsheet. Corrected version is live.{edit 2016-09-06:}Also added a fill factor and a structural factor for better estimates.{edit}I also can't find my notes on how the sheet was put together, so I thought I should document the parts that were updated now so I'll know what I am looking at a few years from now.Before I go into that, I'd like to reference a NASA document (pdf) describing helium ullage tests for the Centaur upper stage. Read it, it's full of retro cool. Their numbers are a tiny fraction (1%) of mine for several reasons: they use ambient temperature helium, assume a gravity-supported temperature gradient (while I assume the helium is pre-chilled to 20 K for hydrogen or 90 K for everything else), rely on vaporization of the liquid hydrogen to maintain pressurization during engine chilldown and assume warm hydrogen from the engine provides pressure during burns. As a result I'd suggest not taking the ullage masses and volumes from my sheet too seriously as my numbers appear to be extremely pessimistic. I've also used some constants that I didn't properly document, something that must have been tricky to calculate with ...

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